3D printing composites Archives - Perfect 3D Printing Filament

RIZE Announces RIZIUM Glass Fiber 3D Printing for Large Color Parts

This morning Massachusetts-based Rize, Inc. announced the release of its RIZIUM Glass Fiber (GF) composite. Founded in 2014 by CTO Eugene Giller (formerly of ZCorp), the 3D printer manufacturer also specializes in materials for applications like life sciences, communications, and branding. Now, the World Economic Forum (WEF) 2020 Technology Pioneer continues its commitment to color 3D printing with a new composite for large, full-color parts, offering the strength to support complex structures—while preventing issues like warping.

On a mission to redefine 3D printing, the company stated in a recent press release that they hope to continue to provide users with the ability to expand their work further with this new material. Sustainability for their users with next-generation technology has always been a focus for the Rize development team too, as they have developed proprietary materials over the years. RIZIUM Glass Fiber is compatible with all of their 3D printers (as well as printers from RIZIUM Alliance partners).

The new GF material was founded on Rize’s cyclic olefin-based matrix, offering the following features:

Low emissions during production
Extremely low moisture absorption
High chemical resistance
Strength, durability, and stability

RIZIUM GF has been “rigorously tested” and proven prior to its release, and is compatible with Rize Augmented Polymer Deposition (APD), combining inks with polymers to make new materials. Rize states that users will also be able to look forward to 3D printing “large build volumes” for many different applications.

RIZE RIZIUM Glass Fiber tooling

“Until now full color 3D printing applications could only deliver weak approximations of the original, and users often avoided large parts or complex geometries because they could warp or crack,” said Andy Kalambi, CEO of Rize. “We’re delighted to help drive a renaissance in industrial manufacturing with better 3D printing materials and technology.

RIZE RIZIUM Glass Fiber hip assembly

This release also marks the fourth time that RIZE has received UL GREENGUARD Certification, based on the ANSI/CAN/UL 2904 Standard Method for Testing and Assessing Particle and Chemical Emissions from 3D Printers. Issues with emissions, toxicity, and safety are an ongoing concern in 3D printing and industrial AM processes, prompting research into the possibility of whether we are unknowingly poisoning ourselves, causing health hazards, as well as seeking out new solutions for users printing at home.

With the UL GREENGUARD Certification, the new materials are verified as safe for use in enclosed spaces, to include areas like schools, hospitals, and offices.

“We like the print reliability that RIZIUM Glass Fiber delivers to the Rize product line. Azoth can be confident in the quality and strength of RIZIUM GF parts. Being able to transform 3D rendered models into accurate full color parts is something our customers love,” said Ronnie Sherrer, application engineer at Azoth, an Ann Arbor based provider of technology and additive manufacturing to large manufacturers.

Other customers include NASA, PSMI, Wichita State University, the U.S. Army and Festo. Rize has also continued to evolve in the manufacturing of new hardware over the past few years from the introduction of their initial RIZE One industrial desktop 3D printer to the XRIZE 3D printer, and the adaptive desktop RIZE 2XC 3D printer.

[Source / Images: Rize, Inc.]

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Researchers Review 3D Printing with Biomass-Derived Composites

Researchers from State University of New York College of Environmental Science and Forestry, University of Tennessee, Oak Ridge National Laboratory, and The University of Tennessee Institute of Agriculture have come together to research materials for 3D printing, specifically with a focus on composites made from biomass.

Composites are being used more widely as users explore materials that are magnetic, PLA additives, mixtures of recycled polymers, graphene, and more. More natural materials like wood, and specifically lignin, have been a source of experimental studies, too, in efforts to strengthen certain materials for given applications.

In this study, the authors focus on lignocellulosic biomass and derivatives, reviewing and analyzing a variety of additives for 3D printing. Their findings have been released in the recently published ‘3D printing of biomass-derived composites: application and characterization approaches.’

The study of materials is often just a means to an end for the manufacturing of high-performance parts; however, there is also a need for more biocompatible and environmentally-friendly polymers. Because lignocellulosic biomass is natural—and plentiful—it is used in creating bio-fuels, paper, and more, composed of:

Cellulose
Hemicellulose
Lignin
Proteins
Other extractives

“The development of biomass-derived materials using 3D printing technology as an alternative to fossil oil-based plastics will provide an opportunity to achieve sustainable and renewable bioeconomy,” explained the authors.

Number of patents for cellulose and biomass-derived in 3D printing.

Renewable materials have been a substantial source of study, especially in terms of cellulose.

(a) Schematic of the tree hierarchical structure illustrating the role of cellulose. Reprinted with permission from ref. 44. Copyright 2011 Chemical Society Reviews. (b) SEM image of the CNF, scale bar 6 μm. Reprinted with permission from ref. 30. Copyright 2019 Advanced Functional Materials. (c) TEM image of CNCs, scale bar 100 nm. Reprinted with permission from ref. 30. Copyright 2019 Advanced Functional Materials. (d) SEM image of BC produced by Komagataeibacter xylinus. Scale bar 5 μm. Reprinted with permission from ref. 46. Copyright 2017 RSC Advances.

There have been 5,100 patents for 3D printing with cellulose since 2015:

“This trend implies that the application of biomass and its components in 3D printing has become a hot topic and cellulose for 3D printing has been widely used,” stated the authors.

