Experimental and numerical characterization of mechanical properties of hemp fiber reinforced composites using multiscale analysis approach

Synthetic fibers are mainly considered as a source of reinforcement in many composites that have been studied so far. As a continuous effort is being made in the entire world to develop more sustainable products and systems, fibers obtained from natural sources (hemp, flax, jute, etc.) are being considered as substitutes to the synthetic fibers which are commonly used these days. In this study, the tensile, flexural and interlaminar shear strength properties of hemp fiber composites, bonded with an epoxy matrix, are characterized. Three-point bending tests were conducted on the hemp fiber composites and their failure modes were inspected using micrographs and documented. The short-beam shear method was utilized to investigate the interlaminar shear strength of these composites. Hemp fiber composites were found to have considerably lower flexural strength as compared to typical glass fiber/epoxy composites. Lastly, multiscale analyses were performed for the tensile case to predict the response of these composites by conducting simulations at fiber tows and matrix level rather than using typical finite element approach of homogenized properties at ply level with Altair's multiscale designer software (MDS). In the multiscale macro-simulations, a unit cell with twill weave configuration was developed, and the response of the unit cell under tensile loadings was compared to the experiment results. Excellent Correlation was achieved between numerical and experimental results for unnotched tension/compression MDS macro-simulation. A parametric study was conducted to investigate the effect of fiber tow minor radius on the tensile response of the hemp/epoxy composites keeping rest of the geometric parameters of unit cell similar. The smaller minor tow radius predicted higher yield and ultimate strengths as compared to larger ones. A stochastic analysis was also performed to investigate the effects of variations in the geometric unit cell parameters on the young's modulus of hemp/epoxy composite.