The Fraunhofer Institute for Structural Durability and System Reliability LBF in Darmstadt makes it possible to calculate the service life of heavily loaded plastic components earlier and with greater certainty. This is based on a fatigue strength database for thermoplastics. It shows how material, manufacturing, geometry, temperature, and load determine fatigue behavior. This enables companies to conduct a well-founded evaluation of plastic components early in the development process, specifically reduce development risks, and shorten development times.

Engineering plastics are increasingly taking on load-bearing roles in household appliances, vehicles, machinery, and electrical applications. For developers, the most important question is how long a component will reliably last under real operating conditions. The Fraunhofer LBF combines experimental expertise, data-driven analysis, and digital tools for structural durability.

Investigate, Understand, Predict: A Data Foundation for Reliable Plastic Design

The fatigue strength database brings together more than three decades of experience to form a unique foundation for design, material selection, and service life prediction. Over 11,000 tested specimens and approximately 1,300 Wöhler curves provide a robust basis for the design of thermoplastic components. The database covers, among other things, various thermoplastics, additives, conditioning treatments, geometries, environmental influences, and mechanical loads. It identifies correlations and makes them immediately usable for development and validation.

Digital tools accelerate service life prediction

It is particularly important to evaluate notches, temperatures, average stresses, and fiber orientations. “The data show when these factors significantly alter the allowable fatigue strength and which external loads require special attention. This helps companies plan evaluations in a more targeted manner and take critical factors such as contact with media, aging, or real-world load combinations into greater account,” explains Dr. rer. sust. Dominik Spancken, Senior Scientist at Fraunhofer LBF.

Based on the database, Fraunhofer LBF is further developing evaluation algorithms and a Wöhler curve generator. The tool uses existing material properties and mathematically described relationships to estimate Wöhler curves for different temperatures, mean stresses, notches, and fiber orientations early in the development process. Fraunhofer LBF is currently working on service life models in combination with the fatigue strength database to determine the remaining service life of components and systems. This is expected to open up new possibilities for repair, second-life applications, and lightweight construction. Verification tests remain part of the validation process but can be used in a more targeted manner.

Real-World Example Demonstrates Benefits for Industry and Development

An example from the white goods industry illustrates the benefits: A component carrier in a dishwasher must reliably protect the door-opening mechanism for 18 years and approximately 100,000 load cycles at 50 degrees Celsius. The Fraunhofer LBF evaluated temperature, fiber orientation, notches, and average stress for the application and derived Wöhler curves. Component tests confirmed the predictions. This enables manufacturers and development service providers to identify risks earlier, reduce costs, and bring reliable plastic components into series production more quickly.

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