Toughness improvement of carbon-fibre/polybenzoxazine composites by rubber modification

Carbon-fibre/polybenzoxazine composites were fabricated in order to examine the toughening effect of amine-terminated butadiene acrylonitrile rubber (ATBN) and carboxyl-terminated butadiene acrylonitrile rubber (CTBN) modifications of polybenzoxazine. The mode II delamination toughness of carbon-fibre/polybenzoxazine composites was measured as a function of rubber content. Transmission optical microscopy (TOM) and scanning electron microscopy (SEM) were used to investigate the fracture mechanism and toughening effect in the carbon-fibre/polybenzoxazine composites. Delamination toughness of the carbon-fibre/polybenzoxazine composites increased by ATBN modification as a result of the enhancement of the toughness of polybenzoxazine and interfacial bonding in the composites with increasing ATBN content. The better interfacial bonding in the ATBN-modified system induced the growth of some cracks allowing the intrinsic resin toughness to be fully extracted during composite delamination. In the case of CTBN modification, the delamination toughness of the composite was hardly increased because of the weak interfacial bonding.