Literature Survey of Progressive Damage in Composite Bolted Joints

Joints are usually designed such that they fail in bearing mode, even though that does not result in an optimum joint. When joints fail in bearing mode the bolt is crushing the composite as the joint fails. The progressive failure redistributes load in the structure and joint such that progressive failure might stop due to other bolts taking more load. The failure process during bearing failure is complicated with crushing of hole surface, chip out, matrix cracking, fibre failure, delamination, kinking in 0o-plies, and major shear cracks. To model all the different kinds of failure going on simultaneously is very difficult and instead different failure criteria are applied and the material properties of the elements are adjusted when failure is predicted. Usually the material properties are reduced instantaneously to 10% of their original value. The obtained damage patterns do not predict the large shear cracks observed in experiments. In most cases the modelled load-deflection curves do not have the experimentally observed horizontal part at maximum load.