Pre-bond quality assurance of CFRP surfaces using optically stimulated electron emission

Adhesive bonding reliably contributes to joining carbon fibre reinforced plastics (CFRP). Manufacturing and in-service effects may reduce the mechanical performance of these joints. Their reliability is governed by assuring the surface quality of CFRP material. Roughness of ready-to-bond CFRP surfaces affects in a complex way their wetting behaviour as determined with a water break test. Therefore, further in-line capable techniques are highly desirable for the assessment of surface quality prior to bonding. In the present work, optically stimulated electron emission (OSEE) was investigated with this purpose. Sensitivity and accuracy of OSEE measurements allow to distinguish favourable surface states of CFRP adherends from surface states which are unfavourable for adhesive bonding. We show that OSEE may be applied in field and without electrically contacting CFRP surfaces for sensing moisture, thermal degradation or thin layers of contaminants.