Toward toughness improvement of foam core sandwich panel inserts through an energy approach

Abstract

In an effort to increase junction toughness in foam core sandwich panels, improved designs of revolution inserts are detected through a simple energy approach. The main idea of this numerical study involves lowering the small-crack thermodynamic driving force using concepts of finite fracture mechanics and asymptotic expansion methods. For panels subjected to prevalent bending loads, an in-depth description of the strain energy triggered by the leading stresses over open sets, spanning areas where the insert, foam core, and face sheets meet shows that the potentially toughest designs are those scoring the highest stress singularities; in contrast, geometries inducing stress smoothing result in no appreciable improvement. The impact of stress singularities was assessed using hexahedral-enriched finite elements whose approximation space density is increased through Lekhnitskii–Stroh eigenmodes. The proposed approach allows us to bypass the meaningless point-wise stresses owing to the lack of any representative elementary volumes within the investigated areas.