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The necessity for more efficient manufacturing approaches of high-performance complex fiber reinforced composites parts is increasing. This study develops a framework to design and produce topologically optimized continuous carbon fiber reinforced composites (CCFRCs) with both high manufacturing efficiency and manufacturability, and experimentally validates via material extrusion (MEX) 3D printing technique in a more than 1-m wing spar for the unmanned aerial vehicle (UAV). The load-carrying structure can be topologically optimized by a solid orthotropic material with penalization method and further designed into a continuous fiber trajectory under the consideration of optimal material density, optimal fiber orientation and 3D printing process limitation. Based on this method, the complex topological CCFRCs can be realized by a single-stroke printing path with intact fiber. The feasibility and effectiveness of the proposed framework have been evaluated on the Messerschmitt-Bölkow-Blohm (MBB) beam which reveals obvious higher performance in specific stiffness and peak load compared with commonly used honeycomb structure. As a case study, a topologically optimized UAV wing spar was designed and validated experimentally. Mechanical testing shows that the designed wing spar can survive in operating loads. Furthermore, a proof-of-concept internal wing structure was presented where conventional wing spar and ribs are replaced by CCFRCs 3D printed structures. It exhibits high load-carrying characteristics, is lightweight and simple to fabricate. [ABSTRACT FROM AUTHOR]

High-specific-surface-area ceramic catalyst carriers with hierarchical pores are conducive to catalytic reactions and filtration processes in the chemical engineering industry. However, conventional processes have difficulty manufacturing porous ceramics with extremely intricate structures. Herein, a novel method was proposed to fabricate alumina ceramic catalyst carriers with a high specific surface area (SSA) and hierarchical porosity by powder bed fusion (PBF) using micromesoporous γ-alumina as a pore-forming powder and an impregnation process of colloidal silica. Hierarchical porosity adjustable on the nm (6.03–32.37 nm), μm (24–30 μm), and mm (0.5~4.4 mm) scales was obtained by adopting and adjusting the PBF, impregnation process on preforms and postsintering process. The impacts of SiO 2 content and post sintering temperatures on mechanical properties, pore characteristics, and SSA have been scientifically researched. The PBF-formed alumina ceramics possessed a crush strength of 45.88 ± 3.79 N/cm, high SSA of 56.324 m2/g, and porosity of 72.88 ± 3.37 % with multimodal distributions at 12.24 nm, 32.37 nm, and 24.18 μm. The improvement of SSA was mainly attributed to the use of micromesoporous γ-alumina and an impregnation process to reduce 3D-printing defects to obtain the hierarchical porosity (nm ~ μm scales) and required strength at a lower sintering temperature. Monolithic catalyst carriers with controllable porous structures have been manufactured to facilitate industrial recycling and improve efficiency. [ABSTRACT FROM AUTHOR]

Biomimetic porous ceramics have great application potential in the petrochemical industry; their biomimetic porous structure is conducive to mass transfer, energy exchange and catalytic reactions. However, it is challenging to produce biomimetic porous ceramics with complex shapes using conventional processes. Herein, we demonstrate a novel structural bionic and 3D printing strategy and a pseudo-boehmite-based slurry for fabricating hierarchical alumina ceramic carriers with biomimetic vein structures. Tuneable hierarchical porosity from nm to mm scales, high specific surface area, and superior strength have been achieved by innovatively combining dehydroxylation and peptisation of pseudo-boehmite, direct ink writing (DIW), and post-sintering processes. The effects of post-sintering temperature and impregnation treatment on the crush strength, porosity, and specific surface area were systematically investigated. The optimised porous ceramics exhibited a crush strength of 54.453 ± 7.359 N/cm, specific surface area of 109.870 ± 0.143 m2/g, and porosity of 60.03 ± 2.72%. The catalytic test for dry reforming of methane was conducted on biomimetic catalysts loaded with nickel (Ni) and phosphorus (P). The biomimetic catalyst had a remarkable methane conversion of 41.27%, in addition to mass transfer and coke inhibition effects. Through the integrated biomimetic design of macro–micro structures, monolithic alumina catalyst carriers with biomimetic vein structures prepared by DIW can potentially be used more efficiently in industrial catalytic reactions. [ABSTRACT FROM AUTHOR]

