Learning more on thermoplastic composites with infrared thermography

Thermoplastic matrix-based composites (TC) are becoming ever more popular due to their many advantages over both thermoset matrix-based ones and metals. In fact, on one side, they are characterized by high damage tolerance and interlaminar toughness, due to the presence of the amorphous phase which can limit the crack propagation and allow larger deformations. On the other side, they show also advantages over the thermoset composites in terms of potential recyclability after life-cycle, reprocessing, faster production processes, chemical and environmental resistance and, usually, reduced manufacturing costs. In addition, TC performances can be tailored by the addition of a compatibilizing agent to the matrix, which allows to create a multitude of different materials. Of course, once a new material is created it requires characterization for its appropriate exploitation. In this context, infrared thermography (IRT) represents a viable inspection means since it is non-contact, non-intrusive and can be used to monitor the entire existence of a product, from its manufacturing process to completion as well as inservice life. In this work, IRT is used to investigate composite materials based on a polypropylene matrix, which may be either neat, or modified by addition of a relatively low amount of a specific compatibilizing agent, and reinforced with glass, or jute, fibres. IRT is used with a twofold function. First for non-destructive evaluation of materials to assure absence of manufacturing defects and to detect damage caused by loading. In particular, non-destructive evaluation is carried out with lock-in thermography which allows assessing the material conditions at different layers in a fast way. Second, IRT is used to visualize thermal effects induced in the material by cyclic bending, or impact. The obtained results show that the presence of a compatibilizing agent in the matrix modifies the material thermal response to two types of load: cyclic bending, or impact. It results possible to follow the failure under impact from the initial deformation, to the appearance of cracks, or breakages. The comprehension of thermal effects may be useful to get information about the laden material behaviour in view of assessing the material performance.