On the Off-Axis Tension Test for Unidirectional Composites

The off-axis tension test was examined experimentally to obtain actual displacement fields over the surface of graphite-polyimide coupon specimens; the experimental results were compared with the approximate analytical solution of Pagano and Halpin and newly generated finite-element results. A new optical method of high-sensitivity moiré interferometry was used to determine the actual displacements to high precision. It is shown that the approximate analytical solution and the finite-element results compare very favorably with the measured centerline displacements in the test section, and the finite-element displacement fields provide excellent agreement with the moiré displacements throughout the specimen. Results are presented for a 15° fiber orientation and coupon aspect ratios of 5 and 15.