Progress Damage Analysis And Strength Prediction Of Composite Bolt Joint

Composite material has been widely used because of outstanding performance. However, theconnection issue of composite structure is increasingly prominent. To take full use of the compositematerial, the extensive research on current situation at home and abroad has being summarized, basedon which the following work has being done:Based on three-dimensional(3D) nonlinear shear Hashin material failure criterion the progressivedamage method(PDM) is built, direct reduction and exponential reduction based on energy releaserate material degradations have being coded for each user-defined subroutines materials (UMAT), thePDM is verified by experiment.To validate the UMAT and interaction for composite material mechanical joint, complete3Dfinite element models of single bolt double lab and single bolt single lab models are analyzed, whichshows the interaction defined in the model is correctly and UMAT is reasonable.By analysising stress distribution and bolt load distribution of different multi-bolt joints models,a simplified model for multi-bolt is established. Different thickness of lap plate have been analyzedwhich shows the stiffness ratio of lap plate and composite laminates has a significant influence on boltload distribution. Different parameters of ladder-type lap plate and lab plate with drop-off model areanalyzed whick shows using these types rationally can make a difference of bolt load distribution.The influence of bolts with different diameters on bolt load distribution and load carryingcapacity has been studied. The results shows the bolt under low load can undertake more afterincreasing diameter. It is also shows increasing diameter of the bolt under high load can undertakemore contributed by increasing contact area which increases the ultimate failure load.