The influence of processing variables on the energy absorption of composite tubes

The aim of this work is to quantify the effect of process-related parameters on the level of specific energy absorption (SEA). This study comprises two sections: the first studies the effect of variable binder levels in the part (0-10% based on equivalent fibre mass). Highly soluble polyester powder binder is added to the resin to simulate the resin state near the end of injection and no binder is incorporated in the preform. The aim for the second part is to study the effect of processing variables on the level of voids in the composite and subsequently characterise the effect of void level on the energy absorption of the parts. Two thermosetting composite materials are examined; a continuous filament random mat (CoFRM) and a non-crimp fabric (NCF) at volume fractions of 22 and 38%, respectively. The parts moulded are generic tubular energy absorbing structures with double cantilever beam (DCB) and in-plane tensile and compressive specimens as secondary tests. An unsaturated polyester resin developed for automotive RTM applications is used for all parts. Mode-I fracture toughness shows significant changes with binder content, however, the SEA of the composite tube is observed to be very tolerant of binder level. Three processing regimes were used yielding void levels between ∼0 and over 10%. The SEA levels for both materials are seen to be tolerant of high void levels allowing potential cost reduction through rapid processing.