Local displacement measurements within adhesives using particle tracking and In Situ computed tomography

ABSTRACT

Strain measurements are essential for understanding the mechanical behavior of bonded joints under different load conditions and for validating numeric simulations. Strain gauges and extensometers are typically used to determine local strains in a specific direction. The introduction of digital image correlation (DIC) allows for the full-field measurement of surface strains both in two dimension and in three dimension. However, these methods observe the strain of the adhesives’ surface which may vary in comparison to the volumetric strains.In this article, a new technique for measuring the internal displacement field in adhesives is proposed. The method is based on in situ x-ray computed tomography (CT) and particle tracking. Basic approach of the measurement is to identify and track characteristic markers within adhesives during loading. The displacement due to the load can be calculated by the different positions of the characteristic markers between two image sets. Initial results for a single lap joint with a thick bond line indicate that a sufficient resolution of the measurement can be reached and motivate further research to develop this novel measurement technique for adhesives.

KEYWORDS:

• Adhesive bonding
• composites
• computed tomography
• digital volume correlation
• internal displacement measurement
• mechanical properties of adhesives
• particle tracking
• polyurethane

Acknowledgements

We thank Dr Roland Kruse from the Institute of Applied Mechanics and Dennis Köhnke from the Institute of Building Materials, Concrete Construction and Fire Protection, both Technische Universität Braunschweig, Germany, for their help, technical equipment, and support for the in situ CT measurement. We would like to thank SIKA Deutschland GmbH for their support with adhesives.