Evaluation of Compressive Nonlinear Response of Unidirectional Carbon Fiber Reinforced Composites using a Modified Sandwich Beam Specimen in Flexure

Nonlinear mechanical behaviors of unidirectional composites were evaluated under compressive loading up to high-strain ranges using a sandwich beam specimen with the emphasis on the elastic material nonlinearity in the fiber direction. Specimen configuration and evaluation method, including material nonlinear effects, were proposed, and the compressive nonlinear behavior and strength of unidirectional carbon fiber reinforced composites were experimentally obtained. The measured compressive behaviors were compared with those from coupon-type compression tests of unidirectional and quasi-isotropic laminates. The compressive strength of unidirectional laminates evaluated, using the present sandwich method, was much higher than that of coupon specimens, whereas the failure strain of the former was almost identical to that of coupon-type quasi-isotropic laminates. The proposed method is expected to contribute to the accurate evaluation technology of compression behaviors of unidirectional laminates up to high-strain ranges.