Browsing by Author "Doddamani, M."

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3D printed functionally graded foams response under transverse load
(Elsevier B.V., 2023) Bonthu, D.; Mahesh, V.; Powar, S.; Doddamani, M.
The applications of 3D printing are rapidly increasing in aerospace and naval applications. Nonetheless, 3D printing (3DP) of graded foams exhibiting property variation along the thickness direction is yet to be explored. In the current work, the different volume fractions of hollow glass micro balloon (GMB) reinforced high-density polyethylene (HDPE) composite based graded foams are 3D printed using the fused deposition modelling (FDM) technique. The bonding between successive layers and porosity distribution of these graded configurations are studied using micro-CT scan. Further, the 3D Printed functionally graded foams (FGFs) are tested for flexural response, and results are compared with numerical values. The micro-CT results showed delamination absence between the layers. In neat HDPE layers, porosity is not evident, while minor porosity creeps in the layers having the highest GMB content. Experimental results of the flexural test showed that the graded sandwiches exhibited better strength than the graded core alone. Compared to neat HDPE, the modulus of FGF-2 (H20–H40–H60) increased by 33.83%, implying better mechanical stiffness. Among all the FGFs, FGF-2 exhibited a better specific modulus. A comparative study of experimental and numerical results showed a slight deviation due to neglecting the induced porosity. © 2023 The Authors
3D Printed Thick Micro-Perforated Panel with Graded Perforation for Practical Wall Sound Absorption Applications
(Springer, 2024) Shafeer, M.; Pitchaimani, J.; Doddamani, M.
In recent years, noise pollution has been recognized as a significant environmental issue, and using sustainable materials as sound-absorbing building materials have drawn considerable attention. The influence of graded perforations on the acoustic characteristics of a 3D printed bio-degradable thick micro-perforated panel (MPP) having graded perforation and made of Poly Lactic Acid is presented. Thicker panels are considered owing to the mechanical strength required for practical wall applications. A fused deposition modeling based 3D printer is used to fabricate the MPPs with graded cylindrical perforations and different patterning of perforations. The sound absorption coefficient is measured using the impedance tube technique and compared with theoretical results obtained using an equivalent electro-acoustic model. Results revealed that for normal incidence, the absorption coefficient is only dependent on the overall perforation ratio of the panel, irrespective of the perforation gradation and patterning of perforation. This gives the freedom to distribute the perforation aesthetically for interior wall application. This work also proposes the effective perforation ratio approach to predict the sound absorption coefficient (SAC) of MPPs with graded perforation. For multi-thickness MPPs and MPPs with linearly graded thickness, improved sound absorption characteristics were observed both in terms of bandwidth of absorption and peak value of SAC compared to the conventional constant thickness MPPs. © Australian Acoustical Society 2023.
3D printing of fly ash-based syntactic foams
(Elsevier, 2021) Doddamani, M.; Gupta, N.
In addition to the ease of fabrication using a wide range of forming processes, thermoplastic polymers are recyclable, which is a strong driving force behind their industrial applications. This chapter deals with manufacturing thermoplastic matrix lightweight composites called syntactic foams (SFs) using in the fused filament fabrication 3D printing process. High-density polyethylene (HDPE) is used as the matrix material and fly ash cenospheres are used as the filler. The development of SFs with cenospheres serves a dual purpose of beneficial utilization of industrial waste fly ash and a reduction in the component cost. Hollow fly ash cenospheres are mixed with HDPE to form a cenosphere/HDPE blend, which is extruded in the form of filaments for commercial 3D printers. Single-screw extruder parameters are optimized to develop eco-friendly SF filaments with minimum cenosphere fracture and homogeneous mixing of constituents. Fly ash-based SFs are successfully 3D printed for mechanical characterization and their properties are observed to be comparable to injection molded specimens of the same compositions. 3D printing of industrial components is successfully demonstrated with potential weight saving capabilities of 8% in addition to reduced polymer consumption to the tune of 4.64 million tons globally per year. © 2022 Elsevier Inc. All rights reserved.
