Laser surface preparation for bonding of aerospace composites

Abstract

Adhesive bonds are critical to the integrity of built-up structures. Disbonds can often be detected but the strength of adhesion between surfaces in contact cannot be determined without destructive testing. Typically the major problem in a bonded structure is surface contamination, and by extension, surface preparation. Standard surface preparation techniques, including grit blasting, manual abrasion, and peel ply, are not ideal because of variations in their application. Etching of carbon-fibre-reinforced plastic (CFRP) panels using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser appears to be a highly precise, controlled, and reliable way to both clean a composite surface prior to bonding and provide a bond-promoting patterned surface akin to peel ply without the inherent drawbacks from the same (i.e. debris and curvature). CFRP surfaces prepared using laser patterns conducive to adhesive bonding were compared with typical pre-bonding surface treatments through optical microscopy, contact angle goniometry and post-bonding mechanical testing. This paper is the work of the US Government and is not subject to copyright protection in the USA.