Surface Pretreatments for Composite Joints: Study of Surface Profile by SEM Image Analysis

The main objective of this research was to obtain an improved understanding of the factors which contribute to bond strength in adhesive joints of carbon fiber/epoxy composites. For this, the most common surface treatments for composites were applied including grit blasting, peel ply and plasma. Also, the untreated adherends were analysed. The topography of the studied surfaces was analysed with a profilometer and through image analysis of scanning electron micrographs. Besides measuring the average roughness, other surface parameters were determined in order to characterise the shape, distribution, height and density of summits on the surfaces. In view of the results obtained, it was confirmed that average roughness alone was not sufficient to interpret the results; the adhesion between the adhesive and the adherends does not depend only on the mechanical interlocking effect. It was confirmed that plasma treatment provides the highest joint strength due to the higher surface energy of the composite when is treated by this method. In contrast, peel ply gives poor results. The joints whose adherends were treated by grit blasting also showed high strength values due to a high density of summits on the surface. (C) Koninklijke Brill NV, Leiden, 2010