Investigating failure in flax-polypropylene natural composites using discrete textile models and continuum damage mechanics approach

摘要

Natural fibre composites (NFCs) are currently applied primarily in secondary structural or non-load-bearing applications, such as in the door panels and underbodies of automobiles. However, improvements in processing and treatment methods for natural fibres point towards their future application to primary structural components. In this context, their fracture and progressive damage behaviour become important, and this paper aims to assess the applicability of anisotropic continuum damage modes to evaluate their failure behaviour under quasi-static tensile loading. The damage approach was applied to composites of polypropylene with unidirectional (UD) and woven flax fabric composites. Elastic properties, strength limits, and notched strengths were obtained for the composites, and notched strengths modelled analytically using the modified point stress criterion. Subsequently, the validity of a continuum damage model for predicting failure modes of NFCs was examined. Simulations were performed on a 0.22 volume fraction UD composite, and a 0.19 volume fraction woven composite. Predictions for notched strengths using the analytical models were good for the smaller radii, but under-predicted strengths for the largest radius, which could be due to the different failure behaviours of NFCs. Results from the damage simulations showed good agreement between the simulated and experimental loading curves for the initial portion of the loading curves. The results show that damage models could potentially be used for more accurate predictions of failure behaviour of natural fibre composites, aiding the design of high strength and fracture resistant structures incorporating such materials.