Abstract
The sources of stress in complete automative paint systems have been identified and measured as a function of weathering. In addition to the stresses developed during cure, the main sources of stresses developed during exposure are thermal expansion coefficient mismatch, humidity expansion mismatch, and densification of the clearcoat. Stresses generally increase during weathering due to a slow densification of the clearcoat and increasing water absorption and desorption stresses. Finite element analysis (FEA) was used to compute the stress distribution in full paint systems. Stresses are typically in-plane and highest in the primer and clearcoat. Stresses approaching those required to propagate cracks can be attained in weathered paint systems. The presence of flaws, either cracks or incipient delaminations, will lead to large stress concentrations that can give rise to peeling forces not present in coatings without cracks.
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Nichols, M.E., Tardiff, J.L., and Gerlock, J.L., to be published.
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Nichols, M.E., Darr, C.A. Effect of weathering on the stress distribution and mechanical performance of automotive paint systems. Journal of Coatings Technology 70, 141–149 (1998). https://doi.org/10.1007/BF02730084
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DOI: https://doi.org/10.1007/BF02730084