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Appl. Sci. 2018, 8(7), 1141; https://doi.org/10.3390/app8071141

In-Situ Strain Measurements in Large Volumes of Hardening Epoxy Using Optical Backscatter Reflectometry

Norwegian University of Science and Technology, NTNU, Department of Mechanical and Industrial Engineering, Richard Birkelands vei 2b, 7024 Trondheim, Norway
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Received: 25 May 2018 / Revised: 29 June 2018 / Accepted: 30 June 2018 / Published: 13 July 2018
(This article belongs to the Section Mechanical Engineering)
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Abstract

Some large engineering structures are made by casting polymers into a mold. The structures can have complicated geometries and may be filled with other components, such as electrical transformers. This study investigated casting of large components made of epoxy. Epoxy is easy to pour, bonds well and has relatively low cure shrinkage. However, the cure shrinkage can lead to significant stresses or strains, causing large deformations that can lead to cracks.Understanding the curing process and related shrinkage is important for designing molds and controlling the production process. This study applied a new experimental method to measure strains due to cure shrinkage allowing many accurate local measurements along the length of an optical measurement fiber. The method is based on Optical Backscatter Reflectometry. Six distinct stages of the curing process can be identified. Previous measurements were limited to a few point measurements in small samples. This paper shows cure shrinkage in large samples and identifies some unexpected changes in behavior when going from small to large specimens. The behavior is explained qualitatively. View Full-Text
Keywords: Optical Backscatter Reflectometry; OBR; strain measurements; shrinkage; hardening; curing, running reference; epoxy; in-situ; DSC; RIMR 135; DGEBA; RIMH 137 Optical Backscatter Reflectometry; OBR; strain measurements; shrinkage; hardening; curing, running reference; epoxy; in-situ; DSC; RIMR 135; DGEBA; RIMH 137
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Heinze, S.; Echtermeyer, A.T. In-Situ Strain Measurements in Large Volumes of Hardening Epoxy Using Optical Backscatter Reflectometry. Appl. Sci. 2018, 8, 1141.

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