Research On The Failure Of Composite Laminates Bolt-Joint

Considering the requirements of design and repair, masses of bolt joints are used in the structureof composite integral fuel tank, which is extraordinarily important for the safety and efficiency ofaircraft structures. To ensure the efficiency and safety of structure as well as to reduce the cost inexperiment, the development of the numerical simulation method for the mechanical connection ofcomposite material has been a key issue in the field of composite material structure technology. In thispaper, learning from the achievements by domestic and foreign researchers, based on the progressivedamage method, following researches has been conducted:(1) The characteristic and the failure mode of the mechanical connection of composite materialwas introduced, after which, a method for estimate the strength of composite joint based on theprogressive damage was put forward. With the3-D Hashin failure criteria, the damage process ofsingle-bolt connection in different load situation was exactly simulated. Compared with experimentaldata, a stiffness degradation model was brought up, and a corresponding coefficient of stiffnessdegradation and characteristic lengths as well.(2) A numerical simulation of terminal failure mode and failure strength of bolt-joint was carriedout in both tension and shear load situation. Compared with the corresponding experimental data,good agreement was reached between numerical predictions and experimental results in both terminalload and failure mode, by which, a proved numerical simulation method of fastener-connection wasestablished.(3) A selection of bolt-joint was proceed to provide advices for the design of fuel tank connectionin wing area by comparing the load capability and failure mode between T-joint and L-joint.