Analysis of the effect of selected factors on the strength of adhesive joints

Abstract

Adhesive joining is one of the well-established methods for joining structural materials, however it was not until the rapid development in chemistry of adhesives that it could gain wide recognition. It is impossible to imagine any branch of modern industry without adhesive joining technology, which proves indispensible in: aircraft, aerospace, automotive or building industries. The importance of adhesive joining and adhesive materials in the economy of modern world is unparalleled. Among the factors of crucial importance to the strength of adhesive joining it is the preparation of adhered surfaces through proper treatment that appears to predominate. The issue is even more important as the decision regarding the surface treatment is undertaken by a technologist, whereas the other elements of joining technology, such as temperature, time or load applied during cure, and the joint seasoning time are known and specified by manufacturers for each adhesive. Another factor relevant to the strength of adhesive joints is the effect of cyclic thermal loading. The disparity in the coefficient of thermal expansion of adhesives and adherends and in their thermal conductivity results in the adhesive joint being subjected to cyclic internal stresses. Thermal fatigue of cured adhesives may implicate ageing processes, increase polydispersity of the substrate and consequently affect its mechanical properties. This paper presents the results of comparative analysis of the shear strength of adhesive lap joints. The tests were performed on samples following different surface treatment methods, which were subsequently subjected to thermal shock in the varying range of temperatures between -40 °C and +60 °C.