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Within the scope of experiments, five kinds of biaxial weft-knitted (BWK) fabrics with various knitting techniques (plain, interlock, tuck, tuck-miss, and interlock2) were used as reinforcement systems to fabricate thermoplastic composites with polypropylene (PP) resin yarn. Then, the final composite became BWK composites with various knitting types. The mechanical properties of composites were investigated by conducting tensile, three-point bending, and three-point bending impact tests on specimens. In all specimens, PP was commingled with glass yarn. Glass was used as reinforcement. Fiber volume fraction (V f ) of weft fibers of the interlock2 was the highest, and the length of straight part of loop shape was the longest in the interlock2 compared with the other four types of specimens. Because of the higher V f of the BWK composites with the interlock2, tensile, three-point bending, and three-point bending impact properties of the interlock2 was higher than the other four types (plain, interlock, tuck, and tuck-miss) of composite structures.

Within the scope of experiments, the effect of aramid and glass yarns as stitch and biaxial (warp and weft) yarns in the biaxial weft knitted (BWK) composite was compared. After production of four types of composite panel using the hand lay-up method, the tensile and bending properties of the BWK composites were investigated both experimentally and numerically. The composite with the glass stitch and biaxial yarns exhibited higher tensile and bending properties than did the composite with the aramid stitch and biaxial yarns. The good agreement between the experimental results and the numerical results validated the applicability of the finite-element method for the BWK composites. The laminate beam theory was utilized as another modeling method for calculation of the bending modulus.

Within the scope of experiments, the effects of stitch yarn type, such as aramid, glass, and nylon, and biaxial, warp, and weft yarn type, such as aramid and glass, on biaxial weft knitted (BWK) composites were investigated. Five different types of composite panel, which include fiber contents, such as glass-glass-glass, glass-glass-nylon, glass-glass-aramid, aramid-glass-aramid, and aramid-aramid-aramid, were fabricated by hand lay-up method. After the production of composite panels, three-point bending impact and plate bending impact tests were conducted on the specimens. Microstructural characterization of the impact-tested materials was performed using an optical microscope. This study shows that composites with BWK preforms consisting of fiber combinations such as glass-glass-aramid had higher plate bending impact and three-point bending impact properties than the other four types of composite structure.

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