Fused Filament Fabrication Technique Research Articles

Influence stacking sequence and heat treatments on the out-of-plane mechanical properties of 3D-printed fiberglass-reinforced thermoplastics

Additive manufacturing of composite materials is a promising technology. It could solve one of the most critical drawbacks of 3D-printed fiber-reinforced thermoplastics: their low out-of-plane mechanical properties. Due to this factor, it is still unknown how most design and manufacturing parameters affect the out-of-plane properties of composite materials. As a solution, this paper proposes an experimental methodology to characterize out-of-plane printed composite materials. For this purpose, existing standards for traditionally fabricated composites are adapted, investigated, and validated for 3D-printed laminates reinforced with long fibers using the fused filament fabrication technique. Consequently, the methodology is employed to study the impact of stacking sequence and heat treatment conditions on the composites’ out-of-plane mechanical properties. The main results showed that increasing the thickness between stacking layers increases the mechanical response due to reducing the number of fiber/matrix interfaces and, consequently, the reduction of porosity. Compared to the initial sample, a heat treatment at 175 °C for 6 h increased the interfacial strength by 101.09% and reduced the porosity in the fiber produced by the additive manufacturing process by 72%.

Preparation of 3D printed calcium sulfate filled PLA scaffolds with improved mechanical and degradation properties

Scaffold is one of the key components for tissue engineering application. Three-dimensional (3D) printing has given a new avenue to the scaffolds design to closely mimic the real tissue. However, material selection has always been a challenge in adopting 3D printing for scaffolds fabrication, especially for hard tissue. The fused filament fabrication technique is one of the economical 3D printing technology available today, which can efficiently fabricate scaffolds with its key features. In the present study, a hybrid polymer-ceramic scaffold has been prepared by combining the benefit of synthetic biodegradable poly (lactic acid) (PLA) and osteoconductive calcium sulphate (CaS), to harness the advantage of both materials. Composite PLA filament with maximum ceramic loading of 40 wt% was investigated for its printability and subsequently scaffolds were 3D printed. The composite filament was extruded at a temperature of 160 °C at a constant speed with an average diameter of 1.66 ± 0.34 mm. PLA-CaS scaffold with ceramic content of 10%, 20%, and 40% was 3D printed with square pore geometry. The developed scaffolds were characterized for their thermal stability, mechanical, morphological, and geometrical accuracy. The mechanical strength was improved by 29% at 20 wt% of CaS. The porosity was found to be 50–60% with an average pore size of 550 µm with well-interconnected pores. The effect of CaS particles on the degradation behaviour of scaffolds was also assessed over an incubation period of 28 days. The CaS particles acted as porogen and improved the surface chemistry for future cellular activity, while accelerating the degradation rate.

Analysis of fused filament fabrication parameters for sliding wear performance of carbon reinforced polyamide composite material fabricated parts using a hybrid heuristic tool

Carbon-reinforced nylon composite material (PA12CF20), i.e., polyamide, has been widely used in the automotive, medical, and electronics industries for fabricating functional parts, especially in gear manufacturing, due to its excellent wear property. The present work investigates the optimal parameters of the fused filament fabrication (FFF) 3D printing technique using PA12CF20 as feedstock to fabricate parts for enhancing the sliding wear performance. The test specimens are fabricated as per the American society for testing and materials (ASTM) G99 standard. The hybrid heuristic tool, i.e., genetic algorithm-adaptive neuro fuzzy inference system (GA-ANFIS), has been used to train, predict, and optimize the sliding wear performance of the fabricated parts using carbon reinforced polyamide composite material. The experimental runs have been performed on 30 combinations of input factors based on face centered central composite design (FCCCD) and further used for training and optimization for the hybrid GA-ANFIS approach. Scanning electron microscopy has been used to characterize the wear crack of the PA12CF20. It is observed that the optimal parameters retrieved using GA-ANFIS have increased the wear performance of PA12CF20 fabricated specimens, and the same has been validated experimentally. Further, a lathe machine spur gear was fabricated using optimal parameters of the FFF technique and checked the suitability for end-use applications.

