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Research and Characterization of Mechanical, Thermal, and Structural Properties of 3D Printed Polymers

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

Deadline for manuscript submissions: 31 May 2026 | Viewed by 3187

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Dr. Dionysis E. Mouzakis

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Department of Military Sciences, Hellenic Army Academy, Attiki, Greece
Interests: composites; smart materials and sensors; nanotechnology; biomaterials
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Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) has revolutionized the design and fabrication of polymer structures. However, its inherent layer-by-layer manufacturing process leads to significant anisotropy in the mechanical and thermal properties of the products, and their macrostructural responses differ fundamentally from those of conventionally machined parts. This Special Issue aims to bring together the latest research in this field, focusing on the impact of material formulation, printing process, and post-processing on final performance, as well as on multi-scale structural failure mechanisms and predictive models. We sincerely invite high-quality submissions on experimental characterization, numerical simulation, and theoretical modeling to advance the development and application of high-performance 3D printed polymers.

Dr. Dionysis E. Mouzakis
Guest Editor

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

thermal properties
mechanical properties
additive manufacturing
3D print
polymer

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Published Papers (4 papers)

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Research

30 pages, 11241 KB

Open AccessArticle

Mechanical and Microstructural Response of FDM-Printed PETG and PETG+CF to Variable Infill Architecture and Lubricant Exposure

by Lidija Rihar and Elvis Hozdić

Polymers 2026, 18(5), 654; https://doi.org/10.3390/polym18050654 - 7 Mar 2026

Viewed by 569

Abstract

Fused deposition modelling/fused filament fabrication (FDM/FFF) enables rapid manufacturing of functional polymer components; however, the reliability of printed parts remains strongly governed by internal architecture, process-induced porosity, and exposure to service fluids. This study quantifies the combined influence of (i) infill pattern (linear, triangular, hexagonal) at 30% density, (ii) infill density (30%, 60%, 100%) for linear infill, and (iii) short-term lubricant exposure on the tensile and microstructural response of FDM-printed polyethylene terephthalate glycol-modified (PETG) and short-carbon-fibre-reinforced PETG (PETG+CF). Specimens were printed following ISO 527-2 and tensile-tested at 5 mm/min. Microstructural analysis coupled quantitative porosity with mechanical response, Young’s Modulus, and strain-to-break. At 30% density, PETG with hexagonal infill achieved the highest tensile strength (18.54 ± 0.67 MPa), exceeding linear (16.99 ± 0.52 MPa) and triangular (14.15 ± 0.70 MPa) patterns, while triangular and linear patterns exhibited higher Young’s Modulus, indicating topology-driven decoupling of stiffness and strength. Increasing linear infill density raised strength to 31.35 ± 0.33 MPa (PETG) and 38.90 ± 0.28 MPa (PETG+CF) at 100%, consistent with reduced porosity. Seven-day immersion in SAE 15W-40 mineral engine oil reduced PETG strength by ~17% while increasing deformation to failure, whereas PETG+CF showed only minor changes. Overall, the results demonstrate that architecture-aware design, supported by quantitative porosity descriptors, is essential for ensuring the reliable mechanical performance of FDM/FFF-printed PETG-based components exposed to service fluids. Full article

(This article belongs to the Special Issue Research and Characterization of Mechanical, Thermal, and Structural Properties of 3D Printed Polymers)

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34 pages, 14216 KB

Open AccessArticle

Wear Behavior and Multi-Technique Characterization of 3D Printed TPU Under Simulated Pharmaceutical Operating Conditions

by Maria Stoica, Marius Gabriel Petrescu, Maria Tănase, Eugen Laudacescu, Elena-Emilia Sirbu, Cătălina Călin, Gheorghe Brănoiu and Ibrahim Naim Ramadan

Polymers 2026, 18(5), 630; https://doi.org/10.3390/polym18050630 - 4 Mar 2026

Viewed by 647

Abstract

This study investigates the wear behavior and multi-technique characterization of 3D printed thermoplastic polyurethane (TPU) intended for friction layers in transmission belts used in pharmaceutical manipulators. Two flexible TPU grades—TPU 51A and TPU 60A—were printed using fused deposition modeling (FDM) with varying printing temperatures (255–265 °C for 51A; 225–235 °C for 60A) and layer counts (three or four layers). Specimens were evaluated for Shore A hardness, wear resistance (mass loss using a Baroid lubricity tester under dry sliding against carton), tensile properties, crystallinity (XRD), chemical structure (FTIR), thermal stability (TGA), and scanning electron microscopy (SEM). The results show that printing parameters significantly influence the mechanical and tribological behavior of the materials. For TPU 51A, increasing the printing temperature to 265 °C and using four layers led to a substantial reduction in cumulative mass loss, although hardness decreased. In contrast, for TPU 60A, higher printing temperature and layer count increased hardness but also resulted in higher wear. Tensile tests indicated that specimens printed with fewer layers exhibited higher yield strength and strain, indicating improved interlayer bonding. XRD analysis confirmed the predominantly amorphous nature of the printed samples, with a reduction in crystallinity compared to the raw filaments. FTIR spectra showed no significant chemical degradation during printing, while thermogravimetric analysis revealed good thermal stability up to approximately 250–260 °C. The results demonstrate that wear behavior is governed by a combination of hardness, interlayer cohesion, and microstructural organization rather than crystallinity alone. Among the investigated conditions, TPU 51A printed at 265 °C with four layers exhibited the most favorable balance between wear resistance and mechanical properties, highlighting its suitability for friction layer applications. Full article

