Laser Pre-Treatment of Composite Structures for Improved Adhesion

In the aerospace industry new design concepts offering weight savings are high in demand. In the recent generation of aircraft (e. g. Airbus 350 XWB, Boeing 787), composite materials have shown new perspectives in terms of structural efficiency and performance. Due to the increasing amount of composite materials used in the aircraft structure, new pre-treatment technologies providing a higher repeatability and a higher degree of automation are discussed. Composite parts, which are manufactured in molds are often contaminated with release agents. However, is well known that bonding on composite surfaces contaminated with release agents cause non acceptable low adhesion performance. Standard surface preparation techniques including grit blasting or manual abrasion are widely applied in aerospace industries. However, these pre- treatments are not ideal in terms of long-term stable adhesion on composite structures. Due to the variations in their applicationno reliablesurface pre-treatment is possible. With the application of UV-Laser treatments to composite surfaces residues from release agents can be removed. By the use of nanosecond pulsed UV-Laser systems the laser energy in only introduced in the first nanometres of the composite material. Therefore, no change in surface morphology is observed. Only the organic contaminations are removed by ablation effects. The achieved results on composite materials demonstrate that the UV-Laser process is a suitable way to activate composite structures. In comparison to grinding or blasting technology the adhesion performance can be significantly improved without any fiber damage. The applied laser technology offers wide range of advantages. Laser processes are environmentally compliant due to avoidance of hazardous chemicals. The tendency to hybridisation in aerospace industry increases the need for local dry pre-treatments like laser treatment which are applicable for integral hybrid structures as well. Due to such processes faster and repeatable and a higher degree of automation in manufacturing is possible.