Experimental investigation and numerical modeling of the behavior of sandwich panels with grooved PVC foam cores and CFRP/GFRP facings

This work presents a thorough experimental and numerical investigation into the mechanical behavior of sandwich panels subjected to three/four-point bending, as well as flatwise and edgewise compression. The studied structure is designed for aerospace and marine applications, aiming to optimize the trade-off between weight and stiffness. The core consists of a 10 mm thick, grooved, closed-cell Airex C70.55 PVC foam. The skins are formed by three-layer laminates combining carbon fiber (CFRP) and glass fiber (GFRP) fabrics of various areal weights. The panels were manufactured using the vacuum resin infusion process with an epoxy matrix. Experimental results reveal that failure initiation consistently manifests as localized compressive wrinkling of the upper skin, which subsequently progresses into direct crushing beneath the load application points. These tests highlight the critical influence of the facing material and the orientation of the grooved core face relative to the loading direction. The sandwich panel with carbon skins (BMS 9 − 8 3 K-70) outperforms all glass fiber configurations, while the “Up” orientation (grooved face positioned in the upper zone) yields the highest flexural strength. This configuration increases the failure load and the apparent ultimate core shear stress by 24% to 38%, an effect attributed to the resin ribs formed in the grooves during infusion, which raise the local indentation resistance of the loaded face by about one order of magnitude. The experimental flexural stiffness ( \(\:{D}ₑₓₚ\) ) also exceeds the classical sandwich-theory prediction based on the facing modulus ( \(\:{E}f\) ). In parallel, a 3D implicit numerical model was developed in Abaqus. The Hashin progressive damage criterion was implemented to predict composite skin failure, while a Cohesive Zone Model (CZM) based on COH3D8 elements was used to model skin–core interface behavior and delamination. The resin-filled grooves are represented explicitly and the core is described by a hyperfoam model calibrated on compression tests. For the reference configuration (BMS 9 − 8 3 K-70 facings, “Up” orientation, three-point bending), the predicted load–displacement curve agrees with experimental data within 3% for the peak load and 6% for the initial stiffness, with predicted damage localizing at the observed transverse compressive failure of the upper skin.