Effect of temperature and strain rate on biaxial warp-knitted composite

Abstract

This investigation aims to study the impact behaviors of biaxial warp-knitted composite materials under the following conditions—strain rates of 1000–3400 s⁻¹; temperatures of 23℃–210℃. Impact compression tests (in the through-thickness direction of specimens) were conducted using the split Hopkinson pressure bar apparatus. A heating device was applied to achieve required temperatures. It was found that high temperatures of 120℃–210℃ led to a softened initial response on the composite’s stress–strain curves. In addition, pre-peak hardening was observed in the specimen when exposed to temperature between 23℃ and 90℃. The latter could be attributed to further compaction with densification effect during through-thickness compression. Finally, two different failure modes were noticed—(1) the shear-oriented failure and (2) the delamination-oriented failure. This was due to the degradation of the tricot, the brittle–ductile transition of the resin, and the thermal stress in the biaxial warp-knitted composite at different temperatures.