On avoiding thermal degradation during welding of high-performance thermoplastic composites to thermoset composites

Advances in Ultrasonic Welding of Thermoplastic Composites: A Review

“…Thermoplastic composite joining to thermoset composite is studied with different thermoplastic films as an interlayer. Some of the investigated polymers are Polyether ether ketone (PEEK) [116], Polysulfone (PSU) [119], Polyphenylene sulfide (PPS), Polystyrene (PS) [120], Polyetherimide (PEI) [118] and Polyvinyl butyral (PVB) [117]. The selection of the coupling film is highly constrained by a multitude of factors, such as the processing temperature, adhesion between the coupling film and the adherend, i.e., compatibility, and other factors [117].…”

“…The manufacturing temperature, i.e., the temperature at which the thermoset composite is cured during the co-curing with the film and processing temperature of the coupling film, i.e., the temperature range at which it is welded plays an important role in the bonding and the failure of the adherends. The other two challenges in the welding of the thermoplastic composite to thermoset composite is the bonding between them and the thermal degradation of the thermoset composite because of the high temperature at the interface during welding [116].…”

“…During the fusion bonding of the thermoplastic composite to thermoset composite, there is always a chance of the thermal degradation of the thermoset composite due to the high temperature. Villegas et al [116] carried out research work to prevent the thermal degradation of the thermoset composite during welding. In the investigation, the major finding was that thermal degradation can be avoided if the welding is carried out under 1 s of time.…”

Ultrasonic Welding of Thermoplastic Composites

“…In other cases, when the melting temperature of the thermoplastic polymer is below the curing temperature of the thermoset resin, e.g., poly-vinyl-butyral (PVB) and highperformance epoxy, the thermoplastic polymer can partially flow into the thermoset composite resulting in mechanical interlocking between both materials (Lionetto et al, 2018). Finally, the thermoplastic coupling layer can be physically and/or chemically treated to promote adhesion with the thermoset resin during the curing process, e.g., poly-ether-ether-ketone treated with ultraviolet-ozone radiation and epoxy (Villegas and Vizcaino Rubio, 2015;Shi et al, 2017). However, the reliability and durability of this last type of connection maybe questionable (Villegas and van Moorleghem, 2018).…”

“…Consequently, thermal degradation of the thermoset composite adherend can be difficult to prevent during the welding process, as reported for relatively slow welding processes such as induction welding (Schieler and Beier, 2016;Lionetto et al, 2018). The very short heating time in ultrasonic welding (which can be as short as a couple of hundred milliseconds) makes it however possible to avoid thermal degradation of the thermoset polymer even when the welding temperature is higher than its degradation temperature (Villegas and Vizcaino Rubio, 2015), resulting in welded joints with excellent quality (Figure 7). To illustrate this point the results of a recent study by Tsiangou et al (2019) show that CF/PEI to CF/epoxy ultrasonically welded joints achieved the same (single-lap shear) strength as reference CF/PEI to CF/epoxy joints obtained through an autoclave co-curing process.…”