Speculative tinkering on circular design materials through 3D printing

Despite the spread of new circular materials and digital technologies, designers’ awareness of how to practically implement them is not fully achieved yet. Therefore, new ways to foster digital craftsmanship skills and experiential knowledge should be implemented. This contribution aims to reflect on digital technologies, especially 3D printing, in speculative design approaches with circular materials through the development of the materials library from the FiberEUse research project. This “materials and product library system” is an adaptive experiential tool that goes beyond merely collecting physical materials samples. It also includes possible products, speculative applications, and non-textual content, merging physical and virtual learning experiences. Its physical section comprises a materials library with flat samples of the materials and a product library with applications or cut-offs of some meaningful details of products. By analyzing the library’s development path, three incremental phases emerge in terms of interaction with circular materials and 3D printing for speculative approaches: experiencing materials, technology, and products. The first phase aims to preliminary explore the potential and qualities of materials through traditional craftsmanship skills. The second phase deals with the first experimentations with the technology, understanding the limits and influence on the expressive-sensorial qualities. The third phase is oriented toward new applications, investigating the possible outcomes from a formal point of view. As a synthesis, the tinkering process emphasizes the active role of experiential tools in spreading the use of circular materials and digital technologies, helping acquire new skills through an experiential approach. It also adds a further level to the exploitation of materials libraries, paving the way for new possible uses, i.e., distributed replication, participation, and implementation. As a result, materials libraries assume a more active role in the experiential knowledge transfer even during their development, representing a practical path to building new skills. Hence, a new model of materials libraries may emerge as a replicative learning and speculative design tool

Materials Libraries: designing the experiential knowledge transfer through prototyping

Experiential knowledge plays a crucial role in exploiting new materials within real contexts, i.e., designing products and applications. As a result, understanding and transferring this kind of knowledge has gained increasing attention, as well as developing new experiential tools addressing this challenge. This contribution investigates the role of physical prototypes in designing new experiential tools for the knowledge transfer of emerging materials and technologies, i.e., Materials Libraries. The analysis is performed through a reflective practice approach based on two practical case studies dealing with new materials from waste for 3D printing. The former Materials Library focuses on the recycling of composite materials from products at their End-of-Life in industrial contexts, i.e., wind turbine blades. The latter one, RepMat Library, is an ongoing experimentation that aims to develop an open source Materials Library to collect new 3D printable materials and applications from waste-based polymers and biomass involving distributed networks and local communities, i.e., makerspaces and fablabs. After briefly explaining the two case studies, this work defines an outline proposal of the main contributions of prototypes in designing new Materials Libraries, which means: (i) generating and detecting the experiential knowledge to transfer; (ii) categorizing and defining the taxonomy of the tool; (iii) testing the experiential knowledge transfer; and (iv) speculating on new possible ways of using Materials Libraries. In short, prototypes were mainly used as a physical learning medium to preliminary tinker with materials and technology, as well as a validating tool for the interaction between the users and the library. Furthermore, prototypes may contribute to envisioning new ways of developing and using Materials Libraries to spread experiential knowledge, i.e., democratizing the design process of the tool by encouraging distributed, accessible, and collaborative work within local communities and distributed networks

Recycled polycarbonate and polycarbonate/acrylonitrile butadiene styrene feedstocks for circular economy product applications with fused granular fabrication-based additive manufacturing

