Transverse impact behavior of knitted carbon-fiber fabric-reinforced thermoplastic composite sheets

Instrumented falling weight impact (IFWI) properties of two-dimensional (2D) weft-knitted carbon-fiber (CF)-reinforced poly(ethyl methacrylate) (PEMA) and poly(ether ether ketone) (PEEK) composites with a reinforcement content of V_f ≈ 35 and 51 vol.%, respectively, were studied under low-energy and perforation impact conditions. Results indicated that the transverse impact response of these thermoplastic composites strongly depends on the ductility of the matrix, on fiber/matrix adhesion, and on the stitch (rib) structure (size, stretching of the fabrics) of the knitted fabric reinforcement. The highest thickness-related perforation impact energy was found for the knitted CF-reinforced PEEK composite (≈ 15 J/mm) due to its high reinforcement content, high matrix ductility, and good fiber/matrix bonding.