Fatigue Properties of 2024-T3 Aluminium Specimens Reinforced With Composite Patches

The maintenance of aeronautic components is an important issue for military aircrafts. Fatigue damage generates crack initiation and growth which reduce the aircraft lifetime. For about thirty years, composite patches have been widely used to repair aeronautic structures [1]. An alternative to repair is to reinforce components before appearance of cracks. Such composite patches are bonded around the highly loaded zones, such as fuselage skins [2]. They enable to avoid or to delay the initiation and growth of fatigue cracks by decreasing the stress levels existing in the critical parts of structural components. From the fatigue point of view, a low decrease of the stress level in the considered zone may significantly increase the residual lifetime of the structure. It is therefore necessary to characterize the beneficial effect of composite patches in terms of extension of the aluminium substrate lifetime and to test small structures reinforced by a composite patch to validate the software developed to predict structures lifetime extension. This software is based on the use of cumulative damage models and multiaxial fatigue criteria. The aim of this work is to evaluate the actual lifetime increase of some aluminium specimens reinforced by composite patch and subjected to different loadings.