Fracture behavior of Al/GFRP/Al sandwich panels under uniaxial static and impact tensile loadings

The present work aims to comprehensively evaluate the fracture behavior of sandwich panels made of fiber-metal laminates (FMLs) under static and impact tensile loadings. Smooth, cracked, and notched specimens are prepared for static tensile, mode I translaminar fracture toughness, and tensile-impact tests. The FMLs’ inner material is epoxy-reinforced by long glass fiber (FRP) and enveloped with 1050 aluminum plates. The investigation parameters comprise the number of layers, the insertion of the [90°] layers within [Al/0 ° /Al] and [Al/0°/0°/Al] FML specimens, the fiber volume fraction, the strain rate, and the lay-up technique. The findings illustrate that increasing [0°] layers or fiber volume fraction enhances all the mechanical properties determined through the abovementioned tests. Additionally, the fibrous polymeric core skinned by aluminum plates displayed two dissimilar types of intralaminar cracking, namely, matrix cracking, followed by plastic degradation within the aluminum plates that ends with a total split through aluminum plates, and interlaminar damage arising between the aluminum plates and the FRP core. Further, inserting [90°] layers into the middle or directly adjacent to the FML specimens’ skins reduced their strength and toughness under static or impact tensile loading and their mode I translaminar fracture toughness. The sandwich lay-up technique, providing a good bond between the core and the skins, demonstrated better performance than the hand lay-up, providing a perfect bond between them. Therefore, the lay-up of FMLs should adopt the sandwich lay-up technique.