Impact perforation resistance of laminated and assembled composite plates

A previous study on impact response of composite laminates concluded that impact perforation was the most important damage stage in composite laminates subjected to impact loading since impact characteristics and degradation of mechanical properties of composite laminates reached critical levels once perforation took place. It was also found that thickness had a greater influence on impact perforation resistance than in-plane dimensions. However, as the composite laminates became very thick, the manufacturing cost for obtaining high-quality composite laminates could become unaffordable. In an effort to meet design requirements and to reduce manufacturing costs, assembled composite plates, which were organized by assembling multiple thin composite laminates together, were considered as alternatives to thick laminated composite plates. Various joining techniques including mechanical riveting, adhesive bonding, stitching and their combinations were used in assembling two- and four-laminate plates. Experimental results revealed that epoxy bonding outperformed other joining techniques. Although good bonding resulted in a higher impact bending stiffness and subsequently a higher perforation threshold, increasing the laminate thickness, or the number of laminates, was found to be more efficient in raising perforation threshold than improving the joining stiffness. As a major finding of the study, the assembled composite plates were found to have perforation thresholds similar to the laminated counterpart. Hence, the former could be used to replace the latter, at least, as far as perforation threshold was concerned.