Non-destructive Testing of Metal-Polymer Laminates with a Digital Holographic Vibrometer
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Non‑destructive Testing of Metal‑Polymer Laminates with a Digital Holographic Vibrometer Jagoda Nowak‑Grzebyta1,2 · Frans Meijer1 · Karol Bula2 · Ewa Stachowska1 Received: 30 October 2019 / Accepted: 12 June 2020 © The Author(s) 2020
Abstract This paper presents the use of a digital holographic vibrometer to investigate metal-polymer laminates by non-destructive testing. A polymer strip was glued to a metal one of the same size. Connection defects could be detected by a local change of the vibration amplitude, even when hidden from view for the observer. The amplitudes of the oscillations excited in the samples were up to 40 nm. This method proved to be non-destructive, allowing the samples to be (re)used after testing, or being studied with other test methods. Keywords Polymers · Laminates · Digital holographic vibrometer · Connection defects
1 Introduction Composite materials are nowadays widely used in many applications: aero-space, cars, wind turbines and others. The reliability of composite materials is based on the quality of the connection. The realization of good adhesion between metal and polymer can cause problems due to the difference of their surface energy. Most synthetic polymers used commercially have a low surface energy; by contrast metallic coatings have a high surface energy. This leads to low adhesion between the two materials. The key to achieve a strong polymer-metal adhesive connection is to choose materials depending on the type of function groups presented in the polymer and properly prepare its surface [1–4]. Most testing methods providing information about the strength of the connection between the components in composites cause irreparable damage to the samples tested. Such examinations make it impossible to use those samples for further analysis or (re)utilization and are called destructive testing. It is therefore desirable-or even necessary-to detect * Jagoda Nowak‑Grzebyta [email protected] 1
Division of Metrology and Measurement Systems, Institute of Mechanical Technology, Poznan University of Technology, ul. Piotrowo 3, 60‑965 Poznan, Poland
Division of Polymer Engineering, Institute of Materials Technology, Poznan University of Technology, ul. Piotrowo 3, 60‑965 Poznan, Poland
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hidden defects in layered structures using Non-Destructive Testing (NDT) [5–7]. During the production of polymer objects defects can occur inside the polymer, not visible from the outside when the polymer is not transparent. Another problem can arise when different parts are glued together and both parts are not sticking together in all places. A typical example is a polymer strip reinforced by a metal plate, with a local failure of the glue. It is important to check components before, during or after use for defects in such a way that they can be used or reused. A well-established method to study defects in laminates are shearographic and ultrasonic measurements [8–12]. Also Laser scanning Doppler Vibrometry [LDV] is used [9, 13–17]. We studied this type of defects wit
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