Bending in two planes of unidirectional composite laminates

Abstract

In this work bending in two planes of long fiber composite laminates is proposed as a test method for knowing the behaviour of this material in case of combined loads. Different samples have been manufactured and tested using carbon/epoxy T6T/F593 material. Three cases have been considered dendending on the value of the ratio between normal stress in fiber direction and normal stress in direction perpendicular to fibre: less tan 1, equal to 1 and greater than 1. In all cases failure has been related to matrix failure, being a linear relation between stress and deformation until failure. Stress values have been analized by three failure criteria: Rankine, Tsai-Wu and maximum strain energy. Rankine criteria fits well the first two cases. The parameter of Tsai-Wu criteria between normal stresses in fiber direction and normal stresses in direction perpendicular to fibre has been obtained using experimental results. When stress in fiber direction is much greater than stress in direction perpendicular to fiber, this small stress can be ignored in the calculus of maximum strain energy.

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