Cellulose fiber laminated composite material

Abstract

To provide a laminated composite material constituted of a plurality of fiber-reinforced composite resin layers which is excellent in high strength and impact resistance, and is effective for reducing the weight.SOLUTION: One or more of a cellulose fiber compound base material produced by compounding a cellulose fiber base material having an average fiber diameter of 100 μm or less and a resin composition, a carbon fiber compound base material produced by compounding a carbon fiber base material and a resin composition, an aramid fiber compound base material produced by compounding an aramid fiber base material and a resin composition, and a glass fiber compound base material produced by compounding a glass fiber base material and a resin composition are laminated.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] In recent years, attention has been focused on switching to renewable resources instead of fossil fuel resources, and the use of biomass resources is one example of this. As an example of how biomass resources can be utilized, attention is being focused on the cellulose that makes up trees and herbaceous plants, and studies are being conducted to see if lightweight, high-strength materials can be obtained by turning it into fibers such as cellulose microfibers and cellulose nanofibers and combining them with other materials. [Background technology]

[0002] For example, Patent Document 1 discloses a carbon fiber reinforced plastic in which cellulose nanofibers and carbon fibers are blended with a matrix resin. However, it is a difficult technical challenge to uniformly blend cellulose nanofibers and carbon fibers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-1872 Summary of the Invention [Problem to be solved by the invention]

[0004] Fiber-reinforced composite resins use various thermosetting and thermoplastic resins as the matrix. On the other hand, high-strength synthetic fibers such as glass fiber (GF), carbon fiber (CF) and aramid fiber (AF) are used as reinforcing fibers. The specific gravity of these is generally GF: about 2.8 g / cm 3 ,CF: approx. 1.8g / cm 3 ,AF:1.5g / cm 3 It is said that... In comparison, cellulose nanofiber (CNF) is approximately 1.5 g / cm 3Although it is lighter than GF, its strength is 400-1500 GPa, which is much stronger than GF's 2.4-3.4 GPa. Therefore, the present inventors have investigated whether cellulose fiber can be used in place of GF, which has a high specific gravity, or in addition to GF, from the perspective of weight reduction, and have arrived at the present invention. [Means for solving the problem]

[0005] The laminated composite material according to the present invention is characterized by being formed by laminating one or more of a cellulose fiber composite substrate obtained by combining a cellulose fiber substrate having an average fiber diameter of 100 μm or less with a resin composition, a carbon fiber composite substrate obtained by combining a carbon fiber substrate with a resin composition, an aramid fiber composite substrate obtained by combining an aramid fiber substrate with a resin composition, and a glass fiber composite substrate obtained by combining a glass fiber substrate with a resin composition. The laminated composite material that can be used in the present invention is designed taking into consideration the strength, weight, etc., required for the product to meet various applications. Therefore, the present invention is a laminated composite material in which glass fiber composite substrates, carbon fiber composite substrates, aramid fiber composite substrates, etc. are laminated in multiple layers, and at least one layer of these is replaced with a cellulose fiber composite substrate, depending on the required product application. For example, among the laminated portions conventionally used by laminating two or more layers of glass fiber composite substrates, one or more layers may be replaced with a cellulose fiber composite substrate. Therefore, the laminated composite material of the present invention includes, as long as it uses at least one layer of a cellulose fiber composite substrate, other laminated materials include those obtained by arbitrarily laminating composite substrates with resin compositions using other fibers, such as carbon fiber composite substrates, aramid fiber composite substrates, and glass fiber composite substrates.

[0006] The cellulose fiber substrate having an average fiber diameter of 100 μm or less is used here because the cellulose fibers used in the present invention include so-called cellulose microfibers with an average fiber diameter of more than 300 nm and 100 μm or less depending on the application, and cellulose nanofibers with an average fiber diameter of 1 nm to 300 nm or less. The fiber length may be a relatively short staple fiber with an average length of about 0.05 μm to 10 μm, or a relatively long staple fiber with an average length of 10 μm to 100 μm.

[0007] The cellulose fiber used in the present invention may be in the form of a nonwoven fabric or a woven fabric, or may be mixed with other pulp materials to form a paper. It is also possible to use a plurality of layers of nonwoven fabrics, woven fabrics, and mixed papers.

