Influence of production based surface topography and release agent amount on bonding properties of CFRP

The application of carbon fiber reinforced plastics (CFRP) has increased in recent years. Besides aerospace applications, automotive industry relies on those materials as they offer the possibility to reduce component weight significantly. A main challenge is the joining of those materials. Due to several advantages, adhesive bonding has been established as the preferred joining method for CFRP. The adhesive bonding process is challenging as the surfaces of CFRP are not suited for adhesive bonding. On one hand, the resulting CFRP-parts have smooth surfaces preventing mechanical interlocking with the adhesive and on the other hand, the release agent is transferred from the mold to the surface of the CFRP contaminating the surface. The resulting surfaces are generally inappropriate to achieve structural and durable bonds, making a surface pre-treatment inevitable. As an alternative approach, this study focuses on the manufacturing method for CFRP with surfaces suitable for adhesive bonding without an additional surface pre-treatment. Therefore, the amount of release agent is varied to achieve a low degree of contamination and laser-structured molds are used resulting in CFRP with varying surface topographies. The surfaces of the CFRP-plates are analyzed. Then the influence of the varied parameters on the bonding strength is investigated by lap-shear tests.