Strain measurement and cure monitoring in thin plates of composite materials by using twisted optical fibers

1996 ◽  
Author(s):  
Huiwen Wang ◽  
Jan Wu ◽  
Naiji Li ◽  
Hongjun Cao ◽  
Di Dai ◽  
...  
Keyword(s):  
Composite Materials ◽  
Optical Fibers ◽  
Strain Measurement ◽  
Thin Plates ◽  
Cure Monitoring

scholarly journals Damage detection in laminar thermoplastic composite materials by means of embedded optical fibers

2006 ◽  
Vol 60 (7-8) ◽  
pp. 176-179
Author(s):  
Aleksandar Kojovic ◽  
Irena Zivkovic ◽  
Ljiljana Brajovic ◽  
Dragan Mitrakovic ◽  
Radoslav Aleksic
Keyword(s):  
Composite Materials ◽  
Optical Fiber ◽  
Real Time ◽  
Optical Fibers ◽  
Impact Damage ◽  
Experimental Testing ◽  
Low Energy ◽  
Thermoplastic Composite ◽  
Woven Fabric ◽  
The Impact

This paper investigates the possibility of applying optical fibers as sensors for investigating low energy impact damage in laminar thermoplastic composite materials, in real time. Impact toughness testing by a Charpy impact pendulum with different loads was conducted in order to determine the method for comparative measurement of the resulting damage in the material. For that purpose intensity-based optical fibers were built in to specimens of composite materials with Kevlar 129 (the DuPont registered trade-mark for poly(p-phenylene terephthalamide)) woven fabric as reinforcement and thermoplastic PVB (poly(vinyl butyral)) as the matrix. In some specimens part of the layers of Kevlar was replaced with metal mesh (50% or 33% of the layers). Experimental testing was conducted in order to observe and analyze the response of the material under multiple low-energy impacts. Light from the light-emitting diode (LED) was launched to the embedded optical fiber and was propagated to the phototransistor-based photo detector. During each impact, the signal level, which is proportional to the light intensity in the optical fiber, drops and then slowly recovers. The obtained signals were analyzed to determine the appropriate method for real time damage monitoring. The major part of the damage occurs during impact. The damage reflects as a local, temporary release of strain in the optical fiber and an increase of the signal level. The obtained results show that intensity-based optical fibers could be used for measuring the damage in laminar thermoplastic composite materials. The acquired optical fiber signals depend on the type of material, but the same set of rules (relatively different, depending on the type of material) could be specified. Using real time measurement of the signal during impact and appropriate analysis enables quantitative evaluation of the impact damage in the material. Existing methods in most cases use just the intensity of the signal before and after the impact, as the measure of damage. This method could be used to monitor the damage in real time, giving warnings before fatal damage occurs.

Integration of optical fibers and piezoelectric ceramics in composite materials

1996 ◽  
Author(s):  
S. Bourasseau ◽  
Marc Dupont ◽  
M. Pernice ◽  
Alain Thiriot ◽  
P. Blanquet ◽  
...  
Keyword(s):  
Composite Materials ◽  
Optical Fibers ◽  
Piezoelectric Ceramics

scholarly journals Microwave Curing Characteristics of CFRP Composite Depending on Thickness Variation Using FBG Temperature Sensors

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1720 ◽  
Author(s):  
Heonyoung Kim ◽  
Donghoon Kang ◽  
Moosun Kim ◽  
Min Hye Jung
Keyword(s):  
Composite Materials ◽  
Thickness Variation ◽  
Specimen Thickness ◽  
Curing Time ◽  
Microwave Curing ◽  
Cure Monitoring ◽  
Curing Characteristics ◽  
Cfrp Composite ◽  
Curing Cycle

Microwave curing technology, which has seen increased commercialization recently due to its ability to cut the curing time and ensure high quality, requires an understanding of the curing characteristics of composite materials of varying thickness. Therefore, this study aimed to perform cure monitoring to evaluate the effects of variations in thickness on the quality of microwave curing. For this study, a fiber Bragg grating sensor was used to measure temperature changes in specimens during the curing cycle for cure monitoring which is generally used for optimization of the curing cycle; then, the time taken for temperature increase and overshoot of the specimen, and the times at which the specimen thickness varied, were quantitatively evaluated. Testing confirmed that microwave curing reduced the curing time in the sections in which the temperature rose; also, the specimen thickness caused overshoot of up to approximately 40 °C at the side, which can affect the curing quality of the composite materials. Furthermore, voids were observed on the side of all specimens. The results indicated that, in order to improve the quality of microwave curing of composite materials, the curing cycle should be optimized by considering the characteristics of the microwave curing equipment.

Composite Cure Monitoring With Infrared Transmitting Optical Fibers

1989 ◽  
Author(s):  
Mark A. Druy ◽  
Lucy Elandjian ◽  
W. A. Stevenson
Keyword(s):  
Optical Fibers ◽  
Cure Monitoring

scholarly journals Comparison among Different Fiber Coatings on the Concrete Shrinkage Test for Distributed Optical Strain Measurements based on Rayleigh Backscattering

2019 ◽  
Author(s):  
Martin Weisbrich ◽  
Klaus Holschemacher ◽  
Thomas Bier
Keyword(s):  
Optical Fibers ◽  
Strain Measurement ◽  
Rayleigh Scattering ◽  
Fiber Optic ◽  
Reference Method ◽  
Shrinkage Strain ◽  
Rayleigh Backscattering ◽  
Advantages And Disadvantages ◽  
Optical Strain ◽  
Fiber Coatings

The fiber optic strain measurement based on Rayleigh scattering has recently become increasingly popular in automotive or mechanical engineering for strain monitoring and in the construction industry in general, especially structural health monitoring. This technology enables the monitoring of strain along the entire fiber length. Several publications have been published, particularly on the applications to the structural component. This article addresses integrating optical fibers of different coatings into the concrete matrix to measure the shrinkage deformations. In this context, three different coating types were investigated regarding their strain transfer. The fibers were integrated into fine-grained concrete prisms, and the shrinkage strain was compared with a precise dial gauge. The analysis shows a high correlation between the reference method and the fiber measurement, especially with the Ormocer coating. The used acrylate coating is also consistent in the middle area of the specimen but requires a certain strain introduction length to indicate the actual strain. The main result of this study is a recommendation for fiber coatings for shrinkage measurement in fine grain concretes using the distributed fiber optic strain measurement. In addition, the advantages and disadvantages of the measurement method are presented.

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