The effect of interlaminar toughening strategies on the energy absorption of composite tubes

The effect of interlaminar fracture toughness on the specific energy absorption (SEA) of composite tubes subjected to axial crushing is investigated. Toughened resin, through-thickness stitching, thermoplastic resin additives and thermoplastic interleaves were used to increase the fracture toughness of continuous filament random mat (CoFRM) and 0/90 non-crimp fabric (NCF) E-glass reinforced polyester composites. Double Cantilever Beam (DCB) and axial crush tube samples were tested to give mode I fracture toughness (GIC) and SEA values for ten test configurations. It was shown that the CoFRM, despite its lower in-plane properties than NCF, gave higher GIC and SEA values. Increasing resin material properties increased GIC and SEA values for both architectures. Through-stitching was shown to increase GIC for both architectures, but only improve SEA for NCF—a slight reduction seen in the CoFRM SEA value was attributed to the reduction in in-plane properties caused by stitching. A thermoplastic resin additive gave significant changes in GIC but little change in SEA. Thermoplastic interleaves increased GIC, but for both reinforcement architectures the SEA decreased. This decrease was attributed to a reduction in friction at the contact surfaces in the crush zone as a result of ductile failure of the thermoplastic interleaf. The manufacturing conditions used were representative of those used in low to medium volume industrial production.

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