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1. Effect of Process Parameters on Mechanical Properties of the 3D Printed Silk-PLA Specimens Fabricated via Fused Deposition Modeling

   https://doi.org/10.1115/IMECE2024-144616  

   Islam, Razaul; Shahriar, Saquib; Jiang, Lai; Peng, Xiaobo; Park, Jaejong (November 2024, American Society of Mechanical Engineers)

   Abstract Fused deposition modeling (FMD) is considered one of the most common additive manufacturing methods for creating prototypes and small functional parts. Many researchers have studied Polylactic acid (PLA), Polycarbonate (PC), and Acrylonitrile butadiene styrene (ABS) as a material for fused deposition modeling printing. Among them, Polylactic Acid (PLA) is considered one of the most popular thermoplastic materials due to its low cost and biodegradable properties. In this study, silk PLA material was used. In Fused deposition modeling (FMD), the selection of printing parameters plays a pivotal role in determining the overall quality and integrity of the 3D-printed products. These parameters significantly influence the quality and strength of 3-D printed products. This study investigates the mechanical properties of silk-PLA printed specimens under different printing conditions, such as layer thickness, nozzle temperature, and print speed. All the tensile specimens were tested using ASTM D638 to characterize Young’s modulus and ultimate tensile strength. The thickness of the layers of tensile specimens was set to 0.1 mm, 0.15 mm, and 0.2 mm. The temperatures of the nozzle used during printing varied from 200°C, 210°C, and 220°C, whereas print speeds of 100 mm/s, 120 mm/s, and 140 mm/s were considered. The other printing parameters were kept consistent for all specimens. The result indicates tensile strength generally increases with increasing temperature of the nozzle, up to 220°C; however, a decline was observed in the average Young’s modulus value when the thickness of the layer increased from 0.10 mm to 0.20 mm. According to the results of the ANOVA analysis, the interaction between layer thickness, nozzle temperature, and printing speed significantly affects the tensile strength and Young’s modulus of Silk-PLA. This study reveals that nozzle temperature is the most critical parameter regarding the ultimate tensile strength and Young’s modulus, providing crucial insights for optimizing 3D printing parameters. 

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2. WOVEN NATURAL FIBER-REINFORCED PLA POLYMERS 3D PRINTED THROUGH A LAMINATED OBJECT MANUFACTURING PROCESS

   https://doi.org/10.33599/nasampe/s.23.0198  

   Jiang, L.; Shahriar, S.; Grady, T.; Peng, X. (January 2023, SAMPE 2023 Proceedings)

   Beckwith, S.; Flinn, B.; Dustin, J. (Ed.)

   A novel additive manufacturing process utilizing the laminated object manufacturing (LOM) technology with woven natural fiber-reinforced biopolymer is investigated in this paper. Traditional synthetic composite materials are products from nonrenewable crude oil with limited end-of-life options, and therefore not environmentally friendly. The continuous woven natural fiber is used to significantly strengthen the mechanical properties of biocomposites and PLA biopolymer as the matrix made the material completely biodegradable. This is one of the promising replacements for synthetic composites in applications such as automotive panels, constructive materials, and sports and musical instruments. A LOM 3D printer prototype has been designed and built by the team using a laser beam in cutting the woven natural fiber reinforcement and molten PLA powder to bind layers together. Tensile and flexural properties of the LOM 3D printed biocomposites were measured using ASTM test standards and then compared with corresponding values measured from pure PLA specimens 3D printed through FDM. Improved mechanical properties from LOM 3D-printed biocomposites were identified by the team. SEM imaging was performed to identify the polymer infusing and fiber-matrix binding situations. This research took advantage of both the material and process’s benefits and combine them into one sustainable practice. 

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3. Tensile testing data of additive manufactured ASTM D638 standard specimens with embedded internal geometrical features

   https://doi.org/10.1038/s41597-024-03369-y  

   AbouelNour, Youssef; Rakauskas, Nick; Naquila, Gabrielle; Gupta, Nikhil (May 2024, Scientific Data)

   Abstract Additive manufacturing (AM) is now widely used for research and industrial production. The benchmark data for mechanical properties of additively manufactured specimens is very useful for many communities. This data article presents a tensile testing dataset of ASTM D638 size specimens without and with embedded internal geometrical features printed using polylactic acid (PLA) in a Fused Filament Fabrication (FFF) additive manufacturing process. The added features can mimic defects of various shapes and sizes. This work is a supplement to the published research articleAssisted defect detection by in-process monitoring of additive manufacturing using optical imaging and infrared thermography(Additive Manufacturing, 2023, 103483). The printed specimens were tensile tested. Stress-strain graphs were developed and used to calculate the mechanical properties such as ultimate tensile strength (UTS) and strain at UTS. The mechanical properties, the correlations between mechanical properties and size, shape and location of geometrical features (defects), and the trends in mechanical properties can be useful in benchmarking the results of other researchers. 

