Metal-alike polymer composites: The effect of inter-layer content on the pseudo-ductile behaviour of carbon fibre/epoxy resin materials

With interfacially engineered pseudo-ductile carbon fibre reinforced polymer composites, a higher energy absorption capacity and metal-like stress-strain response can be achieved during failure. Due to incorporated inter-layer additives deposited with fused filament fabrication, locally weakened zones can be printed on the surface of the reinforcing material, which provides better energy absorption capability during the composite laminates’ damage process by the alteration of crack propagation. The reason for this phenomenon is that cracks near the inter-layered zones require more energy to propagate, which delays the onset of final failure in the form of local damage. The modified layers are then infiltrated with an amine-cured epoxy by vacuum assisted infusion. The change in pseudo-ductile behaviour as a function of the interfacial additive content was investigated, along with the change in mechanical properties. The stress-strain relationship was determined by various tests, quasi-static and dynamic, from unmodified composites (0% interlayer used) up to 100% interlayer content (i.e. polymer film) between the matrix and the reinforcement. We have investigated a method to repair the specimens after the bending tests via melting the thermoplastic interlayer. The results show that with the use of interlayer material, the critical stress intensity factor increased, and ductile behaviour improved thanks to the altered crack propagation.