Hierarchical porous ceramic catalyst carriers, which exhibit good catalytic performance, are widely used in the petrochemical industry. However, the fabrication of ceramic carriers with hierarchically porous structures is highly challenging for conventional preparation processes. Thus, a strategy for designing and manufacturing hierarchically porous alumina ceramic catalyst carriers using aluminium trihydrate as raw material and powder bed fusion (PBF) as the forming process is proposed herein. PBF process parameters were optimised to define the processing window for creating ceramics with complex structures. Controllable pore characteristics in nano- and microscales has been achieved by combining dehydroxylation, PBF, and post-sintering processes. The effects of raw material composition and process parameters on crush strength, porosity, and specific surface area were systematically investigated. The resulting porous ceramics exhibit a crush strength of 86.03 ± 18.10 N/cm, specific surface area of 1.958 ± 0.123 m2/g, and porosity of 64.85 ± 1.15% with a multipeak distribution at 95 ± 1.23 nm and 17.76 ± 0.14 μm. The possibility of complicated monolithic catalyst carrier structures with bionic leaf vein characters has been validated for potential industrial applications. [ABSTRACT FROM AUTHOR]

In this study, the distribution of nineteen ingredients of personal care product (PCPs), including seven metabolites of phthalates (mPAEs), five benzophenone-type ultraviolet filters (BPs), and seven antimicrobial agents (AAs), were investigated in paired human hair, nail and urine samples. The median concentrations of ΣmPAEs, ΣBPs and ΣAAs were 135, 2.76 and 179 ng/g in hair, 37.3, 2.95 and 297 ng/g in nails, and 345, 4.03 and 50.1 ng/mL in urine, respectively. Mono-methyl phthalate (49%), 2,4-dihydroxybenzophenone (45%) and triclosan (71%) were the most abundant mPAE, BP and AA in hair samples, respectively, and had similar abundance in nail samples. In contrast, mono-n-butyl phthalate (45%), 4-hydroxy benzophenone (29%) and methyl paraben (54%) were the predominant mPAE, BP and AA in urine samples, respectively. Significant differences in the concentrations of some target compounds were observed between male and female but inconsistent across different matrices. Moreover, most compounds with significant correlations had quite different correlation coefficients in each matrix. No significant correlations were found between hair, nail and urine samples for most of the target analytes. These results suggest these analytes have matrix-specific distribution, and it is necessary to use multiple matrices to comprehensively assess the risk of ingredients of PCPs to human health. [Display omitted] • mPAEs, BPs and AAs were widely detected in human hair, nail and urine samples. • Composition profiles of analytes in hair and nails differed from those in urine. • Level differences was observed in genders but inconsistent across different matrices. • Most compounds with significant correlations had variable levels in each matrix. [ABSTRACT FROM AUTHOR]

Controllable morphing is still a challenge in the field of 4D printing. In this paper, a novel 4D printing technology of composites with embedded continuous fibers is introduced, and the bilayer prepared by this technology can realize programmable deformation with a high deformation accuracy. The deformation of the composite structure is caused by the difference of coefficients of thermal expansion (CTEs) between continuous fibers and flexible matrix. The angle between the intersecting fibers determines the size of the principal curvature, while the bisector of the angle of the fibers determines the direction of the principal curvature. Utilizing this rule, deformation of arbitrary deployable surface can be realized by designing the fiber trajectories. The high control accuracy of fiber orientation leads to a high deformation accuracy of 4D printed structure. The error between the theoretical value and the experimental value of the conical surface curvature is not more than 6%. In addition, the smart composite structure with the ability of temperature response and self-actuated deforming composite structure have also been prepared by this 4D printing process. [ABSTRACT FROM AUTHOR]

As a kind of high performance polymer with excellent mechanical strength, high temperature property and chemical resistance, the polyether-ether-ketone (PEEK) and its composites are the promising candidates that can satisfy the demands for high stiff and lightweight in aerospace industry. So it is very attractive to fabricate PEEK and its composites parts with additive manufacturing technology, especially the selective laser sintering (SLS), due to its advantage on the fabrication of the parts with complex geometries. However, the strengths of the PEEK and its composites prepared by SLS are obviously lower than their injection molded parts and the laser sintering kinetics of the PEEK composites is seldom studied. In this paper, to fabricate the carbon fibers (CF) reinforced PEEK composites with high strength by SLS, the sintering kinetics of CF/PEEK composites was thoroughly studied based on the high temperature rheological behavior. A novel effective melting zone was defined by combining the simulated temperature distribution with the viscosity-temperature relationship and used to predict the process planning. Finally, the calculation results were validated by employing the simulation parameters in experiments and the tensile strength of CF/PEEK composites reached 109 ± 1 MPa with an elasticity modulus of 7365 ± 468 MPa, which is 85% higher than injection molded pure PEEK. Therefore, methods in this work could be considered as a complement to the numerical analysis of SLS process and the reinforced CF/PEEK composites may be used in aerospace industry for the structure optimization and lightweight design with complex geometries. [ABSTRACT FROM AUTHOR]

