Structural reuse is a promising alternative to recycling of composite materials; it preserves material composition while liberating the materials for reuse in secondary applications. Thermoplastic reinforced composite materials have the potential to expand reuse opportunities by adapting their shape, or reversing them to a laminate blank. In this study, we evaluated reverse forming of glass fibre-polypropylene (GF-PP) laminates by developing a processing method, testing material properties and the effect of three design parameters: forming strain, laminate architecture and material type. Forming strain relates to the deformation mechanism of inter-ply slip, and is imposed through varying the contour depth and bending radius. Laminate architecture relates to resin redistribution, and is imposed by using an orthogonal as well as quasi isotropic layup. Finally, the material type affects both Inter-ply slip as well as resin redistribution, and is imposed by using plain and twill weaves. GF-PP blanks were prepared using a heated platen press and subsequently formed and flattened using convection heating (<165 °C) and vacuum pressure in a novel moulding process. The samples had typical values for flexural strength of 91 - 113 MPa and flexural modulus of 9–16 GPa. Using a Design of Experiments analysis the process was deemed robust for the given boundary conditions. These results demonstrate the feasibility of reverse forming for cases where inter-ply slip is the governing deformation mechanism. The presented reverse forming process and design parameters can be used to create new thermoplastic composite parts, anticipating for structural reuse through reverse forming.

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This document has been prepared in support of IEA Wind Task 45, Subtask 2.1 “Prevention of waste”, Subtask 2.2 on the “Reuse and repurpose of end-of-life wind turbine blades” and Subtask 2.3 on “Recycling and recovery methods”. This document is the outcome of a workshop and a series of meetings gathering experts from academia and industry on the following topics: wind turbine blade materials and design, recycling of wind turbine blades and windfarm operation. The document provides a summary of considerations to evaluate the recyclability of blades and design aspects supporting blade recycling.

The intended audience consists of three main groups: first, project developers, owners, operators, providing information on how to evaluate the recyclability of blade design alternatives (current blades, operational in the field, and new blades currently being developed). Second, designers, engineers, and manufacturers, address how to anticipate for recycling in the development of new blades and providing information to generate design solutions. Finally, decommissioners and recyclers, providing considerations to evaluate recovery pathways. This document provides a structured approach on different aspects to be considered.@en

Construction industry needs large volumes of materials and has a large carbon footprint. And although wind energy is renewable, the blades are hard to recycle leading to material waste. Our goal is to form a virtuous loop between these sectors by reusing wind turbine blades as construction elements. However, designing and building new structures from parts of existing ones raises novel design challenges in terms of geometry, structural properties and performance, processing and assembly. [...]@en

Innovation is crucial to meet the circular economy goals for tire recycling. Devulcanization, an innovative recycling method of reprocessing tire rubber, offers a pathway towards achieving circular economy objectives. While previous research on devulcanization has primarily focused on technical aspects, this study shifts the focus towards identifying opportunities and barriers for innovation through devulcanization. This research utilizes the Technological Innovation System framework as a basis to analyze the dynamics of innovation within value chains and innovation networks. Across Europe, 36 organizations were identified that develop and utilize devulcanization to transform rubber from end-of-life tires into a valuable resource for new rubber products. In this study, a semi-structured in-depth interview approach was applied to interview 12 organizations that have developed or utilize technologies for the devulcanization of tire rubber. It was found that the development of various devulcanization approaches for diverse types of products has created opportunities for upscaling. To capitalize on these opportunities, organizations need to collaborate throughout the entire value chain of tire production and recycling. Achieving this collaboration requires interventions across the industry.@en

Wind turbines are crucial for the energy transition, but their end-of-life treatment presents a challenge. Most wind turbine blades, made from composites, are currently sent for disposal or recycled through methods that degrade the value of the material. Structural reuse through blade segmentation was introduced as a recovery method that maintains high material value throughout subsequent life cycles. Most recovery attempts focus on thermoset composites, but thermoplastics are becoming more common. Unlike thermosets, thermoplastics can be reshaped through thermoforming processes, which offers the opportunity of adapting the geometry of a blade to new reuse applications. This paper introduces selection strategies to identify secondary applications of reshaped thermoplastic blade sections. A new methodology is proposed based on Landru's selection strategies and the Material Driven Design method (MDD). The Circular Applications Through Selection Strategies (CATSS) methodology proposes understanding a material at different levels to identify applications. Each sectioning level of the blades yields different material characteristics, such as the reshapability, that are then put into Landru's three selection strategies: substitution, selection by function, and inverse selection. Substitution directly supplants other materials with blades in an existing application; selection by function compares material properties and performance indices to derive the most relevant functions (i.e. "light-weight beams"); and inverse selection identifies suitable market sectors. The CATSS method is a systematic approach to exploring the reuse of blade sections across multiple life cycles, taking into consideration the changes in blade geometry introduced by each sectioning level. For example, the second use cycle might use blade segments for infrastructural applications like electrical transmission poles, while 3rd and 4th cycles reuse blade elements or blade units for urban furniture or automotive parts, respectively. Thus, by identifying multiple use cycle applications at various sectioning levels, we introduce structural reuse and reshaping as a long-lasting recovery pathway for decommissioned wind turbine blades. The selection strategies presented on the one hand can help identify new applications for thermoplastic composite products at their end-of-life, while on the other hand they indicate which aspects need to be considered in the original design, thus contributing to more circular practices in the composites industry.@en

