Investigation of 3D printing strategy on the mechanical performance of coextruded continuous carbon fiber reinforced PETG

Fused filament fabrication (FFF) has been used to create prototypes and functional parts for various applications using plastic filaments. It has also been extended to the use of continuous fibers for reinforcing thermoplastic polymers. This study aims to optimize the deposition design of a coextruded continuous carbon fiber (CCF) composite filament with a polyethylene terephthalate glycol-modified (PETG) filament. The characterizations on the raw materials revealed that the matrix polymer in CCF composite filament had similar physicochemical properties as PETG, and carbon fibers were homogeneously distributed in CCF filament. The effect of raster orientation and shells number on the mechanical properties of non-reinforced and coextruded CCF-reinforced PETG was investigated. The highest mechanical properties were obtained at a raster orientation of 0° for both reinforced and non-reinforced materials. With the increase of raster orientation, Young's modulus and ultimate tensile strength decreased. The presence of shells improved the tensile strength of non-reinforced PETG. For composite samples printed with unreinforced shells, Young's modulus decreased due to decrease in fibers content, and elongation at break and ultimate tensile strength increased. Tomographic observations showed that the mechanical behavior of printed specimens depended on the anisotropy of porosity in printed specimens.     

FDM用PETG系列耗材的改性研究

对市售聚对苯二甲酸乙二醇酯-1,4-环己烷二甲醇酯（PETG）丝材及原材料进行研究,选用PETG 2012作为制备熔融堆积成型技术（FDM）用PETG丝材的基体树脂。选用聚碳酸酯（PC）对基体PETG进行增韧增强改性,并制成3D打印高分子丝材进行打印测试,探讨了PC含量对PETG耗材及制件性能的影响。结果表明,在低PC含量下,PETG与PC的相容性较好,PETG与PC制件未出现明显的分层,分布比较均匀;共混物的流动性随着PC含量的增加而降低,且打印件的维卡软化温度和热变形温度随着PC用量的增加而增加;此外,PC材料的加入使得PETG打印件的力学性能得到较大改善：打印件的拉伸强度随着PC用量的增加而增大,缺口冲击强度却随着PC用量的增加呈现先增加后减小的趋势; PETG/PC的配比为1∶1时,可制得力学性能优异的3D打印耗材。     

聚己内酯3D打印成型工艺研究及力学性能分析

以聚己内酯（PCL）为材料,采用实验方法,研究了成型温度和打印层高对PCL制品翘曲变形的影响。通过三维（3D）打印制备PCL样条,表征了3D打印PCL的力学性能,并与注射成型进行对比。结果表明,随着成型温度的升高和打印层高的增加,PCL制品的翘曲变形量呈现出先增加后减小的趋势;PCL 的3D打印制品的拉伸强度、弯曲强度和断裂伸长率均高于传统注射成型工艺。     

Investigating the effect of printing conditions and annealing on the porosity and tensile behavior of 3D-printed polyetherimide material in Z-direction

Fused filament fabrication process presents drawbacks in mechanical properties observed when printing in the build direction (Z-direction). Such anisotropic properties will affect the part's performances and have to be minimized during fabrication. This study aims to evaluate the effects of nozzle temperature, printing speed and specimen state (annealed or as-printed) on porosity percentage and tensile properties for 3D printed polyetherimide (PEI) (ULTEM 1010) parts in Z-direction. The results demonstrated that print speed is the most influential process parameter that should be adjusted in consideration with the other printing parameters. The specimens' state did not reveal a noticeable influence, as the amorphous nature of PEI is considered less receptive to annealing. The optimization method to achieve the best results yielded values of 360°C and 30 mm s⁻¹ as printing conditions, followed by heat treatment. This was confirmed by porosity measurements, tensile testing, and scanning electron microscopy observations. The best performances of PEI material were 3425.5 MPa, 102 MPa, and 4.30% for Young's modulus, tensile strength, and elongation at break, respectively.     

