Patent Application
20190376212
The present disclosure relates to a fabric which is intended to be coated with a thermo-setting resin. The resulting composite having the fabric described herein can be suitable for creating strong, lightweight, fire-resistant wall panels or other components for use in cargo containers or other structures.
Manufacturers increasingly are using fiber reinforced plastic (FRP) composite materials for a wide range of products, such as vehicles and sporting equipment. Composite panels also have been employed in the construction of air cargo containers. In many instances, the composite panels are created by laminating together a plurality of separate fiber reinforced resin sheets. In the past, the laminated construction allowed for variety in materials and performance among the separate sheets. For example, a laminated panel may include a first FRP sheet designed for its tensile strength characteristics, a second FRP sheet designed for its impact resistance, and a third FRP sheet designed for its fire-resistance. The use of separate sheets combined in laminated panels can increase the cost of production and the manufacturing cycle time.
Therefore, there is a need for improvements that may produce a FRP composite material that can include a reduced number of required sheets in a laminated panel and possibly provide within a single sheet the performance of a multi-sheet laminated construction.
One embodiment of the present disclosure includes a dual-layer fabric. Another embodiment of the present disclosure includes a fiber reinforced plastic composite having the dual-layer fabric as described. In one embodiment, dual-layer fabric includes a first layer and a second layer. Warp and weft yarns are interwoven with each other to form each of the first layer and the second layer. The warp yarns include both aramid yarns and high temperature organic yarns. The weft yarns include both aramid yarns and high temperature organic yarns.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiments, when considered in conjunction with the drawings. It should be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of the invention as claimed.
Exemplary embodiments of this disclosure are described below and illustrated in the accompanying figures, in which like numerals refer to like parts throughout the several views. The embodiments described provide examples and should not be interpreted as limiting the scope of the invention. Other embodiments, and modifications and improvements of the described embodiments, will occur to those skilled in the art and all such other embodiments, modifications and improvements are within the scope of the present invention. Features from one embodiment or aspect may be combined with features from any other embodiment or aspect in any appropriate combination. For example, any individual or collective features of method aspects or embodiments may be applied to apparatus, product or component aspects or embodiments and vice versa.
The manufacture of fiber reinforced plastic (FRP) composites may involve obtaining a web of woven, non-woven, mat, unidirectional, or knit fibers. The fibers are then coated or impregnated with a resin through processes such as pultrusion or molding. The resin is then cured to form a structural sheet. In the past, a single-layer sheet often did not produce the desired performance, and several sheets would be laminated together. Lamination could occur by embedding a plurality of sheets in an encasing resin, or by adhering the layers together with adhesive or by other means before or after fully curing each sheet. The use of separate sheets followed by the laminating process is labor and material intensive, leading to relatively high manufacturing costs.
The inventors have sought to improve the process of manufacturing a FRP composite such that the finished product can reduce concerns about delamination between several layers, reduce material costs, and reduce labor costs by streamlining the manufacturing process. The inventors determined that these goals can be achieved if a single composite layer was able to provide similar strength and fire-resistance characteristics as a laminated multi-sheet construction. A single layer structure would have fewer manufacturing steps. The inventors further determined that a single-layer composite could replace existing multi-layer composites if the composite were reinforced with an improved fabric as described below. The improved fabric can be coated in a single step, eliminating steps from the manufacturing process. Fewer manufacturing steps can reduce costs.
A fabric 10 for use in reinforcing resin or plastic composite materials according to the present disclosure is photographed in
As shown in
In one example, the first layer 16 is woven in a 3/1 right hand twill where each face pick passes over one face end, and then under three face ends. A 3/1 twill pattern is often considered a warp dominant construction because it relates to the exposed surface of the first layer.
In one example, the second layer 18 is woven in a 1/3 left hand twill such that each back pick passes under one back end and over three back ends. A 1/3 twill pattern is often described as a weft dominant construction.
The first and second layers of the fabric are secured by using both raiser and sinker stitching. Raiser stitching occurs when back ends are raised over face picks. Sinker stitching occurs when face ends are lowered under back picks. This method of stitching is utilized to enable the first and second layers to be interlaced into a woven fabric of two layers. In one embodiment, particular stitch points are selected to provide balance to the weave design.
The fabric 10, photographed in
As mentioned above, the odd numbered ends (warp yarns), which correspond to the odd numbered harnesses 1, 3, 5, and 7 weave the first layer 16, and the even numbered ends (warp yarns), which also correspond with the even numbered harnesses 2, 4, 6, and 8, weave the second layer 18. Similarly, the odd numbered picks (weft yarns), which correspond to the odd numbered harnesses 1, 3, 5, and 7 weave the first layer 16, and the even numbered picks (weft yarns), which also correspond with the even numbered harnesses 2, 4, 6, and 8, weave the second layer 18.
In the illustrated example, a repeat of the weave pattern consists of eight picks and eight ends.