(a) Mechanism of FDM/FFF. (b) “Printing zone” defined in an FDM printing (ABS, HIPS and NBR41–HW represent acrylonitrile–butadiene–styrene, high impact polystyrene and acrylonitrile butadiene rubber with 41 mol% of nitrile contents, respectively). Reprinted with copyright permission from ref. 25. Copyright 2018 Science Advances.

Common methods of 3D printing with composites include fused deposition modeling (FDM), direct-ink writing (DIW), stereolithography (SLA), direct light processing (DLP), and binder jetting.

DIW 3D printing is considered by the authors to be a good candidate for use with cellulose, due to its fluidic properties—meaning that it disperses well in water, acting as a suspension. Hydrogels can be created this way for a variety of bioprinting endeavors, especially due to good rheological properties like shear-thinning, good yield stress for encouraging stability, and both finite elastic modulus and rapid elastic recovery. Previous research recommends CNF hydrogels for use in neural bioprinting, while other additives like chitin (added between the gaps of fibers) may be used in applications like building wind turbine blades. Further crosslinking and ‘enhancing of mechanical performance’ can also result in smart materials, able to respond, and deform to changes in environment like temperature or moisture levels.

Various studies on 3D printing of cellulose and cellulose derivates. (a) The alignment of cellulose nanofibers (CNF) and nanocrystals (CNC) controlled by the flow in a DIW printing (left), leading to a strong aerogel hook (right). Reprinted with permission from ref. 30. Copyright 2019 Advanced Functional Materials. (b) DCW printing of cellulose composites with other biomasses. Reprinted with permission from ref. 36. Copyright 2019 Advanced Materials Technologies. (c) Wood cell mimicking structure combined FDM printing structure with UV-cured resin and CNC. Reprinted with permission from ref. 67. Copyright 2018 Materials & Design. (d) SLA printing of CNC reinforced structure that can be used in medical fields. Reprinted with permission from ref. 39. Copyright 2017 ACS Applied Materials & Interfaces. (e) MC-assisted ceramic slurry showed unique rheology behavior on printing. Below two images showed the prototype (left) and the sintered counterpart (right). Reprinted with permission from ref. 76. Copyright 2019 Journal of Alloys and Compounds. (f) CA-based oil/water separation mesh and its anti-oil-fouling property. Reprinted with permission from ref. 77. Copyright 2019 ACS Applied Materials & Interfaces.

In SLA 3D printing, researchers have also been using resin/cellulose blends more often—and especially in medical applications when materials are biocompatible.

Studies on lignin 3D printing. (a) FDM printing process of lignin-included composite that owns the highest reported lignin contents (60 wt%) and the printed oak leaf. Reprinted with permission from ref. 93 Copyright 2018 Science Advances. (b) SLA printing of lignin-included resin that showed an improvement of the tensile strength. Reprinted with permission from ref. 86. https://pubs.acs.org/doi/abs/10.1021/acsomega.9b02455, Copyright 2019 ACS Omega. Further permissions related to the material excerpted should be directed to the ACS. (c) Modified lignin in SLA printing can be printed with the highest concentration of 15 wt%. Reprinted with permission from ref. 41. Copyright 2018 ACS Applied Materials & Interfaces. Further permissions related to the material excerpted should be directed to the ACS.

“Lignin, the second most abundant terrestrial biopolymer after cellulose, has been under-utilized and, to date, is mostly used for direct combustion,” stated the authors. “Therefore, the valorization of lignin has drawn great attention in the current biorefinery process. Given that lignin contributes to the hydrophobicity, antimicrobial, and antioxidant activities of the plant cell wall, it can be a reinforcing agent in 3D printing composites.”

3D printing of lignin composites

Lignin offers a range of potential uses, but especially in flame retardant products, anti-aging, and absorption of UV rays. Previous research has also proved its uses for improving tensile performance with better layer adhesion, improvement in drug delivery systems with 3D printed PLA/lignin/tetracycline materials, as well as decreases in warpage and shrinkage. Binder jetting was also used in experimentation with starch-based drug delivery systems.

In contrast to production and uses of cellulose and lignin, whole biomass is simpler to deal with—lacking any requirements for complicated processing, whether physical or chemical. Researchers have created materials like for mud-straw walls in construction of basic structures, with wood emerging as ‘one of the most popular biomasses in 3D printing applications.’

3D printing of wood composites

As researchers continue to create new wood composites, FDM 3D printing is being used for increased tensile strength, along with other properties; however, experimenting with printing parameters has also been critical in printing materials like PLA with a recycled pine wood additive.

“… understanding the structure of biomass component(s) remains important, along with the utilization of the supramolecular structures, like crystallinity, material anisotropy and interfacial interactions need to be well-studied to help reach the target property of the 3D printed biomass-derived materials,” concluded the authors. “For the processing, various parameters such as the printing resolution and part production rate are the areas that have to undergo further engineering for making 3D printing competitive with conventional material fabrication technologies.

“In the future, the use of compatibilizers and modification of interfacial chemistry may enhance bonding and distribution of biomass-derived fillers with plastics, which could significantly improve the concentration of the fillers with moderate strength to alleviate depletion, at least partially, of the petroleum-based materials. Moreover, characterization techniques that are tailored to the final commercial application can be valuable to better assess the strengths and weaknesses of printed materials. An in-site characterization that has been applied to metal 3D printing is also a possible approach in this field to promote the printing quality.”

