Off-axis Flexure Test: A New Method for Obtaining In-plane Shear Properties

Abstract

Off-axis three-point flexure test for unidirectional composites is proposed as a new method for obtaining in-plane shear modulus and in-plane shear strength. The method of determination of the in-plane shear modulus G_LT has been explained in a previous work where the displacement field of an off-axis flexure test was analyzed. In the present work, besides summarizing the calculation equations of G_LT, the condition of small displacements is analyzed. Otherwise, an error analysis is carried out in order to study the influence of the calculated value of G_LT on the other elastic parameters.

Normal and shear stresses in the fiber–matrix interface change from point to point in the specimen depending on the fiber orientation angle and specimen geometry. A critical point of failure that depends on the fiber orientation angle is determined and optimum conditions for obtaining in-plane shear strength are discussed. Experiments for different fiber orientations and geometric conditions have been carried out for IM7/8552 epoxy matrix based carbon fiber reinforced unidirectional composite material.

Keywords

in-plane shear strength in-plane shear modulus off-axis flexure unidirectional composite

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