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Composite : Metal connections for the automotive industry

Oosten, M. van (2015) Composite : Metal connections for the automotive industry.

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Abstract:The connection between metals and composites could be an important step to introduce more composite materials into the automotive industry. There are a few possible methods to connect these material together, which are: adhesion, welding and mechanical connections. This report takes a closer look into adhesive connections between metals and composites. The chosen materials for these connections are steel and aluminium as the metal parts and glass fibre reinforced polypropylene and glass fibre reinforced polyamide as the composite parts. The goal is to use this connection method in an automated production line, which means that the adhesive will have to dry quickly. Five adhesives have been chosen based on their adhering properties to the chosen materials and curing speed. The adhesives are tested by using the lap shear testing method. This way it will be possible to compare the adhesives with each other. All materials required some surface treatment prior to the bonding. Only treatments that were recommended by the adhesive manufacturers were used. There are however additional surface treatments which could be used to improve the bonding. A theoretical model was used to predict the stress distribution that would occur in the adhesive layer. This model showed that the stress would not be equally distributed throughout the adhesive layer, stress peaks occur because of the difference in Young’s modulus. The thickness of the materials also contributes to the stress peaks, these peaks become lower when the thickness of the material with the lowest Young’s modulus is increased. The height of the peaks depend on the flexibility and thickness of the adhesive. The higher the flexibility, the lower the peak will be. Also an increased adhesive thickness results in lower peak stresses. The results of the lap shear test showed large deviations in shear stress, which could be caused by a number of factors. The highest strengths were mostly reached on the combination of steel with composite. Only one adhesive managed to get nearly similar results on the connection with aluminium. Additional testing showed that increasing the thickness of the composite part did not show an increase in strength, this should have lowered the stress peaks but does not result in an increase in strength. However, increasing the thickness of the adhesive layer did show an increased strength for one of the adhesives. The double lap shear test was also performed to compare with the single lap shear test. This showed that the single lap shear test was a good method for comparing the adhesives. The results of all the tests that were done showed that it is possible to get a structural connection with almost every combination of materials. Only the combination of aluminium and PP showed a strength which was a fraction too low.
Item Type:Internship Report (Master)
Ten Cate Advanced Composites BV, the Netherlands
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:Composites, Metals, Connection, Adhesives
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