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[Source / Images: ‘3D printing of biomass-derived composites: application and characterization approaches’]

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University of Waterloo: Cellulosic Nanocomposites in Additive Manufacturing & Electrospinning

Andrew Finkle recently presented a thesis to the University of Waterloo, exploring the potential for more effective materials. In ‘Cellulosic Nanocomposites for Advanced Manufacturing: An Exploration of Advanced Materials in Electrospinning and Additive Manufacturing,’ Finkle continues the trend in refining techniques and additives for better performance.

This study centers around polymer nanocomposites; however, today researchers and manufacturers around the world are engaged in research using additives to create other unique materials too like composite hydrogels, bronze PLA, and composite SLS—all in hopes of accentuating specific projects which may require different mechanical properties or distinct features related to functionality.

Schematic diagram of typical electrospinning technique [3].

In terms of hardware and techniques, Finkle examines both electrospinning and fused filament fabrication (FFF) for use with thermoplastic nanocomposites in the production of electrospun fiber mats and 3D printed parts. The new filaments developed in this study contain reinforcements like nanocrystalline cellulose (NCC), meant to improve mechanical properties over traditional methods.

Typical morphology of electrospun polyamide-6 nanofibers observed with scanning electron microscope [4].

Schematic diagrams of fused deposition modeling (FDM) of thermoplastics from the patent “Apparatus and method for creating three-dimensional objects” by S. Crump including an FDM i) 3D printer and ii) extrusion head [8]

Nanocrystalline cellulose (NCC) is a derivative of wood pulp and has demonstrated potential for use as an additive for polymer composites—and specifically for this study, to accompany polycarbonate (PC)—a material offering a wide range of benefits, to include:

Heat resistance
Impact strength
Rigidity
Toughness

“The typical NCC whisker is on the order of 10 nm by 200 nm comprised of many cellulose β-glucan chains tightly bound together to form a very strong crystalline material,” explained Finkle. “The theoretical strength of NCC is on the order 9 of stainless steel and carbon nanotubes but unlike these inorganic reinforcements, is made from renewable and biocompatible sources.”

“The high strength makes this nanoparticle a great candidate for incorporation into composites and more specifically electrospun nanofibers.”

Electrospun mat morphology was based on the following:

Fiber diameter
Bead diameter
Bead density

Schematic diagram of a typical vertical electrospinning apparatus.

SEM micrographs of 15 wt-% PC nanofibers electrospun using chloroform. Fibers i) and ii) were electrospun using Vapp = 20 kV and iii) using Vapp = 15 kV over a gap distance of 15 cm.

“The formulation parameters chosen to explore within the DOEs are the polymer concentration in the solution, the concentration of additives (NCC). The processing parameters chosen to explore within each DOE included the applied voltage, Voltage, and gap distance, Gap Distance. Between the DOEs two other formulation parameters were explored,” explained Finkle.

“This included the solvent the polycarbonate solution was made in either a 60/40 (w/w) THF/DMF mixture or chloroform, both good solvents for PC. The second variable introduced between DOEs with the same solvent was 2-wt.-% of NCC (or DDSA-modified NCC, cNCC) in the solid mass (not including solvent).”

Summary of factors, levels, and formulation parameters for each DOE#0 through DOE#5

Standard order of experiments for a 23 full factorial DOE including the treatment shorthand notation and coded factor levels; high (1), center (0), and low (-1)

Design of experiments (DOEs) were investigated in terms of response to model fiber diameters in terms of:

Function of the PC concentration
NCC concentration
Applied voltage
Gap distance

Center-point measurements evaluated curvatures in the model, and solution properties were noted.

full factorial DOE#1, including the three different factors tested (coded a, b, and c) with their low (-1), high (+1), and center point (0) values

“For most of the experimentation, this involved: following a schedule, often electrospinning as soon as possible following sample preparation; minimizing any error in formulation and mixing of solutions; repeatable collection of nanofiber mats, as well as sample collection, preparation, and imaging of experimental specimens,” concluded Finkle.

“Although controlled as best as possible, some anomalies have still appeared. In particular, the center point replicates of DOE#4 – DDSA-modified Nanocrystalline Cellulose (cNCC) + Chloroform observed in Figure 4.30 show significant variance even though the experimental conditions were identical. This demonstrates that not only that electrospinning in volatile solvents like chloroform at room temperature is difficult to control, but that all possible variables for electrospinning must be considered carefully to achieve desired results.”

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[Source / Images: ‘Cellulosic Nanocomposites for Advanced Manufacturing: An Exploration of Advanced Materials in Electrospinning and Additive Manufacturing’]

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Carbon Fiber Acrylonitrile Styrene Acrylate Composite (CF-ASA): New Material for Large Format Additive Manufacturing

Researchers from Spain are studying materials for more effective large-scale 3D printing, outlining their findings in the recently published ‘Development of carbon fiber acrylonitrile styrene acrylate composite for large format additive manufacturing.’

While 3D printing on the micro- and nanoscale is extremely popular among researchers today, the authors point out that large format additive manufacturing (LFAM) for the industrial user is usually centered around the fabrication of parts that may reach several cubic meters. For this type of production, 3D printers must be accompanied by optimized materials that are suitable for service requirements yet demonstrate high printability.

Today, acrylonitrile styrene acrylate (ASA) is a thermoplastic often being used in LFAM due to excellence in mechanical properties and wettability. ASA also has very good weather resistance and is already used widely in automotive and outdoor applications. Similar materials such as acrylonitrile butadiene styrene (ABS) are extremely popular too due to strength, stiffness, and processability.

