Non-destructive Polymer Testing

Sprachauswahl/Language selection

Dieser Artikel ist auch auf Deutsch verfügbar Zerstörungsfreie Kunststoffprüfung

A service provided by
Polymer Service GmbH Merseburg
Tel.: +49 3461 30889-50 E-Mail: info@psm-merseburg.de Web: https://www.psm-merseburg.de
Our further education offers: https://www.psm-merseburg.de/weiterbildung
PSM on Wikipedia: https://de.wikipedia.org/wiki/Polymer Service Merseburg

Non-destructive testing

Non-destructive polymer testing or analysis encompasses all non-destructive testing methods that can be successfully applied to characterise the defect-free condition of test specimens, components or parts made from plastics or plastic composites.

In the strict sense, therefore, this term refers to non-destructive plastics testing, which, unlike destructive polymer testing, does not affect the integrity of the test specimen or the part. Plastics testing methods are therefore categorised, as in materials testing, into destructive methods (e.g. tensile, bend, compression or torsion testing and impact testing), low-damage testing methods, such as micro- or nanohardness testing, and non-destructive testing.

In contrast to materials testing and polymer testing, which constitute independent scientific disciplines, non-destructive polymer testing is a sub-field of non-destructive testing or materials testing. Whilst there are numerous publications in scientific journals dealing with the non-destructive testing of polymers, only a few specialist books are known to deal comprehensively with this field [1, 2].

Table 1: Application of non-destructive testing methods for glass fibre-reinforced polymers (GFRP) and carbon fibre-reinforced polymers (CFRP) composites ● − without restrictiong ● − with restriction [4]

Test method	Test area		Main type of defect
	Surface	Volume	Crack	Pores	Delamination	Fibre break
Visual inspection	●		●	●
Endoskopy	●		●	●
Sound test
conventional		●	●	●	●
registrering		●	●	●	●
Penetration testing	●		●	●
Radiografic testing
Soft radiation		●		●	●	●
Contrast medium	●	●	●	●	●
Radioskopy		●	●	●	●
Ultrasound teseting
Pulse-Echo		●	●	●	●
Ultrasonic transmission technique		●	●		●
Imaging technology		●	●	●	●
Thermography
Heat flux		●	●	●	●
Vibrothermography	●	●	●	●	●
Heat waves	●	●	●	●	●	●
Sound emission testing	●	●	●		●	●
Field Measurement
Moiré-method	●		●		●
ESPI-method	●	●	●	●	●
Special procedures
Plastography	●	●	●	●	●	●
Hardness­measurement	●

The causes here lie specifically in the diversity of plastics, the possible variations resulting from filling and reinforcement, and the specific failure and damage mechanisms inherent in the plastics themselves and at the interfaces with the organic or inorganic fillers and reinforcing materials. Added to this are the high damping compared to metallic materials, the poor thermal conductivity and electrical insulation (see: electrical conductivity), and the high degree of heterogeneity and anisotropy of plastics, which can in some cases significantly limit the applicability of conventional, non-destructive testing methods (Table 1).

Consequently, in the field of non-destructive testing of polymers, certain other relevant testing methods are sometimes regarded as essential for fault characterisation; based on the classification principles, the following physical principles have emerged as recommended:

• radiographic testing methods (digital X-ray and gamma-ray flaw detection) [5],
• acoustic testing methods (sound, ultrasonic and acoustic emission testing) [6–8],
• thermographic testing methods (heat flux, thermal wave analysis and video thermography, vibrometry, lock-in thermography) [9–11]
• electromagnetic testing methods (coating thickness measurement and terahertz measurement technology) [12],
• crack testing (visual inspection, endoscopy, penetration testing, leak testing) [13],
• microwave testing (transmission and reflection methods) [14, 15],
• optical testing methods (holography, laser speckle interferometrie (ESPI), lock-in ESPI, ultrasonic ESPI, shearography, laser extensometry, stress optics, etc.) [16–18] and
• eddy current [19].

Specialised testing methods such as experimental strain and stress analysis, computed tomography based on various detectors, magnetic resonance testing and vibration analysis round off this list, as do the modern acoustic testing methods of phase array testing and the acousto-ultrasonic method, without claiming to be exhaustive. It can generally be observed that NDT has become an indispensable tool for efficient quality assurance in almost all branches of industry and serves to detect non-conforming defects, monitor the condition of machinery and plant, and carry out failure analysis.

