| Foam and honeycomb core sandwich composites are widely used in structural applications. Nevertheless, possibilities of core-to-face sheet delamination, crushing and buckling instability are major concerns. This study presents an innovative system for FRP panels designed to overcome delamination problems typically encountered in traditional FRP panels. The panels consist of GFRP laminates and foam core sandwich where top and bottom skin GFRP layers are connected together with through-thickness fibers. Addition of the through-thickness fibers increases the out of plane properties of the panel, delays delamination-type failures, allows low cost manufacturing and ensures full utilization of the panel strength. Fundamental material properties in tension, compression, flexure and shear are evaluated both experimentally and analytically. Failure modes and mechanisms are investigated. The influence of the panel thickness, through thickness fiber configuration and density and other parameters on the tension, compression, flexure and shear behavior of the panels will be discussed. Application of sandwich beam theories, Elementary Sandwich Theory and Advanced Sandwich Theory, are studied in the full behavior of the 3-D FRP sandwich beams. A finite element model is developed to be able to predict the behavior of sandwich panels with different panel thicknesses, through thickness fiber configurations, facing sheet thicknesses and different material properties. |
