The impact properties of high-temperature fiber-metal laminates

This study investigates the low and high velocity impact properties of fiber-metal laminates (FMLs) based on carbon fiber-reinforced poly-ether-ether-ketone (CF/PEEK) and glass fiber-reinforced poly-ether-imide (GF/PEI) composites. The aim of this work is to develop a lightweight hybrid material for use in high temperature aerospace applications. Here, low velocity impact tests are undertaken using an instrumented impact tower and high velocity impact tests are conducted using a nitrogen gas gun. Low velocity impact testing has shown that the specific perforation energy of the CF/PEEK-based FMLs is similar to that offered by the CF/PEEK composite. In contrast, the specific perforation energy of the GF/PEI FML system is lower than that of the plain PEI composite. The experimental evidence suggests that the inclusion of strong titanium beta alloy plies does not improve the perforation resistance of these FMLs. High velocity impact tests resulted in failure processes similar to those observed under low velocity loading conditions, with the specific perforation energy of the GF/PEI-based FMLs being higher than those exhibited by the plain GF/PEI composite. An extensive and detailed optical microscope study has shown that interfacial and interlaminar delaminations are the principal energy-absorbing mechanisms during low and high velocity impacts.