The bonding strength of metal-to-metal lap joining of a two-part epoxy-based adhesive employed in an automotive assembly line was investigated under different heating rates (10 to 6000 deg C/min), peak temperatures (room to 250 deg C), and holding times. The results indicate that bonding strength is controlled mainly by the peak curing temperature and the heating rate. The maximum bonding strength appears between 70 and 110 deg C, but the value of it depends on the heating rate. At heating rates of 10, 50, and 100 deg C/min, the peak strength decreases with increasing heating rate. However, a further increase in heating rate to 2000-6000 deg C/min resulted in higher peak bonding strength. The micro-structures and fractured surfaces after shear testing were examined by a scanning electron microscope. The results revealed that many gas bubbles (voids) were formed during the adhesive curing process, and the fracture process was controlled by the link of the voids. At low heating rates (10-100 deg C/min), the mean void size and volume fraction increase with heating rate and peak temperature, causing the weakening of the bonding strength. However, at very high heating rates (2000-6000 deg C/min), the rapid hardening of the adhesive suppressed the development of gas bubbles, so that the mean void size and volume fraction were low, and the bonding strength was high. This result indicates that to effectively improve the adhesive bonding strength, both the chemical reaction (degree of cure) and physical response (gas bubble formation) need to be optimized.
The effect of adhesive curing condition on bonding strength in auto body assembly
Die Auswirkung der Aushärtungsbedingungen auf die Verbindungsfestigkeit von Klebeverbindungen bei der Montage von Autokarosserien
Transactions of the ASME, Journal of Manufacturing Science and Engineering ; 127 , 2 ; 411-419
2005
9 Seiten, 11 Bilder, 19 Quellen
Article (Journal)
English
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