Creating tougher interfaces via suture morphology in 3D-printed multi-material polymer composites by fused filament fabrication

This study presents a facile strategy for architecting the interface morphology to create tougher and stronger interfaces in additively manufactured multi-material polymer composites. A sutural interfacial morphology between two dissimilar polymer phases PLA (hard) and TPU (soft) is designed and fabricated by the fused filament fabrication technique. The proposed strategy utilizes one of the process parameters (i.e., overlap distance) to create sutural interfaces with soft protrusions. The microscopic inspections of the interface suggest that the proposed strategy can control the protrusion amplitude, which indirectly influences the interfacial defect density. A positive correlation between the overlap distance and resulting protrusion amplitude is obtained. The interfacial toughness measurements by the double cantilever beam test reveal a linear correlation between the interfacial toughness and protrusion amplitude. The proposed interfacial architecture can result in up to a 16–18-fold increase in the interfacial toughness in comparison with the baseline interface. Three distinct toughening mechanisms associated with the fracture of the proposed interfaces are identified: (1) geometric toughening associated with the interface roughness, (2) enhancement of the intrinsic interfacial toughness due to the reduced interfacial defect density between the PLA and TPU, and (3) additional plastic (or inelastic) energy dissipation within the TPU layer. The results reported in this study are anticipated to provide guidelines to produce multi-material polymer composites with stronger and tougher interfaces via additive manufacturing.

Bioresorbable polylactic acid (PLA) and bioactive glasses (BG) composite: Influence of gold coated of BG powder on mechanical properties and chemical reactivity

Due to the ageing of the population, the synthesis of biomaterials and the optimization of their physico-chemical characteristics are at the heart of many research projects in regenerative medicine. The emergence of 3D printing techniques has rapidly led to the manufacture PLA-BG composite scaffolds using the FFF (Fused Filament Fabrication) technique. However, this composite presents some problems including a lower mechanical strength than the two compounds alone, probably due to the ionic salting-out induced by the BG. This study aims to counter this phenomenon by coating the BG particles with a thin layer of gold. The 3D composite objects will then be characterized mechanically and biologically to ensure that the bioactive character of the composite is preserved.

Height-to-Diameter Ratio and Porosity Strongly Influence Bulk Compressive Mechanical Properties of 3D-Printed Polymer Scaffolds.

Although the architectural design parameters of 3D-printed polymer-based scaffolds-porosity, height-to-diameter (H/D) ratio and pore size-are significant determinants of their mechanical integrity, their impact has not been explicitly discussed when reporting bulk mechanical properties. Controlled architectures were designed by systematically varying porosity (30-75%, H/D ratio (0.5-2.0) and pore size (0.25-1.0 mm) and fabricated using fused filament fabrication technique. The influence of the three parameters on compressive mechanical properties-apparent elastic modulus Eapp, bulk yield stress σy and yield strain εy-were investigated through a multiple linear regression analysis. H/D ratio and porosity exhibited strong influence on the mechanical behavior, resulting in variations in mean Eapp of 60% and 95%, respectively. σy was comparatively less sensitive to H/D ratio over the range investigated in this study, with 15% variation in mean values. In contrast, porosity resulted in almost 100% variation in mean σy values. Pore size was not a significant factor for mechanical behavior, although it is a critical factor in the biological behavior of the scaffolds. Quantifying the influence of porosity, H/D ratio and pore size on bench-top tested bulk mechanical properties can help optimize the development of bone scaffolds from a biomechanical perspective.

