Damping Properties of Flax/Carbon Hybrid Epoxy/Fibre-Reinforced Composites for Automotive Semi-Structural Applications

Hybridization Effect on Interlaminar Bond Strength, Flexural Properties, and Hardness of Carbon-Flax Fiber Thermoplastic Bio-Composites

Hybridizing carbon-fiber-reinforced polymers with natural fibers could be a solution to prevent delamination and improve the out-of-plane properties of laminated composites. Delamination is one of the initial damage modes in composite laminates, attributed to relatively poor interlaminar mechanical properties, e.g., low interlaminar strength and fracture toughness. This study examined the interlaminar bond strength, flexural properties, and hardness of carbon/flax/polyamide hybrid bio-composites using peel adhesion, three-point bending, and macro-hardness tests, respectively. In this regard, interlayer hybrid laminates were produced with a sandwich fiber hybrid mode, using woven carbon fiber plies (C) as the outer layers and woven flax fiber plies (F) as the inner ones (CFFC) in combination with a bio-based thermoplastic polyamide 11 matrix. In addition, non-hybrid carbon and flax fiber composites with the same matrix were produced as reference laminates to investigate the hybridization effects. The results revealed the advantages of hybridization in terms of flexural properties, including a 212% higher modulus and a 265% higher strength compared to pure flax composites and a 34% higher failure strain compared to pure carbon composites. Additionally, the hybrid composites exhibited a positive hybridization effect in terms of peeling strength, demonstrating a 27% improvement compared to the pure carbon composites. These results provide valuable insights into the mechanical performance of woven carbon-flax hybrid bio-composites, suggesting potential applications in the automotive and construction industries.

Application of Carbon-Flax Hybrid Composite in High Performance Electric Personal Watercraft

Within the herein presented research, we studied the applicability of flax fabrics for composite parts in personal watercrafts in order to enhance damping of vibrations from the engine and noise reduction (which is relatively high for contemporary carbon constructions). Since the composite parts are intended to be exposed to humid environments requiring high levels of mechanical properties, a carbon-flax composite was selected. Samples of carbon, fiberglass, flax, and hybrid carbon-flax twill and biax fabrics were subjected to tensile and three-point bending tests. The mechanical properties were also tested after exposure of the samples to a humid environment. Damping was assessed by vibration and noise measurements directly on the complete float for samples as well as real parts. The hybrid carbon-flax material exhibited lower values of tensile strength than the carbon material (760 MPa compared to 463 MPa), but, at the same time, significantly higher than the other tested materials, or flax itself (115 MPa for a twill fabric). A similar trend in the results was observed for the three-point bending tests. Vibration tests and noise measurements showed reductions in vibration amplitude and frequency when using the carbon-flax hybrid material; the frequency response function for the watercraft part assembled from the hybrid material was 50% lower than for that made of carbon. Testing of samples located in a humid environment showed the necessity of surface treatment to prevent moisture absorption (mechanical properties were reduced at minimum by 28%). The tests confirmed that the hybrid material is satisfactory in terms of strength and its contribution to noise and vibration damping.

Mechanical Properties of Phormium Tenax Reinforced Natural Rubber Composites

The introduction of natural fibers as a filler in a natural rubber (NR) matrix can be of relevance for their eco-friendly and sustainable nature as the substitute for carbon-based fillers. In this work, short Phormium tenax fibers were introduced in random orientation into a NR matrix in different lengths (6, 10, and 14 mm) and various amounts (10, 20, and 30%, taking 100 as the NR weight). The composite was fabricated using a two-roll mill according to American Society for Testing and Materials (ASTM) D3184-11 standard. Several properties were determined, namely tensile and tear characteristics, hardness, and abrasion resistance. The results suggest that the shortest fiber length used, 6 mm, offered the best combination between loss of mechanical (tensile and tear) properties and hardness and the most acceptable resistance to abrasion, with the properties increasing with the amount of fibers present in NR. As a consequence, it is indicated that a higher amount of fibers could be possibly introduced, especially to achieve harder composites, though this would require a more controlled mixing process not excessively reducing tensile elongation at break.