| AVS 61st International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS+MC+SS-TuA |
| Session: | Analysis of Modified Surfaces |
| Presenter: | Timo Hofmann, Bundeswehr Research Institute for Material, Fuels and Lubricants, Germany |
| Authors: | T. Hofmann, Bundeswehr Research Institute for Material, Fuels and Lubricants, Germany J. Holtmannspötter, Bundeswehr Research Institute for Material, Fuels and Lubricants, Germany T. Meer, Airbus Group Innovations, Germany J. Rehbein, Bundeswehr Research Institute for Material, Fuels and Lubricants, Germany G. Härtl, Bundeswehr Research Institute for Material, Fuels and Lubricants, Germany |
| Correspondent: | Click to Email |
Carbon fiber reinforced plastics (CFRPs) are increasingly employed in novel aircraft structures due to their high tensile strength, low weight, favorable fatigue behavior, and ruggedness against outer influences (corrosion). Joining of CFRP structures is currently performed using rivets and bolts. In order to exploit further weight-saving potential, the usage of adhesive bonding is intended.
An important key factor for the success of adhesive bonding is the surface pre-treatment of the adherents. Peel-plies are commonly used for the fabrication of CFRP structures and, in theory, are said to create a pristine and uncontaminated fractured surface upon removal. In reality, the presence of release agents leads to contaminated surfaces that may cause unforeseeable failures of structures in service.
In this contribution, CFRPs (Hexcel 8552 / IM7) were produced using various peel-plies and release foils currently employed in aerospace manufacturing processes. Atmospheric pressure plasma jet (APPJ) was investigated as a method to further improve adhesion and to clean the samples from release agents.
We present a detailed investigation of the surface morphology and composition of CFRPs before and after treatment with APPJ. The peel-plies and the CFRP surfaces were examined by a combination of Field-Emission Scanning Electron Microscopy (FE-SEM), X-Ray Photoelectron Spectroscopy (XPS), and Energy-Dispersive X-ray spectroscopy (EDX).
We studied the approach of surface functionalization and contaminant removal by variation of the type of peel ply, release agent, and plasma treatment parameters. In the experiments particular focus was placed on determining changes in the chemical composition of the surface and morphology. We demonstrate that APPJ-processes offer limited cleaning capabilities for CFRP surfaces. Furthermore, the ability to induce morphological changes is highly dependent on the initial level of surface roughness and chemistry. Finally, we show that overtreatment leads to degradation of the epoxy component and enrichment of the thermoplastic portion of the matrix on the surface.