Influence of Specimen Configuration and Size On Composite Transverse Tensile Strength and Scatter Measured Through Flexure Testing

The influence of specimen configuration and size on the transverse tensile strength of two glass/epoxy materials, and one carbon/epoxy material, loaded in three and four-point bending was evaluated. Transverse tensile strength was typically lower for longer span lengths due to the classical weakest link effect. However, strength was less sensitive to volume changes achieved by increasing specimen width. The Weibull scaling law typically over-predicted changes in transverse tensile strengths in three-point bend tests and under-predicted changes in transverse tensile strengths in four-point bend tests. Furthermore, the Weibull slope varied with specimen configuration, volume, and sample size. Hence, this scaling law was not adequate for predicting transverse tensile strength of heterogeneous, fiber-reinforced, polymer matrix composites.