Two-way bending behavior of 3-D GFRP sandwich panels with through-thickness fiber insertions

This paper presents the details of a research program that was conducted to evaluate the two-way bending behavior of 3-D glass fiber reinforced polymer (GFRP) sandwich panels. The panels consist of GFRP skins with a foam core and through-thickness fiber insertions. While the behavior of these panels under one-way bending is relatively well understood the behavior under two-way bending has not yet been investigated. An experimental program was conducted to evaluate the effect of the fiber insertion pattern and the panel thickness on the two-way bending behavior under the effect of a concentrated load. The experimental results were used to verify a non-linear, static finite element model which was used to introduce a simplified method to predict the behavior. The measured and predicted responses indicate that at lower deflections the panel behavior is dominated by plate bending action while for higher deflections membrane action dominates. The finite element analysis was extended to study the effect of different parameters which were not tested in the experimental program. The parametric study indicates that increasing the relative flexural or shear rigidities of the panel alters the behavior towards the plate bending mechanism thereby reducing the percentage of load carried by membrane action.