Poly(vinylidene fluoride)/thermoplastic polyurethane flexible and 3D printable conductive composites

This work focus on the development of polymeric blends to produce multifunctional materials for 3D printing with enhanced electrical and mechanical properties. In this context, flexible and highly conductive materials comprising poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) filled with carbon black-polypyrrole (CB-PPy) were prepared by compression molding, filament extrusion and fused filament fabrication. In order to achieve an optimal compromise between electrical conductivity, mechanical properties and printability, blends composition was optimized and different CB-PPy content were added. Overall, the electrical conductivities of PVDF/TPU 50/50 vol% co-continuous blend were higher than those found for PVDF/TPU 50/50 wt% (i.e., 38/62 vol%) composites at same filler content. PVDF/TPU/CB-PPy 3D printed samples with 6.77 vol% filler fraction presented electrical conductivity of 4.14 S m⁻¹ and elastic modulus, elongation at break and maximum tensile stress of 0.43 GPa, 10.3% and 10.0 MPa, respectively. These results highlight that PVDF/TPU/CB-PPy composites are promising materials for technological applications.     

二醋酯长丝复合空气变形纱的性能比较

采用5种不同83．3 dtex合纤长丝作芯丝,分别与177．34 dtex二醋酯长丝进行复合空气变形加工, 分析了不同芯丝对变形纱的结构及其性能的影响。结果表明,复合变形纱的强伸性能和沸水收缩率主要由其芯丝决定;5种芯丝中,以PFT FDY作芯丝时,复合空变纱的丝圈稳定性最好,结构膨松性良好、断裂强度较高,断裂伸长率、2 mm高度毛羽数和成纱外观均匀性居中,但沸水收缩率偏大。     

Enhanced mechanical performance of fused filament fabrication copolyester by continuous carbon fiber in-situ reinforcement

As one of the most commonly used thermoplastics, polyester has rarely been used as the raw materials of 3D printing. However, copolyester obtained by copolymerization modifying polyester, such as Poly Ethylene Terephthalate Glycol (PETG), has been proven to be suitable for the fused filament fabrication (FFF) technique in previous studies, but the mechanical performance of printed products is still poor. In this paper, 3D printed PETG is in-situ reinforced by continuous carbon fiber (CCF), and the relationship between the process parameters and the mechanical performance of CCF/PETG is systematically investigated. The results show that the performance of 3D printed PETG is significantly enhanced by CCF in-situ reinforcement due to the effectively impregnation of CCF. By optimizing process parameters, the tensile strength, flexural strength and flexural modulus of CCF/PETG are 597%, 293% and 650% of pure PETG, respectively, with a relatively low fiber mass fraction of 19.2 wt%. This paper demonstrates that CCF in-situ reinforced 3D printed copolyester may be used in the manufacture of complex structural parts that require high mechanical performance in the engineering application.     

Experimental investigation and optimization of printing parameters of 3D printed polyphenylene sulfide through response surface methodology

Today fused filament fabrication is one of the most widely used additive manufacturing techniques to manufacture high performance materials. This method entails a complexity associated with the selection of their appropriate manufacturing parameters. Due to the potential to replace poly-ether-ether-ketone in many engineering components, polyphenylene sulfide (PPS) was selected in this study as a base material for 3D printing. Using central composite design and response surface methodology (RSM), nozzle temperature (T), printing speed (S), and layer thickness (L) were systematically studied to optimize the output responses namely Young's modulus, tensile strength, and degree of crystallinity. The results showed that the layer thickness was the most influential printing parameter on Young's modulus and degree of crystallinity. According to RSM, the optimum factor levels were achieved at 338°C nozzle temperature, 30 mm/s printing speed, and 0.17 mm layer thickness. The optimized post printed PPS parts were then annealed at various temperatures to erase thermal residual stress generated during the printing process and to improve the degree of crystallinity of printed PPS's parts. Results showed that annealing parts at 200°C for 1 hr improved significantly the thermal, structural, and tensile properties of printed PPS's parts.     