Experimental, numerical, and theoretical crushing behaviour of an innovative auxetic structure fabricated through 3D printing

This paper aims to investigate the crushing behaviour and protective performance of an innovative auxetic structure, named the hourglass structure (HGS), under in-plane compressive loads. The HGS was fabricated with a 3D printing method through fused filament fabrication technique. The 3D printed HGS specimens were subjected to a displacement-controlled in-plane quasi-static compressive load. A 3D comprehensive numerical model was developed and calibrated with the experimental results. The calibrated numerical model was used for a parametric study to explore the effects of relative density, functional grading, and crushing velocity on the protective performance of the HGS. Furthermore, a theoretical model was proposed to correlate plateau stress of the HGS with geometric design parameters, effective Poisson’s ratio, and matrix material properties. Verified with a series of numerical analyses of different HGS designs, the proposed theoretical model predicted plateau stress with less than 10% relative error. In addition, experimental, numerical, and theoretical analyses uncovered load–deformation relationship, Poisson’s ratio, crushing mechanism, and energy absorption capacity of the novel auxetic. Overall, the HGS exhibited excellent features for protective engineering applications such as shock mitigation and blast energy absorption.

Strength Properties of 316L and 17-4 PH Stainless Steel Produced with Additive Manufacturing.

The number of additive manufacturing methods and materials is growing rapidly, leaving gaps in the knowledge of specific material properties. A relatively recent addition is the metal-filled filament to be printed similarly to the fused filament fabrication (FFF) technology used for plastic materials, but with additional debinding and sintering steps. While tensile, bending, and shear properties of metals manufactured this way have been studied thoroughly, their fatigue properties remain unexplored. Thus, the paper aims to determine the tensile, fatigue, and impact strengths of Markforged 17-4 PH and BASF Ultrafuse 316L stainless steel to answer whether the metal FFF can be used for structural parts safely with the current state of technology. They are compared to two 316L variants manufactured via selective laser melting (SLM) and literature results. For extrusion-based additive manufacturing methods, a significant decrease in tensile and fatigue strength is observed compared to specimens manufactured via SLM. Defects created during the extrusion and by the pathing scheme, causing a rough surface and internal voids to act as local stress risers, handle the strength decrease. The findings cast doubt on whether the metal FFF technique can be safely used for structural components; therefore, further developments are needed to reduce internal material defects.

FUNCTIONALIZATION OF WOVEN FABRICS BY 3D PRINTED STRUCTURES IN FUSED FILAMENT FABRICATION (FFF): EFFECTS OF INFILL PATTERNS ON TENSILE STRENGTH

Three-dimensional (3D) printing has an increasing popularity in recent years with easy availability and the wide range of applications in many fields. While producing textile-like structures with 3D technology is still a challenging problem, combining textiles with 3D printed structures enables the manufacture of many alternative structures in the field of textile applications. This study investigates the effect of 3D parts with different infill patterns printed onto the cotton woven fabric for tensile strength. For this purpose, 3D parts with concentric, grid and triangle infill patterns were printed onto plain and twill woven fabrics with polylactic acid (PLA) filaments in the Fused Filament Fabrication technique. Adhesion between fabric and 3D parts and tensile strengths of produced structures were measured to assess the effectiveness of 3D printing. Results showed that greater adhesion between 3D parts and fabrics were obtained for plain-woven fabrics. The infill patterns were also found effective for the tensile strength performance.

Biomechanical validation of additively manufactured artificial femoral bones

Replicating the mechanical behavior of human bones, especially cancellous bone tissue, is challenging. Typically, conventional bone models primarily consist of polyurethane foam surrounded by a solid shell. Although nearly isotropic foam components have mechanical properties similar to cancellous bone, they do not represent the anisotropy and inhomogeneity of bone architecture. To consider the architecture of bone, models were developed whose core was additively manufactured based on CT data. This core was subsequently coated with glass fiber composite. Specimens consisting of a gyroid-structure were fabricated using fused filament fabrication (FFF) techniques from different materials and various filler levels. Subsequent compression tests showed good accordance between the mechanical behavior of the printed specimens and human bone. The unidirectional fiberglass composite showed higher strength and stiffness than human cortical bone in 3-point bending tests, with comparable material behaviors being observed. During biomechanical investigation of the entire assembly, femoral prosthetic stems were inserted into both artificial and human bones under controlled conditions, while recording occurring forces and strains. All of the artificial prototypes, made of different materials, showed analogous behavior to human bone. In conclusion, it was shown that low-cost FFF technique can be used to generate valid bone models and selectively modify their properties by changing the infill.

