Polymeric-Based Materials Produced by Additive Manufacturing

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Processing and Engineering".

Deadline for manuscript submissions: closed (15 August 2022) | Viewed by 11242

Special Issue Editor

Department of Mechanical Engineering, Faculty of Sciences and Technology, University of Coimbra, Coimbra, Portugal
Interests: polymer-based composites; polymer-based nanocomposites; mechanical behavior
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

More than design considerations, conventional manufacturing technologies are a real obstacle to innovation. In addition to the lightweight structures with complex inner features that cannot be fabricated by conventional manufacturing techniques, other disadvantages can be found such as: multi-steps, labor intensive processes, high costs for molds and long processing time. For example, the optimization of cellular configurations suggests complex lightweight structures, which cannot be produced with resource to the traditional manufacturing techniques.

Additive manufacturing (AM) is the most recent technique for this purpose, where the components are produced layer by layer directly from a CAD file. It does not require molding and tooling, thus saving time, cost and effort. Related with the fourth industrial revolution (or industry 4.0), additive manufacturing emerges as a very promising global production technology, because it allows for "mass customization" rather than "mass production". 3D printing is expected to be the main responsible for printing high performance structures. However, the use of pure polymers is not a viable option for printing structures with certain characteristics, which is solved by combining polymeric matrices to nano reinforcements. On the other hand, recent advancements in composite production and processing are making thermoplastics a viable option in a wider array of aeronautical/aerospace and defense applications. The fact that thermoplastics can be stored at room temperature, unique properties and have unlimited shelf life reduces waste and allows for more flexible production activities.

In this context, this Special Issue intends to collect original research and comprehensive review papers in order to understand the current state of the art in terms structural integrity of polymers and polymeric composites produced by additive manufacturing. All relevant contributions to this Special Issue are welcome.

Prof. Dr. Paulo Nobre Balbis dos Reis
Guest Editor

Manuscript Submission Information

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Keywords

  • Polymers
  • Polymeric composites
  • additive manufacturing
  • Structural integrity
  • Failure analysis
  • Fatigue and Fracture
  • Viscoelastic behavior

Published Papers (3 papers)

