Effect of Specimen Tab Configuration on Compression Testing of Composite Materials

Standard Test Method for Compressive Properties of Unidirectional or Cross-Ply Fiber-Resin Composites (ASTM D 3410) for compression testing of composite materials recommends that low-carbon steel or a glass/epoxy composite be used as the tab material, and that the tabs be tapered. However, many details remain unspecified. An analytical study of tab configurations was performed in the present study to determine the effect of type of tabbing material and tab-taper angle on the stress distributions within a unidirectional composite specimen in compression. More compliant tab materials and shallower tab-taper angles yielded less stress concentration in the tab-tip region of the specimen. Therefore, specimens with these tab configurations should yield higher measured compressive strengths since premature failure at the tab tip is less likely to occur. Although there are relatively few experimental data available for different tab materials and tab-taper angles, those that are available show the same trends as predicted by the present analytical study