Search

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. [ABSTRACT FROM AUTHOR]

The strength of filled bolt holes of composites is an important parameter in developing the bearing bypass envelope curves for bolted joint structures in engineering design. This paper presents the procedures of tensile failure strengths and damage for a laminate with a filled bolt hole. Tests of two different cases, open‐hole tension (OHT) and filled‐hole tension (FHT), were performed and repeated seven times, respectively. A new type of virtual testing based on the LaRC05 criteria coupling with XFEM crack technique was developed to predict and analyze the crack initiation and early propagation around the bolt hole in the laminates. Two analytical methods were also adopted to predict the residual strength for a laminate after drilling. The results show that the thinner sample would present a higher strength with the same material system. It is also shown that the virtual test can well capture the failure modes, revealing that the 0° fiber has a natural function of crack arrest, the 90° layers that are the fracture pioneers with matrix tensile failure trigger the fiber breakage of 0° layers, and the failure of 45° layers occurs at the last. Additionally, an interesting phenomenon is observed that the initial failure around the filled hole edge does not affect the structural stiffness. Finally, a good agreement is achieved among the experimental, analytical and numerical results. It suggests that the results could provide a valuable guidance for the design of multi‐bolted joint structure. [ABSTRACT FROM AUTHOR]