3D printing of functionally graded nanocomposites: An investigation of microstructural, rheological, and mechanical behavior
(John Wiley and Sons Inc, 2024) Kumar, S.; Rajath, S.; Shivakumar, N.D.; Ramesh, M.R.; Doddamani, M.
Manufacturing functionally graded material through 3D printing is challenging owing to the deposition of different materials with different thermal properties in each layer, leading to a higher thermal gradient between deposited and depositing layers, resulting in improper bonding between them and, hence, reduced mechanical properties. This study focuses on 3D printing of functionalized multi-walled carbon nanotubes (MWCNTs)/high-density polyethylene (HDPE)-based lightweight functionally graded nanocomposites (FGNCs) and their investigation for microstructural, rheological, physical, and mechanical properties. Functionalized MWCNTs (0.5% → 5%) are initially compounded with widely utilized HDPE to develop nanocomposites (H0.5→H5 pellets) for extruding filaments for 3D printing. 3D-printed FGNC samples are investigated through scanning electron microscopy (SEM), rheology, density, tensile, and flexural tests. SEM and rheology confirm the homogeneous dispersion of the filler in HDPE and the processing parameters suitability in blending, extrusion, and 3D printing. Complex viscosity (η*), loss modulus (E″), and storage modulus (E′) of FGNCs increase, while the damping decreases with the MWCNTs rise in the graded layers. Density results revealed the highest weight saving potential (~12%) of FGNC-2 (H1–H3–H5), showing great weight saving potential. Tensile and flexural properties rise when the MWCNTs content rises in the graded layer. The FGNC-2 showed the highest tensile strength and moduli, 37.12% and 90.41% higher than HDPE. Flexural strength and moduli are also found to be the highest for FGNC-2, 28.57%, and 26.83% higher than HDPE. The highest specific moduli and strength are found for FGNC-2, 46.16% and 44.14% higher than HDPE, respectively. Experimental findings are found to be strongly in agreement with numerical findings. 3D-printed FGNC-2 demonstrated the best flexural and tensile characteristics with the lowest weight and hence can be used to make practical parts and structures that need variable stiffness. Highlights: FGNCs functionally graded n anocomposites are concurrently 3D printed. FGNC-2 exhibited the highest weight saving potential of 12%. FGNC-2 showed 90.41% and 37.12% enhanced tensile modulus and strength. FGNC-2 displayed 28.57% and 26.83% improved flexural strength and modulus. FGNCs exhibited better mechanical performance than the homogeneous NCs. © 2024 Society of Plastics Engineers.
3D printing of highly pure copper
(2019) Tran T.Q.; Chinnappan A.; Lee J.K.Y.; Loc N.H.; Tran L.T.; Wang G.; Kumar V.V.; Jayathilaka W.A.D.M.; Ji D.; Doddamani, M.; Ramakrishna S.
Copper has been widely used in many applications due to its outstanding properties such as malleability, high corrosion resistance, and excellent electrical and thermal conductivities. While 3D printing can offer many advantages from layer-by-layer fabrication, the 3D printing of highly pure copper is still challenging due to the thermal issues caused by copper’s high conductivity. This paper presents a comprehensive review of recent work on 3D printing technology of highly pure copper over the past few years. The advantages and current issues of 3D printing methods are compared while different properties of copper parts printed by these methods are summarized. Finally, we provide several potential applications of the 3D printed copper parts and an overview of current developments that could lead to new improvements in this advanced manufacturing field. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
3D printing of highly pure copper
(MDPI AG membranes@mdpi.com, 2019) Tran, T.Q.; Chinnappan, A.; Lee, J.K.Y.; Loc, N.H.; Tran, L.T.; Wang, G.; Vijay Kumar, V.V.; Jayathilaka, W.A.D.M.; Ji, D.; Doddamani, M.; Ramakrishna, S.
