Fracture behavior and damage development in self-reinforced PET composites assessed by located acoustic emission and thermography: Effects of flame retardant and recycled PET

Self-reinforced polyethylene terephthalate (srPET) composites were produced by hot pressing from woven fabrics composed of double covered uncommingled yarns. The mid section of the latter contained recycled PET homopolymer filaments (reinforcement) whereas the covering filaments (overtaking the role of the embedding matrix) were spun from a PET copolymer with and without flame retardant. The fracture of the srPET was studied in tensile loaded notched specimens using located acoustic emission (AE), infrared thermography (IT) and visual inspection in situ. The crack growth was reconstructed by evaluating the located AE and IT results and compared with the observed one. In the knowledge of the crack propagation the J-integral resistance (JR) fracture mechanics concept was followed to characterize the fracture behavior. srPET with fire retardant matrix exhibited lower JR characteristics than the unmodified composite. This was traced to differences in the failure modes considering the amplitude distribution of the AE events and post mortem failure analysis. Size of the damage zone was estimated by considering the located AE (≈20 mm) and IT results (≈15 mm), and the related difference discussed.