A Modified Arcan Test for Mixed-Mode Loading of Bolted Joints in Composite Structures

摘要

A novel modified Arcan test rig has been developed for testing the combined loading performance of bolted joints in composite laminates. The fixture was designed to complement existing bearing test standards (ASTM D5961) and pull-through test standards (ASTM D7332). A mixed-mode loading fixture for bolted joints in composite laminates fills a crucial niche after it was identified that interactions between pull-through and bearing failure modes can potentially reduce the overall joint performance and lead to anti-conservative designs.The test fixture was benchmarked against ASTM standards and was found to reliably reproduce pull-through failure behaviour observed during D7332 (Proc. B) testing. Further work is underway to benchmark the new rig against D5961 (Proc. C).A test program is reported in which bolted joint specimens were loaded at various mixed-mode ratios between pure bearing and pure pull-through. It was found that the initial failure load joint well predicted by a quadratic mode-mixing rule. Ultimate failure load however, was considerably over-predicted by a quadratic mode-mixing rule which could lead to anti-conservative predictions, particularly for dynamic systems in which joints completely fail.Based on the success of the preliminary testing, there is a strong case for further development and benchmarking of the new test fixture. There is scope for this fixture to be added to the suit of accepted test standards for bolted joints in composite structures.