Akiyama, H., Fukata, T., Sato, T., Horiuchi, S., and Sato, C.
Journal of Adhesion. 2020, Vol. 96 Issue 15, p1311-1325. 15p.
POLLUTANTS, FOURIER transform infrared spectroscopy, ADHESION, MINERAL oils, and ALUMINUM plates
Surface contamination of an adherend has an influence on its adhesive bonding properties. To investigate this phenomenon, various contaminants, including silicone oil, mineral oil, a fluorine release agent, and surfactants, were quantitatively applied to an aluminium plate (6061) using a spray apparatus. The contaminated adherends were bonded with acrylic and epoxy adhesives, and their adhesion strengths were examined using single lap-shear tests. Mineral oil did not affect the adhesion strength, but silicone oil and surfactant agents were found to significantly affect the adhesion strength. Atomic force microscopy observations and Fourier transform infrared spectroscopy of these surfaces revealed a specific interaction between silicone oil and aluminium. [ABSTRACT FROM AUTHOR]
de Freese, J., Holtmannspötter, J., Raschendorfer, S., and Hofmann, T.
Journal of Adhesion. 2020, Vol. 96 Issue 12, p1122-1140. 19p.
SURFACE preparation, MILLING (Metalwork), ADHESIVES, PLASTIC fibers, CARBON fibers, ADHESIVE joints, and BOND strengths
In this study, the use of dry end milling of carbon fiber reinforced plastics (CFRP) as surface pretreatment for high-strength (structural) adhesive bonding was investigated. Surfaces were pretreated using different milling parameters; subsequently, they were adhesively bonded and tested. In comparison with sanding and other industrial standard pretreatment methods, the measured adhesive strength was significantly lower. Detailed surface investigations utilizing field-emission scanning electron microscopy could identify two major effects for lower adhesion strength. Intralaminar damages and microparticle residues on the created surface reduced the strength of the CFRP adhesive joints. This eventually explains results from investigations on milling pretreated repairs. By application of power ultrasound cleaning equipment and coating with low viscosity epoxy primers, the authors showed a way to overcome the discovered drawbacks and to improve bond strength significantly. Surface roughness measurements showed that the arithmetical mean roughness Ra can be used as an effective value for assessment of mechanical pretreated CFRP surfaces as well as for the quality of necessarily following cleaning processes. [ABSTRACT FROM AUTHOR]
In this research study two very different surfaces of the same type of a carbon fiber reinforced plastic (CFRP) are deliberately prepared to compare characteristics of the created surfaces and the achieved strength of the adhesively bonded joints. Within this approach, explanatory power of state-of-the-art surface analysis methods, applicability of destructive tests and adhesion mechanisms for high-strength adhesive bonding of CFRP are discussed. One CFRP surface was prepared with a highly optimized atmospheric pressure plasma treatment (APPJ). Another CFRP surface was created with a highly optimized and adjusted vacuum blasting process. Initial CFRP surface and treated CFRP surfaces were characterized with surface analysis methods X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM), contact angle measurements and Field-Emission Scanning Electron Microscopy (FE-SEM). Mechanical strengths of adhesive joints were determined with three different destructive test methods (single lap shear, double cantilever beam, centrifugal adhesion test) for all surfaces. Interestingly, the very different surfaces led to adhesive joints with comparable mechanical strength. After a comprehensive discussion, the author isolates relevant adhesion mechanisms for adhesive bonding of surfaces of thermoset polymers. The study concludes with proposals for necessary future research efforts to achieve the aimed reliable high-strength adhesive joints for safety relevant CFRP structures. [ABSTRACT FROM AUTHOR]