The interfacial adhesion of poly-p-phenylene benzobisoxazole/bismaleimide composites improved by oxygen/argon plasma treatment and surface aging effects

► A large quantity of active groups was introduced onto the fiber surface treated by the oxygen/argon plasma. ► The fiber surface roughness decreased when the treatment time exceeded 7 min. ► After treatment the PBO fibers showed better interfacial adhesion with the bismaleimide resins. ► The PBO/bismaleimide composite failure mode shifted from adhesive failure to primary cohesive failure after treatment. ► The fiber surface modification was not durable due to the surface aging effects.