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- Bonding strength (2) (entfernen)
Multiple-sample approach: reliable ranking and validated statistics of bonding and adhesive strength
(2014)
Bonding strength of adhesive-bonded joints and adhesive strength of coatings have been exclusively determined in
single-sample tests using a tensile testing machine. Necessarily, the single-sample approach was also applied to the
corresponding bonding procedure. As a consequence, reliability and reproducibility of results were restricted. By
applying the newly introduced centrifuge technology, the multiple-sample approach was realized for simultaneous
tensile testing of up to eight samples under identical conditions without any disturbing shear-force effects. In order to
introduce the multiple-sample approach into the bonding procedure, a hydraulic bonding set-up was developed which
enables identical bonding pressure also for slightly different heights of sample assemblies. Both sample approaches
were compared for various application examples: ranking of different classes of adhesives, validated statistics of
adhesive-bonded joints using one particular adhesive and effects of cleaning and plasma-treatment on the adhesive
strength of coatings. The investigated systems included glass, metals and polymer substrates, different adhesives,
metallic and dielectric coatings on polymers.
A new technology for strength determination of adhesive-bonded joints based on analytical centrifugatioon is introduced. Tensile as well as shear strength can be measured for multiple test specimens simultaneously within a very short time. The experimental procedure is described from sample preparation, application of adhesives, sample mounting within the centrifuge to testing parameters and sequences. All requirements of DIN EN 15870 are fulfilled and, in addition, a higher throughput and a better reproducibility can be obtained. The experimental results are discussed regarding bonding strength development over time, comparison of tensile and shear strength and various testing conditions. Furthermore, an additional application field of centrifuge technology is described with respect to the determination of the adhesive strength of coatings. The novel centrifuge based technology provides the determination of bonding, adhesive and shear strength on a statistical basis under identical testing conditions for up to eight samples. Moreover, sophisticated two-sided sample clamping, necessary for a tensile testing machine, is replaced by a simple plug-in procedure.