The tensile strength of carbon fibre (CF) follows a “weakest link in the chain” model, which states that CF is only strong as the worst flaw that exist along the CF where it first undergoes failure when a load is applied. Such weak defective points arise on virgin CF as a result of the CF manufacturing process conditions, and on recycled CF from pyrolysis of composites. These defects result in deteriorated tensile properties of CF which limits potential applications and could be addressed by using an appropriate reinforcement to repair such defects.<br/>Covalent electro-grafting of polyacrylamide on CF surfaces is a successful approach to repair defective CF, which is extremely effective as the film formation originates at the surface and from within the defects and fills up the surface indentations as the polymerization propagates. Optimum surface treatment conditions resulted in 37.65% and 14.77% improvements in tensile strength and Youngs modulus respectively, in surface modified CF compared to pristine unsized PAN CF. Notably, a significant gain in interfacial shear strength (192.5%) in an epoxy resin was observed, relative to the pristine fibres and is an added advantage.<br/>This modification method is ideal for recovering deteriorated tensile properties in recycled CF to be used in high value applications, which is extremely important considering the increasing global demand for CF and underutilised carbon fibre reinforced plastic (CFRP) waste generated each year.

Repair of carbon fibre through surface modification

ACS Fall 2021

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