Nowadays, the development of composites based on recycled materials has become a major concern of different industry sectors. Our work mainly aims to assess the reliability of composites based on thermoplastic matrix for electric applications such as the mechanical support for the HV terminal system of internal combustion engines. We are particularly interested by polymer composites based on recycled Polyethylene Terephthalate (PET). The Polyethylene Naphthalate (PEN) is relatively close polyester to PET since it owns a significant performance in particular in thermal endurance. It will be mainly used for comparison proposes with the recycled PET and to check the possibility to mix them together to form blend composites with improved properties that can be used in automotive engines.
The proposed work is to characterize the dielectric properties of composite materials made with recycled PET and PEN resins, particularly in terms of the electrical and thermal stress endurance as well as the dielectric response. This project is mainly divided into two major tasks:
The first one is to analyse the failure mechanisms that require the preparation of specimens and microscopic observation using both optical (OM) and scanning electronic microscopy (SEM). Dielectric breakdown measurements were performed at temperature in thoroughly degassed oil using high voltage source as per ASTM-D149 and the obtained data was statistically analyzed using the two-parameter Weibull distribution function. Thermal aging tests were also carried out in order to evaluate the dielectric endurance of the different composites. Using accelerated electro-thermal aging, lifetime components may be estimated.
The second task consists of analyzing the state of the matrix-reinforcement interface. The presence (or absence) of interfacial relaxation mechanisms will allow to investigate the state of the matrix-reinforcement interface. This knowledge is of great importance to assess the electrical reliability of the different materials since the failure mechanisms are usually controlled by the polymer /reinforcements interface. This part is less linked to industrial needs but may help to establish the different reinforcements impact (glass fibers and mica) on materials complex permittivity. Dielectric relaxation measurements were carried out at a large temperature window from the room temperature to temperatures below the glass transition and in the frequency domain from 10-2 to 105 Hz. The effective permittivity of the different composites was modeled and different models suggested in the literature are compared with the obtained results.
| Date | 1 Aug 2017 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Éric David (Supervisor) |
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Mebarki, F. (Author),
David (Supervisor),
1 Aug 2017Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering