Clamp Effects in Fiber Testing

Abstract

A probabilistic model for the tensile strength of brittle fibers is presented and related to present conventional testing The relationship of fiber flaw structure to the statistical strength is discussed The probabilistic effects of the clamp on fiber tensile testing at various gauge lengths are treated. Examples using Weibull flaw structure and simulated clamp conditions are provided to demonstrate the marked effects of the clamps on expected tensile test results at “short” gauge lengths. It is shown how the Weibull strength distribution can be modified to include clamp effects when used in conjunction with tensile test data. The effect of discarding the data from fibers that fail within the clamp is also examined. Suggestions for future testing are made.