Copper has been widely used in many applications due to its outstanding properties such as malleability, high corrosion resistance, and excellent electrical and thermal conductivities. While 3D printing can offer many advantages from layer-by-layer fabrication, the 3D printing of highly pure copper is still challenging due to the thermal issues caused by copper’s high conductivity. This paper presents a comprehensive review of recent work on 3D printing technology of highly pure copper over the past few years. The advantages and current issues of 3D printing methods are compared while different properties of copper parts printed by these methods are summarized. Finally, we provide several potential applications of the 3D printed copper parts and an overview of current developments that could lead to new improvements in this advanced manufacturing field. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
3D printing of syntactic foam cored sandwich composite
(Elsevier B.V., 2020) Bonthu, D.; Bharath, H.S.; Gururaja, S.; Prabhakar, P.; Doddamani, M.
In additive manufacturing, fused filament fabrication (FFF) based three-dimensional printing (3DP) is one of the most popular rapid processing technologies. The key benefit of 3DP is the ability to build integrated, complex, and tailored components. Optimization of feedstock material and associated 3DP process to achieve the required properties for various applications has been an important research field in the recent past. The main objective of this paper is 3DP of syntactic foam cored sandwich composite all at once (skin-core-skin printing in sequence at once). High density polyethylene (HDPE) and glass microballoon (GMB) reinforced (20, 40, and 60 by volume%) HDPE blends are fed into the extruder for manufacturing respective filaments. These HDPE and HDPE/GMB filaments are further sent to the FFF based printer to realize skin and syntactic foam core respectively of the sandwich. The selection of substrate for printing and the crucial issues associated with the printing of core and sandwich composites are analyzed. The present work successfully demonstrates that by optimizing the printing parameters, good quality core and sandwich structures can be printed all at once without any defects. Finally, the suitable printing parameters are used as boundary conditions in finite element (FE) simulation of sandwich for carrying out thermomechanical analysis to analyze the thermal stress distributions in the prints. © 2020
3D Printing of Syntactic Foams for Marine Applications
(Springer International Publishing, 2020) Gupta, N.; Doddamani, M.
Syntactic foams are hollow particle filled lightweight composite materials that are widely used in structural applications in underwater marine vessels. Additive manufacturing (AM), also called 3D printing, methods are now being developed for printing parts of syntactic foams. These methods provide advantage that the entire part can be printed without the requirement of machining or joining and eliminates stress concentration locations. The present work is focused on describing the method of creating a syntactic foam filament for fused filament fabrication type printers and then developing parameters for printing syntactic foams parts using commercial printers. High density polyethylene resin is used as the matrix material with fly ash cenospehres and hollow glass microballoons as the fillers for creating syntactic foams. One of the major challenges is to minimize the fracture of hollow particles during filament manufacturing and 3D printing, which is addressed by parameter optimization during processing. Results show that the syntactic foam specimens are successfully printed and their properties are comparable to the injection molded specimens of the same compositions. © Springer Nature Switzerland AG 2020.
4D printing of heat-stimulated shape memory polymer composite for high-temperature smart structures/actuators applications
(John Wiley and Sons Inc, 2024) Kumar, S.; Ojha, N.; Ramesh, M.R.; Doddamani, M.
High temperature shape memory polymers (HT-SMPs) have great utilization in self-deployable hinges/morphing structures for space/aerospace, and high-temperature sensors/actuators for electronics. However, HT-SMPs have many drawbacks, such as low stiffness, strength, thermal stability, and dynamic mechanical properties. This work aims at improving these properties of highly utilized space grade HT-SMP, PEKK (polyether ketone ketone), by reinforcing it with low-cost carbon fibers (CFs), and developing its composite via additive manufacturing. The additively manufactured CF/PEKK composites are annealed at 200 °C (CF/PEKK-A200) and 250 °C (CF/PEKK-A250), and for the first time, investigated for shape memory effect (SME). The shape fixity and the shape recovery of the CF/PEKK-UNA (un-annealed), CF/PEKK-A200, and CF/PEKK-A250 are noted to be 95.97%, 88.95%, and 86.40%, and 88.70%, 92.70%, and 95.19%, respectively with a significant weight saving potential of ?21%. Dispersion of CFs in PEKK and suitability of processing parameters (blending, extrusion, and 3D printing) are confirmed through scanning electron microscopy (SEM). Thermal degradation temperature ((Formula presented.)) of the printed CF/PEKK composite (?568 °C) is found to be ?3.5% higher than PEKK (?549 °C). CF/PEKK-A250 exhibited the highest storage modulus (4438.23 MPa), ~158% higher than PEKK (1722.3 MPa), while CF/PEKK-A200 demonstrated the highest tensile modulus (10.9 GPa), which is 138.5% higher than PEKK (4.57 GPa) and 312.88% higher than CF/PEKK-UNA (2.64 GPa). Moreover, CF/PEKK-A200 exhibited 237.46%, 138.51%, 127.08%, 61.48%, 32.93%, and 50.35% higher tensile modulus than PEEK, PEKK, PEK, CF/PEK, CF/PEEK, and CF/PEKK composites, respectively, showing great potential to replace them. Highlights: Printed CF/PEKK composites are investigated for shape memory behavior. The printed composites exhibited outstanding shape memory properties. Printed-A200 exhibited 138.51% enhanced tensile modulus than pure PEKK. Also, the printed-A200 showed 313% enhanced modulus than printed-UNA. (Formula presented.) (568 °C) of the printed composites is found ?4% greater than pure PEKK. © 2024 Society of Plastics Engineers.
