Improved interfacial adhesion in PBO fiber/bismaleimide composite with oxygen plasma plus aging and humid resistance properties

In this study the radio frequency oxygen plasma was used to strengthen the interfacial adhesion of PBO fiber/bismaleimide composite. The interlaminar shear strength (ILSS) was improved to 57 MPa or by 29% after treatment at 50 W, but higher powers reduced the adhesion. The fiber surface chemistry, topography and roughness were analyzed by XPS and AFM, respectively. Oxygen atoms and polar groups were increasingly introduced onto the fiber surface, which contributed much to better wettability. The fiber surface was roughened by plasma sputtering and etching, generating many protuberances and notches. Results suggested that physical interactions between the fiber and the matrix might play leading roles in strengthening the adhesion. Aging behavior was not observed within the storage time of 1–50 days, which indicated that the plasma created stable structures on the fiber surface. After boiling the ILSS retained above 90%, confirming that the composite had good resistance to humidity.

► The ILSS had great improvement at 50 W, but higher powers reduced it.
► Oxygen atoms and polar groups kept increasing with powers, improving wettability.
► Surface roughness increased, which contributed much to the better adhesion.
► Aging behaviors were not observed.
► The composites had low water absorption and high ILSS retention at moisture conditions.