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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]

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]

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]

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]

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 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]