A comprehensive characterization of 3D printable poly ether ketone ketone
(Elsevier Ltd, 2024) Ojha, N.; Kumar, S.; Ramesh, M.R.; Balan, A.A.S.; Doddamani, M.
The current work focuses on the comprehensive characterization of a 3D printable biomaterial, polyether ketone ketone (PEKK). The PEKK granules are first characterized and then utilized for extrusion of the PEKK filaments. The extruded PEKK filaments are characterized for crystallinity, quality, and printability, wherein they exhibit amorphous nature, good quality, and appropriate printability. Utilizing the filaments, the samples are printed with the appropriate printing parameters, which are further characterized for layer adhesion, voids, and crystallinity, wherein they showed seamless layer adhesion, improper beads consolidation, and the amorphous nature. The as printed samples are further annealed at different temperatures (200 and 250 °C). The scanning electron microscopy (SEM) of the annealed samples (A-200 and A-250) revealed better void consolidation, while the X-ray diffraction (XRD) revealed better crystallinity compared to the un-annealed sample. The printed samples are also investigated for dynamic mechanical analysis (DMA), shape memory, and tensile properties. The storage moduli of the annealed samples are observed to be better than the un-annealed sample. The annealed samples exhibited better shape memory properties: shape fixity and shape recovery ratio of A-200 and A-250 samples, 90.28 and 90.75%, and 99.16 and 94.73%, respectively, compared to the un-annealed samples. The highest shape fixity ratio and the shape recovery ratio are noted for A-250 (90.75%) and A-200 (∼ 100%). The A-200 and A-250 samples showed enhanced tensile modulus and strength, 4.16 and 49.67%, and 36.61 and 35.06%, respectively compared to the un-annealed sample. The highest modulus is noted for A-250, while the strength is comparable (36.61 and 35.06%) for A-200 and A-250. © 2023 Elsevier Ltd
A comprehensive review on 3D printing advancements in polymer composites: technologies, materials, and applications
(Springer Science and Business Media Deutschland GmbH, 2022) Jagadeesh, P.; Madhu, M.; Rangappa, S.M.; Karfidov, K.; Gorbatyuk, S.; Khan, A.; Doddamani, M.; Siengchin, S.
3D printing is a constantly expanding technology that represents one of the most exciting and disruptive production possibilities available today. This technology has gained global recognition and garnered considerable attention in recent years. However, technological breakthroughs, particularly in the field of material science, continue to be the focus of research, particularly in terms of future advancements. The 3D printing techniques are employed for the manufacturing of advanced multifunctional polymer composites due to their mass customization, freedom of design, capability to print complex 3D structures, and rapid prototyping. The advantages of 3D printing with multipurpose materials enable solutions in challenging locations such as outer space and extreme weather conditions where human involvement is not possible. Each year, numerous research papers are published on the subject of imbuing composites with various capabilities such as magnetic, sensing, thermal, embedded circuitry, self-healing, and conductive qualities by the use of innovative materials and printing technologies. This review article discusses the various 3D printing techniques used in the manufacture of polymer composites, the various types of reinforced polymer composites (fibers, nanomaterials, and particles reinforcements), the characterization of 3D printed parts, and their applications in a various industries. Additionally, this review discussed the limitations of 3D printing processes, which may assist future researchers in increasing the utility of their works and overcoming the shortcomings of previous works. Additionally, this paper discusses processing difficulties, anisotropic behavior, stimuli-responsive characteristics (shape memory and self-healing materials), CAD constraints, layer-by-layer appearance, and void formation in printed composites. Eventually, the promise of maturing technology is discussed, along with recommendations for research activities that are desperately required to realize the immense potential of operational 3D printing. © 2022, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.
