Documents published in Scipedia

• Resin infusion monitoring with distributed measurement fiber optic sensors

  A. Pedraza, D. del-Río-Velilla, A. Fernandez-Lopez

  Materiales Compuestos (Online first).

  
  

  Abstract

  Despite advances in composite materials, manufacturing processes still present high uncertainty and variability, which affect quality and structural properties. In the case of resin infusion (RLI) manufacturing methods, methods have been developed to predict resin flow, ranging from analytical and numerical methods based on Darcy's law to active control techniques, although the number of sensors and the difficulties of measuring inside the preforms limit the practical use of these techniques. Fiber optic sensors (FOS) are particularly suitable for process monitoring due to their small size and ability to be embedded without significantly altering material properties. However, FOS monitoring is affected by temperature variations associated with the manufacturing process itself (mold temperature and chemical reactions), as the typical readings of these sensors are a linear combination of temperature and strain. This work will explore whether it is possible to use these sensors to monitor the different manufacturing stages.

  Abstract
  Despite advances in composite materials, manufacturing processes still present high uncertainty and variability, which affect quality and structural properties. In the case [...]

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• Measurement of the influence of residual stresses on the composite material and their influence on the mechanical properties

  A. Pedraza, A. López, D. Velilla

  Materiales Compuestos (Online first).

  
  

  Abstract

  Although the occurrence of residual stresses is inherent to the manufacturing process of composite structures, and although their influence on the mechanical properties of the material is well known, the difficulty to measure the internal stresses in the laminate together with the multiple variables associated with the manufacturing process generally prevent the performance of a systematic study that relates the properties of the material with the stresses that originate in this process, mainly in the curing process. Fiber optic sensors based on Bragg networks have been used to measure stresses in the curing process for a long time. However, their use has not been widespread due to the cost of the sensors, their difficult handling, and the punctual information they provide. Thus, in this study, the results of the monitoring of curing by means of distributed measurement techniques based on Rayleigh scattering are presented. For this purpose, standardized specimens will be fabricated using IM7/8852 prepreg composite material and will be instrumented with fibers embedded in several. The stresses generated during the whole manufacturing process will be monitored, using molds with different thermal expansion coefficients. Additionally, measurements will be performed on symmetrical laminates manufactured by joining non-symmetrical laminates. Both the curing process and the mechanical tests will be continuously monitored using an optical interferometer OFDR (Optical Frequency-Domain Reflectometer) based on Rayleigh OBR (Optical Backscatter Reflectometry) scattering.  The measurements obtained with this instrument will be processed with a technique capable of decoupling temperature and deformation.

  Abstract
  Although the occurrence of residual stresses is inherent to the manufacturing process of composite structures, and although their influence on the mechanical properties of [...]

  • 126
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