Avaliação de métodos de união de materiais compósitos termoplásticos

Abstract

This study presents the results of the fabrication of laminated plates of carbon fiber and Elium®150 resin and glass fiber using the Vacuum Assisted Resin Transfer Molding (VARTM) method. It describes the use of material joining techniques, such as bonding and infrared light welding, using this resin for joining composite materials. Elium® resin was thermally characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and thermomechanical analysis (TMA). The DSC analysis of the pure resin resulted in a peak curing temperature of 82.92ºC, glass transition temperature (Tg) of 94.16ºC, and curing enthalpy of 216.63 J/g. The DMA results showed a Tg of 50.82ºC for the pure resin, 71.9ºC for the carbon fiber, and 98.47ºC for the glass fiber. TMA results showed a Tg of 91ºC for the carbon fiber and 93ºC for the glass fiber. TGA indicated the onset degradation temperature of 300ºC for both the pure resin and the composites. Ultrasound tests did not detect defects or voids in the glass or carbon laminates. Processing parameters were established using 150, 175, and 200ºC with pressures of 0.4 to 0.5 MPa after the heating phase in the welding process. Shear tests demonstrated higher shear stress values of 14.6 MPa for glass fiber composite samples processed at 150ºC and 0.4 MPa pressure. The glass fiber samples showed better anchorage between the fiber and the matrix due to more effective chemical compatibility. The carbon fiber samples exhibited significant adhesive failures, with the resin detaching from the fiber, indicating insufficient adhesion. This behavior is consistent with the loss of matrix rigidity observed through DMA, particularly at higher welding temperatures. All bonded laminate samples exhibited higher shear strength, with values of 14.68 MPa (carbon fiber) and 16.73 MPa (glass fiber) compared to infrared light-welded samples, which showed maximum values of 14.16 MPa (glass fiber) and 9.91 MPa (carbon fiber). These results support the fact that the bonded samples were processed below the glass transition temperature determined by the DMA technique, thus maintaining their rigidity.