Influence of core properties on the failure of composite sandwich beams

Abstract

The initiation of failure in composite sandwich beams is heavily dependent on properties of the core material. Several core materials, including PVC foams and balsa wood were characterized. The various failure modes occurring in composite sandwich beams are described and their relationship to the relevant core properties is explained and discussed. Under flexural loading of sandwich beams, plastic yielding or cracking of the core occurs when the critical yield stress or strength (usually shear) of the core is reached. Indentation under localized loading depends principally on the square root of the core yield stress. The critical stress for facesheet wrinkling is related to the core Young's and shear moduli in the thickness direction. Experimental mechanics methods were used to illustrate the failure modes and verify analytical predictions.

Flexural behaviour of hybrid sandwich panel with natural fiber composites as the intermediate layer

“…It was also clearly demonstrated that the core shear failure existed in both conventional and hybrid sandwich panel. This confirmed the previous finding which stated that core failure due to shear is a common failure mode in a sandwich structure [2,42].…”

“…Figure 3 The results also confirmed the previous finding which stated that hybrid sandwich panel with intermediate layer was superior than an aluminium equivalent structure and sandwich panels that consisted of skins and core only [27]. The failure of sandwich panel can be caused by various mechanisms within the constituent materials [2,42]. If a low density foam core is used in a sandwich panel, it is very likely that they will fail either due to indentation or core shear [27].…”

“…Considering the typical failure for the conventional sandwich panel which was a shear failure of the core as commonly observed for the sandwich structure [2,42], the behaviour can be explained that once the failure occurred within the specimen, the aluminium skins tried to return to its original length as the deformation was still in the range of its elastic region but the strains never returned to zero. This situation was actually not caused by a permanent set already established within the aluminium skin.…”

“…It seemed that the use of a thin aluminium skin with the thickness of only 0.5 mm had triggered this type of failure mechanism. In the case of the sandwich beam, indentation failure commonly occurs under the loading point where significant local deformation takes places of the loaded skins into the core, resulting in high local stress concentrations [42].…”

The Structural Behavior of Hybrid Structural Insulated Panels under Pure Bending Load

“…This phenomenon is normal in sandwich panel testing and analysis where the final achieved loads are determined by the mode of failure encountered. The failure mechanism of the sandwich structure that occur under bending load may arise from various mechanisms (Zenkert, 1995), including compression or tension failure of the skins, core shear, wrinkling, local indentation, debonding at the interface of core and facing, and global buckling (Daniel, 2009). More specifically, sandwich panels with foam core are likely to fail due to indentation, face wrinkling, or core shear (Mamalis et al, 2008), which may result in lower load carrying capacities.…”