Investigation of fluorine-based release agents for structural adhesive bonding of carbon fibre reinforced plastics

Abstract

IntroductionAdhesive joining is increasingly used in many industries because of the advantages it provides compared to conventional structural joining methods (e.g. riveting). This applies in particular to fibre-reinforced composites, as a rivet hole interrupts the fibres and thus weakens the mechanical properties of the laminate. In aerostructures, adhesive bonding is applied in metal-to-metal joints, composite-to-composite joints and composite-to-metal joints both for assembling parts and for patch-repairing.The quality of a bonded joint depends on the adhesive, the manufacturing process, the environmental and loading conditions, as well as from the surface of the substrates to be joined. The surfaces of CFRP components to be joined by adhesive bonding are often textured surfaces resulting from the used peel plies during production or mechanical pre-treatment such a sanding or milling. AbstractPeel plies can be used during the manufacture of fibre-reinforced plastics for two reasons: to protect the surface during transport and storing the parts as well as during subsequent work steps, such as adhesive bonding, the removal of the peel ply can result in bondable surface with required surface characteristics. However, the use of peel plies is not straightforward. It can be difficult to remove peel plies and a surface produced by a peel ply is altered in terms of roughness and elemental composition. In the present work, the influence of fluorine-based release agents on adhesive joining of carbon fibre reinforced composites is investigated. Within the scope of the screening, 14 fluorine-based release agents-ETFE release films, PTFE coated glass fabrics as well as fabrics made of PTFE fibres-were investigated. Preliminary studies (Meer, in: Deutscher Luft-und Raumfahrtkongress 2014, Augsburg, 2015 have shown that ETFE films have advantages in terms of adhesion. The study covers a number of aspects: the determination of the tear strength of the release agent by peel test; the determination of the element composition (XPS) and surface characteristics (SEM) before and after atmospheric pressure plasma pre-treatment, characterization the topology and the characterization of the adhesive strength by centrifugal adhesion test. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Enhancing Fatigue Life and Strength of Adhesively Bonded Composite Joints: A Comprehensive Review

“…Alternatively, surface roughening can be used to increase the mechanical interlocking between the adhesive and the adherend, further enhancing the strength of the bond [169,170]. Roughening the surface can be achieved by various methods, such as sand and bristle blasting [31], grit blasting [171,172], and the peel ply technique [173,174]. This process creates a rough surface topography, which increases the surface area and provides more points of contact for mechanical interlocking between the adhesive and the adherend.…”

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.…”