Canola Fiber as Reinforcement for Composites: Effect of Fiber Extraction and Processing Method on Fiber Properties, Nonwoven Manufacturing, and Composite Properties

ABSTRACT Canola fibers obtained from discarded stalks through various processing methods, including water‐retting and field‐retting followed by mechanical decortication and enzymatic degradation, were utilized as discontinuous fibers to manufacture preforms via needle punching process for composites. The enzyme‐treated canola fibers exhibited higher density and percentage cellulose content than water‐retted and field‐retted fibers. Both the average tensile modulus and strength of water‐retted fibers exhibited approximately 94% increase after enzyme treatment, while the properties of field‐retted fibers were observed to fall in between water‐retted and enzyme‐treated fibers. The volumetric flow rate in mats decreased with increasing fiber length and decreasing fiber diameter. For a given fiber length, water‐retted canola fiber composite with a V _f of 7.9 ± 0.7 exhibited a longitudinal tensile modulus ( E _L ) of 3.7 ± 0.6 GPa and strength ( σ _L ) of 7.4 ± 0.8 MPa, and enzyme‐treated composite with V _f of 24.8 ± 1.9 exhibited E _L of 15.9 ± 1.2 GPa and σ _L of 32.6 ± 2.8 MPa. The field‐retted composite exhibited a V _f of 19.4 ± 2.8, an E _L of 11.3 ± 0.7 GPa, and a σ _L of 10.9 ± 0.4 MPa, lying in between water‐retted and enzyme‐treated composites evaluated for the same fiber length. The difference in longitudinal (15.9 ± 1.2 GPa) and transverse (12.8 ± 0.6 GPa) tensile modulus of the enzyme‐treated composite indicates the preferential alignment of fibers in needle‐punched mats. Needle punching also resulted in a reduction in diameter distribution in the mats, contributing to an increase in fiber modulus, as well as the tensile modulus of composites. Enzyme‐treated canola fibers exhibited the highest surface roughness, and the composites exhibited strong fiber‐matrix interface, as evident from the fractographs.