[0008] When a composite substrate made of cellulose fiber as a reinforcing fiber and a matrix resin is used on the surface of a laminated composite material, if it is broken for any reason, the fractured part will be in shear failure mode, which has the effect of preventing fragments from flying off.

[0009] The resin used for the matrix may be a thermoplastic resin such as polyamide, polylactic acid, polypropylene, or polyethylene, or a thermosetting resin such as epoxy resin, polyurethane resin, phenol resin, polyimide resin, or polyisocyanate resin. Among these, resins having functional groups such as epoxy groups, amide groups, and ester groups, which have high compatibility with cellulose, are preferred. [Effects of the Invention]

[0010] The laminated composite material of the present invention can be widely used for safety components such as helmet materials having a conventional laminated structure, and high-strength plate materials for skateboards, etc., and by using it in these materials, it is possible to achieve lightweight materials while maintaining high strength. Helmets must be strong and impact resistant to protect the head, but if they are not lightweight, they will cause discomfort to the wearer. However, by replacing one or more of the glass fiber reinforced resin composite substrate layers, which have a relatively high specific gravity in the laminated structure that makes up the helmet material, with a cellulose fiber composite substrate, it is possible to reduce the weight while still maintaining safety standards. In this case, a plurality of cellulose fiber composite substrate layers may be used in combination with composite substrate layers made of other fibers depending on the intended use of the product. [Brief explanation of the drawings]

[0011] [Figure 1] The CNF substrate used for the evaluation is shown. [Figure 2] FIG. 1 is an explanatory diagram of a molding method using VaRTM. [Figure 3] The evaluation results of composite substrates made with four types of CNF (A, B, C, and D) and matrix resin are shown below. [Figure 4] An example of the laminated structure used for the evaluation is shown below. [Figure 5] The strength test results and weight comparison table are shown below. [Figure 6] This shows the compressive failure mode. [Figure 7] Examples of laminated structures [3] to [9] are shown below. [Figure 8] Strength test results are shown. [Figure 9] The results of the Charpy impact test are shown. DETAILED DESCRIPTION OF THE INVENTION

[0012] The laminated composite material according to the present invention was compared with commercially available motorcycle helmet materials, and the results are described below.

[0013] First, as a preliminary experiment, a cellulose nanofiber composite substrate was produced using the VaRTM method shown in Figure 2, using nonwoven fabrics made from four types of cellulose nanofibers (CNF), A to D, shown in Figure 1 (all manufactured by Awa Paper Co., Ltd.) and bisphenol A-type epoxy resin (Nippon Seeker Co., Ltd.) as the matrix resin. The manufacturing conditions were as follows: liquid resin was injected into and impregnated into the CNF substrate under reduced pressure of 100 kPa, and after primary curing at 40°C for 12 hours, secondary curing was carried out at 50°C for 8 hours.

[0014] The CNF nonwoven fabrics A, B, C, and D used in the test samples had different thicknesses: A: 0.29 mm, B: 0.33 mm, C: 0.12 mm, and D: 0.04 mm. Therefore, the total thickness was unified by stacking 7 sheets of A, 4 sheets of B, 9 sheets of D, and 24 sheets of D, as shown as PLY in the graph in Figure 3. Figure 3 shows the results of bending tests on sheet-shaped test pieces made from CNF nonwoven fabrics A, B, C, and D, which were impregnated with epoxy resin and cured. <Test conditions> Universal testing machine (Shimadzu Corporation: AG-5kN×plus) Test mode: Single ·Distance between fulcrums: 80mm Test piece width: 15mm - Test piece thickness: approx. 1 mm From the graph shown in Figure 3, the following laminates were produced and evaluated using CNF, D, which had the highest bending strength.

