Design and characterisation of high performance, pseudo-ductile all-carbon/epoxy unidirectional hybrid composites

A variety of thin-ply pseudo-ductile unidirectional interlayer hybrid composite materials comprising high modulus and high strength thin carbon fibre/epoxy prepregs was investigated. The central high modulus carbon plies fragmented and delaminated stably from the outer high strength carbon layers under uniaxial tensile loading in the hybrid materials. These pseudo-ductility mechanisms resulted in favourable, metal-like stress-strain responses featuring pseudo-yielding, a stress plateau and further rise in stress before final failure. The high initial elastic modulus of up to 240 GPa, the early warning and the wide safety margin between damage initiation and final failure make the new hybrids advantageous for safety-critical applications where ultimate performance and low density are key design drivers. A hybrid effect with an increase in the failure strain of the high modulus carbon material was highlighted for very thin plies.