Experimental and numerical investigation of flexural behavior of carbon fiber reinforced aluminum laminates

Fiber metal laminates (FML) combine the strength of carbon fiber composite layer with ductility of the aluminum layer for desirable mechanical characteristics. For these composites, progressive failure behavior can be complex and require attention. In this study, two carbon fiber reinforced aluminum laminates (CARRAL) with a 3/2 configuration, with aluminum in the outer layer for the first case and one with carbon fiber composite layer in the outer layer were prepared using a vacuum press without any adhesive layer between the layers—a significant departure from similar aerospace materials. Epoxy from the prepreg provides adequate adhesion during consolidation in these lower cost FMLs with a pressure level of 0.35 MPa. Three-point flexural behaviors of these two material systems were evaluated under static loading and failure modes were recorded. Primary failure modes observed were crack in lower aluminum layer, carbon fiber (CFRP) layer fracture and delamination between upper aluminum and CFRP layer. A major contribution of this study was to predict the flexural response of these FMLs using LS-DYNA finite element code. Modeling the progressive damage behavior of FML by considering stress based material failure and shear stress based delamination failure between adjacent layers were key aspects of finite element modeling. Predicted mechanical behavior matches well with experimental results and the progressive nature of damage are recovered in the model.