Investigating the damage-tolerant design of stiffener run-outs

In this work, the use of a compliant web design for improved damage tolerance in stiffener run-outs is investigated. Three different configurations were compared to establish the merits of a compliant design: a baseline configuration, a configuration with optimised tapering and a compliant configuration. The performance of these configurations, in terms of strength and damage tolerance, was compared numerically using a parametric finite element analysis. The energy release rates for debonding and delamination, for different crack lengths across the specimen width, were used for this comparison. The three configurations were subsequently manufactured and tested. In order to monitor the failure process, Acoustic Emission (AE) equipment was used and proved valuable in the detection and analysis of failure. The predicted failure loads, based on the energy release rates, showed good accuracy, particularly when the distribution of the energy release rate across the width of the specimen was taken into account. As expected, the compliant configuration failed by debonding and showed improved damage tolerance compared to the baseline and tapered stiffener run-outs.