Which Adhesive Tests Hold Up in the Real World?

Advances in Structural Adhesive Bonding

November 21, 2023

Exponent Senior Managing Scientist Christopher White, Ph.D., and colleagues from Virginia Tech have co-authored a chapter titled "Durability and Accelerated Characterization of Adhesive Bonds," in the second edition of Advances in Structural Adhesive Bonding, a book released through the Woodhead Publishing Series in Materials.

For adhesive bonds, hundreds of national, industry, and company-specific joint tests are available, but in any product case, only a few laboratory tests will be relevant or suitable for developing design data. So how should testing engineers choose a laboratory test to determine the reliability of a bonded structure?

Accelerated short-term environmental testing offers a way for product designers to extrapolate long-term structural durability and reliability providing the short-term accelerated testing correlates to long-term observed performance. Accelerated testing is also a practical alternative to spending years evaluating an adhesive bond against a specific load condition and real-world environments.

As a result, an accelerated test chamber can represent an extreme condition of one damage driver (humidity, temperature, cyclic frequency, concentration level, etc.) so that degradation effects that occur over years in real-world conditions can be observed in days under laboratory settings. 

Using illustrations and figures of ASTM testing apparatuses, the chapter also explains how tests based on the time-temperature superposition principle (TTSP) produce the most relevant results for assessing environmental-induced aging, although product designers should remain aware of multiple degradation mechanisms that may work on adhesive bonds simultaneously.

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Advances in Structural Adhesive Bonding

"Durability and Accelerated Characterization of Adhesive Bonds"

From the publication: "Of the existing techniques for accelerated testing of adhesives, TTSP and the related time-temperature-stress superposition and time-temperature-diluent concentration superposition have the best grounding in polymer physics and are relatively simple to employ."