Effect of Stacking Sequence on Compressive Strength Reduction of Aircraft Composite Structures

Abstract

Compressive strength reduction of composite structures due to notches or impact damage is an important factor for aircraft structure design. Compressive strength reduction is caused by stress concentration around notches such as skin manholes or impact damage due to tool falling during manufacturing. In particular, the compressive strength reduction due to the edge-on impact is large, so it is one of the most important issues for strength design of the aircraft. In this study, in order to evaluate the effect of stacking sequence on compressive strength after edge-on impact, edge-on impact survey test and compression after edgeon impact test using CFRP laminates with different stacking sequence were conducted. As a result, in the Soft laminate, including many ±45°plies, cracks due to edge-on impact spreading in the laminate thickness direction could be observed, and detectability of the damage was better than that of other specimens. And the residual strength after edge-on impact was improved in Hard3 laminate which retained laminate stiffness along the loading direction while suppressing the edge-on impact energy that necessary to apply the dent depth equivalent to the barely visible impact damage (BVID). These results show the possibility of improving the compressive residual strength by the optimization of stacking sequence.