The Effects of Defects and Adherend Material on Adhesive Stress Distribution in Laminated Composite Tubular Joints Under Axial Tensile Loads

This study focuses on the effects of an adhesive defect and adherend type and material on stress distribution in laminated composite tubular joints sustaining axial tensile loads. The tubular joint comprised two hollow tubes joined by a layer of adhesive to form a simple lap joint, hosting a cylindrical void or debond. The adherends were assumed to be either isotropic, quasi-isotropic, orthotropic, or transversely isotropic. Applying linear elasticity, the equilibrium equations were derived and solved using the differential quadrature method. Furthermore, finite element models of the joint were prepared and solved to support the semi-analytical solutions. Good agreements were observed between the results of both methods. Based on the results, for a defect-free joint with a bond length of 30 mm, nearly 80% of the bond length experienced zero peel stress (σr), while this value was about 20% for the peak interfacial shear stress (τrx)max. Additionally, among the selected types of glass/epoxy outer tubes, the [08] lamination setup minimized (τrx)max while (σr)max was the least for the quasi-isotropic arrangement of [0/90/-45/45]S. Moreover, replacing the aluminum inner tube with steel, reduced the tensile peak peel stress by 38% and increased the peak shear stresses by 12%. However, compared to a defect-free joint, a void/debond in the adhesive layer highly affected the magnitudes and locations of the adhesive peak interfacial shear and the tensile peel stresses. Additional results showed that in a defective adhesive hosting a void, the application of [08] transversely isotropic carbon/epoxy can reduce the adhesive peak shear stresses by 200% compared to glass/epoxy.