چكيده به لاتين
Fiber metal laminates (FMLs) are hybrid composite materials composed of several thin metal sheets and composite layers that are joined. These structures possess properties such as high fatigue resistance, high impact resistance, and high energy absorption, which have led to their increasing use across various industries. However, despite these applications, FMLs are prone to failures that reduce their mechanical properties. Failure modes in FMLs include damage in composite layers, damage in metal layers, and delamination between layers. This thesis presents an analytical model for predicting damage in FMLs under static loading, including matrix cracks in composite layers, plasticity in metal layers, and delamination, along with calculations of the residual mechanical properties following these damages. The FML damage model is developed using variational principles, considering boundary conditions, loading, and equilibrium conditions in the FML layers. The model enables the extraction of stress distribution in the metal and composite layers within a unit cell confined between two cracks in a 90-degree composite layer. To predict the damage, the energy criterion was used based on the energy release rate. In this model, the interaction of metal and composite layers was also considered. Using the analytical model, the effects of factors such as crack distance, applied stress, and layer thickness on stress distribution and plasticity of metal layers are investigated. To validate this model, numerical simulations were performed using Abaqus finite element software, with results showing good agreement with the analytical findings In the following, experimental tests were conducted to investigate the initiation and growth of damage in FML, and all stages of damage were recorded using a camera in relation to the stress-strain curve obtained from the tensile test. Tensile tests were performed on Reinforced Aluminum Laminates (CARAL). The first damage mode observed during the tensile testing of [AL/903]s and [AL/902]s laminates was metal plasticity, followed by microcracks in the composite layers. With the continued loading, the microcracks turned into matrix cracks until the matrix cracks reached saturation. Consequently, delamination between the carbon/epoxy and aluminum layers was observed. The tensile test results indicated degradation of the composite layers, followed by the metal layers and the overall FML sample. Lastly, the comparison of analytical and experimental results demonstrated a strong correlation between the findings.
