Analysis of the hybrid composite materials reinforced with natural fibers considering digital image correlation (DIC) measurements

The literature is quite lacking in terms of the values of transverse contraction coefficients (Poisson's ratio) corresponding to the hybrid composite materials whose layers are reinforced with different materials. The main objective is the using of the digital image correlation (DIC) method in order to characterize the mechanical properties under tensile tests in case of four kinds of composite materials: flax/epoxy composite; jute epoxy composite; flax/glass/epoxy hybrid composite; glass/jute/epoxy hybrid composite. The properties were determined both in warp and weft directions in the case of the flax reinforced composites because the flax yarns are different on these directions. Full-field strain measurements including longitudinal strain and transverse strain were performed using two point tracing mode (optical extensometer) from DIC method, which further determined the Poisson's ratio of the tested materials. It is shown that the reinforcing of the top and bottom shell layers with glass fabric leads to the decreasing of the Poisson's ratios in comparison with the composites reinforced just with natural fibers. Tensile test gives the basic properties such as Young's modulus E, tensile strength. Another objective of the work was to use both analytical model and numerical model in order to validate the accuracy of the experimental results. These results provide important reference and basis for further study of the mechanical behavior in case of the composite materials reinforced with such natural fibers (flax, jute).