[0015] As shown in Figure 4(a), new laminated structures [1] and [2] were fabricated for the laminated composite material used in the evaluation, and were compared with the commercially available "helmet model." In the table of Figure 4, CF indicates a carbon fiber composite substrate with a matrix resin using carbon fiber as the reinforcing fiber, GF similarly indicates glass fiber, and AF indicates aramid fiber. These composite substrates have fiber orientation, and so the orientation direction is listed in the table using the definition shown in Figure 4(b). The new laminated structure [1] replaces one of the three GF layers in commercially available helmet materials with CNF, while the new laminated structure [2] replaces all GF layers with a CF layer and a CNF layer. FIG. 5 shows the evaluation results of bending strength and bending modulus. In a study in which only one of the three GF layers, which has a high specific gravity, was replaced with a CNF layer [1], the bending strength increased by 10% and the weight was reduced by 8%. Furthermore, [2] has a 45% increase in bending strength and a 27% increase in bending modulus compared to commercially available helmet materials, and is 18% lighter in weight. Figure 6 shows the failure mode when a compressive load is applied to the surface of the laminated composite material. In the conventional helmet model, the failure mode changes to shear failure mode, whereas the placement of a CNF layer on the compression surface causes the helmet to undergo delamination, potentially resulting in flying fragments.

[0016] As shown in Figure 7, a laminated composite material consisting of a combination of [3] to [9] was produced and evaluated as a new laminated structure. FIG. 8 shows the measurement results of bending strength and bending modulus, and FIG. 9 shows the test results of Charpy impact strength. Structures [3] to [7] are examples in which one or two GF layers are replaced with CNF layers, and structures [8] and [9] are examples in which all GF layers are replaced with CNF layers. Although reducing the number of GF layers slightly reduces strength, it was also revealed that even in structures without GF layers, such as structures [7] and [8], impact resistance can be improved by placing a CNF layer between the AF layer and the CF layer, as in structure [8].

[0017] The results of this evaluation show that in the field of helmet materials, which are made by laminating multiple conventional carbon fiber composite substrates, aramid fiber composite substrates, and glass fiber composite substrates, a high-strength, lightweight laminated composite material can be obtained by replacing the glass fiber composite substrate, which has a relatively high specific gravity, with a cellulose fiber composite substrate. Such a laminated structure can be used not only as a helmet material, but also as a board material for skateboards and various protective laminated materials.

[0018] Although glass fiber composite substrates have a relatively higher specific gravity than those made with other fibers, they are currently cheaper than carbon fiber, aramid fiber, and cellulose fiber. Therefore, for confirmation, we used GF Non-Crimp Fabric manufactured by SHINDO Co., Ltd., with a fiber diameter of 10 μm and a weight of 440 g / m2 in the (0 / 90) orientation shown in Figure 4(b). 2 ,(-45 / 90) Orientation weight 430g / m 2 When a bending test was carried out using epoxy resin as the matrix resin composition, the bending strength was 298 MPa and the bending modulus was 15.6 GPa.

[0019] In this example, an example was shown in which an epoxy resin was used as the matrix resin and impregnation molding was performed using the VaRTM method, but thermoplastic resins can also be used, and the molding method can be any well-known molding method such as heating or pressure pressing.

Claims

1. a cellulose fiber composite substrate obtained by combining a cellulose fiber substrate having an average fiber diameter of 100 μm or less on the surface side with a resin composition; A carbon fiber composite substrate obtained by combining two layers of carbon fiber substrates and a resin composition arranged below the carbon fiber composite substrate; a glass fiber composite substrate formed by compounding one layer of a glass fiber substrate and a resin composition, which is disposed below the glass fiber composite substrate; Further below that, the cellulose fiber composite substrate is provided, and further below that, the glass fiber composite substrate is provided, Further, an aramid fiber composite substrate obtained by combining an aramid fiber substrate with a resin composition is laminated underneath the aramid fiber composite substrate.

2. a cellulose fiber composite substrate obtained by combining a cellulose fiber substrate having an average fiber diameter of 100 μm or less on the surface side with a resin composition; A carbon fiber composite substrate obtained by combining four layers of carbon fiber substrates and a resin composition arranged below the carbon fiber composite substrate; Further, an aramid fiber composite substrate obtained by combining an aramid fiber substrate with a resin composition is laminated underneath the aramid fiber composite substrate.

3. 3. The laminated composite material for a helmet according to claim 1, wherein the cellulose fiber composite substrate is laminated with a cellulose fiber nonwoven fabric.

Images