Mechanical properties of Ti/CF/PMR polyimide fiber metal laminates with various layup configurations

The mechanical properties of Ti/CF/PMR polyimide fiber metal laminates (FMLs) with various layup configurations and fiber layer orientations (0 degrees, 90 degrees, and +/- 45 degrees) were systematically investigated. The results suggest that the elastic modulus and tensile strength of the FMLs were determined by the interfacial adhesion, volume fraction, and layup direction of the carbon fibers. A model has been proposed herein to predict the corresponding relative tensile strengths. The FML specimens were subjected to the compressive stress on the upper surface and tensile stress on the lower surface under the function of flexural strength, while the delamination and local buckling failure occupied the main position. Interlaminar shear strength (ILSS) of the FMLs with surface-coated pretreatment was higher than that of the untreated specimens. The applied load was effectively transferred to the carbon fibers via polyimide resin. Then, the axial load was transferred to the adjacent fibers having the same orientation. The ILSS of unidirectional layered FMLs had the highest value, while that of FMLs with carbon fibers laminated at +/- 45 degrees was relatively low. The interlaminar shear fracture tended to occur inside the layers oriented in the direction of maximum load or in the vicinity of such layers.