Active thermography for quality assurance of 3D-printed polymer structures

ABSTRACT

Additively manufactured test specimens made of polyamide 12 (PA 12) by Laser Sintering as well as of acrylonitrile butadiene styrene (ABS) by Fused Layer Modelling, were characterised with active thermography directly after manufacturing and after artificial weathering. For this, two different excitation methods (flash and pulse heating) were used and compared, regarding their suitability for the detection of constructed and imprinted defects inside the test specimens. To increase the quality of the thermograms, data processing methods like thermal signal reconstruction (TSR) and Fourier Transformation after TSR were applied. To further investigate the long-term stability of the additively manufactured test specimens towards environmental stress, like UV radiation, heat, humidity, water contact and frost with active thermography, an artificial weathering test over 2000 hours (~3 months) was applied to the specimens. The monitoring of the changes in the optical properties of the weathered plastics was supplemented by spectral reflectance and UV/VIS spectroscopy.

KEYWORDS:

• Additive manufacturing
• polymers
• artificial weathering
• active thermography
• UV/VIS spectroscopy

Acknowledgments

This project is funded by the Federal Ministry for Economic Affairs and Energy due to a resolution of the German Parliament. IGF/AiF-Project 19151 N/2 – “Non-destructive characterisation and quality assurance of the material properties and stability of additively manufactured plastics.”

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This IGF/AiF (German Federation of Industrial Research Associations) Project [19151 N/2] was supported by the Federal Ministry for Economic Affairs an Energy on the basis of a decision by the German Bundestag and held in cooperation with the Association for the promotion of the Süddeutsche Kunststoff-Zentrum, FSKZ e. V.

Notes on contributors

Christian Metz

Christian Metz was born in 1981 in Munich, Germany and studied chemistry at Ludwig-Maximilians-Universität (LMU) in Munich. He received his doctorate in analytical chemistry at the Technische Universität München (TUM) in the course of a special priority program (SPP 1315), funded by the Deutsche Forschungsgemeinschaft (DFG), about ‘Biogeochemical Interfaces in Soil’. Since Mai 2017, he is working at Bundesanstalt für Materialforschung und -prüfung (BAM) in Berlin on ‘Non-destructive characterization and quality assurance of the material properties and stability of additively manufactured plastic parts’.

Philipp Franz

Philipp Franz was born in Guben, Germany. He studied physics at the Technische Universität Berlin and finished his masters degree in 2017. Afterwards, he worked as a scientist at Paul-Drude-Institut für Festkörperelektronik (PDI) and Bundesanstalt für Materialforschung und -prüfung (BAM). Currently, he is employed as a test engineer at Sicoya GmbH.

Christian Fischer

Christian Fischer was born in Hechingen, Germany. He studied mechanical engineering at DHBW Stuttgart (bachelor) and material science at Friedrich-Alexander Universität Erlangen-Nürnberg and finished his masters degree in 2013. Since then he works as a scientist at SKZ – Das Kunststoff-Zentrum in Würzburg as a member of the research team additive manufacturing.

Volker Wachtendorf

Volker Wachtendorf received his PhD from the Technical University Clausthal, Germany. He presently works in Bundesanstalt für Materialforschung und -prüfung, BAM, in Berlin. His work is focused on artificial weathering and the ageing of polymers.

Christiane Maierhofer

Christiane Maierhofer studied physics at the Technical University of Berlin where she did her doctorate on the interfacial properties of semiconductor heterostructures. She has been employed at Bundesanstalt für Materialforschung und -prüfung (BAM) since 1993 where she heads the Division of Thermographic Methods in the Department of Non-destructive Testing. Since several years, she focuses on the development of in-situ monitoring and non-destructive testing methods for quality assurance in additive manufacturing. She is convener of national and European technical committees for standardization of passive and active thermography for non-destructive testing.