Composite material

Abstract

A composite material (1) for producing an article by molding; the composite material (1) has a surface film (2) comprising a resin formulation having an areal weight of up to about 700 g / m2; a reinforcing material (4) consisting of an at least partially dried first fibrous material having an areal weight of up to about 900 g / m2; and at least one adhesive (3) which adheres the surface film (2) to the reinforcing material (4); according to some embodiments, the adhesive (3) is a resin interposed between the surface film (2) and the reinforcing material (4).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority of Italian Patent Application No. 102022000017424 filed on August 19, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to composite materials, methods of producing articles and kits comprising such composite materials. Background Art

[0004] In the field of production of composite body panels for industries such as the automotive, railway, aerospace, etc., it is known to superimpose a first film, called "surface film" in the jargon (containing the corresponding resin), in contact with the mold and to apply behind it successive layers of fiber reinforcement impregnated (prepreg) with a thermosetting resin matrix, and / or successive layers of thermosetting resin matrix more or less reinforced with fibers, in order to obtain an intermediate material.

[0005] After lamination of this intermediate material on the surface of the mold, the molding process is carried out by applying different layer compaction pressures and appropriate matrix polymerization temperatures. Given a specific thermal profile, the molding time is adjusted according to the chemical-physical characteristics of the thermosetting matrix.

[0006] In more detail but only by way of example, some molding techniques for composite materials based on thermosetting matrices are reported.

[0007] - Vacuum bag and furnace molding. In this molding process, the fully or partially impregnated reinforcement layers are deposited on the mold surface, combined with appropriate auxiliary materials (inflators, vacuum valves, etc.) and covered with a plastic film of a vacuum bag. After the vacuum bag is sealed, it is connected to the vacuum line through a suitable valve so that (a) the atmospheric pressure outside the vacuum bag can exert its full force by compacting the layers, and (b) at least in the ideal case, all the air is removed from the inside of the vacuum bag, thus eliminating the presence of bubbles between the layers. In fact, if these bubbles are not properly removed, it will inevitably lead to the formation of voids inside the molded laminate, which will constitute weak parts and structural fragility of the product. When the vacuum is applied and therefore the necessary compaction between the layers, the mold is placed in the furnace and heated to a specific temperature, based on the characteristics of the thermosetting resin, by adopting an appropriate heating rate. In this way, first the fluidization of the matrix necessary for sufficient wetting of all the reinforcement materials is achieved, and then the progressive polymerization process is achieved, thus forming the final product.

[0008] - Autoclave forming. This forming technology is derived from vacuum bag forming. The preparation of the mold, the lamination steps of the various fully or partially impregnated reinforcement layers, as well as the preparation and closing of the bag are carried out in a manner analogous to that described above. The only difference is that, while the internal pressure of the furnace into which the bag is inserted with the prior art is equal to atmospheric pressure, the autoclave allows the application of higher pressures. In this way, the compaction forces between the different layers are not limited to atmospheric pressure (approximately 1 bar), but can be significantly increased, typically reaching values ​​of approximately 6 bar. This forming technology, although more expensive, allows obtaining formed parts of better quality than the former, both in terms of aspects relating to the structural strength of the laminate and in terms of the surface quality of the article (essential element for the subsequent painting step).

[0009] - Compression moulding. In this case, the mould consists of two parts (mould and counter-mould). In a first step, the mould is kept open so that there is space between the two mould halves to introduce the reinforcement and matrix layers. When the lamination step is finished, the mould is closed by operating the relevant press, thus ensuring an appropriate closing force between the two mould halves and therefore sufficient compaction between the layers of the laminate. The mould is then suitably heated to allow the polymerisation of the matrix to take place.

[0010] There are several variants of these molding techniques and their hybrid forms. Again, as an example, the use of films that can replace one of the two half-molds of compression molding is mentioned. By means of suitable mechanisms, these films can be pressurized so as to exert pressure on the laminated layer on the half-mold, thus ensuring the necessary compaction. Other examples of variants can be easily retrieved in the literature and industry journals (D. Rosato, D. Rosato, Reinforced Plastics Handbook 3 rd Ed, 2004, Elsevier).

[0011] All of these forming techniques and their variants are used in various industrial fields, including the production of automotive parts, and reference will be made herein primarily to these techniques without limiting their generality.

[0012] The above activities require operators to carry out long manual lamination processes, which has a significant impact on the overall production costs. In addition, the products obtained may have defects, especially when they have to reproduce particularly complex shapes. Typical defects of laminated products can be divided into surface defects, which are sometimes even visible to the naked eye, and defects existing inside the laminate, which can be found by appropriate destructive and non-destructive techniques.

[0013] Some defects found in the production process of composite parts are reported as follows by way of example.

[0014] - Porosity (pitting). This term refers to small cavities, less than one millimeter in size (generally of the order of a tenth of a millimeter), which are present on the surface of the part. In general, these pores are caused by the failure to evacuate the air at the interface between the mold and the first layer of the laminate before the gelation of the matrix during the molding process. This porosity is a defect that must be adequately removed in a surface treatment step before painting. Unfortunately, in the case of excessive porosity, appropriate additional treatment is required before painting can be carried out, which increases the costs.

[0015] -Marking (print-through). This phenomenon consists in the imprint of the underlying reinforcement material on the painted surface. In the case of textiles, this imprint is present in the weft-warp design, in the case of multiaxial reinforcement structures, in the marking of the sewing threads or the spacing between individual fibers, etc. This defect, if present, may not be visible immediately after the painting process, but only during the life of the component exposed to natural atmospheric events. Appropriate accelerated aging tests are widely used by automobile manufacturers in the quality control steps of materials and molding processes, and regulations regulate this. As examples, the main international standards (reference regulations inspired by them) are reported as follows: Standard Practice for Determination of Thermal Cycling Resistance of Cured Coatings, ASTM D6944-15(2020); Standard Practice for Xenon-Arc Exposure of Plastics for Outdoor Use, ASTM D2565-16; Methods for Exposure of Plastics to Laboratory Light Sources Part 2: Xenon Arc Lamps, ISO 4892-2:2013.

[0016] - Irregular surface distribution of the resin. Several factors can lead to visible irregularities on the surface of the component, for example, local increases or decreases in the thickness of the matrix surface to protect the reinforcement fibers of the underlying layer. This can be due to, for example, a lack of adhesion of the first prepreg layer to the mold surface before the matrix has gelled (typically concave areas of the mold). In this case, local thickening of the resin layer to protect the fibers (bridging) can be noticed. A second example concerns wrinkles in the reinforcement layers that may appear when laminating the various layers. In this case, surface irregularities with alternating resin-poor areas (which may even leave the fibers uncovered) and areas with resin accumulation can be noticed. These irregularities can also occur with changes in color tone due to the different colors of the matrix and reinforcement materials.

[0017] - Internal porosity. This type of defect consists in the presence of cavities inside the molded part, either inside the layers or, more often, between them. In these cases, the defect can be highlighted by making cuts on the laminate and analyzing the cross section with the help of an appropriate microscope. Generally, these cavities are caused by gas bubbles trapped in the matrix during gelation. This defect, based on the size and distribution of the pores, can also impair the structural properties of the laminate.

[0018] - Dry fibers. This type of defect (which can also be found by analyzing a cross-section of the molded part) can be attributed to insufficient flow of the thermosetting resin within the reinforcement layer, with the result that areas without matrix are formed. The local absence of matrix precludes a correct distribution of the stress state inside the part, compromising its structural properties. In principle, pre-impregnated reinforcements have a good resin distribution in the reinforcement even before molding, but this does not represent a necessary condition for the success of the molded part. It is important, however, that the reinforcement parts that are not wetted by the matrix before molding are properly impregnated during the molding process following the resin flows generated in the initial steps of the process. Due to these matrix flows, in fact, it is possible to obtain dry fiber-free laminates even with partially or completely dry fabrics, obviously provided that the total amount of matrix and reinforcement in the entire laminate is sufficiently balanced as a whole.

[0019] It is appropriate to prevent the above defects, since surface defects can make the painting process extremely onerous with special additional restoration treatments, while internal defects can represent structural weak points.

[0020] The object of the present invention is to provide a composite material, a method for producing an article and a kit making it possible to at least partially overcome the disadvantages of the prior art while being easy and economical to carry out. Summary of the invention

[0021] According to the present invention, there is provided a composite material, a method of producing an article and a kit comprising such a composite material, as claimed in the accompanying independent claims, preferably in any claim directly or indirectly dependent on the independent claim. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is described below with reference to the accompanying drawings, which show some non-limiting embodiments of the present invention, in which:

[0023] Figure 1 Schematically shows a cross section of a composite material according to the invention;

[0024] Figure 2 Schematic showing a material with overlapping layers (composed of Figure 1 material and reinforcement material layers);

[0025] Figure 3 The shape of the DSC curve in the glass transition temperature range is schematically shown;

[0026] Figure 4 Schematic showing the template required to prepare the samples for mechanical testing (measurements reported are in millimeters);

[0027] Figure 5 is a photograph of a template placed on composite material 1 during preparation of samples for mechanical testing;

[0028] Figure 6 The dressing tool is shown schematically (measurements reported are in millimeters);

[0029] Figure 7 shows the steps of trimming the reinforcement material 4 of a sample of composite material 1 for mechanical testing;

[0030] Figure 8 shows the steps of surface film conditioning of samples for mechanical testing;

[0031] Fig. 9 is a photograph of a sample of composite material 1 used for mechanical testing;

[0032] Fig.10 Schematically shows the geometry of the mold used to test the present invention (measurements reported are in millimeters);

[0033] Fig.11 The lamination steps of Test N1 are shown (Configuration A - Example 5 reported below);

[0034] Fig.12 The lamination steps of Test N2 are shown (Configuration B - Example 5 reported below);

[0035] Fig.13 The lamination steps of Test N3 are shown (Configuration C - Example 5 reported below);

[0036] Fig.14 Schematically shows the typical construction of a mold for an autoclave, which is equipped with molding material (prepreg material) and a vacuum bag with various auxiliary equipment and vacuum lines;

[0037] Fig.15 The results of tests performed with reference materials are shown and described in Example 5 reported below;

[0038] Fig.16 The results of tests performed with reference materials are shown and described in Example 5 reported below;

[0039] Fig.17 The results of tests performed with an embodiment of the material according to the invention are shown and described in Example 5 reported below;

[0040] Fig.18 is a photograph of a mold (Example 6) used to test the present invention;

[0041] Fig.19Included are photos of three molded parts;

[0042] Fig. 20 Include Fig.19 Three light microscopy images of sections performed on the points CSA1, CSB1, and CSC1 reported in;

[0043] Fig.21 Schematically shows Figure 1 A cross section of an alternative embodiment of a composite material. DETAILED DESCRIPTION

[0044] According to a first aspect of the present invention, there is provided a composite material 1( Figure 1 ), which is used to produce articles by molding. The composite material 1 has a surface film 2, which includes an area weight of up to about 700 g / m 2 a first (thermosetting) resin formulation; a reinforcing material 4 consisting of an at least partially dried first fiber material having an area weight of up to about 900 g / m2, taking into account the only fiber component; 2 ; and at least one adhesive 3, which bonds the surface film 2 to the reinforcing material 4.