The fabric 10 photographed in
Also apparent to one of ordinary skill in the art from the weave draft of
The dual layer construction and weave pattern, such as the weave draft in
In one embodiment, the fabric 10 is constructed from a combination of inorganic yarns, for example aramid yarns 30, and organic, high-temperature yarns 40, such as yarns made from e-glass (alumino-borosilicate), s-glass (alumino silicate glass with MgO and without CaO), quartz, silica, ceramic, basalt, or combinations thereof. Aramid is beneficial for high mechanical strength properties. Glass fibers or other organic, high-temperature yarns may support the fire resistance of the fabric 10.
In one embodiment, the organic high temperature yarns 40 are glass yarns, such as e-glass or s-glass. In one embodiment, the glass yarns are S-glass yarns of about 300 denier to about 600 denier. In one embodiment the organic high temperature yarns 40 may be multi-ply yarns, such as 2-ply or 3-ply. Therefore, the organic high temperature yarns 40 may have a total denier of about 1200 to about 1800.
In one embodiment, aramid yarns 30 may be used that are about 1500 to about 3000 denier. Again, each aramid yarn 30 may be plied for each pick or end such that a pick or end having aramid may have a total combined yarn denier of about 3000 to about 6000. In one embodiment, the aramid yarn 40 may be a twisted aramid yarn with between approximately one and approximately two twists per inch. The twist may be an S-twist or Z-twist.
In an example, the yarn count for the fabric 10 is between about thirty and about sixty-five warp yarns and between about thirty and about sixty-five weft yarns per inch total. Half the warp yarns will be face ends and half the warp yarns will be back ends. Similarly, half the weft yarns will be face picks and half the weft yarns will be back picks. One having ordinary skill in the art will appreciate that the yarn count can be related to the size of the yarns selected, with larger yarns requiring fewer yarns per inch to achieve similar performance.
In one embodiment, the organic high temperature yarn are the picks, and the aramid yarns provide the ends. In another embodiment, the picks are aramid and the ends are glass. In some embodiments, one or more of the yarns includes glass filaments and aramid filaments. In a preferred embodiment, the picks include both glass and aramid yarns and the ends include both glass and aramid yarns. In the fabric 10 of the photographed and illustrated embodiment, the ends alternate glass and aramid yarns, and the picks alternate glass and aramid yarns. Particularly, the face ends and face picks are aramid yarns 30 and the back ends and the back picks are organic high-temperature yarns 40, such as glass.
In one example, the fabric photographed in
The number of ends and picks were chosen to produce fabric with a weight from about 25 to about 26 ounces per square yard. The weight target was set for the particular illustrated example. Other fabrics may be heavier or lighter, such as in the wider range of about 20 to about 35 ounces per square yard. The sample fabric meeting the target weight had 48 ends per inch and 40 picks per inch. Again, because the aramid yarns and s-glass yarns were alternating on the picks and ends, half the ends and half the picks were each type yarn. The finished sample fabric weighed approximately 25.5 ounces per square yard.
The sample fabric was between about 65% and about 75% aramid, particularly 70% aramid, and between about 25% and about 35% high temperature organic yarns, particularly 30%, by weight. When tested according to ASTM D5035, the sample fabric demonstrated tensile strength in the warp direction of about 3000 lbs./inch and tensile strength in the fill direction of about 2700 lbs./inch.
The strength of the sample fabric is a result of the weave pattern and selected yarns, and may be specified in terms of the desired weight of the fabric. Therefore, one of ordinary skill in the art will appreciate that allowing for a heavier fabric can often produce even higher strength as the result of increasing the quantity of yarns and/or increasing the size of the yarns. The particular target weight, strength, and other performance characteristics may be impacted by the anticipated end use of the composite material that incorporates the fabrics of the present disclosure. The sample fabric 10 is believed to be particularly useful for composite panels in use environments such as air cargo containers.
As referenced above, the fabric described above may relate to one or more novel processes. For example, the manufacture of the fabric 10 may be described in terms of a method comprising obtaining aramid yarn and glass yarn. The method may also include preparing a weaving machine for weaving a dual-layer fabric where alternating harnesses in the warp direction are set with aramid yarn and glass yarn and alternating harnesses in the weft direction are set with aramid yarn and glass yarn. In one embodiment, the process comprises setting the machine to weave a first layer with the picks and ends having aramid and setting the machine to weave a second layer with picks and ends having glass. The process many further include programming the weaving machine according to the weave draft of
In addition, the fabric 10 may be used in a process to create a fiber reinforced plastic. The method of forming the FRP may include obtaining a dual-layer fabric having aramid yarns and organic, high-temperature yarns. The method may further include impregnating the dual-layer fabric with a resin and curing the resin. The method any also include using the FRP without laminating it to another layer of composite material.
Although the above disclosure has been presented in the context of exemplary embodiments, it is to be understood that modifications and variations may be utilized without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims and their equivalents.
