Experimental studies of mechanical behavior and damage mechanisms of recycled flax/Elium thermoplastic composite

The aim of this study is to investigate the effects of recycling on the mechanical properties of Elium resin reinforced by flax fibers. A thermocompression recycling process is investigated and applied to production waste of thermoplastic composites. Five recycling operations are carried out on the initial material. Specimens are tested under static and fatigue tensile tests. In addition, the acoustic emission technique is used to identify damage mechanisms evolution during mechanical tests. Recorded events are post processed by the k-means unsupervised pattern recognition algorithm. The classes of acoustic emissions obtained are correlated with scanning electron microscopy observations to justify the existence of damage mechanisms detected. Results of static tests show that the ultimate tensile properties of the composites studied decrease with recycling operations. However, an increase in the elastic modulus is reported. In the fatigue tests, results show that stiffness, hysteresis loop and loss factor are affected by recycling operations. Also, a decrease in the life time with reprocessing conditions is observed. In acoustic tests, depending on the recycling operations, two or three classes of events are detected. The acoustic characteristics of these classes are compared. Then, a correlation between these AE classes of events and damage mechanisms observed is proposed.