A comprehensive review on performance and machinability of plant fiber polymer composites
(John Wiley and Sons Inc, 2022) Hemath Kumar, H.; Rangappa, S.; Siengchin, S.; Gorbatyuk, S.; Manimaran, P.; Alka Kumari, C.; Khan, A.; Doddamani, M.
In recent years, the revolutionary utilization of plant fibers in polymer laminates significantly influenced environmental effects. Presently, there is progression attention in advancing bio-based materials by acquiring plant fibers from lignocellulosic components for different applications like non-structural, structural laminates, automobile components, ballistics, flooring, household utensils, and aerospace parts. These bio-based, eco-friendly components have been recognized as next-generation contestants for higher-efficacy, sustainable, cheap, environmentally friendly, and lightweight composites. Different kinds of synthetic and natural biopolymers and bio-based nanoparticles have been applied to produce sustainable materials. Bio-based polymer composites manifest unique characteristics of both eco-reinforcement and sustainable resin. This review comprehensively communicates the general characteristics and principles of nanoparticles, polymers, and their respective composites. In addition to the machining characteristics, challenges and future perspectives of the polymer composites have also been reviewed. © 2021 Society of Plastics Engineers.
A Pragmatic Optimization of Axial Stack-Radial Passive Magnetic Bearings
(American Society of Mechanical Engineers (ASME) infocentral@asme.org, 2018) Lijesh, L.; Doddamani, M.; Bekinal, S.I.
Passive magnetic bearing's (PMB) adaptability for both lower and higher speed applications demands detailed and critical analysis of design, performance optimization, and manufacturability. Optimization techniques for stacked PMB published in recent past are less accurate with respect to complete optimum solution. In this context, the present work deals with a pragmatic optimization of axially stacked PMBs for the maximum radial load using three-dimensional (3D) equations. Optimization for three different PMB configurations, monolithic, conventional, and rotational magnetized direction (RMD), is presented based on the constraints, constants, and bounds of the dimensions obtained from published literature. Further, to assist the designers, equations to estimate the mean radius and clearance being crucial parameters are provided for the given axial length and outer radius of the stator with the objective of achieving maximum load-carrying capacity. A comparison of the load-carrying capacity of conventional stacked PMB using the proposed equation with the equation provided in literature is compared. Finally, effectiveness of the proposed pragmatic optimization technique is demonstrated by analyzing three examples with reference to available literature. © 2018 by ASME.
A Review of Superconducting Magnetic Bearings and Their Application
(Institute of Electrical and Electronics Engineers Inc., 2022) Supreeth, D.K.; Bekinal, S.I.; Shivamurthy, S.R.; Doddamani, M.
Magnetic bearings are being researched for high-speed applications, such as flywheel energy storage devices, to eliminate friction losses. As per Earnshaw's theorem, stable levitation cannot be achieved for a static passive magnetic bearing system. Fully passive stable levitation can be achieved with the help of superconducting magnetic bearings (SMB). This article provides an in-depth review of the modeling, analysis, and development of SMB. The different SMB configurations are highlighted, together with essential methodologies for estimating and improving their performance. The advancements in mathematical models used and the optimization of bearing characteristics are thoroughly discussed. Further, key developments in the application of SMB in flywheel energy storage systems are also reviewed. © 2002-2011 IEEE.
A short banana fiber—PLA filament for 3D printing: Development and characterization
(John Wiley and Sons Inc, 2025) Mohamed Shafeer, P.P.; Pitchaimani, J.; Doddamani, M.
