Interlaminar Stresses at the Delamination Fronts in Tubular Adhesive Joints with Delaminated Composite Adherends

The use of composite materials has been extensively increasing in the recent decades, mainly due to their high strength and stiffness to weight ratios, as well as their non-corrosive attribute. Adhesive joints are used effectively to join composites to composites or to dissimilar materials. Components made of composites may contain some defects in the form of delaminations that may adversely affect their overall behavior and response when subjected to different loading systems. Interlaminar stresses (including out-of-plane stresses) are caused by the mismatch in material properties, especially in Poisson's ratio and the so-called 'coefficient of mutual influence' (between adjacent layers). The goal of this paper is to evaluate the interlaminar stresses that exist at the delamination fronts in a composite pipe, hosting a small delamination, adhesively bonded to an aluminum pipe. The aim is also to study the effect of various parameters (such as delamination length, depth, fiber orientation angles, and stacking sequence) that influence the performance, using the finite element method. The system is subjected to a torsional moment, which can be considered as a critical loading condition in tubular adhesive joints. Results of the study provide valuable information about the behavior of adhesive joints with delaminated composite adherends, and reveal the nature and distribution of interlaminar stresses along various delaminated fronts under torsional moments.