Oxygen plasma processing and improved interfacial adhesion in PBO fiber reinforced epoxy composites

The effects of oxygen plasma processing on the improved interfacial adhesion properties of poly(1,4-phenylene-cis-benzobisoxazole) (PBO) fiber reinforced epoxy composites have been investigated in this paper. Both As-spun (AS) and high-modulus (HM) PBO fiber systems were studied. The characterization techniques included microscopy, surface analysis, and composite interfacial adhesion tests. The results showed that the high-modulus fiber surface free energy could be increased significantly by 42.2% from 46.2 to 65.7 mJ/m2, while the tensile strength was only slightly decreased by 3.4% from 5.87 to 5.67 GPa. In addition, the interfacial adhesion strength of PBO fiber reinforced epoxy composite was improved by 37.5% from 32.5 to 44.7 MPa for the HM fiber system. The improvement has been attributed to the enhanced cohesive failure that dissipated more fracture energy.