Research project for quality control of sealing compounds

In the new IGF research project “SteP-in”, the SKZ Kunststoff-Zentrum and the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM are using several non-destructive testing methods to advance the quality control of sealing compounds.

Modern techniques such as air ultrasound and optical profilometry are used to determine the curing progress inline and AI-based curing models are developed. Air inclusions and other defects are to be detected using a new thermography technique.

Due to their comprehensive functions, sealants have many areas of use, from everyday applications in the home to high-performance applications in the aerospace industry. During application, the curing time specified by the manufacturer is often used and a safety factor is applied or in-process measurements are carried out on separate samples. The additional effort or unnecessarily long holding times before the next process steps are accepted.

Use of airborne ultrasound and optical profilometry

To enable a more efficient process, the SKZ and Fraunhofer IFAM are currently researching non-contact testing methods that can be used to determine the curing progress inline. Air-coupled ultrasound, or air ultrasound for short, and optical profilometry are being used for this purpose. Air ultrasound can be used to determine changes in the density or elastic properties of the sealant, while optical profilometry can measure shrinkage during curing with a resolution in the µm range.

The measured variables, together with other influencing factors such as ambient temperature and humidity, are to be used to train an artificial intelligence. This will enable curing models to be developed that can be used to reliably determine the progress of curing. Various sealants and different joint shapes are to be analysed in order to design the methods for industrial application. In the further course of the project, the measurement methods will also be tested on real components.