[0045] Specifically, the area weight of the first (thermosetting) resin formulation of the surface film 2 was measured according to standard ASTM D 3529 / D 3529M-97 (reapproved in 2008).

[0046] Specifically, the area weight of the first fiber material is measured according to standard BS EN12127:1998.

[0047] In this document, "resin formulation" refers to a formulation comprising a resin (correct name), optionally further comprising other components in addition to the resin (correct name); "thermosetting resin formulation" refers to a formulation comprising a thermosetting resin (correct name), optionally further comprising other components in addition to the thermosetting resin (correct name). Examples of such other components are (except for the crosslinking agent): accelerators, toughening agents, additives for changing rheology / resistance / wetting properties, organic and / or inorganic fillers, etc. (and combinations thereof).

[0048] As used herein, "thermosetting resin" refers to a resin having a crosslinking agent and capable of crosslinking when heated.

[0049] In some cases, the resin is composed of a plurality of types of resins. Alternatively, the resin is composed of only one type of resin.

[0050] Examples of crosslinking agent classes are: aliphatic amines, cycloaliphatic polyamines, aromatic amines, aromatic polyamines, polyamides, polyamidoamines, imidazolines, polyaminoimidazolines, ketimines, enamines, imidazoles, cyanamides, dicyandiamides, ureas, hydrazines, hydrazides, carboxylic acids, carboxylic anhydrides, phenolic resins, polysulfides, polythiols, boron complexes, quaternary Of particular use in the present context are: aromatic amines, imidazoles, cyanamide, dicyandiamide, urea, hydrazides, carboxylic anhydrides, phenolic resins, boron complexes (and combinations thereof).

[0051] In this context, "partially dry" refers to a material that is not completely impregnated with resin (specifically, with adhesive 3). In other words, the at least partially dry material has at least a portion that is free of resin (specifically, adhesive 3; more specifically, adhesive 3 and tacky adhesive - described in more detail below).

[0052] It has been observed experimentally that this material 1 exhibits high drapability (i.e. the ability of the material to deform easily to adhere to and conform to the shape and geometry of the mould). Through the tests carried out (see the examples reported below), it has been observed that the use of the material 1 according to the invention enables to reduce the time and facilitate the production of articles. Furthermore, the articles obtained show fewer defects.

[0053] It is assumed that these results are due to the fact that, when dry, at least a portion of the fibers of the reinforcement material 4 can be easily repositioned during the lamination step to easily conform to the geometry of the mold, thereby minimizing the formation of wrinkles and also allowing the passage (escape) of air between the reinforcement material 4 and the mold surface during the molding step.

[0054] The first fibrous material has fibers that can move independently of each other when dry, compatible with winding and / or stitching constraints; more specifically, such fibers are located on the opposite side relative to one side of the surface film 2. Generally, the fibers that can move independently of each other are substantially dry.

[0055] The dry fiber content (or degree of impregnation) of the reinforcement 4 can be conveniently expressed in terms of water absorption (WPU), which can be measured by the procedure reported in the literature (Simmons M. et al., WO2013186389). In general, the water absorption value increases with the increase in the percentage of dry fibers in a given reinforcement. It is also possible to identify two limiting cases that may apply to any type of reinforcement: (a) a completely dry reinforcement (no impregnation at all), thus having 100% dry fibers, which is the maximum water absorption value expected; (b) a completely impregnated reinforcement, thus having 0% dry fibers, where the water absorption value generally tends to zero.

[0056] Advantageously but not necessarily, the dry fiber content of the reinforcing material 4, expressed in %DF-R4 (based on equation 1 reported below) represents greater than about 20%, specifically greater than about 25%, more specifically greater than about 30%. According to some non-limiting embodiments, the dry fiber content of the reinforcing material 4, expressed as % DF-R4 Meaning, up to about 99.8% (specifically, up to about 99.7%; more specifically, up to about 99.5%).

[0057] It was observed experimentally that composite material 1 provided particularly strong drape, as described in Examples 5 and 6 reported below. The effect and functionality of composite material 1 and the dry fiber percentage (% DF-R4 ) related.

[0058] It has been observed experimentally that the water absorption values ​​are greatly influenced by the fiber properties and the type of reinforcement considered (weave type, areal weight, etc.). Therefore, the WPU measurement of a reinforcement, aimed at assessing its level of impregnation, must always refer to the reinforcement type in completely dry (i.e. non-impregnated) form.

[0059] Merely as an example, consider the following material consisting of a dry reinforcement material made of carbon fibers and a dry reinforcement material made of glass fibers and a corresponding pre-impregnated material with a thermosetting resin formulation:

[0060] - Reinforcement material CBX250R-CAT-C020250R00A200002 - Multiaxial fabric produced and sold by Selcom SRL (Via della Torre, 17-31010 Fregona (TV) Italy). This reinforcement material is a composite biaxial fabric as described below: Carbon fiber T700SC 12K 50C, fiber weight area weight 250 g / m 2 , arranged at -45° / +45°. Carbon fiber polyester thread (stitching yarn) at 0° and 8g / m 2 Area weight stitched / knitted with chain / column knitting pattern; fabric stabilized at 0° with the following stabilizing thread: 136Tex E glass fiber, area weight 7 g / m 2 The total reinforcement area weight (total mass) is 265g / m 2 (In this article, g / m 2 Refers to grams per square meter), the total reinforcement material width is 1270mm.

[0061] - Reinforcement material VR48 GI6224 / 1 sold by GIVIDI Fabrics SRL (Via Giacomo Matteotti, 120, 20861 Brugherio MB, Italy). This reinforcement material is a VR48 style fabric, 2x2 twill weave, composed as follows: warp glass fibers (type and density) 3x EC9 68 1x0, weft glass fibers EC9 204 1x0 or EC11 204 1x0; the glass fibers are coated with GI6224 / 1 primer. The fabric has 7.0 yarns per cm in the warp direction and 7.0 yarns per cm in the weft direction. The minimum tensile strength of the warp yarns is 310 N / cm and the minimum tensile strength of the weft yarns is 250 N / cm. The total reinforcement material area weight (total mass) is 290 g / m 2 , the reinforcement material thickness is 0.23mm and the total reinforcement material width is 1270mm.

[0062] - GG250X(T700)-DT150-40 ME (H 127cm) (code M-PRO19235) is a biaxial fabric impregnated with a thermosetting resin system with the following characteristics: Carbon fiber T700SC 12K 50C, fiber weight area weight 250g / m 2 , arranged at -45° / +45°. Carbon fiber polyester thread (stitching yarn) at 0° and 8g / m 2 Area weight stitched / knitted, chain knit type; fabric stabilized at 0° with the following stabilizing thread: 136Tex E glass fiber, area weight 7 g / m 2 The total reinforcement area weight (total mass) is 265g / m 2 , the total reinforcement width is 1270 mm. The reinforcement is impregnated with the resin system DT150, which has a nominal resin content of 40% by weight and a theoretical molded sheet thickness of 0.27 mm. The resin DT150 (a product produced by Delta-Tech SpA) has the following characteristics: a maximum DMA glass transition temperature (tg) of 140°C; processing by vacuum bag curing and compression molding in an autoclave; storage for 30 days at 21°C; medium viscosity; chemical nature is a thermosetting epoxy resin; polymerization temperature range is 120°C to 150°C; the density of the pure polymerized resin is 1.24 g / cm 3 ; Medium dynamic viscosity, 500-1000 poise at 60°C.

[0063] - VV290T-DT150-40 ME (H 127 cm) (code MVV290T0440) is a glass fabric with a twill 2x2 weave, impregnated with a thermosetting resin system, with the following characteristics: Warp glass fibers (type and density) 3xEC968 1x0, weft glass fibers EC9 204 1x0 or EC11 204 1x0. The fabric has 7.0 yarns per cm in the warp direction and 7.0 yarns per cm in the weft direction. The total reinforcement area weight (total mass) is 290 g / m 2 , the total reinforcement material width is 1270 mm. The above reinforcement material is impregnated with the resin system DT150; the nominal resin content of the material is 40% by weight and the theoretical molded sheet thickness is 0.27 mm. The properties of the resin system DT150 are similar to those of the above materials.

[0064] Table 1 below reports the experimental water absorption values ​​recorded for each material.

[0065] Table 1

[0066]

[0067]

[0068] Conveniently, the percentage (%) of dry fibers of the reinforcing material 4 in the composite material 1 DF-R4 ) can be evaluated based on the following mathematical formula (Eq.1):

[0069]

[0070] WPU R4 is the water absorption measured on the reinforcement material 4 of the composite material 1 (exemplary values ​​for the last two materials are shown in the last column of Table 1), WPU Dry-R4 is the water absorption measured on the completely dry reinforcement material 4 (example values ​​for the first two materials are shown in the last column of Table 1). It should be noted that WPU R4 The determination of the value requires the separation of the reinforcing material 4 from the surface film 2 and, as far as possible, from the adhesive 3 layer placed between the surface film 2 and the reinforcing material 4. In this regard, purely by way of example, such separation can be achieved by applying a peeling force to the overhang of the surface film 2 and the overhang of the reinforcing material 4, or alternatively, according to a procedure appropriately determined based on possible variations of the composite material 1.

[0071] The surface film 2 comprises a carrier 8 of a second fiber material, in particular having a thickness of less than about 200 g / m 2 (Specifically, less than about 100 g / m 2 More specifically, less than about 40 g / m 2) area weight.

[0072] The surface film 2 also includes a first surface layer 7, which defines the outer surface of the composite material 1 and includes (specifically, mainly consists of; more specifically, substantially consists of; more specifically, consists of) a first (thermosetting) resin formulation. A carrier 8 is arranged between the surface layer 7 and the adhesive 3.

[0073] This increases the ease of lamination and improves the surface quality of the finished product (the method of production of which will be described in more detail below).

[0074] According to some non-limiting embodiments, the first surface layer 7 consists essentially of (specifically, consists of) the first (thermosetting) resin formulation.

[0075] Advantageously, but not necessarily, the first thermosetting resin formulation (particularly the surface film 2 ) comprises a (particularly inorganic) dispersed filler (dispersed inorganic filler) (particularly in the surface layer 7 ).

[0076] The use of fillers (particularly inorganic fillers) in the first thermosetting resin formulation (particularly in the surface film 2; more particularly in the first surface layer 7) can improve obtaining a uniform and regular surface on the finished part after molding.

[0077] Alternatively, the surface film 2 (specifically, the first thermosetting resin formulation) has no filler (specifically, an inorganic filler).

[0078] According to some non-limiting embodiments, the filler is composed of inorganic fillers (combinations) of different chemical natures, such as carbonates, silicates, sulfates, metal oxides, etc. (and combinations thereof).

[0079] According to some non-limiting embodiments, the filler is between 5 wt % (specifically 15 wt %) and 60 wt % relative to the weight of the first (thermosetting) resin formulation of the surface film 2 (specifically the first surface layer 7 ).