“Other technical materials such as polyphenylene sulfide (PPS), polyphenylsulfone (PPSU), polyamide (PA), polyether ether ketone (PEEK) or polyethylene terephthalate glycol (PETG) have been also tested in these technologies,” state the authors. “However, their high cost and hard processability restrict their employment to few applications.”

Structure of ASA polymer Based on [41].

In this study, the researchers evaluate ASA and carbon fiber (CF) composites for LFAM, comparing neat ASA to AS with 20 wt% carbon fiber. The following samples were 3D printed on an SDiscovery Cartesian printer.

Discovery LFAM device property of Navantia S.A., S.M.E. (placed at Bay of Cadiz Shipyard, Puerto Real, Cádiz, Spain). Adapted from [12].).

Samples printed along the two different configurations studied: a) neat ASA sample printed along X direction outside the printer (XY plane displayed, being the Z-direction perpendicular to the image plane (outwards)); and b) ASA 20CF sample printed along Z direction inside the printer. X, Y and Z directions are indicated at the images.

The following samples were created:

Five normalized tensile samples
Five flexural test samples
Ten non-notched impact pieces
Two thermal conductivity discs

Mechanical, rheological and thermal properties of the studied neat ASA and ASA composite.

The composites were examined regarding mechanical, rheological, and thermal properties.

“The mechanical properties were addressed by testing injected tensile, flexural and impact pieces. The melting flow rate (MFR) and the glass transition temperature (Tg), determined by differential scanning calorimetry (DSC), were measured for the two compositions,” explained the authors. “The thermal conductivity was measured using cylindrical injected discs. In a second step, X and Z printed specimens were analyzed by tensile and flexural tests, assessing the influence of the printing orientation in the mechanical properties of both, neat ASA and ASA 20CF.

“Specifically, tensile tested samples were study at the fractured surface of printed specimens aiming to discuss and correlate microstructural features with differentiated mechanical performance of the two materials.”

SEM images show that carbon fibers are well-integrated into the polymer matrix, occurring even after the tensile test.

“A pronounced anisotropy, negligible in injected pieces, is observed in the mechanical properties. A maximum UTS of 60 ± 4 MPa is achieved for X orientation in ASA CF composite, while the flexural tests results are similar, even higher, than for injected parts,” concluded the researchers. “This increase might be attributed to the laminar character of the pieces and the preferential alignment of polymer chains.

“A prealignment of the fibers along the printing deposition direction was observed; likely imposing a physical barrier in Z direction avoiding polymer diffusion and explaining this behavior. The addition of CF results in higher roughness porosity and inner-bead porosity, while reducing the inter-bead porosity. The inner-bead is usually considered as an intrinsic defect of extrusion processes, whereas the observed roughness and inter-bead porosity are characteristic of printing procedures.”

SEM images of the fracture surface of ASA 20CF after a) flexural fracture at liquid nitrogen temperature (without mechanical test); b) tensile test and c) detail of the bonding interface between ASA and CF.

The study of composites continues to expand within the 3D printing realm, as researchers explore a wide variety of materials from bronze PLA composites to products that are bioinspired, to combinations of materials integrated with sensors, and far more.

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[Source / Images: ‘Development of carbon fiber acrylonitrile styrene acrylate composite for large format additive manufacturing’]

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Thailand: Comparing Suitable Fillers for Making PLA Composites

Researchers from King Mongkut’s University of Technology Thonburi in Bangkok, Thailand continue to study the science of materials in 3D printing—a topic that has continued to expand throughout recent years especially as the technology has infiltrated the mainstream and been widely embraced not only just in labs but also a wide range of industries, educational systems, and both offices and homes too on the individual level. Their current research is outlined in the recently published ‘Comparison of Filler Types in Polyactic Acid Composites for 3D Printing Applications.’

Through customization of materials, users today can look forward to greater freedom to innovate in their own work, whether designing prototypes, parts, medical devices, DIY projects in the home, and more. PLA is widely used (along with other standards like ABS) due to its accessibility, affordability, and biodegradable nature as a plant-based material. In this study, the researchers examined a variety of fillers suitable for PLA, assessing which additives would be best for preventing brittleness in parts.

Filler types evaluated in this study included:

Wood flour (WF)
Talc (TC)
Calcium carbonate (CaCO3)
Microballoon (MB)
Silicon dioxide (SiO2)

Samples were designed in SolidWorks 2014, and then files were imported into Cura 2.6.2. The researchers used FDM 3D printing to manufacture objects for tensile testing.

Settings in Cura 2.6.2

Sample of 3D Printed Tensile Specimen

Dumb-bell shaped samples were tested for Young’s modulus, tensile strength, and elongation at break.

“It was found that the 3D printed parts were completely fabricated and stable in shape during fabrication,” stated the authors in their research paper. “The 3D printed composites were a difference in color and texture which were dependent on the color and physical of fillers. The PLA/TC, PLA/CaCO3, PLA/MB and PLA/SiO2 composites were a whitish, and smooth surface while the PLA/WF composites were brown and rougher surface.”

Tensile Properties of 3DPrinted Composites

The 3Dprinted parts of PLA composites:(a) neat PLA,(b) PLA/WF, (c) PLA/TC, (d) PLA/CaCO3, (e) PLA/MB, and (f) PLA/SiO2

Through adding TC and MB, the researchers were able to decrease brittleness. With the PLA/TC composites, greater elongation and flexural strength were displayed in contrast to neat PLA and other composites.

