Numerical modeling on load bearing and bypass behavior of bolted single lap joints of laminates

Bolted joints are widely used in aircraft structures. Proper design and accurate strength assessment of these joints are of great importance in aircraft design. In this paper, to investigate the mechanical behavior of single lap shear joints of carbon fiber reinforce plastic, four types of fastener of numerical model methods are developed. Based on the same principle of lap joint, different double bolt, and single-lap joint structures with three distinct width-diameter ratios (w/D) are designed and manufactured. Each specimen is loaded under tension until complete failure. The experimental results are used not only to verify the fastener models, but also to investigate the failure transformation induced from the composite load bypass and the bolt-hole load bearing. It is found that the increase of w/D, the failure model could transfer from the net cross section damage caused by load bypass to the bolt hole failure caused by load bearing. By comparison, the numerical results show that the Cbush+RBE3 model has high adaptability and good fidelity in elastic stage without increasing the model scale in terms of the level of details. To improve the accuracy in nonlinear stage, hole geometry details need to be considered. Additionally, single bolt is created to reveal the nonlinear deformation affected by laminate thickness. Three/four/five row of bolt models are used to show the bolt load distribution characteristics. Finally, the influences of the element size and the bolt modeling methods on the bolt load distribution are analyzed, respectively.