Henkel, Clemson University develop methods to measure thermal expansion in multisubstrate assemblies

Henkel, a Madison Heights, Mich.-based provider of adhesives, sealants, and surface treatments for the automotive industry, in cooperation with Clemson University – International Center for Automotive Research (CU-ICAR) in Greenville, S.C., has announced the development of novel experimental methodologies used to measure thermal expansion for dissimilar substrates used in vehicle development. Thermal expansion, which measures the substrate growth during heating, presents a significant challenge for automotive engineers, particularly as new lightweight materials are introduced.

"When one substrate grows faster than another during heating, potential issues can arise, including distortion, adhesive stress, and potential debonding of adhesive joints," said Michael Flener, innovation program manager, transportation and metals industries, Henkel. "By using these experimental methods in conjunction with our predictive models, OEMs can better determine the ideal location and types of joining areas needed during the vehicle design and development process."

The developed experimental methodologies use noncontact optical measurement systems that were customized and further developed to allow measurements at cold and high temperatures through oven windows. The developed methodologies have been validated through accurate measurements of thermal expansion and material deformation in coupon-level samples, subassemblies, and even large full-scale vehicles.

"These methods can measure full-field thermal expansion within one-tenth of a millimeter of accuracy,” said Fadi Abu-Farha, assistant professor, automotive engineering, CU-ICAR, “resulting in data that provide highly accurate understanding of how substrates and adhesives are interacting within automotive thermal cycles."