With the increasing research into selective laser sintering of composite powders, a modified numerical model was introduced to provide appropriate process predictions for the production of different functional composites. This numerical method included an effective volumetric heat source model and an integrated testing procedure, in which the differences of polyamide/carbon fiber (PA/CF) and PA/NaCl composite powders in thermo-physical and optical properties were studied. The unknown variables in the numerical model were all determined by experiments. The simulated temperature distributions of different powder beds exhibited a big difference in the melting depth. Entirely different processing parameters were planned for the two composites according to their simulation results. In the following experiments, highly porous PA derived from PA/NaCl composites had a maximum porosity of 59%. Compared with pure PA, CF reinforced PA showed a dramatic increase of the flexural strength and modulus by a factor of 100% and 380%, respectively. Therefore, the design objectives of two PA composites were both well accomplished. In addition, the experimental investigation became more efficient due to the process prediction. The accuracy of the model was validated by the microstructures of PA/CF and PA/NaCl, which meant this method could be used to provide appropriate process planning for more composites. [ABSTRACT FROM AUTHOR]

A novel integrated manufacturing process based on continuous fibre reinforced thermoplastic composites 3D printing of continuous fibre reinforced composite lightweight structures (CFRCLSs) was proposed. Cross lap and panel-core lap design strategies were proposed to fabricate the CFRCLSs with a complex shape. The fracture modes during compression loading were analysed. Correlations between the process parameters, structure parameters, density, fibre content, and final performance of the printed specimens were discussed. The fibre content of the printed CFRCLSs were controlled by changing the process parameters. With a fibre content of 11.5% vol, a compression strength of 17.17 MPa was obtained for the 3D printed CFRCLSs. A heterogeneous lightweight sandwich structure specimen was fabricated to demonstrate process feasibility. This new and improved process has great potential for fabricating CFRCLSs with complex shapes, high mechanical properties, and multifunctional benefits. [ABSTRACT FROM AUTHOR]

A novel method to design and manufacture hierarchically porous materials is proposed by combining Selective Laser Sintering (SLS) with particulate leaching technique. Hierarchically structural porous nylon is prepared and pore forming mechanism is discussed. Experimental results show that the porous materials contain the pores caused by the dissolution of the pore-forming agent in water and the pores existing inherently in SLS parts, which can be further divided into intraformational pores and interlaminar pores. The interactions of these pores with different shapes eventually form hierarchically porous nylon with high connectivity and controllable porosity. The influences of processing parameters and content of pore-forming agent on the porosity and water permeability have been studied. Porous nylon filter integrated with complicated structure is designed and directly fabricated by SLS. The fluid infiltration volume is tested and compared with commercially available water purifiers. The results of filtration experiment show that the filtering precision is about 17.6 μm and the rejection is up to 95% for the suspension containing particles with the size range of 15 μm–120 μm. [ABSTRACT FROM AUTHOR]

In this paper, a multidisciplinary framework to design and produce a topological structure with inhomogeneous distributions of fiber orientation and content for 3D printed continuous fiber reinforced polymer composites (CFRPCs) was proposed to maximize load and fiber utilization efficiency. The combination of optimization design and 3D printing for composites with curvilinear fiber was achieved that the fiber orientation and content were progressively designed in the two-stage procedure. The fiber orientation and topological structure were concurrently optimized firstly. Then, the fiber content was designed through finite element analysis (FEA) and realized by changing continuous fiber path with a hierarchical structure design method. Based on this, the topological beam has been additively manufactured and experimentally investigated, showing 38.55% and 25.40% in stiffness and peak load enhancement compared with the original CFRPCs design, while 264.39% and 165.84% increments compared with pure polymer design. The proposed approach has widened design freedom of CFRPCs 3D printing, possessing potential application to solve engineering problem in aerospace, automotive and other fields. [ABSTRACT FROM AUTHOR]

