MICROSTRUCTURAL ANALYSIS OF COMPOSITE TUBES MADE FROM BRAIDED PREFORMAND RESIN TRANSFER MOLDING

This paper investigates the manufacturing method and mechanical proper ties of composite tubes made from braided fiber preforms. The tubes mo lded by Vacuum-Assisted Resin Transfer Molding (VARTM) process with di fferent resins, fiber reinforcements and braiding architecture were te sted for weeping and burst strength. Both biaxial and triaxial braided fiber preforms were used. The failure modes of tubes made from these two braiding architectures were different. For biaxially reinforced tu bes, the initial cracks are aligned along the direction of the fiber t ows, while for triaxially reinforced tubes, the initial cracks along t he longitudinal direction appear first. Tubes with and without flanges were also fabricated. The strength tests indicated that the tube with flanges is much stronger than the one without flanges. Two theoretica l models based upon mechanics of material were employed to predict the mechanical properties. The pressure vs. deformation curves from the w eep/burst tests are consistent with the theoretical predictions in the elastic region.