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Castanet-Tolosan, France

Sonnenfeld C.,Vrije Universiteit Brussel | Sonnenfeld C.,CNRS Crystallography and Material Science Laboratory | Luyckx G.,Ghent University | Collombet F.,CNRS Clement Ader Institute | And 12 more authors.
Proceedings of SPIE - The International Society for Optical Engineering

We report on the use of a fiber Bragg grating (FBG) based sensor written in a photonic crystal fiber (PCF) to monitor the cure cycle of composite materials. The PCF under study has been specifically designed to feature a high phase modal birefringence sensitivity to transverse strain and a very low sensitivity to temperature. We exploit these particular properties to measure strain inside a composite material in the out-of-plane direction. The embedded FBG sensor has been calibrated for transverse and axial strain as well as for temperature changes. These FBGs have then been used as embedded sensors during the manufacturing of a composite material in order to monitor how strain develops inside the composite during the cure cycle. We show that our sensors allow gaining insight in the composite cure cycle in a way that would be very difficult to achieve with any other sensor technology. © 2013 SPIE. Source

Torres M.,CNRS Clement Ader Institute | Torres M.,National Polytechnic Institute of Mexico | Collombet F.,CNRS Clement Ader Institute | Douchin B.,CNRS Clement Ader Institute | And 2 more authors.
Applied Composite Materials

In this paper, the classic embedding technique, with bared sensors, and a recent proposal, the monitoring patch, are compared with the aim to improve the composites in-core instrumentation. The monitoring patch emerges with the need to industrialize sensors integration inside composite structures; thus, a complete evaluation of its mechanical performance has to be done. Numerical and experimental campaigns are carried out on elementary carbon-epoxy coupons to evaluate the benefits and disadvantages of this procedure compared with the typical interlayer sensor embedding. The results show that the use of monitoring patch does not affect significantly the mechanical performance of instrumented coupons. An instrumentation transfer function (ITF) is proposed to link the information that electronic devices can detect, the mechanical phenomena around these electronic devices and the measurements data acquired by global or local techniques (DIC, FEM, gauges). A good correlation between the strain data acquired and the strain values calculated by FEM confirms the approach of the ITF to evaluate the influence of the monitoring patch on the measured signal. © 2013, Springer Science+Business Media Dordrecht. Source

Torres M.,CNRS Clement Ader Institute | Torres M.,National Polytechnic Institute of Mexico | Collombet F.,CNRS Clement Ader Institute | Douchin B.,CNRS Clement Ader Institute | And 2 more authors.
Composite Structures

In this paper, the Multi-Instrumented Technological Evaluator (MITE) is presented as an alternative approach to study the mechanical performance of composite structures with singularity details. The goal is to have an enrichment of the calculation/test correlation by means of the interaction of four complementary aspects: the composite structure, the multi-axial testing machine, the numerical models and the multi-sensor instrumentation. As a first plan, the MITE suggests the testing of a carbon-epoxy composite plate with two drop-offs under combined loads. By means of Finite Element models (FE-models), the kinematics of the testing machine is applied to the composite plate to have a first numerical approach of its behaviour. Then, the experimental campaign is accomplished with multi-instrumentation devices and techniques such as strain gauges and Digital Image Correlation (DIC). The strain values calculated by FE-model and the experimental strain data acquired by gauges and DIC are confronted in order to understand the main fracture mechanisms acting on the drop-off zones, to determine the accuracy of the measurements techniques and to assure that a correct calculation/test correlation is achieved. © 2015 Elsevier Ltd. Source

Torres Arellano M.,CNRS Clement Ader Institute | Crouzeix L.,CNRS Clement Ader Institute | Collombet F.,CNRS Clement Ader Institute | Douchin B.,CNRS Clement Ader Institute | Grunevald Y.-H.,Composites
Applied Composite Materials

Sensor embedding is one of the main operations in dealing with composites incore instrumentation. In this work, an alternative encapsulation technique called "monitoring patch" is proposed to achieve correct sensor embedding, to facilitate the industrialised instrumentation procedure and to adapt the sensors according to the geometry and material heterogeneities required of the composite structures. The monitoring patch is mainly developed with the aim to reduce the variability effects produced if the sensor alone is placed. In this initial study, a first patch's configuration is manufactured with CTMI preimpregnate epoxy-woven glass, hosting two kinds of silicon prism sensors. The monitoring patch is then placed in the thick middle plane of an epoxy-carbon M21 T700GC quasiisotropic plate. The plates are instrumented with strain gauges and tested using digital image correlation (DIC). The strain field maps are calculated to analyse the over-strain zones and to infer fracture paths. At the same time, a FEM model is developed to compare the numerical and the experimental observations. The results show that the mechanical strength of the instrumented plates is not significantly affected by the presence of the patch. The failure path of the instrumented plates with monitoring patch is found along the patch perimeter; therefore, the sensors can be recovered without damage even after the failure of the instrumented structure. The feasibility of the monitoring patch is discussed with other embedding techniques. In further studies, the monitoring patch will host a streaming sensor with an aim to carry out in-core strain measurements. © Springer Science+Business Media B.V. 2011. Source

Torres M.,CNRS Clement Ader Institute | Torres M.,Research Fellow Engineering and Industrial Development Center | Collombet F.,CNRS Clement Ader Institute | Douchin B.,CNRS Clement Ader Institute | And 4 more authors.
Sensors and Actuators, A: Physical

In this work, tunnelling junction sensors (TJS) are proposed for monitoring the curing of Carbon Fibre Reinforced Plastic (CFRP). Tunnelling junction sensors are very sensitive to temperature changes; therefore they are suitable for this application. TJS are manufactured by Low-Pressure Chemical Vapour Deposition (LPCVD) and electronically characterized to obtain their V(I) diagram. One sensor is embedded on a carbon-epoxy plate for measuring temperature evolution during composite's autoclave cycle. By means of a temperature-voltage-time curve, the evolution of sensor's signal related to temperature changes can be tracked. The main goals are to verify the viability to apply this technology to composite's curing process and to provide a first approach of the initial state of the composite plate by verifying the temperatures at each curing stage. Both purposes were achieved and help to better understand the composite polymerization process, which has a strong influence on the composite's mechanical performance. © 2015 Elsevier B.V. All rights reserved. Source

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