Distributed recycling and additive manufacturing (DRAM) holds enormous promise for enabling a circular economy. Most DRAM studies have focused on single thermoplastic waste stream. This study takes three paths forward from the previous literature: 1) expanding DRAM into high-performance polycarbonate/ acrylonitrile butadiene styrene (PC/ABS) blends, 2) extending PC/ABS blend research into both recycled materials and into direct fused granular fabrication (FGF) 3-D printing and 3) demonstrating the potential of using recycled PC/ABS feedstocks for new applications in circular economy contexts. A commercial open source large-format FGF 3-D printer was modified and used to assess the different printability and accuracy of recycled PC and PC/ABS. The mechanical properties (tensile and impact) following the ASTM D638 and D6110–18 standards were quantified. A weather simulation test (ASTM D5071–06) was performed to assess outdoor performance. Finally, two applications in sporting goods and furniture were demonstrated. In general, better printability was achieved with recycled PC/ABS compared to recycled PC, as well as good dimensional accuracy at printing speeds of 30 and 40 mm/s. Minimal qualitative differences and discoloration were visible on the samples after accelerated weather exposure, with results in accordance with the state-of-the-art. The rPC/ABS results from tensile tests show similar values to those of rPC for elastic modulus (2.1 ± 0.1 GPa), tensile strength (41.6 ± 6.3 MPA), and elongation at break (2.8 ± 0.9%), which are also comparable with previous studied virgin 3-D printed filaments. Similarly, impact energy (115.78 ± 24.40 kJ/m2) and resistance values (810.36 ± 165.77 J/m) are comparable in the two tested formulations, reaching similar results compared to FFF 3-D printed filaments, as well as virgin materials for injection molding. Finally, the two demonstration products in the sporting goods and furniture sectors were successfully fabricated with rPC/ABS, achieving complex patterns and good printing speeds for recycled feedstocks. It is concluded rPC/ABS blends represent a potential high-performance feedstock for DRAM, validating its use in direct FGF 3-D printing systems and potential applications for a circular economy

Auxetic materials for MEMS: modeling, optimization and additive manufacturing

Auxetic materials are of interest because of enhanced material properties related to negative Poisson’s ratio, such as increased shear modulus, indentation resistance, fracture toughness, energy absorption, porosity/permeability variation with strain and synclastic curvature. In addition, the Poissons ratio does not depend on scale: deformation can take place at the nano- (molecular), [1], micro-[2], or even at the macro-level, [3]; the only requirement is the right combination of the geometry and the deformation mechanism. The most popular feature of auxetic structures is that it can expand in the direction perpendicular to an externally exerted tension. This property makes auxetic structures strongly appealing for MEMS applications (i.e. motion conversion and resonators) [4]. Here we present a full study of a re-entrant honeycomb structure which can be used in MEMS devices as motion conversion spring. The design of the proposed structure is obtained from a Matlab optimization procedure targeted to reach a Poisson’s ratio equal to -1. An additional nonlinear numerical simulation (see [5]) is done to verify the behavior of the structure under large deformations regime, which is the one required by the MEMS applications and then, a 3D-printed model (see [6]) of the optimized structure is obtained. Finally, a topology optimization is performed to obtain an auxetic structure that, in principle, can amplify the motion in the direction othogonal to the driving one. With this procedure there is no need to create an input structure from which the optimization procedure can start. Also for one of these optimized auxetic structures, an additional nonlinear numerical simulation is done

Material Library System for Circular Economy: Tangible-Intangible Interaction for Recycled Composite Materials

Currently the development of new circular materials has brought up the necessity to transfer their knowledge amongst the interested stakeholders for their real exploitation. This chapter aims to illustrate the design of a physical and virtual library system of the FiberEUse project. In particular, this library system wants to foster the development of new applications and value chains through the showcase of the new recycled composite materials and archetypal remanufactured products developed during the project. After the definition of the system concept, specific taxonomies were designed for the physical and virtual parts considering the technical properties and the expressive-sensorial qualities of the new recycled materials and products. A hierarchical organization was then designed to allow both tangible and intangible interactions with the samples, resulting in a coherent experience to explore these new recycled materials. Meanwhile, the physical exhibitors and the library website were developed to collect the physical and virtual samples. At the end, the whole system will be freely accessible through the library website and by booking a visit to the physical part. Thanks to its transdisciplinary nature, this system can stimulate the real exploitation of new value chains and applications

Recycling Glass and Carbon Fibers for Reusable Components in the Automotive Sector through Additive Manufacturing

This work explores the use of additive manufacturing (AM) to reprocess recycled glass and carbon fibers in the automotive sector. It aims to foster exploitation of recycled Glass Fiber Reinforced Polymers (rGFRPs) and recycled Carbon Fiber Reinforced Polymers (rCFRPs) through two manufacturing workflows: indirect Fused Filament Fabrication (FFF) and UV-assisted Direct Ink Writing (UV-DIW). An industrial case study on vehicle components has been considered by prototyping one real component. After the tensile tests, some molds were fabricated with a FFF 3D printer for the indirect 3D printing process to cast an epoxy-based thermosetting resin with rGFs and rCFs. The second technology consisted in fabricating the parts by hardening in-situ a photo- and thermal-curable thermosetting acrylic liquid resin with rGFs. These results validate the use of AM and recycled composites for applications in the automotive sector. These approaches may be implemented for customizable components for batches below 100 vehicles as the first step for their exploitation

