Surface characterization and adhesive bonding of toughened bismaleimide composites

The use of composite materials in structural applications requires that they be joined or fastened in some manner. The objective of this research was to obtain an improved understanding of the factors which contribute to bond strength and durability in adhesively bonded bismaleimide matrix composites. Composite surface pretreatments included solvent wipe, grit blast, peel ply and gas plasma treatment. The results of lap shear and wedge testing in ambient, hot/dry, hot/wet and chemically aggressive environments were correlated to the surface composition after pretreatment as measured by X-ray photoelectron spectroscopy, ion scattering spectroscopy and contact angle analysis. The topography of the pretreated composite surfaces was analysed by scanning electron microscopy and profilometry. Solvent wiping was not effective in removing processing contamination and resulted in poor bond strengths. Peel ply and oxygen plasma pretreatments provided good initial bond strength as well as superior hot/wet durability; however, grit blasting was detrimental to both strength and moisture resistance.