Flexural behaviour of a polymeric foam/glass-fiber composite: FE modelling and experimental testing

Abstract

The paper describes the experimental testing and FE modelling of sandwich beams under bending loads. The faces are made of glass fibres in epoxy resin. The core is a polymeric foam, with a net of resin walls perpendicular to the faces having a pitch of about 30 mm. Flexural tests were run on the face and core materials and the sandwich structure. For the sandwich, failure occurred due to core shear cracking. Simulation of flexural tests was run up to formation of the first crack within the core. 2D and 3D models of the sandwich beam were implemented. At first, models were validated by comparison with Pagano analytical elasticity theory and Swanson experimental and FEM data. Then, FE models were run to simulate the flexural test on the face and core materials and the sandwich. Comparison with experimental data was made on the value of specimen deflection at failure and of the strain measured in some experimental tests by means of strain gauges. For the sandwich, the model correctly predicted the area of crack formation within the core. In a second part of the work, alternative solutions for the resin-foam core were examined. Three types of foam were selected. Foams with increasing densities obviously exhibit greater mechanical properties. However, modelling showed that by increasing the core density other failure modes become possible, like face indentation. Finally, models were run to investigate the influence on flexural response of the experimentally observed scattering of the mechanical properties for face and core materials and of face thickness and resin wall position. The scattering of experimental results was then discussed.