Metallization of Recycled Glass Fiber-Reinforced Polymers Processed by UV-Assisted 3D Printing

An ever-growing amount of composite waste will be generated in the upcoming years. New circular strategies based on 3D printing technologies are emerging as potential solutions although 3D-printed products made of recycled composites may require post-processing. Metallization represents a viable way to foster their exploitation for new applications. This paper shows the use of physical vapor deposition sputtering for the metallization of recycled glass fiber-reinforced polymers processed by UV-assisted 3D printing. Different batches of 3D-printed samples were produced, post-processed, and coated with a chromium metallization layer to compare the results before and after the metallization process and to evaluate the quality of the finishing from a qualitative and quantitative point of view. The analysis was conducted by measuring the surface gloss and roughness, analyzing the coating morphology and thickness through the Scanning Electron Microscopy (SEM) micrographs of the cross-sections, and assessing its adhesion with cross-cut tests. The metallization was successfully performed on the different 3D-printed samples, achieving a good homogeneity of the coating surface. Despite the influence of the staircase effect, these results may foster the investigation of new fields of application, as well as the use of different polymer-based composites from end-of-life products, i.e., carbon fiber-reinforced polymers

Additive Manufacturing of Recycled Composites

An additive remanufacturing process for mechanically recycled glass fibers and thermally recycled carbon fibers was developed. The main purpose was to demonstrate the feasibility of an additive remanufacturing process starting from recycled glass and carbon fibers to obtain a new photo- and thermally-curable composite. 3D printable and UV-curable inks were developed and characterized for new ad-hoc UV-assisted 3D printing apparatus. Rheological behavior was investigated and optimized considering the 3D printing process, the recyclate content, and the level of dispersion in the matrix. Some requirements for the new formulations were defined. Moreover, new printing apparatuses were designed and modified to improve the remanufacturing process. Different models and geometries were defined with different printable ink formulations to test material mechanical properties and overall process quality on the final pieces. To sum up, 3D printable inks with different percentages of recycled glass fiber and carbon fiber reinforced polymers were successfully 3D printed

UV-Assisted 3D Printing of Glass and Carbon Fiber-Reinforced Dual-Cure Polymer Composites

Glass (GFR) and carbon fiber-reinforced (CFR) dual-cure polymer composites fabricated by UV-assisted three-dimensional (UV-3D) printing are presented. The resin material combines an acrylic-based photocurable resin with a low temperature (140 °C) thermally-curable resin system based on bisphenol A diglycidyl ether as base component, an aliphatic anhydride (hexahydro-4-methylphthalic anhydride) as hardener and (2,4,6,-tris(dimethylaminomethyl)phenol) as catalyst. A thorough rheological characterization of these formulations allowed us to define their 3D printability window. UV-3D printed macrostructures were successfully demonstrated, giving a clear indication of their potential use in real-life structural applications. Differential scanning calorimetry and dynamic mechanical analysis highlighted the good thermal stability and mechanical properties of the printed parts. In addition, uniaxial tensile tests were used to assess the fiber reinforcing effect on the UV-3D printed objects. Finally, an initial study was conducted on the use of a sizing treatment on carbon fibers to improve the fiber/matrix interfacial adhesion, giving preliminary indications on the potential of this approach to improve the mechanical properties of the 3D printed CFR components

Composite Finishing for Reuse

Coating processes are emerging for new applications related to remanufactured products from End-of-Life materials. In this perspective, their employment can generate interesting scenarios for the design of products and solutions in circular economy frameworks, especially for composite materials. This chapter would give an overview of coating design and application for recycled glass fiber reinforced polymers on the base of the experimentation made within the FiberEUse project. New cosmetic and functional coatings were developed and tested on different polymer composite substrates filled with mechanically recycled End-of-Life glass fibers. Afterwards, recycled glass fiber reinforced polymer samples from water-solvable 3D printed molds were successfully coated. Finally, new industrial applications for the developed coatings and general guidelines for the coating of recycled glass fiber reinforced polymers were proposed by using the FiberEUse Demo Cases as a theoretical proof-of-concept