Rate-dependent shear deformation of ductile acrylic adhesive and its constitutive modeling

Recently, new types of structural adhesives with high ductility, as well as high strength, have been developed and are put on the market. Such high ductile adhesives usually have strong rate sensitivity in their flow stress. In order to investigate the rate-dependent deformation behavior of an acrylic adhesive, tensile lap shear tests were performed at various crosshead speeds at room temperature. Stress relaxation tests were also performed. In the tensile lap shear tests, it was found that the shear flow stress of the adhesive resin increased remarkably with increasing shearing speed. In the stress relaxation tests, the stress decreased rapidly at the early stage, and it gradually approached an asymptotic stress value. In order to describe such rate-dependent deformation characteristics of adhesive resin, a viscoplastic constitutive model is presented in this paper. The shear stress-strain responses, as well as stress relaxation behavior, predicted by the present model agree well with the corresponding experimental results.