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.

Abstract

This paper analyses the two-plane bending test to characterise the behaviour of unidirectional composite laminates. This test consists of a flat plate supported at four points to which a point force is applied at the centre. Currently, this configuration is not mathematically solved for orthotropic materials.

Initially, the displacements and bending moments produced in plates of isotropic material have been analysed by means of numerical simulation and analytical approach. The results obtained have been corroborated with other works published in the scientific literature.

Subsequently, the numerical models and the analytical development have been applied to plates formed with orthotropic material, in the configuration of the two-plane bending test. For this purpose, rectangular plates with different aspect ratio have been analysed in order to obtain different stress ratios along the fibre and perpendicular to it.

Finally, the results obtained both by numerical simulation and by the analytical approach have been compared with experimental tests carried out on unidirectional composite specimens made of epoxy matrix and carbon fibre.

Abstract

In this work, a new analytical procedure is developed to obtain the displacement field of a unidirectional composite plate subjected to bending in two planes. The analysed configuration consists of a plane plate supported at four points to which a point force is applied at the centre. The calculation procedure is based on the strain energy. The effects created by bending moments, torsional moments and shear forces in the plate have been considered. The results obtained analytically have been validated by comparing them with existing literature and with numerical simulations performed with the finite element software ABAQUS. High correlations have been obtained for the values corresponding to the vertical displacements in different alignments of points belonging to the plate, however, the same has not occurred with the distribution of moments.