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Research

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24 pages, 4289 KiB  
Article
Optimization of Printing Parameters to Maximize the Mechanical Properties of 3D-Printed PETG-Based Parts
Polymers 2022, 14(13), 2564; https://doi.org/10.3390/polym14132564 - 24 Jun 2022
Cited by 25 | Viewed by 4027
Abstract
Fused filament fabrication (FFF) is the most popular additive manufacturing method, which allows the production of highly complex three-dimensional parts with minimal material waste. On the other hand, polyethylene terephthalate glycol (PETG) has been used to replace traditional polymers for 3D printing due [...] Read more.
Fused filament fabrication (FFF) is the most popular additive manufacturing method, which allows the production of highly complex three-dimensional parts with minimal material waste. On the other hand, polyethylene terephthalate glycol (PETG) has been used to replace traditional polymers for 3D printing due to its chemical resistance and mechanical performance, among other benefits. However, when fibres are added, these PETG-based composites can be suitable for many different applications. Nevertheless, to guarantee their good performance in-service in these applications, and even extend to new ones, it is necessary for their mechanical properties to be maximized. Therefore, this study intends to optimize the printing parameters (nozzle temperature, printing speed, layer height and filling) in order to maximize the mechanical properties of printed PETG, PETG+CF (carbon fibre-reinforced PETG composites) and PETG+KF (aramid fibre-reinforced PETG composites). The Taguchi method was used for the experimental procedure design, and the specimens were produced according to the L16 orthogonal array. Finally, an analysis of variance (ANOVA) was performed, with a 95% confidence interval, to analyse the effect of the printing parameters on the bending properties. It was possible to conclude that the best bending properties for PETG, PETG+CF and PETG+KF were obtained for extrusion temperatures of 265 °C, 195 °C and 265 °C, printing speeds of 20, 60 and 20 mm/s, layer heights of 0.4, 0.53 and 0.35 mm and an infill density of 100% for the three materials, respectively. Full article
(This article belongs to the Special Issue Polymeric-Based Materials Produced by Additive Manufacturing)
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15 pages, 8184 KiB  
Article
Viscoelastic Behaviour of Flexible Thermoplastic Polyurethane Additively Manufactured Parts: Influence of Inner-Structure Design Factors
Polymers 2021, 13(14), 2365; https://doi.org/10.3390/polym13142365 - 19 Jul 2021
Cited by 5 | Viewed by 1920
Abstract
Material extrusion based additive manufacturing is used to make three dimensional parts by means of layer-upon-layer deposition. There is a growing variety of polymers that can be processed with material extrusion. Thermoplastic polyurethanes allow manufacturing flexible parts that can be used in soft [...] Read more.
Material extrusion based additive manufacturing is used to make three dimensional parts by means of layer-upon-layer deposition. There is a growing variety of polymers that can be processed with material extrusion. Thermoplastic polyurethanes allow manufacturing flexible parts that can be used in soft robotics, wearables and flexible electronics applications. Moreover, these flexible materials also present a certain degree of viscoelasticity. One of the main drawbacks of material extrusion is that decisions related to specific manufacturing configurations, such as the inner-structure design, shall affect the final mechanical behaviour of the flexible part. In this study, the influence of inner-structure design factors upon the viscoelastic relaxation modulus, E(t), of polyurethane parts is firstly analysed. The obtained results indicate that wall thickness has a higher influence upon E(t) than other inner-design factors. Moreover, an inadequate combination of those factors could reduce E(t) to a small fraction of that expected for an equivalent moulded part. Next, a viscoelastic material model is proposed and implemented using finite element modelling. This model is based on a generalized Maxwell model and contemplates the inner-structure design. The results show the viability of this approach to model the mechanical behaviour of parts manufactured with material extrusion additive manufacturing. Full article
(This article belongs to the Special Issue Polymeric-Based Materials Produced by Additive Manufacturing)
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Review

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29 pages, 6578 KiB  
Review
Laser Sintering Approaches for Bone Tissue Engineering
Polymers 2022, 14(12), 2336; https://doi.org/10.3390/polym14122336 - 09 Jun 2022
Cited by 6 | Viewed by 4525
Abstract
The adoption of additive manufacturing (AM) techniques into the medical space has revolutionised tissue engineering. Depending upon the tissue type, specific AM approaches are capable of closely matching the physical and biological tissue attributes, to guide tissue regeneration. For hard tissue such as [...] Read more.
The adoption of additive manufacturing (AM) techniques into the medical space has revolutionised tissue engineering. Depending upon the tissue type, specific AM approaches are capable of closely matching the physical and biological tissue attributes, to guide tissue regeneration. For hard tissue such as bone, powder bed fusion (PBF) techniques have significant potential, as they are capable of fabricating materials that can match the mechanical requirements necessary to maintain bone functionality and support regeneration. This review focuses on the PBF techniques that utilize laser sintering for creating scaffolds for bone tissue engineering (BTE) applications. Optimal scaffold requirements are explained, ranging from material biocompatibility and bioactivity, to generating specific architectures to recapitulate the porosity, interconnectivity, and mechanical properties of native human bone. The main objective of the review is to outline the most common materials processed using PBF in the context of BTE; initially outlining the most common polymers, including polyamide, polycaprolactone, polyethylene, and polyetheretherketone. Subsequent sections investigate the use of metals and ceramics in similar systems for BTE applications. The last section explores how composite materials can be used. Within each material section, the benefits and shortcomings are outlined, including their mechanical and biological performance, as well as associated printing parameters. The framework provided can be applied to the development of new, novel materials or laser-based approaches to ultimately generate bone tissue analogues or for guiding bone regeneration. Full article
(This article belongs to the Special Issue Polymeric-Based Materials Produced by Additive Manufacturing)
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