Strain fields in adhesively bonded patch repairs of damaged Metallic beams

Grave, Jon Harald Lambert; Echtermeyer, Andreas T.

doi:10.1016/j.polymertesting.2015.09.013

Cited by 8 publications

(7 citation statements)

References 4 publications

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“…In [30], the reaction is described in more details. It should be mentioned that different types of epoxy were used in composite structures and the same OBR system yielded consistently successful strain results [32,33]. However, for the particular problem of cure shrinkage monitoring, only the above-mentioned epoxy system have been investigated thus far.…”

Section: Methodsmentioning

confidence: 99%

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

Heinze

Echtermeyer

2018

Applied Sciences

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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.

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Section: Methodsmentioning

confidence: 99%

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

Heinze

Echtermeyer

2018

Applied Sciences

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“…It is to be noted that these strain values are still below the maximum absolute strain that could be measured with this same instrument in adhesive joints [35]. Thus, the deteriorating signal cannot be attributed to instrument errors or the OBR technique in general.…”

Section: Strain Determined By the Regular Methodsmentioning

confidence: 71%

“…It is basically a long array of many individual strain gauges. OBR is a relatively new technique and has been used so far in structures to, e.g., determine strain fields under load, assess crack development or in general structural health monitoring [31][32][33][34][35][36][37][38].…”

Section: Introductionmentioning

confidence: 99%

A Running Reference Analysis Method to Greatly Improve Optical Backscatter Reflectometry Strain Data from the Inside of Hardening and Shrinking Materials

Heinze

Echtermeyer

2018

Applied Sciences

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Due to the increasing ease of use and the superiority of the results, distributed strain measurements, utilizing Optical Backscatter Reflectometry (OBR), have become more important and widespread over the last few years. Strains are calculated from the difference between an actual optical Raleigh backscattering measurement and an initial reference value. However, under certain physical conditions, e.g., pinching or microbending of the optical fiber, no meaningful strain values are yielded by the commonly-used method to analyze OBR data. Such conditions were experienced in this study where the optical fiber was embedded into hardening epoxy for measuring shrinkage due to curing. In this work, it is shown that a new data analysis method called the “running reference analysis method” can overcome such obstacles and deliver meaningful strain values in circumstances in which the traditional method fails. In the new approach, each measurement is compared to the previous measurement, and the strain differences are added up to the absolute strain value. This method does not require a new experimental technique and will also work on old measurement files. It is also useful for other types of (OBR) strain measurements that contain many outliers and is not restricted to the investigation of cured epoxy.

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“…The use of CFRP patches is an efficient and economic method for structural reinforcement. In addition to their excellent mechanical properties (e. g., high strength and stiffness), CFRP patches share multiple physical and chemical advantages (e. g., they are light weight, have great formability, and superior corrosion resistance); therefore, they are widely used in engineering fields, such as aerospace, automotive, and civil structures [22–28].…”

Section: Discussionmentioning

confidence: 99%

Digital Image Correlation Measurement of the Deformation and Failure in PBX Brazilian Discs Reinforced with CFRP Patches

Wang

Tang

Liu

et al. 2021

Propellants Explo Pyrotec

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Polymer‐bonded explosive (PBX) is a mechanical weak link in weapons systems. PBX is susceptible to cracking owing to its brittle nature, which seriously threatens the security and reliability of the weapons system. In this work, a novel strengthening method making use of a carbon fibre reinforced polymer (CFRP) patch was adopted to enhance the mechanical performance of the PBX. Brazilian compression tests were conducted on the unreinforced, locally reinforced, and fully reinforced PBX discs to elucidate the strengthening mechanism of the patch. Digital image correlation was employed to characterise the deformation and failure processes of the discs during the full testing period. The results showed that failure of the PBX was caused by initiation and extension of the deformation that localises within the regions near the loading positions. The CFRP patches provided the benefits of load transfer and deformation confinement, which alleviated stress concentration in the disc. Consequently, collapse of the patched discs was delayed, and the load‐carrying ability was improved. The findings of this study may deepen our understanding of PBX failure behaviours, and further the performance optimisation of weapons systems.

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Strain fields in adhesively bonded patch repairs of damaged Metallic beams

Cited by 8 publications

References 4 publications

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

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

A Running Reference Analysis Method to Greatly Improve Optical Backscatter Reflectometry Strain Data from the Inside of Hardening and Shrinking Materials

Digital Image Correlation Measurement of the Deformation and Failure in PBX Brazilian Discs Reinforced with CFRP Patches

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