Fracture behaviour and structural integrity of hemp fibre reinforced composites for low load-bearing aerospace applications

This paper presents a research undertaking on the mechanical performance of hemp fibre reinforced epoxy composites with special attention to tensile, flexural and impact behavior. The hand lay-up technique was used to produce laminates that were composed of different proportions of hemp fibres within the range between 25 wt% and 45 wt% in an epoxy base. The findings showed that composites with 35 wt% hemp fibre had the most balanced mechanical performance. This structure was found to have tensile strength of 67.3 MPa, tensile modulus of 2.85 GPa and an elongation at break of 5.2%, which is the best combination of strength and ductility. Flexural properties were no different and similarly, the 35 wt% hemp fibre reinforced composite showed better performance viz., a flexural strength of 99.7 MPa and flexural modulus of 3.9 GPa. Impact resistance, measured under the charpy test, was 9.4 kJ/m2 for the same composition (35 wt% hemp fibre) indicating better energy absorption ability. The observed improvement in the mechanical behaviour at 35 wt% fibre loading is due to the enhancement in the fibre-matrix contact and efficient stress transfer of the composite structure. These results define an improved reinforcement level that yields further performance improvements because of the potential agglomeration of fibres or loss of matrix continuity. The novelty of this work lies in the determination of the optimum loading of hemp fibre, which maximizes the strength, stiffness, and toughness, resulting in a balanced performance profile, optimized to work in structurally-lightweight applications. Further, the findings demonstrate the possibility of hemp fibre as a viable green reinforcement in semi-structural uses of hemp fibre in automotive body panels, lightweight construction, and framework structures.