Compression behavior of graphite-epoxy and graphite-thermoplastic panels with circular holes or impact damage

An experimental investigation of the compression behavior of laminated specimens made from graphite-epoxy tape (AS4-3502), graphite-thermoplastic tape (AS4-PEEK), and graphite-thermoplastic fabric (AS4-PEEK) was conducted. Specimens with five different stacking sequences were loaded to failure in uniaxial compression. Some of the specimens had central circular holes with diameters up to 65 percent of the specimen width. Other specimens were subjected to low speed impact with impact energy up to 30 J prior to compressive loading. This investigation indicates that graphite-thermoplastic specimens with holes have up to 15 percent lower failure stresses and strains than graphite-epoxy specimens with the same stacking sequence and hole size. However, graphite-thermoplastic specimens subjected to low speed impact have up to 15 percent higher failure stresses and strains than graphite-epoxy specimens with the same stacking sequence and impact energy. Compression tests of graphite-thermoplastic specimens constructed of unidirectional tape and of fabric indicate that the material form has little effect on failure strains in specimens with holes or low speed impact damage.