Why Excimer Laser Treatment

Previous work performed on our composite materials [16] provided clear evidence of the influence of surface pollution prior to the use of any surface treatment on adhesion behavior. Several surface treatments can be performed to remove this surface pollution and increase single lap shear performances. As described in Section 20.1.2, peel ply treatment acts very specifically on composite materials. As several authors have already described [3, 5, 17] removing the peel ply before the application of the adhesive provides a rough (Fig. 20.2) and clean surface, free of pollution from the manufacturing process. 

Such surface cleaning, as weU as several other surface modifications, leads to an increase in adhesion performance. Hence, failures which could previously occur adhesively between the composite surface and the adhesive layer wiU then propagate cohesively into the composite surface (Fig. 20.3) when this kind of treatment is applied, showing complete removal of the superficial polymer layer 

Alternatively, excimer laser treatment can be used to obtain additional improvement of adhesion. By this technique, polymer layers at the surface can be removed selectively before bonding, thus making the adhesive layer directly hnked to the fiber reinforcement itself Hence, crack propagation which occurs cohesively in the material under this polymer layer can no longer take place. Section 20.3.2 provides the results of such an approach. 

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