Effect of aramid bundling yarn types on interlaminar properties of multilayered biaxial weft knitted fabric reinforced epoxy composites

The interlaminar properties of multilayered biaxial weft knitted (MBWK) fabric reinforced epoxy composites were studied by using aramid yarns as bundling yarns. The interlaminar properties of MBWK fabric reinforced epoxy composites and the effects of aramid bundling yarn on the interlaminar properties were analyzed. The bending and interlaminar shear properties of the MBWK fabric reinforced epoxy composites were obtained by three-point bending and short-beam shear tests. The interlaminar strain changes were observed by Aramis V6 digital image correlation system. Compared with the traditional MBWK fabric reinforced epoxy composites bonded with polyester filaments, the bending and interlaminar shear properties of the MBWK fabric reinforced epoxy composites bonded with aramid fibers are improved significantly with the bending strength, interlaminar shear strength and the bending modulus increment of 14.21%, 12.70% and 25.49%, respectively. The longitudinal strain (Epsilon X) and interlaminar shear strain (Epsilon XZ) of MBWK fabric reinforced epoxy composites bound with aramid fibers are larger in the neutral location when the composites are subjected to the out-of-plane loads. And aramid yarns play an effective role in restraining the delamination of composites when subjected to out-of-plane loads.