Thermal Recycling of Glass Fibre Composites: A Circular Economy Approach

Abstract

Composite materials are used in a wide range of applications, but due to their inherent nature of heterogeneity, particularly for thermoset-based polymer composites, their recycling is a problem, and their life cycle management remains one, too. This study applies a circular economy approach to the problem of excess waste of glass fibre (GF) composites and seeks a solution by testing a methodology for thermal recycling of GF composites by combining different times and temperatures. Through the by-hand lay-up process, diverse laminates were manufactured with recycled GF, and the mechanical results were compared with those of the control laminate; in this way, we sought to reinsert recycled fibres into a new life cycle, closing the loop of the material. The static properties, tensile tests, and three-point bending (3PB) tests were studied as well as the viscoelastic behaviour of the recycled fibres and respective laminates. For woven fibres, we highlight the recycling process at 600 °C for 15 min, which revealed a loss of only 15.3% of the tensile strength. The laminates with fibres recycled at 400 °C for 180 min presented a reduction of 52.14% and 33.98% for tensile and flexural strength, respectively, representing the best solution. For all laminates, the bending stress, stiffness, and strain are sensitive to the strain rate, and the tendency observed for these properties can be supported by linear models. Subsequently, for the best results, the stress–relaxation and creep behaviour were analysed, and it is possible to conclude that temperature and time of fibre recycling influence the viscoelastic response of laminates.