A cleaner production pattern for high-performance continuous carbon fiber reinforced thermoplastic composites (CFRTPCs) has been proposed on the base of recycling and remanufacturing of 3D printed continuous carbon fiber reinforced (CFR) PLA composites. Continuous carbon fiber and PLA matrix was recycled in the form of PLA impregnated carbon fiber filament from 3D printed composite components and reused as the raw material for further 3D printing process. The original printing trajectory is reversely applied, allowing for a 100% recycling of the continuous fiber without any effect on the mechanical properties. Tensile performance of recycled carbon fiber filaments was evaluated, which was higher than that of originally printed composites. Remanufactured CFRTPCs specimens also exhibited a 25% higher bending strength than that of original ones, which experimentally demonstrated the first non-downgrade recycling process for CFRTPCs. A material recovery rate of 100% for continuous carbon fiber and 73% for PLA matrix were achieved for a better environmental impact. Energy consumption of 67.7 and 66 MJ/kg respectively for recycling and remanufacturing processes was detected and compared with conventional methods. The proposed cleaner production pattern offered a potential strategy for the low-cost industrial application of fully recyclable composites. [ABSTRACT FROM AUTHOR]

Particle size gradation is regarded as an effective method for overcoming the contradicting requirements in three-dimensional printing (3DP). In present work, particle size gradation was optimized to obtain both acceptable flowability of the powder material and high-strength 3D-printed glass-ceramic products. The effect of gradation on the printing process, sintering process and performance of the 3D-printed glass-ceramic products was investigated comprehensively. The glass-ceramic powders with three size ranges were mixed in certain proportions and applied to print parts. The result showed parts printed with powder mixed by 60 wt% 45–100 µm and 40 wt% 0–25 µm particles had satisfactory density of 1.60 g/cm 3 and bending strength of 13.8 MPa. The flowability decreased with an increasing proportion of fine particles. Part density was determined by the powder bulk density in the powder bed as well as the shrinkage during sintering while strength of part was found to be dependent on the sintering degree. [ABSTRACT FROM AUTHOR]

Over the last few years, three-dimensional printing(3DP) technology has evolved to incorporate composite materials. However, using material extrusion (ME) technology, it is still difficult to improve the stiffness with stable elongation and energy absorption of continuous fiber reinforced composites at the same time. This study aimed to 3D print hybrid threads by merging several types of continuous Kevlar and Carbon fibers. Which were created using material extrusion 3D printing to accomplish cooperative ductility and brittleness augmentation. To analyze the mechanical performance and reveal the failure and deformation mechanisms, tension tests, three-point bending tests, and drop hammer impact tests were performed. The proposed hybrids have substantially greater flexural modulus, flexural strength, tension modulus, and tension strengths with absorbed energies than standard single type fiber composites. Crack resistance during impact test of hybrid composites was enhanced by over 91% compared to carbon fiber non-hybrid composites. SEM images of hybrid specimens provided an insight of the failure mechanisms, resulting in stable hybrid composites. Positive hybrid effect further demonstrates its great energy absorption capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modeling and 3D printing of variable stiffness composites with curved fibers. • Limitations of 3D printing are taken into account in the modeling. • 3D printing of the variable stiffness composites without gaps and overlaps. • 3D printing by the control of positioning a nozzle and the adaptive feed of plastic. • Comparison of numerical and experimental strain fields of the VSCs via FEM and DIC. In this paper, biomimetic continuous fiber reinforced composite structures were modeled and printed on the basis of variable distributions of fiber orientation and the fiber volume fraction, which are similar to the wood structure in the vicinity of a knot. The variable distributions of curved fibers in the variable stiffness composites (VSCs) without gaps and overlaps were realized during the 3D printing process by the control of positioning a nozzle and the adaptive feed of plastic. To demonstrate efficiency of the modeling method and the 3D printing process, a VSC plate with a hole under tensile loading was designed, printed and tested. The results of tensile tests showed that the main failure of the composite plates occurs far from the hole. Furthermore, numerical and experimental strain fields obtained by the finite element method and digital image correlation, respectively, are similar. The efficiency in fiber savings for the composite plates was improved by the change in reinforcement from unidirectional fibers to curved fibers adapted to heterogeneous stress fields. [ABSTRACT FROM AUTHOR]

