Asymptotic analysis of laminated composites with countersunk open- and fastened-holes

摘要

A linear stress analysis reveals singular stress fields at lamina (ply) interfaces in open- and fastened-hole problems, analogous to free-edge stress fields. An asymptotic analysis was performed in the vicinity of orthotropic ply interfaces at open- and fastened-hole edges to assess the power of singularity at critical locations. Three locations were examined through the thickness of the hole; vertical section (shank), countersunk section and intersection of the shank and the countersunk edge. The power of singularity was calculated around the hole edge at three countersunk angles (0 deg, 30 deg and 50 deg) and at three ply interfaces ([45/-45], [0/45] and [45/0]). In the open-hole case, the power of singularity at the vertical edge was weaker than 0.1 in all interface configurations and locations, and that at the 75 deg countersunk edge reached a maximum of 0.2876 at the [45/-45] interface as the countersunk angle increased. No singular root was found at intersection of the shank and any angles of the countersunk edges. In the fastened-hole edge case, the observed trends were largely opposite to the open-hole case. In the shank of the hole, the power of singularity reached 0.3010 at the [45/-45] interface, which was the strongest singularity found for all countersunk angles explored. The intersection of the shank and 50 deg countersunk edges exhibited the highest degrees of singularity of 0.7591 at the [45/-45] interface.