Soudage et réparation de composites thermoplastiques par chauffe par induction

Abstract

This study tries to prove the applicability and advantages of thermoplastic composite induction repair and welding processes in the industrial world in an effort to promote a greener and more durable approach. The heating is provided by the induction process, where a conductive part, named susceptor, generates heat via Eddy currents. Afterwards, the susceptor transmits its heat by conductivity to the workpiece and a pressure is applied to consolidate the sample. The position, the type, and the number of susceptors combined with the type of pressure medium are adapted with the respective process whether reparation or welding is the objective. The resin used is an acrylic resin named Elium 188. This resin has the advantage of having the possibility to be infused at ambient temperature, as epoxies, and presents similar mechanical properties as their competing industrial epoxy counterparts. For the first component of the project, which is repair, compression after impact samples were produced and then impacted by an impact tower at 80 J. Afterwards, an induction repair method was developed with the objective of regaining the most out of the previously lost mechanical properties. The samples were then compressed until failure, then compared with reference and only impacted samples to evaluate the percentage of compressive mechanical properties recovered. The samples were initially degraded of 21,5 % of their base reference value following the impact, then, once repaired, 13,8 % of the lost properties were restored. These values are comparable to the values obtained from the project partner at CDCQ with their infrared heating repair method. But the cycle time of the induction repair proved faster by 4 minutes and 30 seconds for a total cycle time of 10 minutes. The second section of the second component of the project, continuous welding, creates a method to obtain a strong welded joint with a low cycle time. The ideal cycle time is evaluated at 8,33 mm/sec welding speed that represents the equivalent gluing time of a work piece. This objective is fulfilled by continuous welding at a speed of 9 mm/sec. This time, mechanical performance of the lap shear test for a continuously welded joint reaches 9,21 MPa which surpasses the performances of the glue at 7,82 MPa. The values are closer to the moulded joint (10,09 MPa) that represent the apparent maximum performance that can be obtained. A gel coat, which was applied to the upper surface of the lap shear samples to evaluate the effect of the process on the aestheticism, was unaffected. These results are encouraging for induction repair and welding of thermoplastic composites in the industrial world and for thermoplastic usage in general.

Date	19 Jun 2021
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Martine Dubé (Supervisor) & Yves Mathieu (Co-supervisor)