Effect of through thickness metal layer distribution on the low velocity impact response of fiber metal laminates

The effect of distribution of aluminum layer through the thickness of fiber metal laminates (FMLs) on their low velocity impact response was studied. The FMLs were prepared using aluminum 2024-T3 layers (0.3, 0.4, 0.6 mm thickness) and glass fiber reinforced epoxy (two layers of 0° and 90° each) through hand layup followed by vacuum bagging. The four different layups considered had metallic layers placed at different locations through the thickness while maintaining the total metal layer thickness constant. The FMLs were subjected to low-velocity impact using a drop weight testing machine. The performance of FMLs was evaluated using different parameters such as maximum force, energy absorbed, damage degree, dent depth and maximum deflection. Among the four FMLs, it was observed that the FML 2/1-0.6 in which the composite layers were stacked together had lower levels of cracking and deformation and recorded the highest force for the same impact energy level, whereas the FML 4/3-0.3 in which two adjacent composite layers having different fiber orientations were separated by metallic layer recorded the lowest force and maximum cracking and deformation. The lateral spread of delamination and interlayer opening was comparatively greater for 2/1-0.6 when compared to 4/3-0.3, indicating that distributing the aluminum layers in the FML can decrease the lateral spread of damage within the FML.