[0080] It has been experimentally observed that, surprisingly, the sufficient presence of fillers in the first surface layer 7 enables to reduce the coefficient of thermal expansion of this layer itself, making it more stable and obtaining a reduced tendency to print-through effects (see above).

[0081] Advantageously, but not necessarily, the particle size of the filler is below 200 μm (particularly at least 1 μm; more particularly at least 5 μm).

[0082] The size (particle size) is obtained by successive sieving with sieves having holes of decreasing size (diameter). The diameter of the holes of the first sieve that does not allow the particles to pass represents the size (ie diameter) of the particles.

[0083] As long as the size of the particles and the mesh (i.e., diameter) allows (specifically, up to a minimum of 0.05 mm), the measurement is performed by subsequent sieving. Below these sizes (specifically, 0.05 mm), the size of the particles is measured as the average diameter D (v, 0.5), measured by a laser particle sizer, specifically, using a laser particle sizer Mastersizer Microplus Ver. 2.19 (Malvern Ltd).

[0084] According to some non-limiting embodiments, the first surface layer 7 has a thickness of at least 20% (specifically, up to 99.6%; more specifically, up to 98%) of the total thickness of the surface film 2 (for measurement of these parameters, see further description below regarding determining the position of the carrier 8).

[0085] Additionally or alternatively, the first surface layer 7 has a thickness of at least 0.01 mm, in particular up to 0.8 mm.

[0086] Advantageously but not necessarily ( Figure 1 ), the carrier 8 is arranged in a surface area of ​​the surface film 2 opposite to the first surface layer 7 and facing the adhesive 3; specifically, the carrier 8 is (at least partially) arranged to contact the adhesive 3.

[0087] Optionally, the carrier 8 is arranged within (embedded in) the first (thermosetting) resin formulation. In these cases, the surface film 2 comprises a second layer 9 of the first resin formulation, such that the carrier 8 is arranged between the first surface layer 7 and the second layer 9 ( Fig.21 ).

[0088] To measure the position of the carrier 8 within the surface film 2, the following method is followed.

[0089] The position of the carrier 8 within the surface film 2 (specifically, the first thermosetting resin formulation) can be determined by the coordinate system T fs Defined along the relative thickness. Consider T fs = 0, the interface of the surface film 2 is adjacent to the adhesive layer 3. fs =100, the outer surface of the surface film 2, that is, the surface opposite to the adhesive 3, will be in direct contact with the mold. mf as a reference item for its location.

[0090] Advantageously, but not necessarily, the carrier 8 of the composite material 1 is arranged relative to the median plane P mf Dimension T in the range of 0 to 50 sf middle.

[0091] The position of the carrier 8 is evaluated by analyzing a cross section of the composite material 1 with the aid of a suitable microscope. In order not to change the position of the carrier 8 (second fiber material) within the surface film 2 (specifically, the first thermosetting resin formulation layer), it is appropriate to perform the cutting of the composite material 1 at a temperature at least 30° C. below the glass transition temperature of the first (thermosetting) resin formulation, which is necessary to produce the cross section to be analyzed. In this regard, a freezer suitable for reaching this temperature can be used, or liquid nitrogen can be used.

[0092] The following are the relevant procedures for using liquid nitrogen:

[0093] - Cut a sample of the composite material 1 of approximately 5×5 cm in size using scissors or other suitable tools;

[0094] -Use metal tongs to gently immerse the sample into the liquid nitrogen in the Dewar flask;

[0095] - Soak the sample for at least 15 seconds;

[0096] - Extract the sample from the liquid nitrogen and immediately divide it in half by making a clean cut using scissors or other suitable tool;

[0097] - Analyze freshly made internal sections with the aid of a suitable microscope;

[0098] It should be noted that a similar sequence can be performed in the case of a freezer. In these cases, it must be ensured that the sample reaches a condition of thermal equilibrium with the temperature inside the freezer, which must be at least 30°C below the Tg of the first (thermosetting) resin formulation.

[0099] After obtaining a cross section of the material, it is analyzed using an optical microscope or a scanning electron microscope (SEM).

[0100] By following the above-described process, the thickness of the first surface layer 7 can also be determined.

[0101] According to some non-limiting embodiments, the first thermosetting resin formulation includes a first thermosetting resin selected from the group consisting of epoxy resins, cyanate resins, vinyl ester resins, acrylic resins, phenolic resins, melamine resins, urethane resins, siloxane resins, alkyd resins, benzoxazine resins, maleimide resins, furan resins, polyesters (and combinations thereof). Generally, the first thermosetting resin formulation includes (more accurately, the first resin is) an epoxy resin. In other words, in these cases, the first resin includes (specifically, is) an epoxy resin.

[0102] Advantageously but not necessarily, the first resin formulation comprises at least 40 wt % (specifically at least 50 wt %; more specifically at least 60 wt %; even more specifically at least 90 wt %) of the first resin relative to the weight of the first resin formulation. Additionally or alternatively, the first resin formulation comprises up to 95 wt % (specifically 85 wt %; more specifically up to 40 wt %) of the first resin relative to the weight of the first resin formulation.

[0103] In some specific and non-limiting cases, the first resin formulation consists of a first resin.

[0104] Advantageously but not necessarily, the first thermosetting resin formulation (specifically, the first resin) has a crosslinking agent in its interior. In some non-limiting cases, the crosslinking agent is selected from the group consisting of aliphatic amines, alicyclic polyamines, aromatic amines, aromatic polyamines, polyamides, polyamidoamines, imidazolines, polyaminoimidazolines, ketimines, enamines, imidazoles, cyanamides, dicyandiamides, ureas, hydrazines, hydrazides, carboxylic acids, carboxylic anhydrides, phenolic resins, polysulfides, polythiols, boron complexes, quaternary Onium salts, ternary sulfonium salts (and combinations thereof).

[0105] Particularly useful in this context are: aromatic amines, imidazoles, cyanamide, dicyandiamide, urea, hydrazides, carboxylic anhydrides, phenolic resins, boron complexes.

[0106] Particularly useful in this context are: aromatic amines, imidazoles, cyanamide, dicyandiamide, urea, hydrazides, carboxylic anhydrides, phenolic resins, boron complexes.

[0107] According to some non-limiting embodiments, the first (thermosetting) resin formulation has a viscosity of at least about 30 g / m 2 (Specifically, at least about 120 g / m 2 More precisely, but not necessarily, the first (thermosetting) resin formulation has an area weight of up to about 600 g / m 2 (Specifically, up to about 400 g / m 2 ) area weight.

[0108] Advantageously, but not necessarily, the first thermosetting resin formulation (particularly, the first resin) has a controlled viscosity change and low to medium viscosity upon heating.

[0109] In some cases, the second fiber material has a thickness of at least about 3 g / m 2 (Specifically, at least about 10 g / m 2 ) area weight.

[0110] According to some non-limiting embodiments, the second fiber material includes (specifically, mainly includes; more specifically, is made of) carbon fiber, glass fiber, basalt fiber, natural fiber (such as flax fiber), synthetic fiber (such as polyester fiber and / or aromatic polyamide fiber. Specifically, the second fiber material includes (specifically, mainly includes; more specifically, is made of) synthetic fiber (such as polyester fiber).

[0111] According to some non-limiting embodiments, the area weight of the first (thermosetting) resin formulation is at least about 0.7 times (specifically, at least about 1 times; more specifically, at least about 2 times; even more specifically, at least about 5 times; specifically, up to about 100 times; more specifically, up to about 30 times) the area weight of the second fiber material.

[0112] According to some non-limiting embodiments, the first fiber material has a fiber weight of less than about 500 g / m 2 (Specifically, less than about 300 g / m 2 ) area weight.

[0113] More precisely, but not necessarily, the first fiber material has a thickness of at least about 30 g / m 2 of area weight, and includes (specifically, mainly includes; more specifically, is made of) carbon fiber, glass fiber, basalt fiber, natural fiber (such as flax fiber), synthetic fiber (such as polyester fiber and / or aromatic polyamide fiber).

[0114] Advantageously, but not necessarily, the first fiber material (fabric) is selected from the group consisting of: woven fabrics, unidirectional fabrics, multiaxial fabrics (optionally stabilized by sewing threads) and nonwoven fabrics (particularly, fibers stabilized by adhesives). In some specific cases, the first fiber material is a unidirectional fabric or a multiaxial (particularly biaxial) fabric. Additionally or alternatively, the first fiber material is a multiaxial (particularly biaxial) fabric.

[0115] Note that in this document, the material referred to as "fabric" includes both woven and non-woven fibers.

[0116] The adhesive 3 includes (specifically, is) a tacky adhesive, and is arranged between the surface film 2 and the reinforcing material 4 .

[0117] Specifically, the area weight of such adhesive materials is measured according to standard ASTM F2217 / F2217M-13 (reapproved in 2018).

[0118] Advantageously, but not necessarily, the adhesive 3 comprises (in particular, is) a tacky adhesive having a glass transition temperature (Tg) of less than about 20°C.

[0119] It has been experimentally observed that when a tacky adhesive has these properties, it is sufficiently tacky (sticky) to be able to perform its function of connecting the surface film 2 and the reinforcing material 4 (even in small amounts). Specifically, the glass transition temperature is less than about 15°C (more specifically, less than about 0°C).

[0120] In some non-limiting instances, the glass transition temperature is above about -80°C.

[0121] Advantageously but not necessarily, the area weight of the adhesive is less than the area weight of the reinforcing material 4 (specifically, less than half of the area weight of the reinforcing material 4). According to some non-limiting embodiments, the area weight of the tacky adhesive is greater than 2% (specifically, greater than 4%; more specifically, greater than 6%) of the area weight of the reinforcing material 4.

[0122] Additionally or alternatively, the adhesive has an area weight of less than about 300 g / m 2 (Specifically, less than about 150 g / m 2 More specifically, less than about 60 g / m 2 ; Even more specifically, less than about 30 g / m 2 ).

[0123] In some non-limiting cases, the tacky adhesive has an area weight greater than about 5 g / m 2 .

[0124] According to some non-limiting embodiments, the adhesive comprises (specifically, is) a second (specifically, thermosetting) resin formulation, which in turn comprises (specifically, is) a second (specifically, thermosetting) resin, which is selected from the group consisting of epoxy resins, cyanate resins, vinyl ester resins, acrylic resins, phenolic resins, melamine resins, urethane resins, siloxane resins, alkyd resins, benzoxazine resins, maleimide resins, furan resins, polyesters (and combinations thereof). Specifically, the second resin (specifically, the tacky adhesive) comprises (more specifically, is) an epoxy (more specifically, thermosetting) resin.

[0125] In some cases, but not necessarily, the thermosetting tacky adhesive (second resin) includes a cross-linking agent.

[0126] Preferably, but not necessarily, the binder (specifically, the second resin formulation; more specifically, the second resin) is not crosslinked (specifically, the second resin formulation (more specifically, the second resin) is not crosslinked).

[0127] It was experimentally observed that in this way the composite material proved to be particularly drapable.

[0128] More precisely, but not necessarily, the tacky adhesive (specifically, the second resin formulation; more specifically, the second resin) does not contain (the second resin does not contain) a cross-linking agent.

