EXPERIMENTAL STUDY OF COMPOSITE PATCHES SUBJECTED TO A THERMAL LOADING

Composite patches are used in several fields of engineering such as civil engineering [1] or aeronautics [2]. Designing at best the bonded joint between substrate and composite patch is a key-issue because a correct loading transfer between both components must be insured in practice. The present work deals with the mechanical response of the bonded joint when some temperature variations take place. In aeronautics, bonded joints are indeed subjected to temperatures which lie between 100°C and-50°C. The difference of the coefficients of thermal expansion (CTE) between the metallic substrate and the composite induces some shear stress peaks in the adhesive, especially near the free edge. These shear stress peaks are a consequence of the load transfer mechanism between metallic substrate and composite patch. Some well known theoretical models are available for describing this load transfer mechanism owing to a thermal load [3]. To the knowledge of the authors, all these approaches are unidimensional and cannot take into account two-dimensional effects due for instance to the difference of Poisson’s ratios and the difference of CTE in the transverse direction. The aim of this work is to compare some results obtained during a thermal test with their numerical counterparts. A rectangular carbon/epoxy patches is first bonded on each side of an aluminium specimen (see Figure 1). The specimen is then cooled with a refrigerator and its averaged temperature reaches 5°C. Once the temperature i