Graduate student and professor, Georgia Institute of Technology, Atlanta, GA
Hybrid composite laminates consisting of layers of metal foils bonded together with fiber-reinforced resin show great promise as a fatigue-resistant material. The hybrid titanium composite laminate (HTCL) incorporates the mechanical advantages of existing hybrid composite laminates such as ARALL and GLARE while extending their applications to elevated temperatures. Titanium layers are bonded by prepreg layers of high-temperature resin reinforced with carbon fibers. The constituent materials used in this study are a metastable β titanium alloy (Ti-15-3), a high-temperature polyimide (LARC™-IAX), and an intermediate modulus carbon fiber (IM7). This study includes quasi-static and fatigue testing of HTCL materials at room temperature and 177°C (350°F). Experimental stress-strain response of HTCL laminates are compared with predicted results by a laminate analysis code called AGLPLY. A stress-based fatigue study was performed to determine the fatigue properties of HTCL laminates. The roles of residual stress in the mechanical behavior and fatigue properties of HTCL are addressed. The development of damage in HTCL specimens during fatigue is shown to include titanium ply cracking, interfacial debonding, and PMC layer failure. The influence of the fatigue properties of titanium layers on the fatigue of HTCL is discussed. The performance of HTCL laminates in fatigue is shown superior to that of the monolithic titanium alloy for room-temperature and elevated-temperature conditions.
Paper ID: CTR10494J