Computational analysis of surface-tension-driven coating-defect flow

Abstract

Bondline readout (BLRO) is a coating defect frequently exhibited on adhesively-bonded, polymeric automotive body panels painted with high-glamor/flow clearcoats. BLRO or telegraphing results from Marangoni-type, surface-tension-driven flows. An efficient numerical code was developed to predict temperature- and concentration-induced BLRO flows to use it as an effective tool for screening and developing potential clearcoat systems. Two numerical codes were developed: a 1-D code based on the lubrication approximation; a 2-D code based on the SIMPLER (Semiimplicit method for pressure-linked equations revised) algorithm. The 1-D code produced BLRO profiles in agreement with those predicted from the 2-D code and those measured from BLRO flow experiments, thus confirming a proposed BLRO mechanism. Moreover, the 1-D code was vastly more time-efficient than the 2-D code due to a severe time-step stability limitation found with the latter.