This study aims to develop a 3D printable composite filament using short banana fiber and polylactic acid (PLA). The filament was acquired through a single screw extruder, employing various blending techniques. Various fiber loadings were examined, impacting PLA's mechanical, thermal, and printability properties. The results revealed altered mechanical characteristics, with reduced tensile and flexural properties compared with pure PLA. However, these values are at an acceptable level for non-structural applications. Compared with previous works, the filament developed in the present work is found out to be second strongest among the cellulose fiber-reinforced PLA filaments. 3D printing with the composite filament encountered no significant issues. A modified mixing method improved mechanical characteristics, although 3D-printed samples showed deteriorated mechanical characteristics due to poor interfacial bonding. This research introduces an environmentally viable strategy for advancing 3D printing technology by integrating banana fibers into PLA filament. The proposed strategy can be effectively utilized in making cellulose/PLA filaments for 3D printing applications. This innovative approach preserves PLA's natural biodegradability while carefully managing the integration of banana fibers and their potential effects on mechanical properties. Highlights: Fiber loading influences mechanical, with minimal impact on thermal properties. Solution casting improved fiber/matrix bonding and filler homogeneity. Plasticizing effect reduces the tensile strength. Modified mixing resulted in even filament diameter and improved tensile properties. © 2024 Society of Plastics Engineers.
Acoustic behaviour of 3D printed bio-degradable micro-perforated panels with varying perforation cross-sections
(Elsevier Ltd, 2021) Sailesh, R.; Yuvaraj, L.; Jeyaraj, J.; Doddamani, M.; Mailan Chinnapandi, L.B.
Influence of perforations having arbitrarily varying cross-sections on the acoustic behaviour of 3D printed bio-degradable panels made of Poly Lactic Acid (PLA) is presented. Circular perforations having six different types of cross-sectional variations namely convergent-divergent (CD), divergent-convergent (DC), convergent (C), divergent (D) with two different perforation diameters are realized using Fused Filament Fabrication (FFF) based 3D printing. Sound absorption and transmission loss characteristics of these perforated panels are estimated through impedance tube technique. Results revealed that sound absorption of perforated panels with varying cross-section is better than uniform cross-sectional perforation for the given frequency range. Among, the different cross-sectional variations explored, comparable and lower transmission losses are exhibited by DC and D perforation pattern with respect to constant diameter 1 mm panel. The sound transmission results of all other five specimens were significantly higher than constant diameter 8 mm panel and observed to be increasing with frequency. Geometrical perforation variations are noted to be a very crucial factor in designing soundproof panels as presented in this work. The experimental results are compared with the numerical results and found to be in good agreement. Such numerical analysis paves the guidelines for designing optimum perforation geometries prior to the on-field testing of the functional prototypes. © 2020 Elsevier Ltd
Additive Manufacturing of Short Silk Fiber Reinforced PETG Composites
(Elsevier Ltd, 2022) Kn, V.; Bonthu, D.; Doddamani, M.; Pati, F.
The growing demand for customized medical devices like prostheses, orthoses, and implants is the prime motive for a surge in the investigation of 3D printable biocomposites. PETG (Polyethylene terephthalate glycol) based composites can be a good choice for biomedical applications. Specific characteristics of this material like biocompatibility, ease of formability, stable thermomechanical properties, and high chemical, and abrasion resistance make it suitable for biomedical applications. However, there are very few studies on the 3D printing of PETG-based composites. Development of a robust 3D printing protocol is required for any novel natural fiber reinforced PETG composites. This study presents natural fiber-reinforced PETG biocomposite filament preparation and 3D printing with the developed composite filaments. Silk was used as a filler material due to its high thermal stability and high tensile strength. Composite filaments with 2 wt%, 5 wt%, and 10 wt% silk were prepared using the extrusion process. Further, we developed a protocol for 3D printing with the developed composites to fabricate various 3D structure. Both filaments and printed specimens were characterized morphologically, structurally, and mechanically. The melt flow rate of the filaments decreased with an increase in fiber content which was a bottleneck for printing 10% silk-PETG composites. Micro-CT results validate an increase in void content in filaments on filler addition. The highest flexural modulus and flexural strength were exhibited by 2% silk-PETG printed parts and a 60% increase in compressive modulus compared to pure PETG. Tensile tests show that 2 wt% fiber addition significantly increased elastic modulus (2466.72 MPa) compared to pure PETG (902.81 MPa), whereas the surface roughness of printed composites increased with filler content. Finally, a lower limb prosthetic socket prototype was printed with a desktop 3D printer to demonstrate its potential for biomedical applications. © 2022 Elsevier Ltd
Additive Manufacturing of Syntactic Foams: Part 1: Development, Properties, and Recycling Potential of Filaments
(2018) Singh, A.K.; Patil, B.; Hoffmann, N.; Saltonstall, B.; Doddamani, M.; Gupta, N.
