Analysis of Shear Properties of Bonded and Riverted Joints with CFRP Composite Tubes
AbstractCarbon fibre reinforced composites (CFRP) generate increasing interest automobile industry, especially for electrical and hybrid vehicles in recent years due to their high specific stiffness and specific strength to weight ratios, high fatigue properties and design optimisation in different directions as dictated of the structural component. Carbon fibre reinforced composites are generally 30% lighter than aluminium and 50% lighter than steel [1]. Fabrication of car components with composite materials, however, needs specially designed joints in assemblies of structural components. In this respect, joints have crucial importance because they act as a transfer member where high stress concentrations and potential failures can occur during fatigue life of joined structures [2]. The design of joints strongly depends on geometrical parameters, joint materials and their properties (stiffness, strength) and properties of fasteners (rivets, bolts, pins) and adhesive materials (epoxy). Lap joints were commonly characterised by different design factors in laminar composites. However, the limited numbers of study are available with these design parameters in tubular composites. Previous studies calculated theoretical analysis of tubular lab joints in tension load and investigated the effect of adhesive layer thickness in terms of shear and normal stresses. They showed the infinite number of shear and normal stresses in overlapping ends. However, most of the study was limited to isotropic material properties in FEM and analytical results [3, 4]. Jena and Pradhan were also applied FEM model adhesively connected joints on composite tubes in terms of thickness, overlap length and adhesive end fillets. They showed that optimum overlap length of 20-25 mm. The stress concentration values in CFRP composites were found less than isotropic material when an overlap length is more than to be of 20 mm. The optimum adhesive thickness also found to be 0,25 mm. The triangle and elliptical shape of end fillets of adhesive enhanced the joint strength [5].