3D printability of highly ductile poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)-EMAA blends

In this work, ionomers were employed to improve the adhesion between 3D printed layers of poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate) (PETG), a commonly used polymer in 3D printing. The printability, rheology, and mechanical properties of PETG were tailored by incorporating poly(ethylene-co-methacrylic acid) neutralized with sodium (EMAA), a soft ionomer. PETG/EMAA polymer blends were prepared by melt extrusion to yield filaments for 3D fused filament fabrication (FFF) printing in different compositions by weight: 70/30, 50/50, and 30/70. The filaments and 3D printed samples were characterized by scanning electron microscopy, rheological and tensile tests. The results revealed that the interaction between PETG and EMAA favored the production of 3D printed samples with enhanced adhesion of layers, ductility, and toughness compared to neat PETG. Increases of 83.5 times in toughness and 86.4 times in ductility were achieved. The blends 30/70 and 50/50 presented the best printability in terms of adhesion between printed layers and mechanical properties.     

Enhancement of Mechanical Properties of PA6 Blending with Talcum for Fused Deposition Modeling

The objective of this work is to fabricate polyamide 6 (PA6) composite filament with enhanced mechanical properties and low cost for fused deposition modeling (FDM). The composite filaments are obtained by compounding PA6 and talcum fillers and then single screw extruding. Virgin PA6 and commercial e‐PA6 are set as controls. First, the rheological behaviors and thermal properties of PA6/talc, PA6, and e‐PA6 pellet materials are investigated, including viscosity, melting temperature, crystallinity, and decomposition temperature, which are important parameters for fabricating filament feedstocks. The results show that 10 wt% addition of talcum content accelerates the increase of the viscosity among the processing temperature. Accordingly, virgin PA6 and PA6/talc5 with good flowability are produced and subsequently evaluated by tensile and flexural tests. It is notable that the introduction of talcum increases the diameter constant and shape stability of PA6‐based filament. Also, it is found that both PA6 and Pa6/talc5 filaments exhibit superior tensile properties to the commercial e‐PA6 counterparts. Especially, PA6/talc5 filaments achieve the maximum tensile yield strength of 67.1 MPa and modulus of 3.10 GPa. Finally, auxetic lattice parts are successfully printed via FDM using lab‐made PA6, PA6/talc5, and commercial e‐PA6 filaments, and PA6/talc5 exhibits remarkable loading and energy absorption capability.     

PBS/PLA/滑石粉3D打印线材制备及熔融沉积成型工艺研究

以聚丁二酸丁二醇酯(PBS)为基体,滑石粉和聚乳酸(PLA)为改性剂,采用熔融挤出法制备了PBS/PLA/滑石粉三维 （3D）打印线材,并对其进行了熔融成型研究。通过分析结晶性能、流变性能、力学性能、断面形貌和打印效果对PBS/PLA/滑石粉体系进行了探究。结果表明,PLA的加入使PBS的结晶温度下降了5 ℃;随着PLA含量的增加,材料的复数黏度、储能模量和损耗模量均得到提高;而拉伸强度则随PLA含量的增加下降了1.71 MPa,缺口冲击强度下降了2.63 kJ/m2;PLA含量的增加使断面逐渐粗糙;在打印效果上复合材料的打印模型随PLA含量的增加而变得美观规整,当底板温度高于110 ℃时,打印制件的翘曲度较低,同时拉伸强度随着打印温度的升高而增加。     

Preparation and Rheological and Mechanical Properties of Poly(butylene succinate)/Talc Composites for Material Extrusion Additive Manufacturing

In this paper, poly(butylene succinate) (PBS) with a low melting point and a similar performance to polyethylene is employed as a printing material; talc is introduced into the matrix to enhance the melt strength of pure PBS during printing. The PBS/talc composite 3D printing filament is prepared by melt extrusion, and the thermal, mechanical, morphological, and rheological properties of the composites are investigated. The results show that the addition of talc to PBS leads to an increase in crystallization temperature. In addition, the tensile and flexural strengths of the injection‐molded specimens increase when the talc concentration increases. However, the mechanical properties of the printed specimens exhibit an opposite variation trend due to their distinct forming process. The printing temperature is 135 °C, which is far lower than those of commercial grade polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) printing filaments. Scanning electron microscopy (SEM) images show that increasing the talc concentration creates better printed formability and well‐organized fracture surface structures. By comparing printed fishbones, the results suggest that the presence of talc leads to a good printing performance with the composite. Furthermore, the rheological results reveal that η^*, G′, and G″ are enhanced by the addition of talc.     