The design of composite products for a circular economy is challenging. Materials such as glass-fibre-reinforced plastics have long product lifetimes but are hard to recycle. For the effective reuse and recycling of products, parts, and materials, recovery strategies must be selected and implemented in the product design stage. This extends the scope and complexity of the design process and requires additional skills from the designers. We developed a novel circular composites design method for products containing composite materials to support designers and improve product circularity. This method, which is the first of its kind to address the circular design of composite products, helps designers explore recovery pathways and generate design solutions. In this study, we evaluated the method’s effectiveness, accessibility, and usability in design practice. We tested the method with five design case studies in the construction, furniture, and automotive industries. The method was used to generate, evaluate, communicate, and detail product designs. We found that two of the five cases used the method to develop circular product concepts. In the other three cases, recycling rather than product-level recovery strategies was the result, with a focus on improving the material formulations instead of the overall product design. Although the designers considered the method accessible and usable, its effectiveness was restricted by the existing business, logistics, reprocessing technology, and policy contexts. These factors are intertwined and partly dictate the boundary conditions of the design, which means that to successfully implement the proposed method, the transition to a circular economy requires a holistic approach to adjust the design process, organisations, and value chains.@en

In this dissertation, I investigate how to design products for a circular economy using composite materials. The circular economy is a potential solution to achieving a sustainable use of resources. Reuse of products and recycling materials lowers pressure on resource stocks, saves energy, and reduces the accumulation of waste. This requires a new approach to product design. Products have to be designed for long life, reuse and recycling. Composite materials partly meet these requirements; they offer the potential for efficient material use and have a long product lifespan. However, there are still challenges considering their reuse and recycling....@en

Composite materials are an attractive material choice as they enable lightweight, low-maintenance products with a long lifespan. Recycling these materials, however, remains a chal-lenge. Homogeneous material composition and the use of thermoset matrices complicate repro-cessing, and result in low-grade recyclate. This means that closing the loop for these materials in a circular economy remains challenging, especially for glass fibre-reinforced thermoset composites. For a circular economy, products need to be designed to preserve product functionality, material properties, and economic value for as long as possible. However, recovery strategies, design aspects and their interconnectedness are currently largely unexplored for products containing fibre-rein-forced polymers. The aim of this study was to identify circular strategies and determine design aspects for products containing composites. To achieve this, we conducted a systematic literature review and consulted experts. The circular strategies are largely similar to generic circular economy strategies as far as product integrity is concerned. However, on a material level, we identified addi-tional approaches, the most notable of which is structural reuse, which preserves the material quality and thereby value. The design aspects were clustered and positioned along the product design process to support implementation. Finally, the strategies and design aspects we identified were brought together in a framework to support product design and design research for products containing composite materials in the context of a circular economy.

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Composite materials are an attractive material choice as they enable lightweight, low maintenance products with a long lifespan. But closing the loop for these materials in a Circular Economy (CE) is challenging, especially for thermoset composites. In a CE, products should be designed for minimal impact while preserving their environmental and economic value for as long as possible. However, design strategies for composite products in a CE are currently largely unexplored. Insights from literature on design for a CE as well as on composites recovery are combined to create a set of design principles for composites in a CE. In addition to well-known long life, lifetime extension and product recovery approaches, literature indicates the potential value of structural recycling. Structural recycling preserves most of the functional value of the product, which is largely lost in materials recycling. Experts from composites industry were interviewed in focus groups to further explore CE strategies and design principles for a set of reference products, such as car interior components. The resulting framework connects Circular strategies to design principles for composite products and supports design of new composite products for use, reuse and recycling in a CE.@en

Composite materials, in particular fibre reinforced polymers, present a challenge when reaching their end of life. Current recycling processes are unable to capture the high-end material quality, thus challenging (re)use of composite materials in a Circular Economy. Structurally reusing segmented parts of end-of-life products as construction elements has been demonstrated to provide a promising alternative. However, reflection on the consequences for the initial design of composite products is still missing. This study investigates the effect of the original product design on the recovery and reuse of composite products, taking wind turbine blades as case material. Construction elements were cut from a decommissioned blade and reused in a design study. Observations from the recovery and design process were connected to decisions made in the original product design. The insights were discussed with experts from the field of blade design. This resulted in identification of design aspects that enable multiple lifecycles of the composite material as construction panels, if considered during initial product design.

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Composite materials offer many advantages during the use phase, but recovery at the end of a lifecycle remains a challenge. Structural reuse, where an end of life product is segmented into construction elements, may be a promising alternative. However, composites are often used in large, complex shaped products with optimised material compositions that complicate reuse. A systematic approach is needed to address these challenges and the scale of processing. We investigated structural reuse taking wind turbine blades as a case product. A new segmentation approach was developed and applied to a reference blade model. The recovered construction ele- ments were found to comply to geometric construction standards and to outperform conventional construction materials on specific flexural stiffness and flexural strength. Finally, we explored the reuse of these construction elements in practice. Together, the segmentation approach, structural analysis and practical application provide insights into design aspects that enable structural reuse.@en

A significant part of wind energy in the Netherlands is generated by offshore wind farms at sea. In the coming decades, the number of wind farms will be scaled up in line with current energy transition and sustainability objectives. What happens to these wind turbines when they reach the end of their operational life? What volumes of material are involved? How can we prevent an adverse impact of this dismantling on the environment? What forms of economic activity may result from this removal task? This report investigates the material flows, activities and future outlook for decommissioning of offshore wind until 2050.@en