In-plane compressive properties and failure mechanisms of modified three-dimensional multi-axial warp knitted fabrics reinforced composites at different temperatures

Three-dimensional multi-axial warp knitted (3D MWK) reinforced composites are important components of advanced structural composites. The interfacial bonding between fiber and matrix is key to achieving high mechanical properties. In this work, graphene oxide (GO) and poly(oxypropylene) diamines (D-400) were grafted on glass fiber (GF) multi-axial warp knitted (MWK) fabrics to construct a "flexible-rigid" structure. The surface morphologies of GF were characterized by SEM and EDS. Then, 3D MWK-reinforced composites were prepared based on four kinds of modified fabrics using the VARTM method. The in-plane compression properties were obtained at different high temperatures and their failure modes were analyzed. The strain-stress curves showed that the composites exhibited brittle fracture modes. D-400 and GO-modified multi-scale composites exhibited outstanding compression properties. The strength of the related composited was improved by 55.78%, 76.78%, 52.19%, and 56.78% compared to that of desized composite at 30 degrees C, 60 degrees C, 120 degrees C and 150 degrees C, respectively. The damage to D-400-GO modified and D-400 modified composites was the most serious, where shear fracture modes were obvious in addition to layer debonding features. This protocol provides a potential strategy to manufacture of D-400 and GO-modified hierarchical reinforced composites.