“The 3D printed PLA/TC composites had greater elongation and flexural strength compared to neat PLA and PLA composites because of the plated of talc that would be terminated the cracks and then it supported the further force. The PLA filled with glass microballoons gave the best impact strength, the reasons being associated with the highest melt flow rate that led to a great fusion and bonding between layers. Moreover, the TC-filled and MBfilled PLA composites were stable in shape during fabrication that was satisfied both in the manufacturing and the tough properties,” concluded the researchers.

“For the thermal properties, the PLA slightly deteriorated Vicat softening point when adding the fillers, except for PLA/MB. Next, we focused on the investigate the properties of PLA filled with glass microballoons for 3D printing application in the tooling holder for CNC machine. Next, we focused on investigating the friction and wear properties of 3D printed parts of PLA filled with glass microballoons for making the tool holder in the milling CNC machine.”

If you are a 3D printing user today you have access to an overwhelming number of different types of software, hardware, and materials. Composites are being studied widely, from silver-nanowire photopolymers to PLA antioxidants, to wood composites, and more.

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SEM Micrographs of the Fractured Surface of Filament Composites: (a) neat PLA,(b) PLA/WF, (c) PLA/TC, (d) PLA/CaCO3, (e) PLA/MB, and (f) PLA/SiO2

[Source / Images: ‘Comparison of Filler Types in Polyactic Acid Composites for 3D Printing Applications’]

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Parameter Optimization for 3D Printing of Continuous Carbon Fiber/Epoxy Composites

In the recently published ‘A Sensitivity Analysis-Based Parameter Optimization Framework for 3D Printing of Continuous Carbon Fiber/Epoxy Composites,’ researchers continue to explore the world of enhanced materials for fabrication of prototypes and functional components. Focusing on improving continuous carbon fiber/epoxy composites (CCF/EPCs), the researchers performed a sensitivity analysis for optimizing parameters, as well as 3D printing and evaluating samples.

Today, fiber-reinforced polymer composites (FRPCs) are used in critical applications like construction, transportation, and aerospace, attractive due to qualities like:

Low density
High strength
Outstanding designability
Modulus

While traditional methods may be more time-consuming and expensive, 3D printing offers a host of benefits—from higher speeds in manufacturing to the elimination of molds, affordability, the potential for greater innovation, lightweight (yet stronger) products, and more. In relation to FRPCs, scientists and manufacturers have made huge strides with a range of materials, to include continuous fibers. More so, however, they have made strides in understanding the effects of even the slightest changes in printing parameters like speed, temperatures, and pressure.

“A slight variation may cause a significant change in the final mechanical properties,” stated the researchers. “Although the experimental method would be a preferred and reliable way to acquire the optimal parameters, it is practically difficult or even impossible to carry out sufficient experiments because it would be a time-consuming and unaffordable process. Sensitivity analysis (SA) evaluates how the variations in the model output can be apportioned to variations in model inputs.”

“In addition to being used in biology and chemistry, SA has also been applied in engineering and environmental science.”

The 3D printing process for continuous carbon fiber/epoxy composites (CCF/EPCs).

For this study, the researchers analyzed experimental data, along with creating a surrogate model for process parameters. SA was used to calculate parameters and mechanical properties, followed by further testing to verify the SA-based framework. And while 3D printing CCF/EPCs may be easy, the researchers found that controlling parameters is another matter. Parameters such as printing speed, thickness, and space are ‘critical,’ but challenging to manipulate.

Three experiments were conducted to confirm results, regarding flexural strength and flexural modulus, resulting in averages of 912.1 MPa and 69.28 GPa.

“ … the results showed that the sensitivity analysis-based optimization framework can serve as a high-accuracy tool to optimize the 3D printing parameters for the additive manufacturing of CCF/EPCs and to predict the flexural strength and flexural modulus of the printed samples.”

“While multivariate sensitivity analysis techniques can identify the important parameters for all the mechanical properties considered based on the SVR model of each property, the multi-objective optimization method can search the important parameters which optimize all the mechanical properties simultaneously. Further detailed research for multiple properties will be conducted in future work.”

The flexural strength and flexural modulus of the printed CCF/EPCs samples under the optimal parameters.

As users continue to transform software, hardware, and materials for specific project requirements, a wide range of composites is becoming available—from conductive silver to antioxidant PLA, wood composites, glass composites, and more.

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[Source / Images: ‘A Sensitivity Analysis-Based Parameter Optimization Framework for 3D Printing of Continuous Carbon Fiber/Epoxy Composites’]

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Nanocomposites: SLA 3D Printing with Graphene Oxide Elastomers

In ‘GO-modified flexible polymer nanocomposites fabricated via 3D stereolithography,’ authors CHA Tsang, Adilet Zhakeyev, Dennis Y.C. Leung, and Jin Xuan are exploring challenges for creating stronger materials in SLA 3D printing. While graphene oxide and other metals are often used in additive manufacturing processes today, for this study they were integrated into photopolymer resins for the first time.

Composites continue to grow in popularity, giving materials that added boost which may allow a researcher or user on any level to create successful parts or prototypes. ‘Foreign materials’ as an addition can improve properties, with graphene oxide allowing for better mechanical strength as well as impressive conductivity.

Elastomers, plastics exhibiting viscoelastic behavior, encompass a wide range of chemicals, including:

Polyvinylidene fluoride (PVDF)
Polyurethanes
Styrene-butadiene rubber
Natural rubber latex
Natural rubber

Graphene oxide (GO) elastomer has been developed in varying research in recent years, combined through:

Melt mixing
Solution/latex binding
In-situ polymerization
Film processing

Modified elastomers have demonstrated superior mechanical properties over pure elastomers, but challenges arise in creating them due to a ‘complicated synthesis process.’ 3D printing has changed this, but as the authors explain, there is still great progress to be made regarding optimization.

