Numerical Analysis of Stiffener Runout Sections |
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Authors: | Andrea Faggiani Brian G Falzon |
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Affiliation: | (1) Department of Aeronautics, South Kensington Campus, Imperial College London, London, SW7 2AZ, UK |
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Abstract: | The recent trend of incorporating more composite material in primary aircraft structures has highlighted the vulnerability
of stiffened aerostructures to through-thickness stresses, which may lead to delamination and debonding at the skin–stiffener
interface, leading to collapse. Stiffener runout regions are particularly susceptible to this problem and cannot be avoided
due to the necessity to terminate stiffeners at rib intersections or at cutouts, interrupting the stiffener load path. In
this paper, experimental tests relating to two different stiffener runout specimens are presented and the failure modes of
both specimens are discussed in detail. A thinner-skinned specimen showed sudden and unstable crack propagation, while a thicker-skinned
specimen showed initially unstable but subsequent stable crack growth. Detailed finite element models of the two specimens
are developed, and it is shown how such models can explain and predict the behaviour and failure mode of stiffener runouts.
The models contain continuum shell elements to model the skin and stiffener, while cohesive elements using a traction-separation
law are placed at the skin–stiffener interface to effectively model the debonding which promotes structural failure. |
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Keywords: | Composites Delamination Debonding Stiffener runout Finite elements |
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