Experimental and numerical investigation of sandwich structures under 4-point bending using progressive damage models

Sandwich structures are widely applied in aerospace, marine, transportation, and renewable energy industries, where enhanced strength-to-weight ratios and impact resistance are essential. However, accurate predictive models that capture their complex failure mechanisms are required. This study investigates the mechanical behavior of sandwich panels subjected to four-point bending (4PB) through both experimental testing and finite element modelling. The structures were composed of composite skins bonded to a polymethacrylimide (PMI) foam core (ROHACELL®) using the adhesive SikaForce® 7710 L100. Two composite skin configurations were considered. The numerical analysis was conducted using Cohesive Zone Models (CZM) to simulate adhesive behavior, a fractured foam model for the core, and the Tsai-Wu criterion for skin failure. The experimental-numerical comparison demonstrated a good correspondence between both outcomes, with deviations below 20% in critical parameters.