Failure particularities of adhesively bonded joints between pultruded GFRP composite profiles

Abstract

The failure particularities of the adhesively bonded joints between fibre reinforced polymer (FRP) composite elements represent a set of critical parameters in assessing the performance of these systems. If the failure process is not properly evaluated and controlled, it can lead to significant decrease of the overall efficiency of the joint. Usually, if the bond length is greater than the effective one, the failure process for these types of joints can be either progressive, if the initial failure is initiated in the adhesive layer, or brittle, if the failure occurs in the FRP elements. The ultimate failure occurs if any stress or strain component reaches a limit state, referring to the components (adherents and adhesive) or to the interfaces between them. This paper presents some particularities related to the failure process of the adhesively bonded joints between pultruded glass fibre reinforced polymer (GFRP) composite members. The results were obtained through a complex experimental program conducted at the Faculty of Civil Engineering and Building Services from Iasi, where the structural behaviour of adhesively bonded single lap joins (SLJ) and thick adherents' joints (TAJ) between pultruded GFRP composite flat profiles was studied. For the experimental program, 30 specimens were prepared by varying the connection type (SLJ, TAJ), the bond length (70, 100, 150 mm), the adhesive type and its thickness (1, 2, 3 mm). All specimens were loaded in axial tension, up to failure and the characteristic failure modes were investigated by in-depth microscopic analysis of the failure surfaces.