DAMAGE TOLERANCE OF CARBON/EPOXY QUASI-INTERWOVEN COMPOSITES SUBJECTED TO LOW VELOCITY IMPACTS

Robotic dry fibre placement (RDFP) is a preforming technology with the potential of mass-producing laminar composite preforms at the speed and quality required for the automotive and aerospace industries. The RDFP technology enables the placement on unidirectional (UD) fibres in arbitrary in-plane directions, producing a laminate with tailored mechanical properties. Due to the layered nature of these lay-ups, the resulting composites exhibit poor out-of-plane properties.
Quasi-interwoven lay-ups produced by the RDFP methodology present a potential method for creating preforms with layer connectivity and crimp. The RDFP carbon fibre preforms produced for this work were based on the Advanced Placed Ply (AP-Ply) structure, with pin spacing ranging from 2.5mm to 10mm. The narrowest pin spacing creates a cross-ply non-crimp preform whilst the widest spacing creates a quasi-interwoven composite upon consolidation, with high levels of layer crimp. Rectangular test coupons were cut according to the Queen Mary test protocol and subjected to low velocity impact and compression after impact testing. A distinguishable improvement in damage resistance was observed for the quasi-interwoven lay-up when compared with the non-crimp lay-up. Despite the high layer undulation levels seen with the quasi-interwoven lay-ups, these specimen have comparable compression after impact strengths to those with lower levels of undulation.