Post-impact moisture absorption in hybrid glass, aramid, carbon/epoxy composites

Replacement of glass-fibre/polyester resin laminates, traditionally used in shipbuilding by advanced hybrid composites requires detailed knowledge about the behaviour of the materials in service conditions. In the present study the effect of impact on water absorption has been studied for hybrid aramid-carbon-fabric and aramid-glass- fabric/epoxy laminates as well as carbon and glass reinforced laminates for comparison. It bas been found that the protective layer of gelcoat (with a small opening) prevents the important moisture absorption of the laminates, consequently for unimpacted specimens the effect of conditionig in room and boiling water was confined to that of pure epoxy resin and no significant differences in the behaviour of different composites were found. For impacted specimens water absorption was highest for aramidglass and aramid-carbon - fibre/epoxy composites (3,1% and 2,9% respectively). Closure of impact induced cracks decreased the real differences between the weight uptake of different laminates. Preliminary tests of residual compression strength after impact (10 J) and conditioning (2,6% weight uptake) performed for glass fibre composites show that there is a reduction of initial compressive strength of 19% and 17%, respectively. Joint action of both impact and water resulted in 1/3 loss of materials compression strength.

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