3D printing of continuous fiber reinforced thermoplastic composites (CFRTPCs) enables the fabrication of multiscale structures, whose features can simultaneously span the microscale fiber trajectory and macroscale topological structure. In this study, a multiscale design and manufacturing strategy integrating concurrent optimization of micro fiber orientation and macro structural topology was developed for CFRTPCs and realized by ingenious path planning for 3D printing process. Typical structures, such as Messerschmitt-Bölkow-Blohm (MBB) beam and cantilever beam, were verified experimentally in comparison with the monoscale structures. Structural stiffness and peak load could be improved by 36.27% and 64.43% respectively for MBB beam, 123.07% and 52.16% respectively for cantilever beam, showing the significant influence on concurrent material and structure design for CFRTPCs. Multiscale concurrent design and 3D printing could promote the potential of CFRTPCs, and even challenge traditional design and manufacturing mechanism relating material and structure scale. [ABSTRACT FROM AUTHOR]

Overall performance of curvilinear fiber reinforced composite structures (CFRCSs) can be designed by adjusting the local fiber orientation and content. In this paper, an optimized design method based on stress gradient distribution for CFRCSs was proposed to improve the efficiency in strength of continuous fiber reinforced composites. The mechanism of fiber content regulation in continuous fiber reinforced composites 3D printing was studied. The adaptive feed calculation method of resin was proposed, and the 3D printing of CFRCSs was realized. A 3D printed composite perforated plate with a hole under tensile loading was optimized and fabricated to verify the effectiveness of the proposed methods. After the optimized design, the maximum stress concentration factor was reduced by 36%, and the ultimate tensile strength was increased by 42%. Through the proposed optimization design method, the fiber content distribution corresponds to the stress distribution, and the fiber direction distribution corresponds to the maximum principal stress direction distribution. At the same time, the stress was redistributed to reduce the stress concentration. Therefore, the ultimate strength was improved. The optimized design method and 3D printing method of CFRCSs have potential application prospects in aerospace, automotive and other fields. Image 1 [ABSTRACT FROM AUTHOR]

3D printing provides a new technical means for the preparation of functionally controlled continuous fiber reinforced composites (CFRCs) with variable fiber content. The constitutive model of 3D printed CFRCs with different fiber contents are the basis for establishing mechanical analysis models and design methods of functionally regulated CFRCs based on 3D printing. In this paper, stiffness and strength properties of 3D printed CFRCs with different fiber contents were systematically studied, and the mapping relationship between material properties and fiber content was obtained. The failure processes of 3D printed CFRCs under different loads were studied by microstructural morphology and interfacial performance analysis, revealing the formation mechanisms of the material properties. The constitutive model and finite element analysis method of 3D printed CFRCs were established by using the material properties of 3D printed CFRCs with different fiber contents. The mechanical analysis mode was used to predict and analyze the performance of functionally graded CFRCs with variable fiber content. The results show that the mechanical analysis mode can be used for the optimization design and mechanical analysis of functionally controlled CFRCs. [ABSTRACT FROM AUTHOR]

The local properties of continuous fiber reinforced heterogeneous composites (CFRHCs) can be tailored through fiber arrangement design to maximize load and fiber utilization efficiency. Design method and integrated manufacturing process for CFRHCs have been investigated in the current research, based on 3D printing of continuous fiber reinforced composites (CFRCs). Based on the tensile and compressive properties of 3D printed CFRCs, the optimal design method of CFRHCs under process constraints and actual working conditions was studied. The mapping relationship between fiber volume content and process parameters was studied, and a digital transition from optimized design to 3D printing solutions was implemented. The flexural strength of the optimized CFRHCs is 207 MPa, and the maximum increase ratio is 115% compared with other heterogeneous designs with the same fiber volume content. The failure process of CFRHCs was analyzed by the simulation model, and the damage mechanism of CFRHCs under bending load was revealed. The optimization design and integrated manufacturing solution of the CFRHCs have potential applications in aerospace, automotive and other fields. [ABSTRACT FROM AUTHOR]

