INFLUENCE OF UNIDIRECTIONAL COMPOSITE COMPRESSION SPECIMEN THICKNESS AND LOADING METHOD

Ming Xie and Donald F. Adams

ABSTRACT

A combined numerical and experimental study was performed to investigate the effect of both specimen thickness and loading method on the compressive strength of a unidirectional fiber-reinforced polymer composite. A three-dimensional finite element analysis was used to study the stress distribution within a tabbed coupon specimen. The compressive load can be applied directly on the ends of the specimen, or be generated by longitudinal shear forces on the tab surfaces. The end loading method was found to be superior to the shear loading method, yielding a less severe stress concentration at the tab termination points and a similar stress concentration at the outer ends of the specimen. For thick specimens this benefit is more obvious and therefore a higher compressive strength should be obtained for a thick specimen subjected to end loading. Hercules AS4/3501-6 unidirectional carbon/epoxy composite specimens of various thicknesses were tested using both ASTM D3410, Procedure B (shear loading) and the Wyoming End-Loaded Side-Supported Test Method (end loading). The experimental data were found to correlate very well with the numerical predictions.