Safety Enhancement of Composites Via Periodic Proof Testing

The development of new composite materials, which lack the historical field data base, has led to the need for an accelerated life testing method applicable to composites. Accelerated life testing by increasing the sustained stress levels requires the modeling and validation of a strength-life relation. Proof testing of composite fibers by over-loading is one step in the understanding of the relationship. It is also important in the reliability and safety assurance in deployment of composite structures. A parametric study examined the strength-life relation of composite fibers and a methodology to analyze the fiber failures after proof testing. The fiber statistical strength was modeled by a probability of failure model while a deterministic approach was taken considering individual fibers and the associated life reduction each fiber experienced during the proof testing procedure. Also studied was the distribution of the first failure to occur after proof testing in order to understand the effects of the sustained load and the proof load on fiber life. Composite fiber reduced life fractional life distribution.