Shredding and sieving thermoplastic composite scrap: Method development and analyses of the fibre length distributions

Recycling of thermoplastic composites has attracted considerable attention in the recent years. Several recyclingsolutions include shredding scrap to centimetre-sized flakes to retain long fibres, followed by a remanufacturingstep that prevents fibre breakage. Determining the exact fibre length distribution (FLD) for these routes iscrucial, as it is of importance for the processibility of the material as well as the mechanical performance ofthe recycled parts. In this paper, novel analysis methods are introduced to calculate FLDs based on photographsof flakes. The reliability of the method and of the sampling was found to be high. The relation between flakesize and FLD was studied, showing that offcut layup barely influences the FLD in comparison to flake size.The effects of shredding settings and sieving were studied, showing a strong correlation between machineparameters and FLD, whereas the offcut size was found to have no effect on FLD.