This work focuses on developing filaments of high-density polyethylene (HDPE) and their hollow particle-filled syntactic foams for commercial three-dimensional (3D) printers based on fused filament fabrication technology. Hollow fly-ash cenospheres were blended by 40 wt.% in a HDPE matrix to produce syntactic foam (HDPE40) filaments. Further, the recycling potential was studied by pelletizing the filaments again to extrude twice (2 ) and three times (3 ). The filaments were tensile tested at 10?4 s?1, 10?3 s?1, and 10?2 s?1 strain rates. HDPE40 filaments show an increasing trend in modulus and strength with the strain rate. Higher density and modulus were noticed for 2 filaments compared to 1 filaments because of the crushing of some cenospheres in the extrusion cycle. However, 2 and 3 filament densities are nearly the same, showing potential for recycling them. The filaments show better properties than the same materials processed by conventional injection molding. Micro-CT scans show a uniform dispersion of cenospheres in all filaments. 2018, The Minerals, Metals & Materials Society.
Additive Manufacturing of Syntactic Foams: Part 1: Development, Properties, and Recycling Potential of Filaments
(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Singh, A.K.; Patil, B.; Hoffmann, N.; Saltonstall, B.; Doddamani, M.; Gupta, N.
This work focuses on developing filaments of high-density polyethylene (HDPE) and their hollow particle-filled syntactic foams for commercial three-dimensional (3D) printers based on fused filament fabrication technology. Hollow fly-ash cenospheres were blended by 40 wt.% in a HDPE matrix to produce syntactic foam (HDPE40) filaments. Further, the recycling potential was studied by pelletizing the filaments again to extrude twice (2×) and three times (3×). The filaments were tensile tested at 10?4 s?1, 10?3 s?1, and 10?2 s?1 strain rates. HDPE40 filaments show an increasing trend in modulus and strength with the strain rate. Higher density and modulus were noticed for 2× filaments compared to 1× filaments because of the crushing of some cenospheres in the extrusion cycle. However, 2× and 3× filament densities are nearly the same, showing potential for recycling them. The filaments show better properties than the same materials processed by conventional injection molding. Micro-CT scans show a uniform dispersion of cenospheres in all filaments. © 2018, The Minerals, Metals & Materials Society.
Additive Manufacturing of Syntactic Foams: Part 2: Specimen Printing and Mechanical Property Characterization
(2018) Singh, A.K.; Saltonstall, B.; Patil, B.; Hoffmann, N.; Doddamani, M.; Gupta, N.
High-density polyethylene (HDPE) and its fly ash cenosphere-filled syntactic foam filaments have been recently developed. These filaments are used for three-dimensional (3D) printing using a commercial printer. The developed syntactic foam filament (HDPE40) contains 40 wt.% cenospheres in the HDPE matrix. Printing parameters for HDPE and HDPE40 were optimized for use in widely available commercial printers, and specimens were three-dimensionally (3D) printed for tensile testing at strain rate of 10?3 s?1. Process optimization resulted in smooth operation of the 3D printer without nozzle clogging or cenosphere fracture during the printing process. Characterization results revealed that the tensile modulus values of 3D-printed HDPE and HDPE40 specimens were higher than those of injection-molded specimens, while the tensile strength was comparable, but the fracture strain and density were lower. 2018, The Minerals, Metals & Materials Society.