By analogy with the definition of non-destructive materials testing, non-destructive polymer testing involves the examination of materials, components and structures made of plastics for quality defects such as faults or imperfections that could impair or prevent their integrity or usability before and during use, whereby the application of the non-destructive testing method must under no circumstances affect the functionality of the test object [3].

The fundamental aim of [[non-destructive testing (NDT) of plastics is therefore also to prevent damage through reproducible and repeatable testing procedures, in order to avoid risks to people, property and the environment. It produces a static, visible representation of macroscopic and microscopic defects, taking into consideration the damage tolerance of these defects with regard to the integrity and functionality of the structure or the component.

The growing importance of polymer matrix composites in the aerospace and automotive industries, as well as in alternative energy generation (wind turbines), naturally has implications for non-destructive testing of polymers. In these structures, the costs caused by component failure can be orders of magnitude higher than the component costs themselves [1]. For this reason, non-destructive testing of plastics – usually via indirect feedback – also aims to obtain information on the condition of the material or component, to detect and characterise damage conditions without causing further damage, in order to replace operationally critical components in good time or to avoid the unnecessary preventive replacement of fully functional parts.

NDT on plastics is therefore primarily aimed at characterising properties – that is, determining a physical interaction – and is thus, in terms of its methodology, a branch of measurement technology. The accuracy of the results, or the ability to detect defects, depends on the ‘responsiveness’ of the respective measured variable to the characteristic of interest, and specifically on the magnitude of the error range of the NDT measurement, as a larger error range requires higher safety factors and thus, for example, greater wall thicknesses. Non-destructive testing of plastics is, in principle, based on the component under investigation being excited in some way (thermally, mechanically or acoustically) and its ‘response behaviour’ being used to characterise defects. Thus, every testing method applied reveals both the test object and any existing defects in their interaction with specific vibrations or waves. As composite plastics have significantly more influencing factors than metals and considerably more complex failure modes, the required range of relevant NDT methods is very broad, although many of these testing methods are still at an experimental stage [1].

In contrast to non-destructive testing of polymers, polymer diagnostic utilises NDT methods by combining various hybrid methods whilst simultaneously applying different types of mechanical, thermal or environmental stresses to test specimens or components. This coupling serves primarily to determine the temporal and local damage kinetics and to elucidate relevant damage mechanisms, as well as to identify material-specific limit states, and is carried out with the following objectives:

• to increase the information content of conventional testing methods,
• to elucidate the relationships between microstructure and the properties of plastics and their composites,
• to evaluate correlations between structure or morphology and properties,
• to establish physically based functionalities,
• to record and describe local material properties in order to enhance design reliability (see: plastic component),
• to provide event- and structure-related interpretations of deformation phases (see: deformation mechanisms),
• to identify material damage and failure kinetics, and
• to characterise material limit states and diagnostic functions.

In principle, any NDT method or sensor technology is suitable for use as a hybrid method of material diagnostics, provided it exhibits sufficient damage sensitivity and meets the material-specific requirements of plastics.

See also

• Polymer testing
• Polymer diagnostic
• Plastography
• Non-destructive testing (NDT)