“There are a few reports detailing the marriage between GO coatings and 3D printed elastomers resulting in a practical application,” state the researchers. “However, none of them involve direct 3D printing of GO/commercial elastomer composites.”

There is still a learning curve for most research teams: A suitable solvent for GO dispersion must be chosen. There may be pre-treatments required for resin. And, greater reporting is necessary regarding 3D printing with such composites in SLA.

For this study, the bottom-up SLA approach was used, and once parts were dried, they were cured with UV lighting. Afterward, the researchers finished the samples with polishing.

“For comparison, two pure resin 3D structures were also prepared, with one of them containing no GO and no pre-treatment steps, while another containing no GO but was further treated with chloroform with the steps similar to the GO/resin mixture processing as mentioned above,” explained the authors.

“Tensile stress was calculated as the measured force normalized to the cross-sectional area of the sample, whereas the applied strain was measured as displacement normalized to the gauge length of the sample. Young’s Modulus was calculated as the slope of the normalized stress-strain curve using linear regression of the linear region of the curve.”

Digital image of the 3D structure from pure polymer and GO/Formlabs flexible nanocomposite with different GO concentrations: (a) 0 wt-% GO; (b) 0 wt-% GO after CH3Cl evaporation; (c) 0.1 wt-% GO; (d) 0.2 wt-% GO; (e) 0.3 wt-% GO.

While 3D printed blocks were created with flexible, semi-transparent resins with different GO content, GOmodified SLA printed flexible polymer nanocomposites changed to a dark green color upon resin being combined with raw GO.

TEM image of 0.1 wt-% GO/MA raw gel (Scale bar: (a) 0.5 µm, (b) 0.2 µm, (c) 100 nm, and (d) 1 µm).

(a) and (b) TEM images of raw GO dispersed in chloroform under different magnification; (c,d) corresponding SEM images (Scale bar: (a) 0.2 µm, (b) 100 nm, (c) 10 µm, (d) 1 µm).

“Despite the successful incorporation of GO, both the mechanical strength and stiffness (Young’s Modulus), as well as the elongation of the resulting polymer decreased with the addition of GO. The thermal properties were also adversely affected upon the increase in the GO content based on DSC and TGA results,” concluded the researchers. “It was proposed that the non-uniform dispersion of GO within the SLA resin, causing large GO agglomeration within the 3D printed composites, can significantly change both mechanical and thermal properties of the resulting nanocomposites.”

“Further in-depth investigations on effective approaches to achieve uniform GO dispersions in SLA resins, as well as the annealing treatment of the GO/ elastomer nanocomposites for mechanical and thermal enhancements were proposed for future development of 3D printed nanocomposite elastomers.”

Composites are a common focus in many research studies today as users demand greater functionality—and perfection—in 3D printed parts. From conductive polymer nanocomposites to lignin biocomposites to continuous wire polymers, many materials are strengthened for better performance.

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[Source / Images: ‘GO-modified flexible polymer nanocomposites fabricated via 3D stereolithography’]

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Conductive Silver-Nanowire Photopolymer Composites: 3D Printing for Greater Functionality

A large group of researchers convened to explore more about additives and new combinations of materials in 3D printing, outlining their findings in the recently published ‘Functional Printing of Conductive Silver-Nanowire Photopolymer Composites.’

Explaining that the use of polymers in 3D printing—and the inherent challenges found therein—has caused significant limitations, the researchers experimented with silver-nanowire-polymer composites, noting that conductive layers can be critical to specific manufacturing needs such as electronics applications; however, composites must be strong against tunneling resistance (as electrons transfer from one nanoparticle to another), and previous researchers have struggled to create materials with suitable conductivity due to issues like agglomeration and strong photon absorption. With nanowires, another route is available as it ‘circumvents the tunneling resistance in the direction of the wire.’

Silver-nanowire (Ag-NW) composites offer ‘scalable processes’ requiring conductivity, to include:

Electronics
Touch screens
Integrated photovoltaics
Advanced optoelectronic devices
Biosensors

Samples were coated with an Ag-NW layer, cured with UV light, and then synthesized via the polyol route. The result was nanowires exhibiting high aspect ratios—in this case, from 100-1000. Resins tend to compress while curing, with shrinking of the matrix pressing on nanowires during the process of polymerization. Lack of density also results in greater sensitivity for nanowire connections and networks.

Characterization and 2D printing of the tough Ag-NW-polymer composite. (a) Impact of the polymer crosslinking on the Ag-NW composite conductivity by comparing the sheet resistances of Ag-NW networks (black dots) and Ag-NW composites (red dots) for 3 different Ag-NW densities (26 µg/cm2, 39 µg/cm2 and 65 µg/cm2). At high Ag-NW densities, the reproducibility of the measured sheet resistance is enhanced, but the impact of the polymer coating on the conductivity is reduced. (b) Transmission of visible to near-infrared light through Ag-NWs and Ag-NW composites. Solid lines indicate pure polymer or Ag-NW films, whereas dashed lines indicate Ag-NW composites. The transmission is larger than 87% for all composites between 600nm and 800nm normalized to a bare glass substrate. The polymer coating decreases scattering and refection at the glass interface resulting in an enhanced transmission compared to a bare glass slide. (c) Exemplary layer thickness and roughness of the produced polymer samples: pure polymer layer, Ag-NW (7 µg/cm2) composite and polymer-Ag-NW (22 µg/cm2 )-polymer multilayer sample. Please note that layer thicknesses between 20–300 µm represent typical thicknesses in functional printing. Te thickness to surface roughness ratio is >1000:1. (d) Photograph and optical microscopy image of a blank solar cell (monocrystalline, 60010, Sol-Expert). A photocurrent I of 650 µA was measured during exposure with an Ulbricht sphere. (e–g) Photographs, optical microscopy images and measured photocurrents of coated solar cells ((e) Ag-NWs, (f) polymer, (g) composite).

