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Materials 2017, 10(7), 685; doi:10.3390/ma10070685

Early Damage Detection in Composites during Fabrication and Mechanical Testing

I-Composites Lab, School of Materials, University of Manchester, Manchester M1 3NJ, UK
Aerospace Research Institute, University of Manchester, Manchester M1 3NJ, UK
Authors to whom correspondence should be addressed.
Received: 2 May 2017 / Revised: 30 May 2017 / Accepted: 19 June 2017 / Published: 22 June 2017
(This article belongs to the Special Issue Structural Health Monitoring for Aerospace Applications 2017)
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Fully integrated monitoring systems have shown promise in improving confidence in composite materials while reducing lifecycle costs. A distributed optical fibre sensor is embedded in a fibre reinforced composite laminate, to give three sensing regions at different levels through-the-thickness of the plate. This study follows the resin infusion process during fabrication of the composite, monitoring the development of strain in-situ and in real time, and to gain better understanding of the resin rheology during curing. Piezoelectric wafer active sensors and electrical strain gauges are bonded to the plate after fabrication. This is followed by progressive loading/unloading cycles of mechanical four point bending. The strain values obtained from the optical fibre are in good agreement with strain data collected by surface mounted strain gauges, while the sensing regions clearly indicate the development of compressive, neutral, and tensile strain. Acoustic emission event detection suggests the formation of matrix (resin) cracks, with measured damage event amplitudes in agreement with values reported in published literature on the subject. The Felicity ratio for each subsequent loading cycle is calculated to track the progression of damage in the material. The methodology developed here can be used to follow the full life cycle of a composite structure, from manufacture to end-of-life. View Full-Text
Keywords: acoustic emission; composites; distributed strain; optical fibre; piezoelectric sensors; structural health monitoring acoustic emission; composites; distributed strain; optical fibre; piezoelectric sensors; structural health monitoring

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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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Chandarana, N.; Sanchez, D.M.; Soutis, C.; Gresil, M. Early Damage Detection in Composites during Fabrication and Mechanical Testing. Materials 2017, 10, 685.

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