Fatigue behavior and electromechanical properties of additively manufactured continuous wire polymer composites for structural health monitoring

AbstractThe fatigue behavior of continuous wire polymer composite (CWPC) fabricated by fused filament fabrication (FFF) was investigated. Four compositions were examined: polylactic acid (PLA), PLA with copper wire (Cu), thermoplastic polyurethane (TPU), and TPU with Cu wire. Residual properties were measured after different sets of number of cycles (102, 104, 105). Residual strengths were 89.7% and 70.5% of the ultimate tensile strength of the original material after 105 cycles for PLA CWPC and TPU CWPC, respectively. A one‐way analysis of variance (ANOVA) statistical tests showed insignificant changes in the residual strengths of PLA‐based materials after an increasing number of cycles and significant changes for the TPU‐based materials. CWPC electromechanical properties under fatigue test demonstrated reverse piezoresistance behavior. A strain‐controlled fatigue life analytical model was compared with the experimental results showing good agreement. This study demonstrates the applicability of FFF technique to print sensors with continuous integrated wire with tunable properties.

Surgery Training System Supported by Organic Materials.

The aim of the study was the qualitative assessment of new materials based on a polycarbonate matrix in terms of its use in 3D printing and its processing and geometric modification (cutting). Filaments made of the new material doped with talc in five different proportions were visually inspected with a microscope. The calibration and test models were made using the FFF (fused filament fabrication) technique. In addition, its susceptibility to the drill and the behavior of the shavings were assessed and the temperature changing during drilling was measured. The implant was inserted to measure its resonance stability in each of the holes made and translated into the value of the implant stability quotient (ISQ) ranging from 1 to 100. The results were compared to those obtained for the training model of the skull bone. The amount of filler has been shown to affect the composite. Moreover, due to the properties of talc, a compatibilizer (polyol) was used. Differences were observed between the model made of the commercial material, the model made of the dried, tested material, and the model made of the undried material. It was confirmed that the presence of water in the material during its processing is important.

Characterization of industry grade soybean wax for potential applications in natural fiber reinforced composite (NFRC) filaments

A characterization study was conducted to obtain and analyze the thermal, chemical, and mechanical properties of industry grade wax soybean (Glycine max) for coating soy hull fibers from soybean processing in order to incorporate the soy wax coated soy fibers in additive manufacturing applications. The waxes when coated onto soy hull fibers are expected to better the fiber-polymer interface to produce additive manufacturing filaments with improved mechanical properties to be printed using fused filament fabrication technique. The printed parts can then be used in the automotive industry because the parts will be more sustainable, have less carbon footprint, and increased mechanical properties. The information obtained from this characterization study will be the preliminary step to determine the suitability of the waxes for fiber coating application. Applying soybean waxes in this manner increases the value of soybean waxes from being a source for candle making to being incorporated in manufacturing parts. Four wax samples were analyzed by thermogravimetric analysis, differential scanning calorimetry, viscometry, Fourier Transformed Infrared Spectroscopy, X-Ray Diffraction, Vickers micro-hardness testing, compression, and flexural testing. One sample was chosen with the most suitable properties for polymer composites and 3D printing filaments were produced.