During increased nanowire concentration, there was decreased transmittance, and optimized conductivity at fairly low nanowire concentrations, demonstrating a ‘delicate interplay’ between the polymer matrix and Ag-NW network. The researchers also found it remarkable that surface roughness was at 110–160nm for the Ag-NW composites—attributed to polymer roughness.

“These results show that the composite Ag-NW-polymer materials can act as competitive materials for conducting and light-transparent electrodes,” stated the researchers.

Two-dimensional (2D) GISAXS pattern from the samples. (a) Ag-NWs (58 µg/cm2
). (b) Ag-NWs (7µg/cm2) coated with UV-cured polymer layer. (c) Bare UV-cured polymer. The intensity scale bar is shown on the right side. Clear fares at 36°±2° (indicated by red lines) stemming from the facets of the pentagon morphology
starting from the sample horizon are visible for (a,b). (d) Simulation of the key scattering features of Ag-NWs. (e) SEM image of Ag-NWs on a silicon substrate (Ag-NW density around 120 µg/cm2). (f) Sketch of the faceted Ag-NW (adapted from44,45). (g) Horizontal cuts of the intensity (I(qy,qz1=0.63nm−1)), (h) I(qy,qz2=0.78nm−1), (i) I(qy,qz3=0.96nm−1). All cuts are normalized to the intensity at I(0,qz1,2,3) correspondingly. The color code corresponds to (a–c).

During the initial stages of synthesis, five-fold twinned seeds formed, with pentagonal structure and twinned tops of Ag-NWs also confirmed during SEM evaluations (although not applicable for the material). Pentagonal morphology was established as the researchers simulated key features of the GISAXS pattern, via specialized software.

For 3D printing, the research team fabricated a capacitator made up of Ag-NWs and Flexible photopolymers by Formlabs. They were not only able to show the potential for 3D printed electronics, but also the role that composites play in improving functionality.

Flexible Ag-NW composite capacitor. (a) Illustration of the cross-section of the capacitor. (b) Photograph of a produced Ag-NW capacitor (10×10 mm2
). The dashed white line depicts the position of the cross-section, which is presented in (a). (c) Photograph of the capacitor bent over a glass rod in order to
demonstrate its flexibility. (d) Cross-sectional view of the lower part of the stripped of the capacitor with Ag-NWs.

“By applying two different polymers, we have fabricated composites with different properties that were tested for two specific applications. Firstly, we have optimized Ag-NW composites for use as transparent top contacts by tuning the Ag-NW concentration within a tough and transparent HDDA-based polymer matrix. We have accomplished a sheet resistance of 13Ω/sq and a corresponding transmission at 700nm of 90%,” concluded the researchers. “Secondly, we have used a flexible polymer matrix in the composite for a 3D-printed flexible capacitor.”

“The capacity of around 7pF agrees well with the estimated value of about 5 pF. Our characterization involves GISAXS, which enables the investigation of embedded nanostructures and interfaces with high statistical relevance. Tis shows that GISAXS can develop further to an excellent technique for the investigation of embedded nanostructures in 3D-printed and technically relevant films.”

The science of materials continues to grow, and within that, composites are becoming a large part of refining functionality for many different applications. Researchers are working with a wide range of different additives, from glass fibers to lignin and other wood composites, while many different materials show potential, like antioxidants. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘Functional Printing of Conductive Silver-Nanowire Photopolymer Composites’]

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Belfast: 3D Printing with Antioxidant PLA Composites Shows Potential in Medical Applications

In the recently published ‘Antioxidant PLA Composites Containing Lignin for 3D Printing Applications: A Potential Material for Healthcare Applications,’ Belfast researchers experiment with new 3D printing materials. Due to its strength as a biopolymer and an antioxidant, the research team combined lignin with poly(lactic acid) in FDM 3D printing.

Scheme of the different meshes produced using FFF.

Coating PLA pellets with LIG powder and castor oil, which is biocompatible, they extruded the material at 200 °C. The researchers reported LIG loadings that ranged from 0% to 3% (w/w). With the goal of providing additional, beneficial features to PLA, the research team tried varied strategies, to include incorporating molecules with antioxidant properties to PLA.

“The unrestrained production of free radicals and reactive oxygen species is linked with the onset of diseases such as rheumatoid arthritis, atherosclerosis or cancer,” stated the researchers. “Accordingly, the development of antioxidant compounds/materials can contribute to reduce the concentration of these compounds. Moreover, it has been shown that the excess of reactive oxygen species prevents wound healing. Accordingly, antioxidants have been proposed to control oxidative stress in wounds to accelerate their healing.