Effect of printing temperature on microstructure,thermal behavior and tensile properties of 3D printed nylon using fused deposition modeling

The present investigation aims at the thermal conditions for the printability of nylon using fused deposition modeling (FDM). Dog-bone like specimens are manufactured under two printing temperatures to measure the tensile performance of 3D printed nylon with respect to the feedstock material properties. Both Scanning Electron Microscopy (SEM) and X-ray micro-tomography analysis are conducted to shed more light on the microstructural arrangement of nylon filaments. Finite element computation based on microstructural implementation is considered to study the main deformation mechanisms associated with the nylon filament arrangement and the process-induced porosity. The results show a narrow temperature range for printability of nylon, and a significant influence of the printing temperature on the thermal cycling, porosity content and mechanical performance. With the support of both numerical and experimental results, complex deformation mechanisms are revealed involving shearing related to the filament sequencing, compression at the junction points and tension within the raster and the frame. All these mechanisms are associated with the particular and regular arrangement of nylon filaments.     

Optimization of printing parameters for improvement of mechanical and thermal performances of 3D printed poly(ether ether ketone) parts

Many processing parameters can be adjusted to optimize the fused filament fabrication (FFF) process, a popular and widely used additive manufacturing techniques for plastic materials. Among those easily adjusted parameters are the nozzle temperature, printing speed, raster orientation, and layer thicknesses. Using poly(ether ether ketone) (PEEK) as the base material, a design of experiments analysis was performed on the main FFF parameters. A response surface methodology was applied to analyze the results and to maximize the output responses. Results have shown that the nozzle temperature is the most influential parameter on tensile properties and the crystallinity degree of printed PEEK by FFF process. Parts produced with optimized FFF parameters were then subjected to an annealing treatment to induce a relaxation of residual stress and to enhance crystallinity. The best properties for 3D printed PEEK parts were achieved with annealed parts prepared at 400°C with a printing speed of 30 mm/s, 0.15 mm layer thickness and raster orientation of [0°/15°/−15°]. The resulting parts have mechanical properties comparable to those of injected PEEK.     

3D打印条件对可降解聚乳酸力学性能的影响

采用3D打印方式制备降解左旋聚乳酸（PLLA）样品,通过冲击及拉伸试验研究不同打印条件对样品冲击强度、拉伸强度、拉伸模量及断裂伸长率的影响。结果表明,随着打印填充密度的增加,样品的冲击强度、拉伸强度及拉伸模量增大,断裂伸长率先增后减;随着打印速度的增加,样品的拉伸强度和拉伸模量增大,冲击强度及断裂伸长率减小;随着打印温度的增加,样品的冲击强度、拉伸强度和拉伸模量增大,断裂伸长率减小;打印填充密度、打印速度、打印温度分别为70 %、100 mm/s、210 ℃时,样品的综合性能最佳。     

一种回转体类构件用中低温固化环氧树脂体系研究

采用等温黏度实验和浇铸体力学性能测试来优选自制改性固化剂CUR–1的配比,通过不同升温速率下的固化过程差示扫描量热并对固化物进行傅立叶变换红外光谱分析,确定了体系的固化制度,研制出一种适用于发动机壳体或结构复杂的回转体类结构件的碳纤维湿法缠绕树脂基复合材料的中低温固化环氧树脂体系,用湿法缠绕工艺制作单向纤维缠绕成型复合材料环(NOL环)并进行了性能测试。结果表明:当CUR–1的含量为15份时,树脂体系具有适于湿法缠绕工艺的黏度和使用期,树脂可在80℃完全固化,同时浇铸体拉伸强度为84 MPa,拉伸弹性模量为3.8 GPa,断裂伸长率为5.4%,热变形温度为131℃。该树脂体系与纤维粘结性好,NOL环力学性能高,NOL环拉伸强度为2 451 MPa,拉伸弹性模量为146 GPa,层剪切强度为55 MPa。     