(This article belongs to the Special Issue Research and Characterization of Mechanical, Thermal, and Structural Properties of 3D Printed Polymers)

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19 pages, 3467 KB

Open AccessArticle

Combined Use of Vibrational Spectroscopy, Ultrasonic Echography, and Numerical Simulations for the Non-Destructive Evaluation of 3D-Printed Materials for Defense Applications

by Dimitra Apostolidou, Afrodite Tryfon, Dionysios E. Mouzakis, Nektarios K. Nasikas and Angelos G. Kalampounias

Polymers 2026, 18(1), 104; https://doi.org/10.3390/polym18010104 - 30 Dec 2025

Viewed by 540

Abstract

This paper describes how the thermal treatment of 3D-printed PLA samples, fabricated by Fused Deposition Modeling (FDM), affects elastic properties by means of vibrational spectroscopy and ultrasonic echography. Longitudinal and shear sound velocities were measured experimentally to determine Young’s, bulk, shear, and longitudinal moduli, as well as Poisson’s ratio. The results were complemented with two different simulation approaches—the elastodynamic finite integration technique (EFIT) and the equivalent electric analog technique implemented with LPSpice—whose predictive performance was assessed using statistical performance metrics. The circuit-based simulation method demonstrated superior agreement with experimental behavior compared to EFIT. Both measured and simulated data reveal that PLA chains undergo overall structural strengthening and enhanced packing up to 2 h of heating, followed by a clear reduction in these enhancements as thermal degradation emerges with further heating. Poisson’s ratio remained relatively stable throughout, indicating minimal impact on strain distribution characteristics despite observable stiffening and subsequent softening. Vibrational ATR (Attenuated Total Reflection) spectra corroborated these findings through systemic shifts in C-COO, C-O-C, and C-O stretching modes associated with the same structural modifications. Overall, this combined experimental–simulation framework provides an integrated understanding of thermally induced mechanical and molecular evolution in 3D-printed PLA relevant to defense applications. Full article

(This article belongs to the Special Issue Research and Characterization of Mechanical, Thermal, and Structural Properties of 3D Printed Polymers)

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45 pages, 8034 KB

Open AccessArticle

Mechanical Parameters and Microstructural Evolution of FDM-Printed PLA and PLA+CF Under Variable Infill Architecture and Lubricant Exposure

by Emine Hozdić and Elvis Hozdić

Polymers 2026, 18(1), 72; https://doi.org/10.3390/polym18010072 - 26 Dec 2025

Cited by 1 | Viewed by 1011

Abstract

This study examines the influence of internal infill geometry, infill density, and short-term mineral oil exposure on the tensile and microstructural behavior of Fused Deposition Modeling (FDM) 3D-printed Polylactic Acid (PLA) and Carbon-Fiber-Reinforced PLA (PLA+CF). Standardized ISO 527-2 specimens were fabricated using linear, triangular, and hexagonal infill patterns at 30%, 60%, and 100% densities, followed by seven-day immersion in mineral oil. Mechanical testing and quantitative optical image analysis were performed to correlate porosity characteristics with tensile response. For PLA, the linear 30% infill achieved the highest tensile strength (31.5 MPa), while the hexagonal pattern exhibited the greatest ductility (ε = 4.9%). Oil exposure caused slight reductions in strength (−1.2%) and modulus (−4.1%) but increased elongation by 76%, indicating mild matrix plasticization. For PLA+CF, tensile strength and stiffness increased with density, reaching 33.4 MPa and 500 MPa at 100% infill, while oil exposure enhanced strength by 6.9% and reduced the average pore size from 475 µm² to 146 µm². Overall, the results demonstrate that optimizing infill topology, density, and fiber reinforcement significantly improves load transfer efficiency and environmental stability. These findings establish quantitative correlations between pore morphology and tensile behavior, providing a framework for the predictive design of environmentally resilient FDM polymer–composite components for semi-lubricated or tribological applications. Full article

(This article belongs to the Special Issue Research and Characterization of Mechanical, Thermal, and Structural Properties of 3D Printed Polymers)

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