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A Novel Through-Thickness Reinforcement Method of Cured Composites
Abstract
A through-thickness reinforcement method for a fully cured carbon/epoxy composite laminate is proposed and characterized. The method consists of embedding the interlaminar rods into the holes drilled in the cured laminate with further bonding the rods to the laminate with an epoxy resin. Such a technique has the same rod/laminate stress transfer mechanism responsible for the improvement in laminate fracture resistance as the conventional z-pinning. The composite resulting from the proposed interlaminar reinforcement technique possesses the benefits of a uniform surface quality and consolidation of the original unreinforced laminate. The technique was found to be highly effective in suppressing the damage propagation in DCB test specimens under mode I loading conditions. It was experimentally shown with DCB specimens in the paper that increased aspect ratio (length to diameter ratio, AR) of through-thickness rods significantly elevates mode I maximum delamination fracture resistance of a laminate. This effect is explained through the analysis of rod/laminate interfacial stress transfer.