[0129] It has been observed experimentally that in this way the tacky adhesive successfully performs its function of connection between the surface film 2 and the reinforcing material 4 for a longer period of time (in fact, ages more slowly).

[0130] Specifically, in these cases, during the molding process, the tacky adhesive can be hardened by utilizing the crosslinking agent of the first resin formulation (formulation of the surface film 2) and / or the crosslinking agent present in the back layer 5 (described in more detail below).

[0131] According to some non-limiting embodiments, the adhesive 3 (in addition to the above-mentioned viscous adhesive) also includes a fiber material (specifically, a fiber layer) immersed in the viscous adhesive. For example, the third fiber material includes (specifically, mainly includes; more specifically, is made of) carbon fiber, glass fiber, mineral fiber (such as basalt fiber), natural fiber (such as flax fiber), synthetic fiber (such as polyester fiber and / or aromatic polyamide fiber), metal fiber and a combination (mixture) thereof. Specifically, the fiber material (of the adhesive 3) includes (specifically, mainly includes; more specifically, is made of) synthetic fiber (such as polyester fiber).

[0132] Advantageously, but not necessarily, the adhesive 3 (particularly a tacky adhesive) has a connection force (between the surface film 2 and the reinforcing material 4) of at least about 0.6 N (particularly at least about 1.0 N) measured on a sample of about 25 mm x 200 mm.

[0133] According to some non-limiting embodiments, Adhesive 3 (specifically, a tacky adhesive) has a connection force of up to about 200 N (specifically, up to about 150 N) measured on a sample of about 25 mm x 200 mm.

[0134] Advantageously, but not necessarily, the adhesive 3 (particularly, a tacky adhesive) has a connection stress (between the surface film 2 and the reinforcing material 4) of at least about 0.1 kPa (particularly, at least about 0.2 kPa).

[0135] According to some non-limiting embodiments, adhesive 3 (specifically, tacky adhesive) has a connection stress of less than about 40 kPa (specifically, less than about 30 kPa).

[0136] Force and stress referred to herein were measured as described in Example 4.

[0137] According to some non-limiting embodiments (such as Figure 1As shown), the adhesive 3 is arranged between the surface film 2 and the reinforcing material 4 so as to form a continuous layer and be evenly distributed.

[0138] According to an embodiment not shown, the adhesive 3 is distributed unevenly (so that there are areas without adhesive 3 between the surface film 2 and the reinforcing material 4) or in a disordered shape (randomly distributed) according to a defined design (e.g. forming dots, circles, lines, etc.).

[0139] According to another aspect of the present invention, a method for producing an article is provided. The method comprises a first lamination step, in which the composite material 1 as described above is placed on a mold (specifically, the surface film 2 is in contact with the mold), specifically, the composite material 1 substantially acquires the shape of the mold; a second lamination step after the first lamination step, in which a back layer 5 ( Figure 2 ) to obtain a material 6 having overlapping layers substantially in the shape of the mould (see Figure 2 ); and a molding step after the second lamination step, in which the material 6 with overlapping layers placed on the mold is compressed (extruded, specifically, subjected to a pressure greater than atmospheric pressure) and heated. More precisely, during the molding step, the back layer 5 and the composite material 1 are compressed (extruded) toward each other. Specifically, during the molding step, the material 6 with overlapping layers placed on the mold is appropriately compacted and heated so as to obtain polymerization of the thermosetting matrix.

[0140] According to some non-limiting embodiments, the rear layer 5 comprises a third fiber material (which is understood as such and is therefore dry and without resin content) and an amount of a third resin formulation.

[0141] Specifically, the third resin formulation is thermosetting and includes (specifically, is) a third (specifically, thermosetting) resin selected from the group consisting of epoxy resins, cyanate resins, vinyl ester resins, acrylic resins, phenolic resins, melamine resins, urethane resins, siloxane resins, alkyd resins, benzoxazine resins, maleimide resins, furan resins, polyesters (and combinations thereof). More specifically, the third thermosetting resin includes a crosslinking agent.

[0142] Advantageously but not necessarily, the fiber content of the material 6 having overlapping layers, expressed as fiber volume fraction (FVF), ranges from a minimum of about 20% (particularly a minimum of about 35%) to a maximum of about 75% (particularly a maximum of about 65%).

[0143] The following points report the criteria for evaluating the fiber volume fraction of the (entire laminate) material 6 with overlapping layers:

[0144] 1) The surface film 2, the entirety of which (resin preparation and carrier) must be excluded as a non-structural element.

[0145] 2) The three layers of adhesive must be considered in the overall calculation. leg ), the relative area weight as the base, and the relative area weight as the resin preparation (R leg ) and fiber (F leg )'s relative area weight of the combination.

[0146] 3) Reinforcement material 4, i.e. the first fiber material, must be counted as fiber (F rinf,4 ).

[0147] 4) The fiber composition of the back layer 5 must be considered (F sp ) and its resin component (R sp The distribution of resin components and related fiber components has no effect on the calculation of fiber volume fraction.

[0148] Then, the FVF can be calculated according to the following formula:

[0149]

[0150] in:

[0151] F leg is the area grams of the fiber material of binder 3 (if present), D fleg is the fiber density of the fiber material of binder 3 (if present), F rinf,4 is the area gram weight of the fiber of the reinforcing material 4, D rinf,4 is the material density of the fiber-reinforced material 4, F sp is the area gram weight of the fiber of the back layer 5, D fsp is the fiber density of the rear layer 5, R leg is the area gram weight of adhesive 3, D rleg is the density of the resin formulation of Adhesive 3, R sp is the area grams of the resin formulation present in the rear layer 5, D rsp is the density of the resin formulation of the rear layer 5.

[0152] If there is only a binder and no fiber material, the term F leg / D fleg will be considered invalid. In this case, the FVF can be calculated according to the following formula:

[0153]

[0154] In contrast, if the binder contains fibrous material, then F must be considered when calculating FVF (Eq. 2). leg / D fleg and R leg / D rleg Two terms.

[0155] Based on these considerations, advantageously (but not necessarily), the back layer 5 combined with the composite material 1 provides a suitable ratio between the area weight of the fibers and the area weight of the matrix, so as to place the overall FVF of the entire laminate within the above range.

[0156] For example, where composite material 1 has an insufficient content of resin formulation such that the FVF of the material with overlapping layers is greater than 75%, then rear layer 5 should contain a sufficient excess of the third resin formulation to rebalance the FVF of material with overlapping layers 6 (the entire laminate).

[0157] The fiber component of the back layer 5, i.e. the third fiber material, has a fiber content of at least about 100 g / m 2 (Specifically, at least about 350 g / m 2 ; Specifically, up to about 2000g / m 2 ; More specifically, up to about 1500 g / m 2 The rear layer 5 includes a certain amount of the third resin formulation to satisfy the total FVF of the laminate based on Equation 2 (or Equation 3).

[0158] Specifically, the area weight of the fiber components of the back layer 5 is measured according to standard ASTM D 3529 / D 3529M-97 (reapproved in 2008).

[0159] In particular, the third fiber material is selected from the group consisting of: a woven fabric, a unidirectional fabric, a multiaxial fabric (in particular, a biaxial fabric; optionally stabilized by sewing threads), a nonwoven fabric (and combinations thereof). More particularly, the third fiber material is selected from the group consisting of: a woven fabric and a multiaxial (in particular, a biaxial) fabric. Even more particularly, the third fiber material is a woven fabric.

[0160] According to some preferred but non-limiting embodiments, the third thermosetting resin includes a cross-linking agent.

[0161] Advantageously but not necessarily, the third fiber material includes (specifically, mainly includes; more specifically, is made of) carbon fiber, glass fiber, basalt fiber, natural fiber (such as flax fiber), synthetic fiber (such as polyester fiber or aromatic polyamide fiber).

[0162] According to some non-limiting embodiments, during the forming step, the material 6 having overlapping layers is subjected to at least about 1 kgf / cm2 (Specifically, up to about 150 kgf / cm 2 ; more specifically up to about 50 kgf / cm 2 ).

[0163] In some non-limiting cases, the material 6 having overlapping layers placed on the mold is molded using a vacuum bag (the material 6 having overlapping layers and the mold are placed in the vacuum bag) and a furnace by applying low pressure in the vacuum bag so that the absolute pressure in the bag is less than 0.5 bar (specifically, greater than 0.001 bar).

[0164] Advantageously, but not necessarily, during the shaping step, the material 6 with overlapping layers is inserted into a furnace at a temperature of at least 50° C., in particular up to 200° C.

[0165] In some non-limiting cases, the material is formed in an autoclave at an absolute pressure of at least 2 bar (specifically, up to 10 bar).

[0166] Alternatively, by applying a force typically greater than 2 kg / cm 2 The forming step is carried out in a press with a compaction pressure of 1.5°.

[0167] According to another aspect of the present invention, a kit for implementing the above method is provided. The kit comprises the composite material 1 and the back layer 5 as described above.

[0168] Further features of the invention will become apparent from the following description of some purely illustrative and non-limiting embodiments.

[0169] Example 1

[0170] This example describes the realization of some adhesives reported in Table 2 below, where the values ​​are expressed as percentages (phr) in the resin.

[0171] Table 2

[0172]

[0173]

[0174] F1-F4 represent four different adhesive formulations (with alternatives therein) that can be prepared and used according to the invention, more precisely: F1 is an epoxy adhesive without a crosslinker; F2 is an epoxy adhesive with a crosslinker; F3 is a rubber-containing adhesive (containing a crosslinker); and F4 is a cyanate ester adhesive.

[0175] ( GY2600, by (produced and sold) is an unmodified, medium viscosity bisphenol A diglycidyl ether (DGEBA) epoxy resin obtained by the reaction of bisphenol A and epichlorohydrin. The main feature of this resin is its low hydrolyzed chlorine content. It provides high mechanical properties and imparts good chemical resistance.

[0176] Main properties of Araldite GY2600:

[0177] ■ Epoxy equivalent weight EEW (ISO 3001): 184-190g / eq;

[0178] ■Viscosity at 25°C (falling ball viscosity, ISO 12058-1): 12000-14000 mPa·S;

[0179] ■Density at 25°C (ISO 1675): 1.17 g / cm 3 ;

[0180] ■(Visual) Appearance: Transparent liquid;

[0181] ■Color (Gardner, ISO 4630): ≤1;

[0182] ■Epoxy index (ISO 3001): 5.26-5.43eq / kg;

[0183] ■Hydrolyzable chlorine content (VTM 116): ≤170ppm.

[0184] ( GT 7071, by Production and sales) is a low melting point bisphenol A diglycidyl ether (DGEBA) solid epoxy resin with medium to low molecular weight (Type 1). It is used in the production of high-performance coating materials due to its excellent adhesion and chemical resistance to various substrates (such as metal, cement, wood, etc.). It provides greater flexibility and high impact resistance.

