GFRPP thermoplastic composite recycling route. Reproduced from Composites Science and Technology 241 (2023) 110125.
Overview of process from recycling to printing of MEX samples.Fiber-reinforced polymer composites are lightweight and strong, ideal for structural engineering components like wind turbine blades. But waste material generated during turbine blade manufacture, as well as end-of-life components, are generally consigned to landfill. Now researchers from the University of Galway, I-Form, MaREI, and ÉireComposites Teo in Ireland have demonstrated that industrial thermoplastic composite waste can be recycled into filaments suitable for additive manufacturing [Sam-Daliri et al., Composites Science and Technology 241 (2023) 110125, https://doi.org/10.1016/j.compscitech.2023.110125].
“Additive manufacturing, in particular material extrusion additive manufacturing (MEX), is a transformative approach to thermoplastic composite production as it enables the creation of complex, lightweight parts and improves industrial sustainability through the recycling of waste material,” explains Omid Sam-Daliri, first author of the study.
By 2025, the European Commission’s Plastics in a Circular Economy Strategy demands that 50% of all plastic and composite waste must be reused or recycled. While many efforts are focusing on the economic recovery, recycling, and remanufacturing of end-of-life composite components, the researchers turned their attention to unavoidable waste generated during the manufacture of glass fiber-reinforced polypropylene (GFRPP) turbine blades instead.
“There is little incentive to harness this low economic value waste stream, but a circular approach could enable the introduction of GFRPP cut-offs into production processes, creating new revenue streams and jobs,” points out co-author Pouyan Ghabezi.
The team collected waste thermoplastic composites from turbine blade manufacturing, along with end-of-life blades, and converted the material into 3D printer filament feedstock. The GFRPP is combined with PP material from recycled mushroom cartons, shredded, and fed into a filament maker, allowing the fraction of fiber content to be varied. The filament prepared in this way can be printed and shredded again, achieving cradle-to-cradle circularity. The researchers’ mechanical analysis of MEX samples with different glass fiber contents indicates that 30-40% fiber produces a composite with the best tensile properties, although increases in filament strength do not directly lead to equivalent increases in printed part strength.
“By studying how fiber and thermoplastic materials evolve during recycling we can ensure they continue to work together as a composite. This also gives us insight into what print settings should be used with recycled composite filaments” adds senior author, Noel Harrison. “Getting this right unlocks great disruptive potential.”
Repurposing waste offcuts could diminish demand for raw material and recycling end-of-life components could reduce disposal requirements, while simultaneously creating the opportunity to foster localized, closed-circuit manufacturing practices.
The team is exploring applications for printed composite components [1] and undertaking a broad sustainability assessment of the approach.
Footnote:
[1] MI-DRONE project led by William Finnegan is investigating the fabrication of parts for last-mile delivery drones:
https://www.eirecomposites.com/research-and-development/mi-drone/