Quasi-static indentation and impact in glass-fibre reinforced polymer sandwich panels for civil and ocean engineering applications

Abstract

Sandwich structures comprising glass-fibre reinforced polymer faces and low-density core constitute an efficient and versatile constructive system for civil and ocean engineering structures. However, being multilayered with relatively soft core materials, they are particularly susceptible to damage under concentrated loads. Whilst numerous studies exist on the indentation and impact behaviour of sandwich composites, the great majority considers the thin-skinned laminates used by the aeronautical industry. To mitigate the lack of studies on the significantly thicker and more robust civil and ocean engineering sandwich laminates, the quasi-static indentation and low-velocity impact behaviour of such panels is experimentally studied. Three types of core materials (polyurethane and polyethylene terephthalate foams and end-grain balsa) and five different indenters, of varying shape (hemispherical versus flat) and diameter (10, 20 and 30 mm), are considered. Flat and larger indenters required higher loads and energies for first damage and perforation. The first damage and peak resistance values of the polyethylene terephthalate panels were, respectively, 15 and 8% higher than in the polyurethane panels; for the balsa panels, such figures were 20 and 10%. The polyurethane panels showed the highest energy absorption capacity. Predictions of first damage resistance given by two analytical models (for flat and hemispherical indenters) were assessed against the gathered experimental data. The obtained predictions were reasonably accurate, but indicate a need for further calibration, mainly concerning the effects of core material.

Experimental study on the behaviour of grid-scored foam-cored sandwich composites under low-velocity and quasi-static punch shear loads

“…The onset of damage occurs with the linear form change in the graph. 38,39 However, the end of the elastic region cannot be determined at 150 J impact energy. The contact force increased until the top face sheet was completely perforated.…”

Review of balsa core sandwich composite structures

“…Using a steel ball, it was found that the deformation resistance of the balsa was equivalent or slightly higher than other core materials (such as PVC and Nomex) that were studied. Similarly, Garrido et al [207] found that the indentation resistance of a sandwich structure with a balsa core was superior to polymer foam of near-equivalent density. Garrido and colleagues reported that the indentation stiffness and loading resistance were higher and the out-of-plane displacement of the facesheet pressing into the core was lower for the balsa core sandwich structure.…”

“…Many studies have compared the low energy impact response of sandwich structures with a balsa core with other types of core material [100,102,195,196,198,[201][202][203][205][206][207][208][209],…”

“…Most studies of the indentation properties have been performed on sandwich structures with foam cores [225,226,[230][231][232], with only a few studies into balsa core materials [31,43,207]. Armstrong [43] performed the first published experimental study into the indentation resistance of balsa core sandwich structure.…”

Damage evolution in sandwich components at different extreme temperatures

“…Garrido et al. 13 discuss about sandwich panels for civil and ocean engineering applications comprising glass-fibre reinforced polymer faces and low-density core producing an efficient and versatile constructive system for civil and ocean engineering structures. Impact tests have been conducted varying impactor shape and damage resistance has given by two analytical models.…”