In-plane Shear Response of a Flax Fiber-epoxy Resin Composite Subjected to Repeated Loading and Creep-recovery Cycles

The present paper is aimed at studying the in-plane shear response of a flax fiber - epoxy resin composite laminate. Rectangular specimens, with �45� laminate orientation with respect to loading direction were used for the experimental procedure. Tensile testing up to failure allowed to extract the shear strain-shear stress curve, which have shown a linear domain, up to approximately 25 MPa, where a shear modulus was calculated, of 1.67 GPa and a Poisson ratio of 0.7, value which is typical for off axis laminates. Strain measurement during these tests, using Digital Image Correlation, have shown that, at high stress levels, concentrators occur in the specimen in the region of failure. Repeated loading tests have shown that the material stiffens approximately 9% when increasing loading speed, leading to conclude that a viscoelastic component of the deformation is present during loading. Repeated creep-recovery tests showed that, for longer periods of time, viscoplastic deformations appear as well, with an exponential evolution with respect to the creep duration.