An investigation of the skin/core bond in honeycomb sandwich structures using statistical experimentation techniques

Experimental design has been used to investigate the effect of processing parameters on the peel strength of Nomex honeycomb core/carbon fibre-epoxy prepreg skin sandwich panels, manufactured by vacuum bagging. The four processing parameters considered were: (i) consolidation pressure; (ii) temperature cure cycle; (iii) temperature ramp rate and (iv) vacuum pressure application time. Each parameter was considered at three levels. It was found that (ii) was the dominant parameter. Panels manufactured under the optimum combination of processing parameters gave a mean peel strength more than twice that of the worst panels. Qualitative microscopy has associated the higher peel strengths with larger, regular shaped adhesive fillets between honeycomb cell walls and skin laminate.