On demand thermal surface modification of carbon fiber for improved interfacial shear strength

A thermally triggered, on demand, surface modification method was exploited using carbon fibers (CFs). Bisdiazomethanes undergo thermal activation to generate extremely reactive carbene intermediates, able to react with the CF surface. Herein, the surface modification of continuous CFs is demonstrated by dipping the fibers in a solution of bisdiazomethane at three different concentrations of 1 mmol, 5 mmol, and 10 mmol, followed by air drying and heating at 120 °C. Tensile strength and Young's Modulus values were preserved in the treated fibers, while the interfacial shear strength (IFSS) values showed significant improvement. The highest IFSS improvement was found (189 %) for the fibers dipped in the 5 mmol solution, with significant increases noted for the 1 and 10 mmol modifications, of 54 % and 97 %, respectively. When the thermal modification was repeated with parameters analogous to a sizing application used in CF manufacture (30 s dip, 2-min heating), 74–79 % improvements in IFSS resulted. Hence, this approach can serve as a simple, scalable, and tunable surface modification method for discontinuous CFs that promotes their use in high value applications.