Structural Health Monitoring of Multifunctional Fibre Metal Laminates under Mode I Loading

Abstract

Delamination is one of the most common degradation mechanisms in fibre reinforced polymer (FRP) composites and occurs due to low interlaminar strength. Such defects are difficult to detect and yield often to catastrophic failure of the composite. In this work a new approach for structural health monitoring (SHM) of fibre metal laminates (FML) for structural applications is investigated, which does not require additional sensors. Therefore, FMLs consisting of glass fibre reinforced polymer (GFRP) with different metal plies are manufactured by the resin transfer moulding process. The interlaminar fracture toughness G (Mode I) is determined and the capacitance change between the metal plies during crack propagation is measured insitu. Within one FML configuration, a metal sheet is applied additionally, which undergo a pre-treatment before application, to improve the mechanical adhesion of the metal/matrix interface bond. Metal sheets are conventionally used in FMLs to improve the mechanical performance such as the bearing behaviour. The experimental test results show a high potential detecting defects in FMLs. Delamination, which occurs between the fibre/matrix interface, can be electrically detected using the capacitance measurement. The FML with the surface structured metal sheet demonstrates promising results for designing tough composites for structural applications. The fractography demonstrates a higher interfacial bonding between the metal sheet and matrix compared to the glass fibre/matrix interface. Consequently, the pre-treated metal leads to higher resistance against delamination in comparison with the GFRP layers.