Basalt fabric material

Abstract

Woven basalt fabric material with perforations. The perforations may be circular and may have a diameter between 1 and 5mm. The perforations may be positioned in rows 13mm from one another and in columns 13mm from one another, where the rows and columns may be perpendicular to one another. The material may be impregnated with a resin during lay-up of the material. The material may be formable over multi compound curved surfaces. A composite material may comprise reinforcing fibres of the fabric and a resin matrix impregnated throughout the fabric.

Description

Field of the Invention The present invention relates to a basalt fabric material, in particular a basalt fabric material comprising a plurality of perforations useful in composite structures. Background to the Invention Conventionally, composite parts are manufactured by stacking layers of a fibrous reinforcement material against a mould. The layers are impregnated with a curable resin material. The impregnation may be completed prior to the formation of the layers (so called lay-up procedure), in which case the fibrous material may be referred to “Pre-Preg”. Alternatively, impregnation may be performed during the lay-up procedure. The fibrous reinforcement material is commonly a woven material. The advantage of a woven fabric in composite structures is that the fabric is very pliable as well as strong. These characteristics are advantageous when laying the fabric inside or against an open or closed mould, where the resin is either applied or injected. Subsequently, the lay-up including the resin is cured by heating the stack. Compression may be applied at this point also to cause the resin to flow to consolidate the fibrous stack, and then to subsequently cure. This results in an integral laminar composite structure. In other methods it is not necessary to heat the structure, or apply compressive force. The resin commonly contains curing agents which force the curing of the structure of its own accord, at much lower temperatures approaching Room Temperature. Composite laminar structures are strong and light-weight. Their use is well known and they are frequently used in industrial applications such as automotive, aerospace and marine applications. For example, these structures are widely used in wind energy applications such as wind turbine blades, and in particular the outer shells of the blades, the internal spars and the root ends of the spars. They are also used for sporting goods such as for skis, skate boards, surf boards, windsurfing boards and the like. Typically the resin material which is used to produce composite parts is a thermosetting resin such as an epoxy resin or a polyurethane resin. However thermoplastic resins may also be used. The selection of the resin material depends on the application and use of the laminate. Also, the reinforcement material can be selected from a range of suitable fibres, commonly these comprise carbon, aramid, basalt or glass fibres. Basalt derived fabrics are well known in the composites industry. Basalt fabric has many favourable characteristics such as fire and heat resistance, strength, and chemical resistance. As basalt fibres are very stiff they are commonly used as additional reinforcement elements within carbon or glass fibre mat / fabric. A further advantage is that basalt fibres, being derived from a natural earth rock, have a low ecological and environmental footprint. Therefore basalt fabrics are favoured by companies who work within a set environmental footprint standard, or wish to reduce the environmental footprint of their products. The comparative stiffness of basalt fabrics, compared to that of glass fabrics or carbon fabrics presents a problem though. Even though basalt fabrics can be rolled for packaging and transport, when unrolled before use the fabrics are semi rigid, stiff and inflexible. This makes them impractical to use against curved or multiple curvature moulds, as the fabrics will simply not bend to shape. As such, basalt fabrics are used mainly in low curvature work, such as flat panelling or even rebar equivalents. There has now been devised a basalt fabric material that substantially overcomes or mitigates the above referenced and / or other disadvantages associated with the prior art. Summary of the Invention In an aspect of the invention there is provided a woven basalt fabric material, wherein the material comprises a plurality of perforations. The perforations allow the otherwise semi rigid fabric to be manipulated in multiple directions and bent over many curvatures. This makes it possible therefore to use basalt fabric in any composite lay-up process that requires the lay-up on multiple compound curves, such as car panels for example. Another effect which is the result of the perforations is to increase the resin and gas permeability through the fabric. This reduces the likelihood of any air pockets residing underneath any lay-up and allows for even resin saturation of the fabric. The inventors have surprisingly found that this improves the overall strength of the cured material. The perforations are distinguished from other openings within the fabric that might be the result of the normal weaving process. The perforations are added post weaving of the material into a fabric. It will be recognised that the perforations may have any shape. Example shapes for the perforations include but are not limited to square, triangular rectangular or multi sided. Preferably however, each of the perforations are circular. This creates evenness in the gaps created by the perforations between the warp and weft in the fabric weave. This in fact improves the strength o the material by not providing weak points, or focus points for structural failure. It also prevents warping or folding of the fabric during lay-up. Preferably each of the perforations are between 1 and 5 mm in diameter. This dimension has been found by the inventors to surprisingly lead to a marked increase in flexibility and resin permeation without compromising strength. More preferably, each of the perforations are between 2.5 and 3.5 mm in diameter. Preferably the plurality of perforations are positioned in rows between 10 and 15 mm from one another, and in columns between 10 and 15 mm from one another, and wherein the rows and columns are perpendicular to one another. These dimensional characteristics has been found by the inventors to surprisingly lead also to a marked increase in flexibility and resin permeation without compromising strength. More preferably, the plurality of