Surface modification and interfacial adhesion of rigid rod PBO fibre by methanesulfonic acid treatment

PBO is a rigid rod polymeric material with potential applications as reinforcement fibres for advanced composites. The adhesion between fibre and matrix in a composite system is a primary factor for stress transfer from matrix to fibre. In this report, we investigated the surface modification of PBO fibres by acid treatments under various treatment conditions, using methanesulfonic acid solution. Both commercially available as-spun and high-modulus type PBO fibres were studied. The experimental effects on the changes in the surface morphology, mechanical strengths, and surface free energies of the fibres were carefully evaluated. In addition, the interfacial adhesion properties of the epoxy-based composites were studied by microbond pull-out tests. The results showed that the surface free energy could be significantly increased up to 62 mJ/m(2) or by 34%, while the interfacial shear strength was improved to 40 MPa or by 22% with the proposed treatment process. The failure mode also changed from fibre/matrix interface adhesive failure to partly cohesive failure mode. On the other hand, the corresponding reduction in fibre tensile strength has been only 1-5% for the same treatment process. (C) 2004 Elsevier Ltd. All rights reserved.