Fibre-reinforced composite thin-walled structures are often subjected to complex working conditions with multiple loads. By combining various fibres, continuous hybrid fibre-reinforced composites (CHFRCs) can achieve good comprehensive performances and positive hybrid effects, which will improve the ability of composite structures to withstand complicated loads. Coaxial CHFRCs were prepared quickly without the use of a mould by 3D printing. The influence of the hatch spacing on hybrid effect, dynamic and static bending properties and failure mode were investigated by the research of fibre content, hybrid ratio, and interface. The results showed that the 3D-printed coaxial CHFRCs had a positive hybrid effect for the impact strength. A high positive hybrid effect could be attained by modifying the process parameters. At the same time, the composite's comprehensive performances were enhanced. The impact strength of 3D-printed coaxial CHFRCs was 1.94 times greater than that of the continuous carbon-fibre-reinforced composites, and its flexural strength was 1.75 times greater than that of the continuous Kevlar-fibre-reinforced composites at same process parameter. With their high comprehensive performances and high positive hybrid effect, 3D-printed coaxial CHFRCs have a lot of potential use in thin-walled structures in areas such aerospace. • Coaxial continuous hybrid fibre-reinforced composites (CHFRCs) were prepared quickly without a mould by 3D printing. • The effect of the hatch spacing on hybrid effect, dynamic and static bending properties and failure mode were investigated. • The 3D-printed CHFRCs had an impact strength 1.94 times than CCFRCs and a flexural strength 1.75 times than CKFRCs. • The 3D-printed CHFRCs performed high comprehensive performance and had a positive hybrid effect on the impact strength. [ABSTRACT FROM AUTHOR]

A gradient-refractive-index radar absorbing structure(GRINRAS) for stealth aircraft is proposed in this paper. It is a layered shell composed of a gradient-refractive-index (GRIN) refractor, an absorber and a reflector. The GRIN refractor consists of the isotropic non-resonant woodpile metamaterials, which was designed according to the permittivity distribution equation of the electromagnetic(EM) black hole to bend and match the waves from the air to the radar absorbing structure. The absorber dissipates the EM waves and transforms them into the heat energy. The reflector reflects the EM waves to the absorber and prevents them from entering the inner space of the structure. A ring and a board GRINRAS were designed, and then fabricated by the three-dimensional (3D) printing process of stereolithography (SL). Simulation and experimental results show that the GRINRASes can control the wave propagation and their absorption capacity is better than −10 dB in the broadband of 12–18 GHz. The GRIN refractor and the absorber have almost equal contributions to the absorption capability. This is the first radar absorbing composite structure composed of the gradient 3D metamaterials. It demonstrates the feasibility of using the metamaterials and 3D printing technology in the innovative radar absorbing structure (RAS) of the stealth aircraft. [ABSTRACT FROM AUTHOR]

A novel method to prepare porous resin mould for pressure slip casting was proposed by using Selective Laser Sintering (SLS), which is one of Additive Manufacturing (AM) processes. The mixture of polyamide and salt (NaCl) were designed as raw materials, in which polyamide acted as matrix material and NaCl as pore-foaming agent. To investigate the feasibility of the pressure slip casting with the mould, the compressive strength and porosity of the porous specimens were measured. Experiments showed a compressive strength of 7.19 MPa and an elastic modulus of 32.26 MPa were reached. Meanwhile, the porosity of the specimens was 59.75%, and the aperture concentrated in 25–75 μm. The water permeability was verified and the maximum permeability reached to 0.921 mL/(mm 2 ·s). Pressure slip casting with porcelain slurry was performed using SLS porous specimens as the mould. Results showed the moisture content of the green body was about 23% and the relative density was 68.4%–74.1%. At last, a green body of whiteware with complex surface was prepared by the proposed method to demonstrate the feasibility of pressure slip casting with this mould. This method could be used in porcelain industry to realize rapid development of new products and customized production with further improvements. [ABSTRACT FROM AUTHOR]

A shape-performance synergistic design and additive manufacturing strategy was developed for the transfemoral prosthetic sockets (TPS) to fulfill the demands of customized geometry and long-term load bearing. The 3D printing path of the continuous fiber reinforced polymer composites (CFRPC) was generated by reversing the milling path of subtractive manufacturing. The mechanical properties of the 3D printed CFRPC samples were investigated as a foundation, and the customized fiber trajectories were designed based on the analyzed stress pattern of the TPS in daily gait. The CFRPC TPS with weight of 28 % less than those made by pure resin had a safety factor larger than 3 and passed the fatigue testing of 3 million cycles. The design and additive manufacturing strategy developed in this study was also applicable for other parts with freeform surfaces. • Fiber trajectory was designed based on the stress analyses of prosthetic socket. • Multi-DOF system enabled 3D printing of thin-walled freeform surface with CFRPC. • Self-adjusting printing speed and feeding rate improved surface quality of CFRPC. • Shape-performance synergistic strategy can apply to other freeform surface parts. [ABSTRACT FROM AUTHOR]