[0185] Main properties of Araldite GT 7071:

[0186] ■Epoxy equivalent weight (ISO 3001): 500-525g / eq;

[0187] ■ Softening point (Mettler softening point, DIN 51920): 77-82℃;

[0188] ■Density at 25°C (ISO 1675): 1.19 g / cm 3 ;

[0189] ■(Visual) Appearance: Transparent solid resin;

[0190] ■Color (Gardner, ISO 4630): ≤1;

[0191] ■Viscosity at 25°C (falling ball viscosity, ISO 12058-1): 200-250 mPa·s-40% butyl carbitol solution.

[0192] (Depend on HyPox RA95 is a high viscosity mixture of butadiene-acrylonitrile elastomer dissolved in bisphenol A epoxy resin. Based on solid CTBN elastomer, HyPox RA95 combines the functionality of epoxy resin with toughness and impact resistance. Its use improves impact resistance, peel resistance and cut resistance compared to traditional epoxy resin systems.

[0193] Key properties of HyPox RA95:

[0194] ■Epoxy equivalent weight (ASTM D1652-90): 195-210 g / eq;

[0195] ■CTBN content: 5%;

[0196] ■Viscosity at 25°C (Brookfield, ASTM D2196-05): 150,000-550,000 mPa.s;

[0197] ■Color (Gardner, ASTM D1544-80): <4;

[0198] ■(Visual) Appearance: Matt amber viscous liquid.

[0199] ( PT-30, made of (produced and sold) is a versatile cyanate ester resin that provides a highly cross-linked structure with high thermal stability. If properly polymerized, the resulting Tg can exceed 300°C. This high-performance thermosetting resin is characterized by excellent dielectric and mechanical properties and allows epoxy-like processing.

[0200] Main properties of Primaset PT-30:

[0201] ■Viscosity at 80℃: 300-500mPa.s;

[0202] ■Appearance: viscous liquid;

[0203] ■Color: from yellow to red;

[0204] ■Specific gravity: 1.2g / cm 3 ;

[0205] ■Ion chlorine: <10ppm;

[0206] ■Water content: <0.5%;

[0207] ■Gel time at 200℃: 70-240min.

[0208] (Depend on Production and sales) is a micronized dicyandiamide (DICY) based crosslinker. If exposed to 145-160°C for 30-60min, one-component systems containing DICY are able to crosslink. After sufficient polymerization, DICY based epoxy resin systems form a very dense polymer structure with high heat and chemical resistance.

[0209] Main properties of 100S:

[0210] ■Particle size 98%: Maximum 10μm;

[0211] ■ Melting point: 209-212℃-without anti-caking agent;

[0212] ■ Anti-caking agent content: maximum 1.60%;

[0213] ■Water content: maximum 0.30%;

[0214] ■Appearance: white powder.

[0215] (Depend on Production and sales) is a micronized bifunctional accelerator based on substituted urea. It is commonly used as an accelerator for DICY to reduce the polymerization temperature of epoxy resin preparations to 80°C. The resulting cross-linked matrix shows a dense polymer network with good mechanical properties. Despite its high reactivity, Dyhard UR500 can also be used as a single cross-linker with a potential incubation time of up to 2 months. In addition, due to its low enthalpy development during hardening, it is particularly suitable for thick carbon fiber reinforced laminates.

[0216] Main properties of UR500:

[0217] ■Particle size 98%: Maximum 10μm;

[0218] ■ Melting point: minimum 180℃;

[0219] ■Purity: minimum 95.0%;

[0220] ■Maximum volatile matter (105℃) 1.0%;

[0221] ■Appearance: White to whitish powder;

[0222] Manganese(II) acetylacetonate (from Production and sales) is a metal complex that can be used as a catalyst for cyanate resins to promote cyclotrimerization reactions.

[0223] Main properties of manganese(II) acetylacetonate:

[0224] ■Appearance: light brown powder;

[0225] ■Manganese content: 21.0%-23.0%.

[0226] The adhesive containing formulation F1 has high tack, with a viscosity of 20 Pa.s at 50°C and a density of 1.17 g / cm at 25°C. 3 , which is obtained by the following method. A certain amount of Araldite GY 2600 (60 g) and Araldite GT 7071 (40 g) preheated to 50°C were added to a 250 mL glass beaker, mixed with a spatula, and heated in a furnace at 120°C for 1 hour. The mixture was stirred with a spatula every 15 minutes to ensure that the solid components were completely dissolved to obtain a colorless and transparent mixture.

[0227] The adhesive containing formulation F2 was obtained by the following method. A certain amount of Araldite GY2600 (60 g) and Araldite GT 7071 (40 g) preheated to 50° C. were added to a 250 mL glass beaker, mixed with a spatula, and heated in a furnace at 120° C. for 1 hour. The mixture was stirred with a spatula every 15 minutes to ensure that the solid components were completely dissolved. The resulting mixture was cooled to 70° C. and a certain amount of Dyhard 100S (8 g) and Dyhard UR500 (2 g) were added. The final formulation was then vigorously stirred with a spatula to obtain a uniform white mixture.

[0228] The adhesive containing formulation F3 was obtained by the following method. A certain amount of HyPox RA95 (80 g) and Araldite GT 7071 (20 g) preheated to 70°C were added to a 250 mL glass beaker, mixed with a spatula, and heated in a furnace at 120°C for 1 hour. The mixture was stirred with a spatula every 15 minutes to ensure that the solid components were completely dissolved. The resulting mixture was cooled to 70°C and a certain amount of Dyhard 100S (8 g) and Dyhard UR500 (2 g) were added. The final formulation was then vigorously stirred with a spatula to obtain a uniform white mixture.

[0229] An adhesive containing formulation F4 was obtained by the following method. A certain amount of Primaset PT-30 (100 g) preheated to 50°C and manganese (II) acetylacetonate (1 g) were added to a 250 ml glass beaker. The resulting mixture was then stirred vigorously with a spatula to obtain a brown mixture.

[0230] Example 2

[0231] This example describes the method for measuring the glass transition temperature (Tg) and determining the Tg of the adhesive described in Example 1.

[0232] The Tg values ​​of fresh neat resin were determined by DSC measurements from -40°C to 50°C under a constant nitrogen flow (50 mL / min). The analysis was performed on a Mettler-Toledo DSC 1 equipped with an autosampler using a 40 μL aluminum crucible with a perforated lid. 6-10 mg of fresh resin were used for the analysis. The DSC method used for the analysis is reported below.

[0233] Step 1: In N 2 Under the condition of 50mL / min, keep the temperature at -40℃ for 1 minute;

[0234] Step 2: In N 2 The flow rate was 50 mL / min and the scan was performed at 10°C / min from -40°C to 50°C.

[0235] Only the curve from step 2 is used for Tg determination. A scanning temperature interval from -40°C to +50°C is selected because the glass transition temperature should fall in this region. The glass transition value is determined according to ASTM D3418-15, where Tg is equal to the average between T1 and T2, such as Figure 3 shown.

[0236] Note that if the Tg value is less than -20°C, the scan start temperature can be appropriately set below -40°C to improve the readability and reliability of the Tg calculation. By way of example only, if the glass transition temperature value is expected to be around -60°C, then a scan start temperature of -90°C can be used to conveniently perform DSC measurements. Equipment with a scan temperature starting at -150°C is used to measure glass transition temperatures below -60°C.

[0237] The Tg of the Example 1 adhesive was measured as described above and is reported in Table 3 below.

[0238] Table 3

[0239] Adhesives DSC Tg (ASTM D3418-15) F1 -1.5℃ F2 -0.7℃ F3 -8.2℃ F4 -9.7℃

[0240] Example 3

[0241] This example describes the production of composite material 1. The following were used as starting materials.

[0242] ● Surface film FS011-200-20-1260G (code MF020001200), a commercial product produced and sold by Delta-Preg SpA (Loc. Bonifica del Tronto km 16, 64016 Sant'Egidio alla Vibrata (TE)), is a film composed of a resin system and a carrier and has the following characteristics: resin FS011, resin area weight 200 g / m 2 , polyester fiber carrier, carrier area weight 20g / m 2 , theoretical sheet thickness 0.15 mm. Resin FS011 (product of Delta-Tech SpA) has the following characteristics and properties: maximum DMA Tg of 160°C; processable by vacuum bag curing in autoclave, vacuum bag curing in furnace and compression molding; can be stored for 30 days at 20°C; chemical nature thermosetting epoxy resin; polymerization temperature range 80 to 135°C; density of pure polymerized resin 1.48 g / cm 3 ; Very high dynamic viscosity; Medium viscosity.

[0243] • An adhesive as described in Example 1 containing formulation F1, which is referred to as Adhesive 1 in the following examples.

[0244] ●Reinforcement material CBX250R-CAT-C020250R00A200002 as described above.

[0245] For the production of composite materials, it is carried out as follows:

[0246] After preheating to a temperature of 55°C, the adhesive F1 was spread on a support (specifically, silicone paper) by a continuous film-forming process (using a rotating roller at a temperature of 55°C) to obtain an area weight of 50 g / m 2 A continuous layer of adhesive F1.

[0247] - The previously unrolled reinforcement material CBX250R-CAT-C020250R00A200002 is placed on the continuous layer of adhesive F1 by means of a continuous production line at a temperature of 40° C. This intermediate material is identified by the code M-LAB-22035, corresponding to the specification Adhesive 1-050 / GG250X (T700S) (H 127 cm).

[0248] The composite material thus obtained was laminated at room temperature with the surface film FS011-200-20-1260G so that the surface of the reinforcing material CBX250R-CAT-C020250R00A200002 moistened with the adhesive F1 was in direct contact with the polyester support of the surface film FS011-200-20-1260G. The composite material 1 obtained was then wound into a roll.

[0249] A relevant aspect of the production process of the composite material 1 concerns the bonding of the dry reinforcement material CBX250R-CAT with the layer of adhesive F1. As mentioned above, it is relevant that the adhesive does not wet all the fibers of the reinforcement material, so that the latter layer remains at least partially dry. It is also important to maintain the dryness level of the reinforcement material CBX250R-CAT after the intermediate material is bonded to the surface film.

[0250] Example 4

[0251] As described in Example 3, composite material 1 has sufficient adhesive stability to allow it to be used and handled in lamination operations. In fact, due to its tacky nature, the presence of the adhesive ensures sufficient adhesion between the reinforcing material CBX250R-CAT-C020250R00A200002 and the surface film FS011-200-20-1260G, otherwise the surface film would easily separate, complicating the manual lamination operation.

[0252] This example describes the quantification of the adhesive force (joining force) exerted by the adhesive of formulation F1 between a surface film and a reinforcing material CBX250R-CAT-C020250R00A200002, evaluated by force measurement under sliding conditions of the two layers.

[0253] Since the stability of the two layers of the composite material 1 can be affected by the amount of adhesive present, the following two forms are considered in this example, characterized by different adhesive area weights:

[0254] FS011-200-20 / / BINDER1-017 / GG250X (T700) (code M-LAB22046) corresponds to the composite material shown in Example 3 and has an area weight of 17 g / m 2 adhesive layer.

[0255] FS011-200-20 / / BINDER1-050 / GG250X (T700) (code M-LAB22036) corresponds to the composite material shown in Example 3 and has an area weight of 50 g / m 2 adhesive layer.

