H. Dittmar
C. J. A. Beier
J. Weiland
A. Schiebahn
P. Jäschke
S. Kaierle
U. Reisgen
L. Overmeyer

Individualized and controlled laser beam pre-treatment process for adhesive bonding of fiber-reinforced plastics. III. Effects of contaminants

J. Laser Appl.
Type: Zeitschriftenaufsatz (reviewed)
Adhesive bonding of plastic components is a well-established process for various applications. Specifically for thermoplastic parts, surface pre-treatment is required to achieve optimum bonding quality. However, automated surface pre-treatment is not established yet. Reasons are missing process monitoring and significant challenges arising from conventional monitoring techniques that hardly identify surface contaminants. In a recent research project, the authors investigated how process monitoring by spectrometry during a laser-based surface pre-treatment might solve this challenge for fiber-reinforced plastics and generic surface contaminants. This article describes experiments conducted on two composite materials with different contaminants. A nanosecond-pulsed UV-laser was used to pretreat a glass-fiber reinforced 2C-polyurethane (GF-PUR) and a glass-fiber reinforced polyamide 6 (GF-PA6). Each composite had coupons contaminated with an industry standard mould release agent or artificial silicate-based dust as well as uncontaminated samples. The samples were laser pretreated and compared to reference coupons that did not receive laser treatment. The samples were analyzed after laser pre-treatment for their free surface energies by the detection of the contact angle and measured for the surface roughness. The bonding improvement due to the laser process was determined by shear strength and peel resistance tests. The results show that UV-laser pre-treatment has an advantageous impact on the bonding strength of GF-PUR and GF-PA6. Combined with a fast spectrometric process monitoring that robustly identifies contaminants during the laser process, an inline process control is feasible.