Manufacturing Polymer Model of Anatomical Structures with Increased Accuracy Using CAx and AM Systems for Planning Orthopedic Procedures

Currently, medicine uses typical industrial structure techniques, including reverse engineering, data processing, 3D-CAD modeling, 3D printing, and coordinate measurement techniques. Taking this into account, one can notice the applications of procedures used in the aviation or automotive industries based on the structure of Industry 4.0 in the planning of operations and the production of medical models with high geometric accuracy. The procedure presented in the publication shortens the processing time of tomographic data and increases the reconstruction accuracy within the hip and knee joints. The procedure allows for the partial removal of metallic artifacts from the diagnostic image. Additionally, numerical models of anatomical structures, implants, and bone cement were developed in more detail by averaging the values of local segmentation thresholds. Before the model manufacturing process, additional tests of the PLA material were conducted in terms of its strength and thermal properties. Their goal was to select the appropriate type of PLA material for manufacturing models of anatomical structures. The numerical models were divided into parts before being manufactured using the Fused Filament Fabrication technique. The use of the modifier made it possible to change the density, type of filling, number of counters, and the type of supporting structure. These treatments allowed us to reduce costs and production time and increase the accuracy of the printout. The accuracy of the manufactured model geometry was verified using the MCA-II measuring arm with the MMDx100 laser head and surface roughness using a 3D Talyscan 150 profilometer. Using the procedure, a decrease in geometric deviations and amplitude parameters of the surface roughness were noticed. The models based on the presented approach allowed for detailed and meticulous treatment planning.

Characterization of PLA-CF Composites Fabricated by Fused Filament Fabrication Technique

Characterization of PLA-CF Composites Fabricated by Fused Filament Fabrication Technique

Solid-State and Super Solidus Liquid Phase Sintering of 4340 Steel SLM Powders Shaped by Fused Filament Fabrication

4340 steel powders were processed with an additive manufacturing process using the FFF (Fused Filament Fabrication) technique. A composite filament was developed to print samples and study the effect of the bed and nozzle temperatures on its physical and microstructural properties. The printed samples were debinded and sintered by: Solid State (SS) at 1300 °C or SLPS (Supersolidus Liquid Phase Sintering) at 1420 °C. Metallography and scanning electron microscopy (SEM) identified the microstructure and phases. The hardness of the sintered samples was measured with the Vickers method. The SLPS process contributes to better densification and volume contraction; however, it promotes geometrical distortion of the samples compared to the SS samples. The microstructure of the sintered samples consists of ferrite situated in the original austenite grain and bainite. The sintering mechanism significantly influenced the hardness of the samples. Finally, a part was designed, printed, debinded, and sintered with the aim of studying the maximum inclination angle, the minimum vertical and horizontal holes, and the minimum vertical layer thickness, which can be obtained through the whole process.

Fused Filament Fabrication 3D Printing: Quantification of Exposure to Airborne Particles

Fused Filament Fabrication (FFF) has been established as a widely practiced Additive Manufacturing technique, using various thermoplastic filaments. Carbon fibre (CF) additives enhance mechanical properties of the materials. The main operational hazard of the FFF technique explored in the literature is the emission of Ultrafine Particles and Volatile Organic Compounds. Exposure data regarding novel materials and larger scale operations is, however, still lacking. In this work, a thorough exposure assessment measurement campaign is presented for a workplace applying FFF 3D printing in various setups (four different commercial devices, including a modified commercial printer) and applying various materials (polylactic acid, thermoplastic polyurethane, copolyamide, polyethylene terephthalate glycol) and CF-reinforced thermoplastics (thermoplastic polyurethane, polylactic acid, polyamide). Portable exposure assessment instruments are employed, based on an established methodology, to study the airborne particle exposure potential of each process setup. The results revealed a distinct exposure profile for each process, necessitating a different safety approach per setup. Crucially, high potential for exposure is detected in processes with two printers working simultaneously. An updated engineering control scheme is applied to control exposures for the modified commercial printer. The establishment of a flexible safety system is vital for workplaces that apply FFF 3D printing.

