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New Sensor Design has Improved Performance in Pultrusion

  • Tuesday, 24th March 2015
  • Reading time: about 3 minutes

As part of the European COALINE project, Synthesites are working alongside other partners to develop an in-line clean one-stage process, which is free of VOCs and small particles emissions, able to produce properly coated composite pultruded profiles by means of the development and integration of the sensing technology and advanced die design and microwave aided curing to foster an improved composite coating adhesion with a reduced labour and process cost.

According to Synthesites, the COALINE advanced die configuration will allow to precisely determining: the point of injection of the resin, the length needed for its forming and polymerisation, the point in which the coating is injected and the length needed to obtain a coated composite profile.

It explains that the monitoring of composites manufacturing, the correlation of the electrical properties of the resin with process milestones is widely accepted as the most mature tool. However, the most popular dielectric systems have not managed to penetrate the market yet due to several drawbacks, such as the complexity of the measurements and the lack of quantitative correlation with useful material properties (such as the degree of cure or the glass transition temperature, Tg).

Three years ago, Synthesites says it launched a DC-based system measuring (in real-time and in- situ) the electrical resistivity of the resins, which has already penetrated the market showing besides simplicity and robustness at industrial level a good correlation between resistivity and Tg.

It says the system has many advantages of the dielectric systems as it is faster, cheaper and more accurate at industrial conditions and can be combined with several types of sensors for measuring in or around the mould.?Pultrusion and microwave curing of composites are very?particular processes with respect to monitoring and quality control (for instance in the pultrusion process, the part is moving through the die in contrast to the rest of composites’ manufacturing processes where the part is attached to the mould).

Regarding the monitoring of the transformation of the thermoset matrix during microwave curing, it has been demonstrated that the monitoring technology that has been developed by Synthesites can monitor successfully and without any problem the curing of composites that are cured with microwave heating. Furthermore, new sensing elements have been developed for the enhancement of the contact quality between the sensors and the running profile either in the die or after it. It explains that the flexible sensors can be used for in-situ and in-the-laminate cure monitoring to make possible the optimisation of the process. These models and sensing techniques are being validated in realistic trials at industrial conditions.

A LabView-based interface will be developed in order to show in real time the evolution of the process parameters measured directly in the equipment as well as the predicted parameters obtained in the modelling.

It is expected to read and show, in real time:

  • Power applied for each magnetron, reflection.
  • Temperature on each stage of the die.
  • Pulling force, pulling speed.
  • Curing degree.
  • Output of the modelling in regards to the curing degree and profile temperature at different positions inside the die.

Challenges achieved by the COALINE project are described as:

  • Manufacturing curved electrodes.
  • Attain good contact with the curved profile.
  • Ensure durability.

The COALINE project has received funding from the European Commission’s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement number 609149.

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