Multifunctional heat flux manipulation plays an essential role on the industrial processes. A well-designed spatial distribution of thermal conductivity enables a variety of thermal functions, including thermal cloaks and rotators. Despite the promising potential of metamaterials in achieving multifunctional heat transfer in complex nonconformal geometries, significant challenges remain due to limitations in design methods. In this work, a novel approach based on conformal discretization was proposed to address these major challenges, in which the thermal conductivity tensors of discrete functional cells were diagonalized with the local thermal conductivity tensors as inputs. To verify the effectiveness of the conformal discretization, a nonconformal thermal rotating cloak was designed and manufactured. Both simulations and experiments confirmed the effectiveness of this approach in obtaining multifunctional thermal metamaterial with remarkable thermal cloaking and rotating capabilities. Moreover, the nonconformal thermal rotating cloak still maintained thermal functionality well under the condition of omnidirectional heat flow. This work provides a feasible approach to realize multifunctional thermal manipulation in arbitrarily transformed regions, and thus shows significant application potential in the fields of aerospace engineering and civil engineering. [ABSTRACT FROM AUTHOR]

Selective Laser Sintering (SLS) is one of the advanced additive manufacturing technologies which can build the geometrically complex structure from a three-dimensional CAD model. Poly ether ether ketone (PEEK) is one of the available materials for SLS and has received numerous interesting due to its excellent properties. In this research, a novel approach, thermally induced phase separation (TIPS) was employed to produce neat PEEK and PEEK/CNT composite powders with near spherical shape, desired particle size and size distribution for SLS application. Powders produced by TIPS demonstrated good flowability and processability. SEM images proved that CNT was embedded in PEEK powder. PEEK/CNT composite powder had shown an increased crystallinity in comparison with neat PEEK powder. Sintering rate of produced powders were studied with hot stage microscopy. Single layer films were built successfully by high temperature selective laser sintering (HT-SLS) using the powder developed via TIPS. Thermodynamics characteristics of single layer films were studied by DMA. Results revealed that addition of 0.1% CNT improved both storage and loss modulus of PEEK. PEEK powder is prepared by TIPS and laser sintered into 3D component by HT-SLS Unlabelled Image • The first study on preparation of PEEK and PEEK/CNT composite powders by TIPS. • Resulting powders have near spherical shape and preferred particle size for SLS application. • Resulting powders have shown good flowability and processability. • Powders have been successfully sintered into single layer films in the HT-SLS system. [ABSTRACT FROM AUTHOR]

Continuous fiber reinforced thermoplastic composite (CFRTPC) auxetic honeycomb structures were fabricated using the 3D printing technology with a specific printing path planning. For comparison, auxetic honeycombs were also fabricated with pure polylactic acid (PLA). In-plane compression tests were conducted, with corresponding damage types explored using Scanning Electron Microscopy (SEM) images. A printing path-based finite element (FE) method was developed to mimic both small and large deformations of CFRTPC auxetic honeycombs, while analytical model was proposed to predict their effective stiffness and Poisson ratio. Good agreement was achieved among analytical predictions, FE simulation results and experimental measurements. A systematic parametric study was subsequently carried out to quantify the dependence of in-plane mechanical properties on geometrical parameters. Compared with pure PLA structures, the presence of continuous fibers efficiently prohibited crack propagation in the matrix for each ligament of CFRTPC auxetic honeycombs. Adding continuous fibers increased the mass only by 6%, but led to dramatic increase in compressive stiffness and energy absorption by 86.3% and 100% respectively and smaller Poisson ratios. The proposed 3D printing technology has great potential in integrated fabrication of continuous fiber reinforced composite lightweight structures having complex shapes, attractive mechanical properties, and multifunctional attributes. • The continuous fiber reinforced composite auxetic honeycomb was fabricated by 3D printing technology. • A combined experimental, analytical and numerical approach was employed to investigate the in-plane behaviors. • Adding continuous fibers lead to dramatic increase in mechanical properties and smaller Poisson ratios. [ABSTRACT FROM AUTHOR]