[0256] 5 samples of each material (i.e., 5 samples of material M-LAB22046 and 5 samples of material M-LAB22036) were measured using an MTS Insight dynamometer equipped with a 100N load cell and configured for tensile measurements. The applied measurement speed was 2 mm / min. All measurements were performed at a temperature of 20 ± 1 °C.

[0257] use Figure 4 Schematically represented in (and in Figure 5 The samples of composite material 1 required for the measurements were obtained using a template (photographed in the middle). The tool was handmade by a machine shop and consisted of an 8 mm thick metal frame with external dimensions of 300 × 75 mm and internal dimensions of 250 × 25 mm, with two slits of about 15 mm long and 8 mm deep along each internal corner. The preparation of the samples was carried out at a temperature of 20 ± 1 ° C. Each sample was obtained according to the procedure reported below:

[0258] - Place the composite material 1 roll on the cutting plane and unroll a section of about 1 m in length, leaving the reinforcement material 4 (the side with the polyethylene) visible;

[0259] -Take the template( Figure 4 ) and gently place it on composite material 1 without applying any pressure ( Figure 5 );

[0260] - Align the long sides of the template parallel to the direction of the visible carbon fibers of the reinforcement material 4, i.e. relative to Figure 5 The clearly visible sewing line is at a 45° angle;

[0261] - Cut a strip of the sample along the inside of the template using a suitable leather cutter;

[0262] - Remove the template and gently pull out 1 strip of composite material;

[0263] - Repeat the previous operation until you have 5 samples, taking care to place the template at least 3 cm away from the area corresponding to the previous sample (relative to the long side).

[0264] In the case of using woven fabrics, unidirectional fabrics, various multiaxial fabrics as reinforcement materials4, in order to minimize the deformation of the sample itself before relative fracture during the force test, the sample must be aligned with the direction of the highest fiber content. In other cases, the direction of the template must be consistent with the direction of the larger tensile elastic modulus (ASTM D3039-3039M-08).

[0265] After obtaining the samples, each sample is appropriately trimmed to form the gripping area necessary to attach the sample to the grips of the dynamometer. In this regard, in order to minimize the influence of the article, these operations are performed by using Figure 6 This is performed using a trimming tool schematically shown in . This tool, handmade by a machine shop, consists of a thin bent metal sheet, approximately 1 mm thick, with a slit on its front side and close to the lower edge. On the same side, there is also a dividing line at a height of 25 mm from the lower edge, which is used to check the length of the material overhang to be trimmed. The trimming procedure adopted is as follows:

[0266] - After removing the polyethylene layer (protective layer covering the reinforcing material 4) from the reinforcing material 4, place the sample on the cutting plane with the surface film 2 layer facing downward;

[0267] - Place the trimming tool on the sample 2.5 cm from the short edge, ( Figure 7 A);

[0268] - Gently lift the reinforcement material layer CBX250R-CAT-C020250R00A200002 to separate it from the bottom layer of the surface film FS011-200-20-1260G;

[0269] - Fold the reinforcement overhang onto the front wall of the trimming tool; check that the position of the edge of the folded overhang is consistent with the reference line ( Figure 7 B), and use the groove below to cut with a leather cutter ( Figure 7 CD);

[0270] - Remove the trimming tool and turn the sample over so that the paper layer faces upwards;

[0271] - Place the trimming tool on the sample 2.5 cm from the untrimmed short edge ( Figure 8 A);

[0272] - Gently lift the surface film layer FS011-200-20-1260G to separate it from the underlying reinforcement material layer CBX250R-CAT-C020250R00A200002;

[0273] - Fold the surface film overhang over the front wall of the trimming tool; check that the position of the edge of the folded overhang is consistent with the reference line ( Figure 8 B), and use the groove below to cut with a leather cutter ( Figure 8 CD);

[0274] -Store samples until they are measured, taking care not to place anything on them or expose them to temperatures above their preparation temperature.

[0275] like Fig. 9 As shown, each sample obtained in this way consists of two clamping areas with a size of approximately 25×25 mm and an overlapping area (TZ) between the two layers, one clamping area corresponds to a separate reinforcing material (CZ1), and one clamping area corresponds to a separate surface film (CZ2), and the size of the overlapping area (TZ) between the two layers is approximately 200×25 mm.

[0276] Force measurements were performed according to the following reported procedures:

[0277] - Measure the dimensions of the overlap area between the reinforcement layer and the surface film by using an appropriate instrument and record the two width measurements ( Fig. 9 points MP1 and MP2) and a long side measurement ( Fig. 9 of TZ);

[0278] - Place the sample between the jaws of the dynamometer;

[0279] - Clamp the sample CZ1 and CZ2 clamping area with the fixture, and try to clamp the entire area;

[0280] - Start the measurement and record the sliding force.

[0281] In this way, it is possible to record the force-displacement curve (stress-strain) for each sample. The bonding force (joining force) exerted by the adhesive on the two layers of composite material 1 is determined by evaluating the maximum force recorded before the irreversible failure of the sample, which corresponds to the absolute maximum of the force-displacement curve. The values ​​recorded on the various samples of the materials considered in this example are summarized in the following table:

[0282] Table 4

[0283]

[0284] Table 5

[0285]

[0286] In Tables 3 and 4, stress represents the joint stress, which is calculated by dividing the joint force of each sample by the overlapping area between the layers (the results are expressed in kPa). From the comparison of the two versions of Composite 1, characterized by different area weights of the adhesive 3 layer, they provide different force values ​​in the adopted test configuration. In particular, when the test area of ​​the samples has the same size, the force of the adhesive 3 layer is 50 g / m 2 In the case of the composite material 1 consisting of an adhesive layer, a force of about 10 N and 17 g / m 2 The version provided a significantly lower value of 1.6N (average).

[0287] The difference in the sliding force of the layer 2 relative to the reinforcement 4 is reflected in the bonding stability of the composite material 1 as a whole. 2 The version with adhesive 3 can be used in the molding process (as described in Examples 5 and 6 reported below), maintaining its structure during all processing steps (cutting, lamination on the mold, etc.). 2 Composite material 1 with adhesive 3 showed slightly poorer adhesive stability (1.6 N), but was still sufficient for molding operations.

[0288] Example 5

[0289] An essential characteristic of fiber materials impregnated with thermosetting resins (prepreg materials) concerns drapability, i.e. the ability of the material to easily deform to adhere and conform to the shape and geometry of the mold. In fact, high drapability offers the advantage of being able to laminate on molds with complex geometries in a shorter time, thus reducing the overall production time of the part.

[0290] The purpose of this example is to evaluate the drapability of the composite material 1 relative to a reference material by shaping the laminate according to an appropriate geometry.

[0291] The solutions tested vary depending on the degree of impregnation of the reinforcement, the possible form of pre-layers and the nature, quantity and distribution of the resin matrix. The term pre-layering refers to the operation of joining two or more layers into a roll, whether they are pre-impregnated materials, resin layers or dry fabrics or a combination thereof. These pre-layers are usually available from pre-impregnated material manufacturers.

[0292] The forming can then be done by laminating the different layers or pre-layered materials in sequence on the mold. Unfortunately, the fact that pre-layered systems lose drapability is very common, which greatly limits their adoption. The fact that the laminator is more difficult with the mold shape leads to longer total lamination times and / or lower quality finishing of the molded part.

[0293] In this example, three different forms were performed based on three different configurations starting from different materials. However, the order and properties of the fiber reinforcement were similar in all three cases.

[0294] The tests in this example were performed using the materials reported below, produced and sold by Delta-Preg SpA:

[0295] Material P1

[0296] FS011-200-20-1260G (Code MF020001200)

[0297] This is a surface film composed of a resin system and a carrier, with the following characteristics: Resin FS011, Resin area weight 200g / m 2 , polyester fiber carrier, carrier area weight 20g / m 2 , theoretical sheet thickness 0.15 mm. Resin FS011 (product of Delta-Tech SpA) has the following characteristics and properties: maximum DMA Tg of 160°C; processable by vacuum bag curing in autoclave, vacuum bag curing in furnace and compression molding; can be stored for 30 days at 20°C; chemical nature thermosetting epoxy resin; polymerization temperature range 80 to 135°C; density of pure polymerized resin 1.48 g / cm 3 ; Very high dynamic viscosity; Medium viscosity.

[0298] Material P2

[0299] GG250X(T700)-DT150-40(H 127cm)(Code PGG250B0340)

[0300] This is a multiaxial fabric impregnated with a thermosetting resin system and has the following characteristics: Carbon fiber reinforcement with 265g / m 2 The material is a polyester nylon with an area weight of 125 gsm, a biaxial weave pattern of ±45°, a first layer with a weight of 125 gsm, a fiber T700SC12K50C and an angle of -45°, a second layer with a weight of 125 gsm, a fiber T700SC 12K 50C and an angle of +45°, a stabilizing thread of E-glass, a polyester sewing thread, a chain stitch pattern, impregnated with the resin system DT150; the material has a nominal resin content of 40% by weight and a theoretical molded sheet thickness of 0.28 mm. The resin DT150 (a product produced by Delta-Tech SpA) has the following properties: a DMA tg of up to 140°C can be achieved; it can be processed by vacuum bag curing in an autoclave and compression molding; it can be stored for 30 days at 21°C; it has a medium viscosity; the chemical nature is a thermosetting epoxy resin; the polymerization temperature range is 120 to 150°C; the density of the pure polymerized resin is 1.24 g / cm 3 ; Medium dynamic viscosity, 500-1000 poise at 60°C.

[0301] Material P3

[0302] GG600T(T700)-DT150-38(H 125cm)(Code PGG600T0038)

[0303] This is a woven fabric impregnated with a thermosetting resin system and has the following characteristics: Carbon fiber reinforcement with 600g / m 2The area weight of the material is 1.500mm, the yarn type is T700SC 24K 50C, the weaving style is twill 2x2, the warp yarn is 1.80 threads / cm, the weft yarn is 1.80 threads / cm, and the material is impregnated with the resin system DT150; the material has a nominal resin content of 38% by weight and a theoretical preformed sheet thickness of 0.63 mm. The characteristics of the resin system DT150 are similar to those described for material P2.

[0304] Material P4

[0305] FS011-200-20 / GG250X(T700)-DT150-40(H 127cm)(Code MF020200PGG250B001)

[0306] It is composed of materials 1 and 2 pre-laminated in a single roll. Specifically, the surface film is represented by FS011-200-20-1260G (code MF020001200), corresponding to the above-mentioned material P1. The carbon reinforcement material impregnated with a thermosetting resin is represented by GG250X (T700) -DT150-40 (code PGG250B0340), corresponding to the above-mentioned material P2. The lamination is performed so that the side of the surface film FS011-200-20-1260G (code MF020001200) rich in less resin is in direct contact with GG250X (T700) -DT150-40 (H 127cm) (code PGG250B0340).

[0307] Material P5

[0308] FS011-200-20 / / BINDER1-050 / GG250X(T700)(Code M-LAB22036)

[0309] Corresponding to the 50 g / m 2 A composite material 1 of 3 layers of adhesive.