Photographs of: PLA and PLA coated pellets (A); LIG and TC containing PLA filaments (B); LIG and TC containing 1 cm × 1 cm squares prepared using 3D printing (C); and different shapes printed using the filament containing 2% (w/w) LIG (D).

Previously, SLA 3D printing was used to fabricate antioxidant vascular stents with bioresorbable abilities, while SLS 3D printing was used to create materials with antioxidants to promote cell growth. While the actual compound was not disclosed, the researchers reported that they used UV-stable polyamide 12 material with antioxidant properties. LIG is known to possess both antioxidants and antimicrobes and incidentally, is also the second most abundant polymer on our planet—with researchers still having plenty of studying to do—especially for biomedical applications.

As the researchers combined LIG with PLA here, the intent was to develop a composite for healthcare as the materials were combined through extrusion, characterized, and then actually used in FDM 3D printing. It is expected that these composites can be used for wound dressings due to the potential for localized antibacterial qualities. Here, the researchers used tetracycline (TC) as the antibacterial agent.

Used in wound dressings, the composite made up of LIG and PLA would allow for customization of size and shape—and not only that, PLA offers a biodegradable form.

“The present work showed that PLA and LIG can be combined easily by coating PLA pellets with LIG. Other alternatives to prepare PLA/LIG composites have been explored but they require organic solvents or more complex equipment such as twin screws extruders,” concluded the researchers.

“Antioxidant packaging can be used to improve the condition and increase the shelf-life of packaged food. Due to the enhanced cell proliferation on antioxidant materials, these materials can be used for tissue culture applications or even for regenerative medicine. Due to the versatility of FFF, complex geometries can be prepared such as scaffolds. However, before this type of material can be implanted into humans, the safety of lignin-based materials should be evaluated. It has been reported before that LIG-based materials are biocompatible, but more studies should be performed.”

Experimental setup used to measure drug diffusion trough the 3D printed meshes (A); photographs of the 3D printed meshes made of PLA and 2% (w/w) LIG (B); and CUR release through 1.5 mm (C) and 1 mm (D) 3D printed meshes (n = 3).

As the range of 3D printing materials continues to expand, so does research and development of composites, from thermoset composites for aerospace to glass composites, nanocomposites, and more.

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[Source / Images: ‘Antioxidant PLA Composites Containing Lignin for 3D Printing Applications: A Potential Material for Healthcare Applications’]

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Researchers Designing Modular 3D Printed Composite Hollow Beams

In ‘Designing modular 3D printed reinforcement of wound composite hollow beams with semidefinite programming,’ researchers from the Czech Republic improve on composites used to make lattices for bioprinting. Their goal is to create a new and fully automated process for creating structural composites with both thin walls and hollow beams in structures. Ultimately, what they required was a basic optimization of a beam cross-section shape with an outer shape already set.

This type of research is not exactly new; in fact, in recent decades numerous structural optimization problems have been semidefinite programs. Here, the team considered ‘an industrial problem of designing the least-weight internal structure of a thin-walled filament-wound composite machine tool component prone to shear and buckling wall instabilities.’

Beam laminate was created for the load of dynamic loads, with wall instabilities defined regarding free-vibrations eigenfrequencies. The weaknesses were reduced here with a foam core structure inserted into the beam; however, it was found to be cost-prohibitive and labor intensive to do so:

“Conversely, we have aimed to automatically design a structurally-efficient internal structure which can easily be manufactured using conventional low-cost 3D printers,” stated the researchers.

They also ‘extended’ the linear semidefinite programming to create globally-optimal least-weight lattice-like internal structures.

Greater rigidity was enabled in creating a prototype with a more lightweight internal structure created with a more efficient ‘convex linear semidefinite programming formulation.’ This allowed for basic free-vibration frequency elevated above a specific level, while still avoiding typical differentiability in multiple eigenvalues. The basic structure for the sample here was a ‘prismatic, laminated composite beam, measuring 1000 mm long, with an 80 × 80 mm thin-walled cross-section 2.2 mm thick.

Case study setup. (a) Outer dimensions and simply supported boundary conditions, (b) prismatic cross-section, and (c) compression molding load case.

The researchers noted that they had to be cautious upon creating a rigid connection between the internal structure and carbon composite. After creating a successful prototype, the team put it through the paces, beginning with the roving hammer test. There, they discovered ‘good agreement with model predictions’ in terms of bending, torsional, and shear eigenmodes.

The entire structure of considered composite beam design: internal structure (used for the reduction of wall instabilities and for increase of the lowest free-vibration frequency); casing of the internal beam structure (to allow for winding the final composite layer); composite layers, which transmit working load applied to the beam.

“The optimization output of the non-uniformly distributed lattice-like internal structure was further automatically post-processed and converted into a solid model ready for support-less additive manufacturing.”

“Improving the structural response with a material more than two orders of magnitude more compliant when compared to CFRP suggests concentrating on substituting ABS with high-stiffness continuous carbon fiber in future studies,” concluded the researchers. “Another essential future enhancement resides in accelerating the optimization algorithm by exploiting the range-space sparsity associated with the segment-based internal-structure decomposition.”

Selected experimentally determined natural frequencies and mode shapes, (a)–(h) top, and finite element model predictions of eigenmodes and eigenfrequencies, (a)–(h) bottom.

Researchers today are extremely interested how the creation of composites can improve 3D printing processes, mainly in strengthening materials, from the use of glass composites, to copper metal composites, to wire polymer, and so much more.

What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: ‘Designing modular 3D printed reinforcement of wound composite hollow beams with semidefinite programming’]

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