Alternatives for a hand lay-up composite structure: E-glass/epoxy adhesive joint or tapered laminate

Two alternative geometries were considered for the manufacture of a 6-mm thick component by band lay-up stacking of an E-glass-epoxy twill-weave laminate, with 50(±1) wt% glass fiber content. In the first case, two 3-plies laminates were bonded together using modified epoxy adhesive, using sand paper for surface preparation and compressing the adherents at 60°C during the cure cycle. In the second case, a tapered laminate was produced from a 5-plies laminate, introducing drop-offs on both sides of the outer ply, covering then the laminate with an additional ply. As a whole, the tapered laminate showed higher properties than the adhesive joint. In addition, tridimensional stress field present in resin pockets was demonstrated to be detrimental for the residual strength of tapered laminates.