[0310] Forming tests were carried out using a disc-shaped aluminum mold (180 mm in diameter) characterized by the presence of a convex parabolic relief with a height of 31.5 mm in the center ( Fig.10 ). Before each test, the mold was properly prepared according to the following procedure.

[0311] The aluminum mold was cleaned with a cloth and thinner (acetone) to remove grease and dust; subsequently, a cleaner manufactured by Chem-Trend L.P. (1445 W. McPherson Park, Howell, Michigan) was used. Treat molds with Mold CleanerEZ, which consists of a solvent blend that removes contaminants and waxy residues from mold surfaces.

[0312] Subsequently, a release agent produced by Marbocote Ltd (Unit 9, Dalton Way, Middlewich Cheshire, CW100HU, UK) was applied. PK4, which has the following characteristics: appearance is a transparent liquid, a composition polymer resin in a mixture of non-chlorinated organic solvents, specific gravity 0.756g / cm 3 The ideal application temperature is between 20-30℃, thermal stability is 250℃, and coverage is 80-100m 2 / L, storage time 12 months. According to the instructions provided by the manufacturer, apply Marbocote PK4 with a clean and dry cloth in an even manner, covering the entire surface of the mold; in general, apply five coats, waiting 10 minutes between two coats. After applying the last coat and observing that the release agent film is completely dry, place the mold at room temperature for 60 minutes to obtain complete curing of the product.

[0313] After the mold preparation step, the molding material lamination step is carried out on the mold to achieve the following three configurations:

[0314] Test N1; construct A( Fig.11 )

[0315] Material P1 is laminated in direct contact with the mold (note that the resin-rich side is laminated in direct contact with the mold. Fig.11 A);

[0316] Material P2 is laminated in contact with the first layer ( Fig.11 B);

[0317] Material P3 is laminated in contact with the second layer ( Fig.11 C).

[0318] Test N2; construct B( Fig.12 )

[0319] Material P4 is laminated in direct contact with the mold (note that one side of the surface film FS011-200-20-1260G (code MF020001200) is in direct contact with the mold ( Fig.12 A);

[0320] Material P3 is laminated in contact with the first layer ( Fig.12 B).

[0321] Test N3; construct C( Fig.13 )

[0322] Material P5 is in direct contact with the mold (note that one side of the surface film FS011-200-20-1260G (code MF020001200) is in direct contact with the mold for lamination ( Fig.13 A);

[0323] Material P3 is laminated in contact with the first layer, material P5 ( Fig.13 B).

[0324] The preparation of the three constructs was performed by the following procedure:

[0325] ■ Prepare a circular section with a diameter of 220 mm for each material (first, second and third layers);

[0326] ■Starting from the top of the relief, spread the first layer on the mold, trying to avoid forming wrinkles and make it adhere well to the flat part of the mold;

[0327] ■ Lay the second layer on the back of the first layer, making sure it also perfectly replicates the geometry of the mold;

[0328] ■If there is a third layer (construction A), lay it on the back of the second layer, making sure it also completely replicates the geometry of the mold;

[0329] ■Finally, remove excess material from the bottom of the mold.

[0330] At the end of the lamination steps of the various configurations, the following final forming operations were performed, which are common to all the tests listed so far.

[0331] Molding steps:

[0332] Imagine using the following auxiliary materials for the forming step ( Fig.14 ):

[0333] ■Vacuum bag G: Airtech 600V-LFT, 50μm

[0334] ■Aerator H: Airtech N10

[0335] ■Mold release film I: Airtech 3900R-SHT, 50μm

[0336] The various operations required for the molding step are carried out through the following procedures:

[0337] ■ Place the mold J and the already laminated related molding material F on the aerator H (if necessary, use the support plate L);

[0338] ■ Cover the mold J with release film I, carefully isolating the molding material F from contact with the aerator H;

[0339] ■Put the package (aerator (H) / mold (J) / molding material (F) / release film (I) / aerator (H)) into the vacuum bag G;

[0340] ■Insert the vacuum valve O so that it contacts the aerator H, taking care not to place it above the molding material F.

[0341] ■Seal the vacuum bag G with sealant N;

[0342] Pull the vacuum to at least -0.95 bar, making sure there are no leaks, and hold for at least 3 minutes to check that the vacuum bag G is correctly bonded to the shape of the mold J.

[0343] After the above operations are completed, the actual molding step begins, that is, the step of curing the thermosetting matrix of the molding material. In this regard, the sealed mold is placed in an autoclave (produced by Italmatic Presse Stampi srl, model AIC1300X3000) and a curing cycle is carried out by adopting the following parameters:

[0344] ■Heat to 135℃ at a rate of 2℃ / min.

[0345] ■Keep the temperature at 135℃ for 90 minutes.

[0346] ■Cool to 60℃ at a rate of 2℃ / min.

[0347] ■Maintain vacuum - 0.95 bar during the entire cycle.

[0348] ■ At the beginning of the cycle, pressurize to 6 bar at a rate of 2 bar / min and maintain a pressure of 6 bar until the end of the cycle.

[0349] The specific geometry of the mould used requires that the material to be laminated has a strong drapability in order to obtain a shaped part without wrinkles and with a good surface finish. In fact, if the layers to be laminated have a low drapability, the relief present in the centre of the mould during the layer deposition step will lead to the immediate formation of wrinkles, since it is not possible to make each layer fully conform to the specific geometry.

[0350] Despite the similarity of the order of reinforcements, the three configurations tested yielded different behaviors in terms of wrinkles and overlap defects that were detectable both during the lamination step and after autoclave forming. Specifically, during the deposition step of the layers on the mold, the following behaviors could be observed:

[0351] -Test N1, construct A( Fig.11 ): Lamination of the surface film P1 as the first layer produces wrinkles in the polyester carrier ( Fig.11The subsequent deposition of the second layer P2 leads to the formation of very large wrinkles (B1, B2, B3, Fig.11 B), which is a manifestation of the low deformation of the material; similar results were found after laminating the third layer P3 (C1, C2, C3, Fig.11 C).

[0352] -Test N2, build B( Fig.12 ): The use of pre-layered material P4, although on the one hand it reduces the number of layers to be laminated, on the other hand it leads to the formation of wide folds (A1, A2, A3, A4, Fig.12 A), these wrinkles are then overlapped with the wrinkles produced by laminating the second layer P3 (B1, B2, B3, Fig.12 B).

[0353] -Test N3, construct C( Fig.13 ): Due to the high drapability of composite material 1 (P5), it is easy to deposit the first layer exactly in accordance with the strict geometry of the mold without any folds or wrinkles ( Fig.13 A). The regular surface thus obtained allowed adequate lamination of the second layer (P3) without any wrinkles being found ( Fig.13 B).

[0354] The excellent drape and softness of composite material 1 (P5) are attributed to the presence of dry and non-impregnated fibers of reinforcement 4. In fact, the absence (at least partially) of a resin matrix inside the reinforcement gives the fibers excellent fluidity and therefore deformation during the lamination step, providing a high degree of adaptability of the material to mold geometries, even complex ones.

[0355] On the contrary, in the case of constructions A and B, both based on the use of reinforcements impregnated with thermosetting resins, the presence of the resin matrix inevitably confers less fluidity to the fibers. Therefore, during the lamination process, each layer has a higher stiffness, which corresponds to a higher resistance to forming a geometry that conforms to the mold.

[0356] It should be stressed that in the context of the production of composite parts, wrinkles and folds should be avoided during the lamination step, especially for structural parts. In fact, in these folded areas of the reinforcement, more or less structural weakenings or thickness variations of the formed laminate are produced. Precisely in order to avoid the formation of these wrinkles, it is usually necessary to resort to pre-cut prepreg profiles with smaller dimensions, which on the one hand requires longer lamination times and, on the other hand, leads to structural weakening of the formed part compared to the use of continuous layers with larger dimensions.

[0357] After the autoclave forming process, the different behaviors observed between the three configurations during the lamination step were also evaluated. Considering the bag-side surface of the formed piece, the laminates of the three configurations accurately reproduced the results obtained after laminating the third layer. Specifically, while configuration A ( Fig.15 A) and construct B( Fig.16 A) shows the presence of fairly obvious raised folds (A1, A2, A3, A4), but structure C ( Fig.17 A) is compact and neat except for small wrinkles near the edges (A1, Fig.17 A).

[0358] In contrast, the differences in surface defects between the three configurations are more pronounced when comparing the side of the laminate that was initially in contact with the mold. Fig.15 B and 15ZB) and B( Fig.16 B and 16ZB) show diffuse porosity in the inner edge region due to incomplete contact of the first layer with the mold due to low drape. Specifically, construction B shows a higher incidence of this defect ( Fig.16 B and 16ZB), which may be related to the fact that the stiffness of the first layer is greater than that of structure A.

[0359] Another defect found in both constructions is color non-uniformity along the radial direction of the part, resulting in e.g. Fig.15 The dark line forms shown by arrows B1, B2, B3, and B4 in B and 16B.

[0360] In contrast, in the case of configuration C (involving the use of composite material 1 as an embodiment of the present invention), the surface of the shaped laminate has no porosity ( Fig.17 B and 17ZB), which is due on the one hand to the high drapability of composite material 1 (P5), which makes it contact along the entire surface of the mold, and on the other hand to the presence of dry reinforcement material 4, which ensures effective air evacuation during the molding process. In contrast, only radial color inhomogeneities ( Fig.17 B and 17ZB), but not as obvious as structures A and B.

[0361] Example 6

[0362] In the production scenario of composite parts, one of the relevant factors that contributes most to the total production cost of the part is the lamination operation. In this regard, high drapability and sufficient adhesion of the material to be laminated are considered necessary in order to reduce the lamination time and make the overall production process more competitive.

[0363] The purpose of this test was to evaluate the quality of the molded parts and measure the savings in lamination time of Composite Material 1 compared to conventional materials, using the 3 different molded material configurations shown in the examples above.

[0364] Use composite molds ( Fig.18 ) were subjected to molding tests with composite molds whose geometry, shape and size represented medium-complexity automotive body parts. Prior to each test, the molds were appropriately conditioned according to the following procedures related to mold preparation.

[0365] Similar to the procedure shown in the previous example, first use a diluent (acetone) and then a cleaning agent Mold Cleaner EZ was used to clean the carbon mold. Subsequently, a sealer produced by Marbocote Ltd (Unit 9, Dalton Way, Middlewich Cheshire, CW10 0HU, UK) was applied. Mould Sealer, the sealer has the following characteristics: appearance is transparent colorless liquid, aliphatic hydrocarbon composition, flash point ≤ 10℃, curing film stability 250℃, each layer coverage is 80-100m 2 / L, application type is rubbing and spreading, storage time is 12 months. The use of the sealer eliminates the micropores and small scratches that may exist on the surface of the composite mold, providing a smooth and shiny surface. Specifically, two layers of Marbocote Mould Sealer are applied on the mold, with an interval of 10 minutes between each layer, and finally the mold is placed in a 60°C furnace for 10 minutes to obtain complete polymerization of the product.

