Toughness and fracture mechanisms of glass fiber/aluminum hybrid laminates under tensile loading

Tensile properties and fracture toughness of monolithic aluminum (At), glass fiber reinforced plastics (GFRPs) and glass fiber/aluminum hybrid laminates (GFMLs) were examined in relation to the fracture processes of plain coupon and single-edge-notched specimens. Elastic modulus and ultimate tensile strength of GFMLs showed characteristic dependences on the kind of At, fiber orientation and the Al/fiber layer composition ratio. Fracture toughnesses K-C and G(C) of A-GFML-UD were comparable to those of GFRP-UD and were much superior to monolithic Al. However, GFML with a transverse crack parallel to the fiber layer deteriorated largely in toughness. Microscopic observation of the fracture zone in the vicinity of the crack tip revealed various modes of micro-cracks in the respective layers as well as fiber fractures and delamination between fiber/Al layers. Such damage advances in GFMLs dependent on the orientation of the fiber layer and the Al/fiber composition ratio strongly influenced the strength and toughness of GFMLs.