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4. Bioactivity and Mechanical Performance of Centrifugally Spun Poly(D,L‐Lactide)/Poly(3‐Hydroxybutyrate) Submicrometric Fibers Containing Zinc Oxide and Hydroxyapatite Nanostructures

   https://doi.org/10.1002/app.56756  

   Padilla‐Gainza, Victoria; Rodríguez‐Tobías, Heriberto; Lozano, Karen; Rodríguez, Cristóbal; Gilkerson, Robert; Ledezma‐Pérez, Antonio_S; Anaya‐Barbosa, Narcedalia; Morales, Graciela (January 2025, Journal of Applied Polymer Science)

   ABSTRACT This study investigates the morphological, thermal, mechanical, and bioactive properties of centrifugally spun fibrous composites made from poly(D,L‐lactide)/poly(3‐hydroxybutyrate) (PLA/PHB) blends with zinc oxide (ZnO) and hydroxyapatite (Hap) nanoparticles. A 75/25 PLA/PHB weight ratio was chosen to balance mechanical and thermal properties. The precursor solution viscosities ranged from 0.25 to 0.50 Pa s, increasing with nanoparticle incorporation probably due to polymer‐nanoparticle interactions. SEM revealed a uniform fibrous morphology, with diameters of 1.21 for PLA/PHB, 2.65 for PLA/ZnO/Hap, and 1.80 μm for PLA/PHB/ZnO/Hap. TGA showed two‐step degradation for PLA/PHB fibers, while PLA/PHB/ZnO/Hap degraded in a single step at 249°C, leaving a residue of 9.95%. DSC indicated partial miscibility, with cold crystallization at 85°C (enthalpy: 7.72 J/g), slightly modified by nanoparticle addition. PLA/PHB fibers achieved a Young's modulus of 24.96 ± 3.91 MPa, three times that of pure PLA, but adding ZnO and Hap reduced modulus and tensile strength to 6.03 and 0.29 MPa, retaining suitability for biomedical applications. PLA/PHB/ZnO/Hap fibers exhibited 90%Escherichia coligrowth inhibition and enhanced MC3T3‐E1 cell viability by 120% on day 7. These results highlight their potential for antimicrobial, biocompatible medical devices. 

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5. Development of a Resilience Parameter for 3D-Printable Shape Memory Polymer Blends

   https://doi.org/10.3390/ma16175906  

   Cavender-Word, Truman J.; Roberson, David A. (September 2023, Materials)

   The goal of this paper was to establish a metric, which we refer to as the resilience parameter, to evaluate the ability of a material to retain tensile strength after damage recovery for shape memory polymer (SMP) systems. In this work, three SMP blends created for the additive manufacturing process of fused filament fabrication (FFF) were characterized. The three polymer systems examined in this study were 50/50 by weight binary blends of the following constituents: (1) polylactic acid (PLA) and maleated styrene-ethylene-butylene-styrene (SEBS-g-MA); (2) acrylonitrile butadiene styrene (ABS) and SEBS-g-MA); and (3) PLA and thermoplastic polyurethane (TPU). The blends were melt compounded and specimens were fabricated by way of FFF and injection molding (IM). The effect of shape memory recovery from varying amounts of initial tensile deformation on the mechanical properties of each blend, in both additively manufactured and injection molded forms, was characterized in terms of the change in tensile strength vs. the amount of deformation the specimens recovered from. The findings of this research indicated a sensitivity to manufacturing method for the PLA/TPU blend, which showed an increase in strength with increasing deformation recovery for the injection molded samples, which indicates this blend had excellent resilience. The ABS/SEBS blend showed no change in strength with the amount of deformation recovery, indicating that this blend had good resilience. The PLA/SEBS showed a decrease in strength with an increasing amount of initial deformation, indicating that this blend had poor resilience. The premise behind the development of this parameter is to promote and aid the notion that increased use of shape memory and self-healing polymers could be a strategy for mitigating plastic waste in the environment. 

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