The impact resistance of fiber-metal laminates based on glass fiber reinforced polypropylene

The high velocity impact response of a range of fiber-metal laminates (FMLs) based on a woven glass fiber reinforced polypropylene and an aluminum alloy has been investigated. Tests on FMLs, based on 2024-O and 2024-T3 aluminum alloys, were undertaken using a nitrogen gas gun at velocities up to 150 m/s. The failure processes in the FMLs were investigated by examining the samples after impact and by sectioning a number of specimens through the point of impact. The impact response of these multilayered samples was also characterized by measuring the residual out-of-plane displacement of the targets after testing. Energy absorption in the FMLs occurred through gross plastic deformation, membrane stretching and tearing in the aluminum plies, as well as delamination, fiber fracture, and matrix cracking in the composite layers. In the multilayered FMLs, the permanent displacement at the perforation threshold remained roughly constant over a range of target configurations, suggesting that the aluminum layers deform almost independently through a membrane stretching mechanism during the perforation process. The impact resistances of the laminates investigated were compared by determining their specific perforation energies (s.p.e.), where it was shown that s.p.e. of several of laminates was almost three times that of the corresponding aluminum alloy. The perforation resistances of the FMLs as well as those of the plain composite were predicted using the Reid-Wen perforation model. Here good agreement was noted between the model and the experimental data for the range of laminates investigated here.