An Analysis of Selected Technological Parameters’ Influences on the Tribological Properties of Products Manufactured Using the FFF Technique

This study investigates how layer deposition in printing 3D models made of polyetherimide (PEI) using the fused filament fabrication (FFF) technique affects resistance of these models to abrasive wear. Samples made by additive manufacturing with different setting of build orientation and path generation strategy of extruded fibers were used in the experiment. The experiments were conducted on a tribometer according to the ASTM G65-16 standard. The friction force, normal force, and temperature in the contact area during the tribometer operation were measured using a strain gauge sensor. The tribometer allowed us to perform the tribological experiments using a rubber-coated or a metal disc without a lubricant in the so-called “dry” operation. Following the ASTM G65-16 standard, a rubber-coated disc and Fe3Al2 (SiO4)3 garnet abrasive were used for the wear resistance tests. The analysis of experimental data showed correlations among orientation selection, the strategy of layer deposition by the FFF technique, and the surface life in terms of abrasive wear. The results of this research also showed the suitability of the chosen building orientation and deposition strategy for part production by additive manufacturing, depending on the required tribological properties, such as the coefficient of friction (yield path) and wear behavior. Based on the results of the study, it is concluded that continuity of wear and friction force depends on the path traveled under the model production orientation. The size of wear (material loss) ranged from 0.451–0.809%. It was shown that the weight loss of the sample under loading was greater, on average, with the chosen fiber orientation strategy in the Z direction than in the X direction.

Effect of carbon nanotubes on mechanical properties of polyamide 12 parts by fused filament fabrication

Polymer parts fabricated by fused filament fabrication (FFF) technique usually exhibit weak and anisotropic mechanical properties, compared with their injection-molded (IM) counterparts. Thus, the evolution of FFF from rapid prototyping into manufacture tool requires three-dimensional enhancement ways for FFF-printed parts. To this end, we develop a series of carbon nanotubes (CNTs)-embedded polyamide 12 (PA12) filaments and investigate the effect of CNTs on the mechanical properties of the FFF-printed PA12 parts. In the direction parallel to the deposited strands, PA12/CNT parts show considerable mechanical reinforcement compared with neat PA12 specimens, including the increase of tensile and impact strength by 18% and 125%, respectively. The marked improvement in impact strength arises from the oriented structures induced by the shear field during FFF process as well as the layer-by-layer microstructure, which provide multiple ways to dissipate impact energy. However, these oriented CNTs and inter-filament voids tend to act as stress concentration points under the tensile stress, thus accounting for a slight increase in tensile strength. In the direction perpendicular to the deposited strands, the FFF-printed PA12/CNT parts also exhibit improved tensile strength, i.e. interfacial weld strength, as CNTs allow the rapid transfer of the thermal energy from the newly-deposited filament to the weld interface and thus provide longer time for molecular interdiffusion. Altogether, the anisotropy in tensile strength of the FFF-printed parts is reduced from 0.36 for neat PA12 parts to 0.28 for PA12/CNT specimens. This work is believed to provide a facile route to overcome mechanical limitations in FFF technique.

Attenuation properties of common 3D printed FFF plastics for mammographic applications

The aim of this study was to evaluate the feasibility of using acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) 3D printing filaments as materials for mammography phantom construction, comparing their attenuation properties at two different set-ups: at a Calibration Laboratory and directly to a mammography unit. The attenuation of 3D printed test phantoms of two types of common 3D printing Fused Filament Fabrication (FFF) filaments (ABS and PLA) were characterized in comparison with polymethylmethacrylate (PMMA). The measurements were carried out with standard IEC 61267 X-rays, using RQR 2-M and RQR 4-M beam qualities at the Instruments Calibration Laboratory, and then applied to a mammography unit, with measurements with 28 kVp and 35 kVp. Attenuation characteristics evaluated indicates the suitable equivalence of PLA to PMMA for 3D printing breast tissue equivalent complex phantoms. The plastic materials used in this study suggest that the FFF technique may be suitable for mammography phantom development.