Delamination is one of the most common defects in FRP and occurs due to low interlaminar strength. Such defects are difficult to detect and lead often to catastrophic failure of the composite. In this work a new approach of a multi-functional FML for structural applications is investigated. The interlaminar fracture toughness is determined and the capacitance change between the metal plies during crack propagation is measured in-situ.
Metal sheets are embedded into the hybrid composites by means of lass fibre reinforced polymer (GFRP) ply substitution, avoiding any laminate thickening and providing high bearing and compression after impact (CAI) capabilities. The Al sheets (AA6082) are nanoscale sculptured to prevent premature delamination between the metal and the matrix, which commonly occurs in conventional FMLs. The laminates are manufactured by resin transfer moulding.
As a result the FMLs show drastically increased mechanical properties compared to conventional GFRP laminates for structural applications, achieving values for static pin-bearing (up to 21%), static bolt-bearing (up to 2%), resistance under fatigue pin-bearing (up to 100 times), resistance under fatigue bolt-bearing (up to 28 times) and CAI (up to 9%). The pre-treatment leads to a three-dimensional mechanical interlocking surface structure with highly improved inter-ply bonding between metal surface and resin. The fracture surface demonstrates that the adhesive bond between the nanoscale sculptured surface structure of the Al and matrix remains intact.