Fatigue of multiple-row bolted joints in carbon/epoxy laminates: ranking of factors affecting strength and fatigue life

In this study, factors affecting the strength and fatigue life of multiple- row bolted composite laminates are ranked in order of importance using line ar regression analysis. Eight different factors related to the hole quality , geometry, material properties, laminate configuration, fastener type, and environmental conditions were included. Fourteen different specimen config urations were tested according to a design of experiments test-matrix. The results show that, of the investigated factors, the most significant are th e ratio of bolt diameter to specimen width, bolt type (flush- or protruding head), and ratio of hole diameter to laminate thickness. During fatigue lo ading (constant amplitude), specimen deflections were measured at maximum a nd minimum loads. Only small changes in deflection (less than 0.05 mm) were detected up to approximately 90% of the fatigue life. The deflections incr eased rapidly after that point. (C) 1999 Elsevier Science Ltd. All rights r eserved.