A finite element simulation and experimental validation of a composite bolted joint loaded in bending and torsion

The paper describes the FE modelling and experimental validation of a composite bolted joint loaded in bending and torsion. The selected material is a hybrid glass-carbon non-woven fabric in epoxy matrix; the manufacturing technology is hand lay-up with vacuum bagging. Following a material characterization run on standard specimens, six joints were subjected to monotonic or cyclic loading, followed by monotonic loading until failure. Results show that components exhibit lower reduction in stiffness and strength due to cycling compared to standard specimens. Also, the ratio between the maximum load for which no stiffness or strength degradation was observed in 106 cycles and the static ultimate load were higher for components than for specimens. The modelling activity focuses on the simulation of the monotonic test. Numerical results show a good correlation with experiments in terms of material stiffness in the linear range and in predicting the regions of failure as highly stressed areas. However, being the analysis linear, a quantitative correlation between calculated stresses and ply strength properties was only found for the first ply failure.