perforations are positioned in rows between 12.5 and 13.5 mm from one another, and in columns between 12.5 and 13.5 mm from one another, and wherein the rows and columns are perpendicular to one another. This allows the fabric to curve around corners and sharp edges without springing back off the edges during lay-up. Whilst it is recognised that the material maybe impregnated with resin prior to lay-up and thereby form a pre-preg, preferably, the material is impregnated with a resin during lay-up of the material. This means that there is no chance of air pockets forming between the material and the mould onto which the lay-up is applied. In a second aspect of the invention there is provided a composite material, the composite material comprising a) reinforcing fibers woven into a fabric according to any of claims 1-6, and b) a resin matrix impregnated throughout the fabric. With reference to the first or second aspect of the invention the term basalt fabric includes basalt derived fabrics and fabrics made entirely from basalt fibres. Brief Description of the Drawings The invention will now be described by way of example and / or illustration only with reference to the accompanying drawings in which: Figure 1 shows a plan view of an example of the fabric material and Figure 2 shows a cross sectional view of multiple layers of the moulding material stacked during moulding. Detailed Description of the Illustrated Embodiment Figure 1 shows an example of the fabric material generally designated 100. A single layer of a portion of fabric 100 is shown with various warps 101 and wefts 102 that at typical of fabric sheets used in composite lay-up. Interspersed in a regular array across the surface of the fabric 100 are a plurality of circular perforations 105. These perforations extend through the entire thickness of the fabric 100. Each perforation 105 is approximately 3mm in diameter. The perforations 105 are arranged in rows and columns. Each row is approximately 13mm from its neighbouring row. Each column is spaced approximately 13 mm from its neighbouring column. The columns and rows are perpendicular to each other. Therefore each perforation is spaced apart diagonally from its nearest neighbour by approximately 18mm. The fabric 100 is a basalt fabric and has a plain woving pattern and density of between 140-400g / m3. The fibre diameter ranges from 130-400 pm. The warp density is between 5 and 10 roots / cm and the weft density is between 5 and 10 roots per cm. The thickness is between 0.18 and 0.4 mm. ln use, the fabric 100 is laid up in or on a mould 300 by stacking one or more layers of the moulding material 100 on top of one another to form a stack 110 as is shown in Figure 2, with a resin matrix material 200 being used to impregnate the fabric 100. The resin matrix 200 consists of a thermoset epoxy based resin matrix which contains both resinous components and a curative. Alternatively the resin matrix 200 consists of a polyester based resin matrix which contains both resinous components and a curative. The laying up process can thus be achieved in at least two general ways. The first way involves impregnation of the fabric with the resin 200 post placement of the fabric 100 against the mould 300, or impregnation prior to the fabric 100 being applied to the mould 300. In the first method the mould 300 is wetted with the resin 200 in order to coat the surface completely and provide an uncompromised and unbroken surface to the lay-up material. Prior wetting also aids bonding of the lay-up material to the mould. Pieces of fabric 100 are laid on top of the wetted surface, and further coats of resin 200 applied in order to fully wet the applied pieces. Further pieces are applied along with further resin 200, with the pieces overlapping and until the required thickness of the lay-up is achieved. The formed stack of layers 110 is covered in a vacuum bag enclosure (not shown) which is subsequently evacuated to remove all air. The temperature of the stack is raised, which causes the resin 200 to flow and to impregnate the fibrous reinforcement of the individual layers. The resin 200 subsequently cures, and after cure, the moulded stack 110 can be removed from the mould 300. Alternatively, the vacuum bag enclosure step and / or the temperature raising step may be removed, to allow the resin to cure naturally, albeit over a longer time. In the second method strips or sheets of fabric 100 are pre wetted with the resin 200 to completely impregnate the fabric 100. Thus a so called “pre-preg” is formed. To improve handleability, the pre-preg has a layer of release liner applied on each side. When ready each piece of pre-preg is then taken and one of the release liners removed therefore exposing the resin coated fabric. This side of the pre-preg is laid against the mould and then the top release liner removed. Consecutive layers are then built up in the lay-up process in a similar manner. The lay-up is then cured as described above. In an example of use, the fabric 100 is used to construct a mannequin. It will be appreciated though that the fabric has uses which are not limited to man-5 nequin production. Other uses for the fabric include but are not limited to the construction of products for the automotive, marine, aviation or leisure industries. Other uses for the fabric include but are not limited to the retail industry (such as providing store fixtures), visual merchandise (such as podiums and display boxes) and the amusement industry (such as coin operated rides and fairground 10 rides).

Claims

1. A woven basalt fabric material, wherein the material comprises a plurality of perforations.

2. A material according to claim 1, wherein each of the perforations are cir-5 cular.

3. A material according to claim 1 or claim 2, wherein each of the perforations are between 1 and 5 mm in diameter.

4. A material according to any preceding claim, wherein the plurality of perforations are positioned in rows 13 mm from one another, and in columns 13 mm 10 from one another, and wherein the rows and columns are perpendicular to one another.

5. A material according to any preceding claim, wherein in use the material is impregnated with a resin during lay-up of the material.

6. A material according to any preceding claim, which in use is formable over 15 multiple compound curved surfaces.

7. A composite material, the composite material comprising a) reinforcing fibers woven into a fabric according to any of claims 1-6, and b) a resin matrix impregnated throughout the fabric.

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