A study of laser surface treatment in bonded repair of composite aircraft structures

Abstract

Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

Enhanced Surface Properties of Carbon Fiber Reinforced Plastic by Epoxy Modified Primer with Plasma for Automotive Applications

“…Carbon fiber reinforced plastics (CFRPs) are used in various fields, including the aviation and automotive industries. The greatest advantages of CFRP materials are their light weight, high strength, corrosion resistance, and high rigidity [1,2].…”

Low-pressure plasma treatment of CFRP substrates for epoxy-adhesive bonding: an investigation of the effect of various process gases

“…Obviously, this behavior is emphasized when optimized O2-plasma treatment was performed, which represents the clearest case in which a substantial reduction of C-C/C-H bonds (-43.4% compared to the reference) is followed by an equally clear increment of oxidized species. Indeed, free radicals can be created on the treated surfaces, which can then couple with active species from the plasma environment; these reactions are believed to be essential for the changes in the surface functionalities [28,29]. High-resolution survey on O 1s spectrum and subsequent deconvolution of this peak also highlighted the presence of two different chemical species (Fig.…”

Developments in Laminate Modification of Adhesively Bonded Composite Joints

“…Many different chemical and physical surface treatments are currently available for composites. These employ different methodologies, such as mechanical abrasion [ 51 ], degreasing the surface with solvent [ 52 , 53 ], laser ablation [ 54 , 55 ], plasma treatment [ 56 , 57 ], peel ply technique [ 57 , 58 , 59 , 60 , 61 ], irradiation [ 62 ], grit blasting [ 63 , 64 ] and chemical surface activation [ 65 ]. It is important to take into account the fact that the bulk mechanical properties of a composite can be strongly affected by surface treatments.…”