Structural behavior of hybrid CFRP/steel bolted staggered joints

Abstract Although the staggered arrangement in bolted connections can offer an efficient area usage especially for narrow members, it has the most complex stress fields. In this paper, experimental tests were performed to identify the initial stiffness of the bolted staggered joints. A 3D finite element model was developed to analyze single and double lapped bolted composite plates. The current modeling technique was validated by comparing its results against earlier experimental and numerical findings. Different bolt arrangements, including the staggered arrangement, were examined and combined with other parameters such as number of bolts, clamping force, and friction coefficient. Experimental tests showed that the double lapped joints have a higher stiffness than that of the single lapped joints. The numerical results showed that in the absence of clamping force, part of the load was transferred by friction due to the effect of secondary stresses, which can be increased by increasing the friction coefficient. Furthermore, the staggered patterns produced horizontal forces that could cause cracks in the composite material if it was not taken into consideration during the composite laminates design.