Burst Tests of Filament-wound Graphite-epoxy Tubes

Abstract

A test program was conducted to investigate the failure modes of undamaged and damaged graphite-epoxy cylindrical tubes subjected to internal pressure. Some tubes were intentionally damaged by either a longitudinal-line cut or a single-point impact. Both types of damage were intended to simulate fiber breakage caused by a local damage. The objectives of the program were to investigate the failure modes of graphite-epoxy cylindrical tubes subjected to internal pressure, with and without local damage, and to qualitatively determine the relative burst pressure degradation associated with preexisting local damage to the tubes. A high-speed motion analyzer was used to record images of the fractures. The images provide the failure mode information that was not available in existing literature. Testing was conducted under three conditions: hydraulic pressurization, pneumatic pressurization with solid inserts, and pneumatic pressurization with inert propellant inserts. A tube with a longitudinal cut can fail by three different modes: a local leakage mode, a bursting mode with fracture initiating from the cut, or a bursting mode with complete tube disintegration. In testing of impact-damaged tubes, the results show that the burst pressure decreases with increasing impact load. At an impact load of 1493N (335 lb), the burst pressure decreases by 33% compared to the undamaged condition.

Keywords

graphite epoxy tubes filament wound composites internal pressurization impact damage fracture

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