Biodegradation of composite materials

Fiber-reinforced polymer composites were examined for susceptibility to microbiologically-influenced degradation. Composites, resins, and fibers were exposed to sulfur/iron-oxidizing, calcareous-depositing, ammonium-producing, hydrogen-producing, and sulfate-reducing bacteria (SRB) in batch culture. Surfaces were uniformly colonized by all physiological types of bacteria; however, the microbes preferentially colonized surface anomalies including scratches and fiber disruptions. Epoxy and vinyl ester neat resins, carbon fibers, and epoxy composites were not adversely affected by the microbial species. SRB degraded the organic surfactant on glass fibers. Hydrogen-producing bacteria appeared to disrupt bonding between fibers and vinyl ester resin and to penetrate the resin at the interface. Acoustic emission testing demonstrated reduction of tensile strength in a stressed carbon fiber-reinforced epoxy composite after exposure to SRB.