Development and evaluation of surface teratmetns to enhance the fiber‐matrix adhesion in PAN‐based carbon fiber/liquid crystal polymer composites. Part II: Electrochemical teatments

Various electrochemical surface treatments, designed to improve the fiber‐matrix adhesion, were applied to commingled as‐received continuous AS4 carbon reinforcing fiber/liquid crystal polymer (LCP) matrix fibers. Unidirectional composite plates (norminally 60 vol% carbon fiber) were fabricated and short beam shear (SBS) tests were conducted to provide an indication of the effect of the treatments on AS4 carbon fiber‐LCP matrix adhesion. The mean SBS strength of the as‐received AS4/LCP system was 49 MPa. Three elecrtrochemically polymerized coatings‐poly‐para‐phenylene (PPP), polyphenylene oxide (PPO), and polyaniline (PA)‐were applied. Only the PPO coating, however, had a beneficial effect on the composite shear strength. The coating enhanced the shear strength by 14% relative to the as‐received AS4/LCP system. Scanning electron Microscope (SEM) observations of the PPO treated shear failure surface indicated the presence of a strong fiber‐matrix bond. That is, the failure location was in the LCP matrix material.