Microstructural analysis in asymmetric and un-balanced composite cylinders damaged by internal pressure

Damages in matrix and in fibre has been studied in asymmetric and un-balanced composite cylinders that were loaded to failure in mode 3 (unrestrained-end) internal pressure, developing an uniaxial state of stress, specifically hoop stress. The samples tested, in a total of five cylinders, were collapsed by internal pressure of 15 MPa. Optical and scanning electron micrography of fractured surfaces of the cylinders are presented and they show that the failures occurred by matrix failures, as debonding, transversal cracks and delamination and fibre failure, as transversal and longitudinal failures. The fracture types and modes were also determined.