[0366] Subsequently, the release agent Marbocote PK4 was applied similarly to that reported in Example 5; in general, three coats were applied, waiting 10 minutes between coats. After application of the last coat and observation of complete drying of the release agent film, the mold was left at room temperature for 60 minutes to obtain complete curing of the product.

[0367] After the mould preparation step, a lamination step of the moulding material is carried out on the mould, achieving, based on the steps detailed above, the three configurations A, B, C reported in Example 5. Subsequently, by carrying out the curing cycle described in Example 5, autoclave moulding is carried out.

[0368] In terms of the quality of the molded parts, the various tests provided cured laminates with fully comparable structural characteristics and surface finish. More specifically, as Fig.19 As shown, in terms of surface quality, the three different molding tests produced cured parts with similar surface finish, without porosity and covered with a uniform surface film.

[0369] Similarly, from a structural point of view, as in Fig.19 The optical microscopy analysis of the cross sections (cross sections) performed on the CSA1, CSB1 and CSC1 points in Fig. 20 As reported in , a good distribution of the resin matrix was obtained between the reinforcement fibers in all three molded parts.

[0370] Even in the case of configuration C based on the embodiment using composite material 1 (P5), the presence of dry fibers was not emphasized even in the area of ​​the dry reinforcement material 4. Therefore, this result demonstrates the ability of the resin to flow out of the post reinforcement material 5 during the curing process and effectively impregnate all the fibers of the dry reinforcement material 4.

[0371] Ultimately, it was confirmed that all three tests produced molded parts of similar quality and in line with expectations in the reference industrial environment.

[0372] The three tests provided different responses in terms of lamination time, as shown in Table 6 reported below:

[0373] Table 6

[0374] Test N1, build A 33 minutes Test N2, build B 29 minutes Test N3, build C 14 minutes

[0375] Test N3 provided the best results, requiring less "operator time" due to the presence of composite material 1 (P5). Specifically, the lamination time recorded in test N3 was reduced by about 58% compared to test N1, due to the smaller number of layers to be laminated and the higher drapability of composite material 1 (P5) compared to material P1, which resulted in an easier and faster placement of the first layer on the mold. Conversely, compared to test N2, with the same number of layers to be laminated as test N3, the lamination time of test N3 was reduced by about 55%, due to the higher drapability of composite material 1 (P5) compared to material P4.

[0376] It should also be emphasized that the use of composite material 1 (P5) generally allows to avoid long intermediate degassing (debulking) operations during the lamination step. In fact, depending on the geometry of the mold, in order to minimize the appearance of surface porosity defects, air removal cycles by means of vacuum bags and pumps are generally required, which leads to a prolongation of the lamination time and a reduction in production efficiency. On the contrary, in the case of composite material 1 (P5), the debulking operation can be conveniently avoided, thereby obtaining a higher production efficiency at the same surface quality. In fact, the presence of at least partially unimpregnated reinforcement material 4 in composite material 1 (P5) ensures an effective evacuation medium for all the air present between the layers during lamination, removing the air directly during the shaping step.

[0377] The molding process performed in this example is represented by autoclave molding. Alternative molding steps, such as compression molding, differ in that they do not provide a vacuum bag. However, the comparison of the lamination time target and the main target according to this example is still valid.

[0378] Unless expressly stated to the contrary, the contents of the references (articles, books, patent applications, etc.) cited herein are hereby incorporated by reference in their entirety. Specifically, the references mentioned are incorporated herein by reference.

Claims

1. A composite material for producing an article by molding; The composite material (1) comprises a surface film (2), a reinforcing material (4) and at least one adhesive (3); the surface film (2) comprises a surface weight of up to about 700 g / m 2 The reinforcing material (4) is composed of at least partially dried first fiber material, taking into account the only fiber component, and its area weight is up to about 900g / m 2 ; The adhesive (3) bonds the surface film (2) to the reinforcing material (4), and includes a viscous adhesive arranged between the surface film (2) and the reinforcing material (4); The surface film (2) comprises a first surface layer (7) and a carrier (8); the first surface layer (7) defines the outer surface of the composite material (1) and is substantially composed of a first thermosetting resin formulation; the carrier (8) is composed of a second fiber material having a molecular weight of less than about 200 g / m 2 (Specifically, less than about 100 g / m 2 More specifically, less than about 40 g / m 2 ) of an area weight, which is arranged between the surface layer (7) and the adhesive (3).

2. A composite material according to claim 1, wherein the first surface layer (7) has a thickness of at least 20% relative to the total thickness of the surface film (2); the area weight of the first thermosetting resin formulation is at least about 0.7 times (specifically, at least about 2 times) the area weight of the second fiber material; specifically, the first thermosetting resin formulation includes a first thermosetting resin, and the first thermosetting resin is selected from the group consisting of: epoxy resin, cyanate resin, vinyl ester resin, acrylic resin, phenolic resin, melamine resin, urethane resin, silicone resin, alkyd resin, benzoxazine resin, maleimide resin, furan resin, polyester and combinations thereof.

3. The composite material according to claim 1 or 2, wherein: Taking into account the sole fiber component, the first fiber material has a thickness of less than about 500 g / m 2 (Specifically, less than about 300 g / m 2 )'s area weight; specifically, the first fiber material is selected from the group consisting of: a woven fabric, a unidirectional fabric, a multi-axial fabric (specifically, a biaxial fabric; specifically, stabilized by a sewing thread), a non-woven fabric (specifically, stabilized).

4. A composite material according to any one of the preceding claims, wherein the carrier (8) is arranged in a surface area of ​​the surface film (2) opposite to the first surface layer (7) and facing the adhesive (3); specifically, the carrier (8) is at least partially arranged to contact the adhesive (3).

5. A composite material according to any one of the preceding claims, wherein the first thermosetting resin formulation has a viscosity of at least about 30 g / m 2 The first fiber material has an area weight of at least about 30g / m 2 Area weight; Specifically, the first fiber material includes (specifically, mainly includes; more specifically, is made of) carbon fiber, glass fiber, mineral fiber (such as basalt fiber), natural fiber (such as flax fiber), synthetic fiber (such as polyester fiber and / or aromatic polyamide fiber), metal fiber and combinations (mixtures) thereof.

6. The composite material according to any one of the preceding claims, wherein the second fiber material has a thickness of at least about 3 g / m 2 (Specifically, at least about 10 g / m 2 )'s area weight; specifically, the second fiber material includes (specifically, mainly includes; more specifically, is made of) carbon fiber, glass fiber, mineral fiber (such as basalt fiber), natural fiber (such as flax fiber), synthetic fiber (such as polyester fiber and / or aromatic polyamide fiber), metal fiber and a combination (mixture) thereof.

7. The composite material according to any one of the preceding claims, wherein the tacky adhesive has a glass transition temperature of less than about 20°C, in particular above about -80°C.

8. The composite material of claim 5, wherein the tacky adhesive has a glass transition temperature of less than about 15°C, specifically, less than about 0°C.

9. A composite material according to any one of the preceding claims, wherein the area weight of the tacky adhesive is less than the area weight of the reinforcing material (4); in particular, the tacky adhesive comprises (in particular, the tacky adhesive is) a second thermosetting resin formulation, the second thermosetting resin formulation comprising a second non-crosslinked thermosetting resin (in particular, without a crosslinking agent).

10. A composite material according to any one of the preceding claims, wherein the tacky adhesive has an area weight of less than about 300 g / m 2 (Specifically, less than about 60 g / m 2 More specifically, less than about 30 g / m 2 ; Specifically, greater than about 5g / m 2 ).

11. A composite material according to any one of the preceding claims, wherein the tacky adhesive comprises (in particular, the tacky adhesive is) a second resin, the second resin being selected from the group consisting of epoxy resins, cyanate resins, vinyl ester resins, acrylic resins, phenolic resins, melamine resins, urethane resins, siloxane resins, alkyd resins, benzoxazine resins, maleimide resins, furan resins, polyesters and combinations thereof.

12. A composite material according to any one of the preceding claims, wherein The tacky adhesive has a connecting force of at least about 0.6 N measured on a sample of about 25 mm by 200 mm.

13. The composite material according to any one of the preceding claims, wherein the tacky adhesive has a joint stress of at least about 0.1 kPa, in particular at least about 0.2 kPa.

14. A composite material according to any one of the preceding claims, wherein the first thermosetting resin formulation comprises a filler and a first resin; the filler is inorganic and dispersed in the surface film (2) (specifically, dispersed in the first surface layer (7)); specifically, the first resin is selected from the group consisting of: epoxy resins, cyanate resins, vinyl ester resins, acrylic resins, phenolic resins, melamine resins, urethane resins, silicone resins, alkyd resins, benzoxazine resins, maleimide resins, furan resins, polyesters and combinations thereof.

15. A composite material according to any one of the preceding claims, wherein the dry fiber content of the reinforcing material (4) is greater than about 20%, the dry fiber content being expressed as % DF-R4 , obtained by the following equation 1 WPU R4 is the water absorption measured on the reinforcing material (4) of the composite material (1), WPU Dry-R4 is the water absorption measured on the completely dry reinforcement material (4).

16. A method for producing an article; the method comprises a first lamination step, in which the composite material (1) described in any one of the preceding claims is placed on a mold; a second lamination step after the first lamination step, in which a rear layer (5) in contact with the composite material (1) is placed on the composite material (1) to obtain a material (6) having overlapping layers substantially having the shape of the mold; and a molding step after the second lamination step, in which the material (6) having overlapping layers placed on the mold is compressed and heated; the rear layer (5) comprises a third fiber material and a certain amount of a third resin formulation, so that the fiber volume fraction of the material (6) having overlapping layers is in the range of about 20% to about 75%.

17. The method of claim 16, wherein the third fiber material has a thickness of at least about 100 g / m 2 (Specifically, at least about 350 g / m 2 ; Specifically, up to about 2000g / m 2 ; More specifically, up to about 1500 g / m 2 ) area weight.

18. The method according to claim 16 or 17, wherein: During the forming step, the material (6) with overlapping layers placed on the mold is subjected to at least about 1 kgf / cm 2 compression; specifically, the third resin formulation includes (specifically, the third resin formulation is) a third thermosetting resin, and the third thermosetting resin is selected from the group consisting of: epoxy resin, cyanate resin, vinyl ester resin, acrylic resin, phenolic resin, melamine resin, urethane resin, silicone resin, alkyd resin, benzoxazine resin, maleimide resin, furan resin and combinations thereof; specifically, the third resin formulation (specifically, the third thermosetting resin) includes a crosslinking agent.

19. The method according to any one of claims 16-18, wherein the third fiber material comprises (specifically, mainly comprises; more specifically, is made of) carbon fiber, glass fiber, mineral fiber (such as basalt fiber), natural fiber (such as flax fiber), synthetic fiber (such as polyester fiber and / or aromatic polyamide fiber), metal fiber and combinations (mixtures) thereof.

20. A kit for carrying out the method according to any one of claims 16-19, comprising a composite material (1) according to any one of claims 1-15 and a back layer (5) as defined in any one of claims 16-19.

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