Structural Behaviour of Thermoplastic Welded Single-Lap Shear Joints with Recycled Core Material
Topic(s) : Special Sessions
Co-authors :
Arne SCHILLER (NETHERLANDS), Chiara BISAGNIAbstract :
Considering the need to build a more sustainable economy for the future, the transportation sector and especially the aerospace industry are required to significantly reduce their impact on the environment. Hence, recyclability is a desirable advantage of thermoplastic composites when compared to laminates with a thermosetting matrix material. In addition, thermoplastic composites may be manufactured cost-efficiently and in high volumes using thermoplastic welding [1]. While many studies have been published on the effects of either recycling or of welding on the mechanical response of thermoplastic structures [1,2], their combination has yet to be investigated thoroughly. Therefore, a test campaign was conducted to evaluate how recycled material in thermoplastic welded single-lap shear (SLS) joints influences their structural behaviour.
Virgin fabric T300/PolyPhenylene Sulfide (PPS) and unidirectional T700/Low-Melt Polyaryletherketone (LM-PAEK) laminates are consolidated and subsequently joined to form SLS joints via induction and conduction welding. Scrap material from this production cycle is collected and milled to a fine shred with chip sizes of less than 5 mm. The recycled material is placed between two face sheets of corresponding virgin fibre-reinforced polymers and re-consolidated. These laminates with recycled core material are then welded with the same processes as their virgin counterparts. In total, there are two sets each of virgin and partly recycled SLS joints: one manufactured from induction welded T300/PPS and one made from conduction welded T700/LM-PAEK.
Mechanical tests are performed based on the ASTM standard D5868. The test setup is illustrated in Figure 1. Displacement fields are measured on the front and side of the specimens using 2D and 3D digital image correlation. An additional camera tracks the crack propagation along the weld line on the back side of the samples. Final fracture is captured with a high-speed camera. Together with the loading history recorded by the test bench, stiffness, strength, damage evolution, as well as the failure mode of the samples are evaluated.
Figure 2 showcases representative load-displacement curves for each of the four specimen types. A clear reduction in stiffness and strength is evident when comparing virgin and partly recycled samples of the same material due to the degradation of material properties associated with the recycling process. For example, the average maximum load of T300/PPS drops from 13.42 kN to 11.39 kN which corresponds to apparent shear strengths of 20.40 MPa and 17.59 MPa. The final contribution will include a discussion of the observed damage evolution and failure modes to correlate them to the different raw materials and manufacturing processes in order to improve future recycled composite structures.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101006952, SUSTAINair.
Virgin fabric T300/PolyPhenylene Sulfide (PPS) and unidirectional T700/Low-Melt Polyaryletherketone (LM-PAEK) laminates are consolidated and subsequently joined to form SLS joints via induction and conduction welding. Scrap material from this production cycle is collected and milled to a fine shred with chip sizes of less than 5 mm. The recycled material is placed between two face sheets of corresponding virgin fibre-reinforced polymers and re-consolidated. These laminates with recycled core material are then welded with the same processes as their virgin counterparts. In total, there are two sets each of virgin and partly recycled SLS joints: one manufactured from induction welded T300/PPS and one made from conduction welded T700/LM-PAEK.
Mechanical tests are performed based on the ASTM standard D5868. The test setup is illustrated in Figure 1. Displacement fields are measured on the front and side of the specimens using 2D and 3D digital image correlation. An additional camera tracks the crack propagation along the weld line on the back side of the samples. Final fracture is captured with a high-speed camera. Together with the loading history recorded by the test bench, stiffness, strength, damage evolution, as well as the failure mode of the samples are evaluated.
Figure 2 showcases representative load-displacement curves for each of the four specimen types. A clear reduction in stiffness and strength is evident when comparing virgin and partly recycled samples of the same material due to the degradation of material properties associated with the recycling process. For example, the average maximum load of T300/PPS drops from 13.42 kN to 11.39 kN which corresponds to apparent shear strengths of 20.40 MPa and 17.59 MPa. The final contribution will include a discussion of the observed damage evolution and failure modes to correlate them to the different raw materials and manufacturing processes in order to improve future recycled composite structures.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101006952, SUSTAINair.