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The effects of specimen geometry on the Poisson's ratio of a quasi-isotropic carbon-fiber-reinforced polymer laminate were examined using compression tests. In particular, the divergence of the apparent Poisson's ratio from the theoretical value was experimentally determined for a decreasing specimen width/thickness ratio (b/t). The observed tendency was then confirmed by simulations using a finite element analysis (FEA). The FEA was performed using a 3D model of the specimens to investigate the strain and stress distribution. In the evaluation of the apparent Poisson's ratio, the strain in the width direction was shown to vary under the condition of low b/t. The FEA results revealed that changes to the width strain were caused by cross-sectional deformation under compressive loading, resulting from differences in layer angles and stiffness between the outermost and inner layers. [ABSTRACT FROM AUTHOR]

To propose a test method for the out-of-plane tensile modulus of laminated carbon fiber-reinforced plastics, 3-point bending tests using a laminated CFRP with the span direction coinciding with out-of-plane (through-the-thickness) direction were performed. It was demonstrated that the apparent bending modulus depends on the length of span to thickness ratio (L/t) and the tensile modulusEto shear modulusGratio (E/G). Sensitivity analyses were performed to select the length of span to thickness ratio in order to evaluate the bending modulus near material modulus. Consequently, it is predicted that the bending modulus performed with theL/t > 25 bending specimen is equivalent to tensile modulus, if the apparent bending modulus were evaluated from 1 to 15 GPa, while modified equations for the out-of-plane modulus of QI-CFRP laminates obtained by three-dimensional laminate theory were also derived. This modification took stress condition in consideration of the small in-plane size like bending specimens into account. Moreover, it is demonstrated that apparent bending moduli were evaluated between upper and lower bound solutions. The upper bound solution is an out-of-plane modulus based on existing three-dimensional laminate theory, and the other is modified out-of-plane modulus. [ABSTRACT FROM PUBLISHER]