3D Numerical Simulation and Dynamic Analyses of Debonded GFRP Composite Slabs

Abstract

Fibre Reinforced Polymer (FRP) composites are continuing to gain eminence in structural and non-structural applications around the world due to their exceptional properties such as high strength to weight ratio, corrosion resistance, good thermal performance and reduction of carbon dioxide emissions both through its method of production and their effective thermal insulation qualities. The new generation composite sandwich developed in Australia, made up of Glass Fibre Reinforced Polymer (GFRP) skins and high strength phenolic core material, has a carbon foot print similar to timber, making it environmentally sustainable, in addition to highly improved strength characteristics. Due to complicated manufacturing methods, composite sandwiches can contain a variety of defects such as skin-core debonding. Depending on the loading conditions, this debond may propagate creating larger debonding areas, causing changes to the free vibration behaviour in addition to the strength reductions. Dynamic behaviour of sandwich panels containing debonding is more complex and a key factor limiting the prime usage of sandwich panels for structural applications. This paper deals with dynamic analyses of debonded GFRP slabs by developing 3D finite element models and conducting numerical simulations using Finite Element Software Program STRAND7. Developed models for fully bonded and debonded slabs have been validated using results from literature. The results show that the presence of relatively small debonding has an insignificant effect on the natural frequencies and associated mode shapes of the GFRP slabs considered. Interestingly, the free vibration characteristics are negligible for small debonds, in the order of 1% of the slab area, for the slabs considered in the analysis. Another stimulating observation is that the percentage increase in debonding size results in the appearance of local modes even for the lower mode numbers. Thus, by the observation of such swift variations in the modes, the severity of debonding may be evaluated.