A study on the microstructural changes and mechanical behaviors of carbon fibers induced by optimized electrochemical etching

In this study, surface defects and the surface layer of carbon fibers (CFs) were etched using a well-known electrochemical oxidation method to enhance the CFs’ mechanical properties. The CFs were etched using ammonium bicarbonate as an electrolyte, and the change in surface properties, microstructures, and mechanical strength were evaluated after the treatment. The mechanical interfacial strength of the modified CFs were also investigated in terms of interfacial shear strength (IFSS). Depending on the process conditions, it was found that the surface roughness, average surface charge, and/or surface free energies of the CFs were changed dynamically. The tensile strength and IFSS of the CFs increased significantly in a certain range after etching. The electrochemical modification of the CFs in this work was understood to mainly remove surface defects and amorphous structure, while enhancing various surface functional groups and crystalline-rich microstructures.