References

[1]	Busse, G.: Non-destructive polymer testing. In: Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, pp. 431–495 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see AMK-Library under A 22)
[2]	Bierögel, C.: Zerstörungsfreie Prüfverfahren. In: Schmiedel, H. (Ed.): Handbuch der Kunststoffprüfung. Carl Hanser, Munich (1992), 2nd Edition, pp. 417–442 (ISBN 978-3-446-16336-2; see AMK-Library under A 3)
[3]	Erhard, A.: Aufgaben und Abgrenzung der Zerstörungsfreien Prüfung. DGZfP-Jahrestagung, Fürth (2007), V11 Download as pdf
[4]	Rufke, B., Hentrich, R., Bierögel, C.: Zerstörungsfreie Prüfmethoden und detektierbare Fehlerarten an Kunststoffverbunden auf Basis von GFK und CFK, unveröffentlichte Studie, DOW BSL Schkopau, Technische Diagnostik (2002)
[5]	Nordmann, S., Hentrich, R., Schröter, H., Rufke, B., Sirch, C., Bierögel, C., Grellmann, W.: Durchstrahlungsprüfung von GfK-Bauteilen unter besonderer Berücksichtigung der Wanddickenmessung. In: Frenz, H., Wehrstedt, A.: Kennwertermittlung für die Praxis. Proceedings Werkstoffprüfung, 2002, Wiley-VCH Weinheim 2003, pp. 345–350 (see AMK-Library under B 3-99)
[6]	Grellmann, W., Steiner, R., Kotter, I. u. a.: Faserverstärkte rotierende Bauteile. Forschungshefte Forschungskuratorium Maschinenbau (FKM) Heft 202 (1995), pp. 1–67; DOI: https://doi.org/10.1007/978-3-642-58766-5_28
[7]	Bierögel, C., Sirch, C., Grellmann. W.: Korrelationen der mechanischen und akustischen Eigenschaften von Kunststoffen in Abhängigkeit von der Temperatur. In: Grellmann, W., Frenz, H.: Fortschritte in der Werkstoffprüfung für Forschung und Praxis – Werkstoffeinsatz, Qualitätssicherung und Schadensanalyse. Tagungsband Werkstoffprüfung, 2014, Wiley-VCH Weinheim 2015, pp. 155–160 (ISBN 978-3-9894516-8-9; see AMK-Library under B 3-99)
[8]	Schoßig, M., Zankel, A., Bierögel, C., Pölt, P., Grellmann, W.: ESEM investigations for assessment of damage kinetics of short glass fibre reinforced thermoplastics: Part 1: Results of in situ tensile test coupled with acoustic emission analysis. Composite Science and Technology 71 (2011) 257−265; DOI: https://doi.org/10.1016/j.compscitech.2010.12.004
[9]	Dillenz, A., Gerhard, H., Krohn, N., Pfleiderer, K., Stößel, R., Zweschper, Th., Busse, G.: Zerstörungsfreie Prüfung nichtmetallischer Werkstoffe: Neue Entwicklungen, DGZfP-Jahrestagung 2001, Berlin, Berichtsband https://www.ndt.net/article/dgzfp01/papers/v19/v19.htm (access on July 13, 2026)
[10]	Krohn, N., Busse, G.: Nichtlineare Vibrometrie zur Schadenscharakterisierung. DGZfP-Jahrestagung 2001, Berlin, Berichtsband https://www.ndt.net/article/dgzfp01/papers/v26/v26.htm (access on July 13, 2026)
[11]	Eyerer, P., Busse, G.: Photothermische Wärmewellenanalyse von Kunststoffen. Kunststoffe 73 (1983) 9, pp. 547–549; https://www.researchgate.net/publication/273760354_EYERER_P_BUSSE_G_Photothermische_Warmewellenanalyse_von_Kunststoffen_Kunststoffe_73_1983_9_S_547-549 (access on July 13, 2026)
[12]	Feige, V. K. S., Berta, M., Nix, S., Ellrich, F., Jonuscheit, J., Beigang, R.: Berührungslose Mehrlagen-Schichtdickenmessung industrieller Beschichtungen mittels THz-Messtechnik. Technisches Messen 79 (2012) 2, pp. 87–94; DOI: https://doi.org/10.1524/teme.2012.0198
[13]	Wallentowitz, H., Reif, K. (Eds.): Handbuch Kraftfahrzeugelektronik. Vieweg Verlag, Wiesbaden, 2. Auflage, (2008), (ISBN 978-3-528-03971-4)
[14]	Hinken, J. H.: Einführung in die Mikrowellenprüftechnik. DGZfP-Fachseminar 2015, V1 Download as pdf (access on Juli 13, 2026)
[15]	Hinken, J. H., Horst, G.: EMIR – ein direkt bildgebendes Verfahren der Mikrowellenprüfung. DGZfP-Jahrestagung 2013, Dresden, A1 Download as pdf (access on July 13, 2026)
[16]	Menner, P.: Erweiterte Möglichkeiten der Shearografie durch Verwendung thermischer Wellen. DGZfP-Zeitung 117 (2009) 12, pp. 45–47 Download as pdf (access on July 13, 2026)
[17]	Bierögel, C.: Hybrid methods of polymer diagnostics. In: Grellmann, W., Seidler, S. (Eds.): Polymer Testing. Carl Hanser, Munich (2022) 3rd Edition, pp. 497–513 (ISBN 978-1-56990-806-8; E-Book: ISBN 978-1-56990-807-5; see AMK-Library under A 22)
[18]	Föppl, L., Mönch, E.: Praktische Spannungsoptik. Springer, Berlin Heidelberg, 3rd Edition (1972), (ISBN 978-3-642-52169-0)
[19]	Mook, G., Simonin, J.: Wirbelstromprüfung – Lehren und Lernen. DGZfP-Jahrestagung 2012, Graz, P2 Download als pdf (access on July 13, 2026)