The 2-dimensioiial stiffness reduction in longitudinal loaded thin-walled tubes was investigated by experimental procedures and compared to an analytical displacement model. Two fiber-lay-ups, ±45° and ±55° tubes, were manufactured for testing. The tubes were step loaded, and normalized stiffness was plotted as a function of the normalized matrix crack density. The experimental results were analyzed and compared lo an analytical model (Vedvik, 1999). A model that was developed for predicting the stiffness degradation in angle-ply laminates, and which assumes transverse microcracks with equal spacing throughout the structure. Failure initiation took the form of distributed microcracks, which in turn coalesced into approximately evenly spaced macrocracks. As the damage grew, the stiffness of the damaged ply as well as the stiffness of the entire laminate was reduced. For both ±45° and ±55° tubes, the experimental tests corresponded well to the analytical model. According to the findings, one can conclude that the experimental results meet well with the analytical results. However, better agreement between experiments and current analytical model can be achieved by taking into account pre-existing imperfections in the structures.
展开▼
