Failure Analysis of Single and Double Bolted Joints for Composite Laminates

The paper presents study of failure initiation and complex failure mechanisms in bolted joints for fiber reinforced composite laminates using two different progressive damage models simulated through combination of FEA package ABAQUS (R) and FORTRAN. Maximum stress failure criteria and Yamda-Sun failure criteria are used along with different (compatible) sudden material degradation rules for identification of initial damage as well as detailed study of damage progression in the composite laminates with single bolted and double bolted joints having different geometries and different bolt arrangements. Selection of numerical models was based upon possibly simple and conservative approaches to save computation time as well as to predict safe values of joint strength. Both numerical models, programmed in FORTRAN, were simulated with and without assembly clearance as well as with different design parameters including margin distance, end distance, pitch distance, array pitch distance and the models found to be capable of tracing failure onset in all FE models and provided a very good understanding of failure mechanisms. Static strength prediction by both numerical models had an excellent agreement with each other for all the specimens. Though the static strength prediction by proposed PDMs is reasonably less from experimental value but the error in simulated values and experimental data is found to be very stable. Apart from the stability of error, excellent agreement has been found in the tendency of numerical model predictions to the scattered experimental data. The study also has a great potential to provide a strong basis for a very realistic and computationally inexpensive advanced PDM for bolted joints in composite Laminates as well as an easy and simple tool for comparing different laminate geometries and bolt arrangements.