Material extrusion additive manufacturing of advanced ceramics: Towards the production of large components

Thermoplastic extrusion based additive manufacturing (MEX-AM), is a very interesting fabrication method for the shaping of larger ceramic parts. Commercial filaments are currently available in the market, but due to the lack of information from the suppliers, it is not easy to select the suitable filament material for the 3D printing of individual ceramic objects. In this study, three commercial yttria-stabilized zirconia (YSZ) filaments provided by Fabru GmbH, SiCeram GmbH and PT+A GmbH were investigated. According to our results, it is possible to print YSZ filaments with extremely different flexibility and rheological properties. Compared to the other two filaments, the Fabru filament resulted in significantly higher flexibility, but the extrusion pressure to print it through a 0.25 mm nozzle was significantly higher at 150 °C. Interestingly, in the SiCeram filament, a grain orientation effect could be observed. Based on STA analysis it can be assumed that for the Fabru filament, the polymer which decomposes at a high temperature can already be removed by solvent debinding (SD). Finally, 70 mm tall cup structure including overhang features and different wall thicknesses was used to evaluate the printing and post-processing of YSZ filaments.     

Thermal decomposition behavior of 3D printing filaments made of wood-filled polylactic acid/starch blend

Dynamic thermogravimetric analysis under nitrogen environment was used to understand the thermal decomposition process of 3D printing filaments made of wood-filled polylactic acid (PLA)/starch blend. The characteristic temperatures and apparent activation energy (AAE) of the filaments with various starch contents were calculated with well-known kinetic models by Friedman, Flynn–Wall–Ozawa, Coats–Redfern, and Kissinger. With the increased starch content in the filament, the onset thermal decomposition temperatures of the filaments decreased gradually from 272.4 to 155.1°C. The thermal degradation degree became smaller, and the transitional temperature interval became larger with increased starch proportion. The AAE values of the three types of filaments with different starch ratios varied between 97 and 114 kJ/mol, depending on material composition and method of calculation. The four kinetics methods provide complementary techniques for analyzing thermal stability behavior of composite materials. The improved understanding of thermal decomposition behavior of PLA-starch-wood composites can help develop PLA/starch-based filaments for 3D printing.     

Impact of processing conditions and sizing on the thermomechanical and morphological properties of polypropylene/carbon fiber composites fabricated by material extrusion additive manufacturing

For the 3D printed composites, fiber alignment is affected by the direction of melt-flow during extrusion of filaments and subsequently through the printing nozzle. The resulting fibers orientation and the fiber-matrix compatibility have a direct correlation with mechanical properties. This study investigates the impact of processing conditions on the state of the carbon fiber types and their orientation on the mechanical properties of 3D-printed composites. Short and long carbon fibers were used as starting reinforcing materials, and the state of fibers at the beginning and on the printed parts were evaluated. Strong anisotropy in terms of mechanical properties (flexural and impact properties) was observed for the samples printed with different printing orientations. Interestingly, the number of voids in the printed composites was found to be correlated with the fiber types. The present work provides a step towards the optimization of tailored composite properties by additive manufacturing.     

热处理条件对PET/PTT双组分复合长丝力学性能的影响

详细分析了PET/PTT双组分复合长丝的典型拉伸曲线及其表现出的独特的二次屈服现象。研究了PET/PTT双组分复合长丝在不同温度、不同张力、不同介质热处理条件下的力学性能。结果表明:热处理后纤维模量、断裂强力均较原丝大幅度下降,而断裂伸长率显著上升,但是在不同温度、介质及张力条件下,长丝的力学性能变化趋势存在显著差异。