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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]

The increasing needs for new types of computing lie in the requirements in harsh environments. In this study, the successful development of a non‐electrical neural network is presented that functions based on mechanical computing. By overcoming the challenges of low mechanical signal transmission efficiency and intricate layout design methodologies, a mechanical neural network based on bistable kirigami‐based mechanical metamaterials have designed. In preliminary tests, the system exhibits high reliability in recognizing handwritten digits and proves operable in low‐temperature environments. This work paves the way for a new, alternative computing system with broad applications in areas where electricity is not accessible. By integrating with the traditional electronic computers, the present system lays the foundation for a more diversified form of computing. [ABSTRACT FROM AUTHOR]

With an increase in electromagnetic interference pollution, composites for electromagnetic interference shielding (EMIS) with good shielding performance and friendly processability are widely demanded. Herein, a methodology for preparing composites with controllable shielding effectiveness (SE) is proposed. Carbon fiber (CF)-reinforced polylactic acid composites were fabricated by a 3D printing process, and the SE of the composites was controlled by varying the process parameters. To systematically investigate the feasibility of the methodology, the shielding properties, processability, and mechanical properties of the composites were investigated. The results showed that the SE was controlled in the ranges of 25.1–69.9 dB, 51.1–75.6 dB, and 6.8–78.9 dB by tailoring the number of layers (2–12), hatch spacing (1.6–0.8 mm), and filling angle (90°–0°), respectively. The critical mechanism of the controllability is that the content, spatial distribution, and orientation of CFs can be facilely and digitally controlled during processing. A conformal shell with a SE of 38.5 dB was fabricated to demonstrate superior processability of a complex geometry. The maximum tensile and flexural strengths of the composites were 111.0 and 152.9 MPa, respectively, which were much larger than those of most engineering plastics. Using this methodology, an appropriate SE that is neither excessive nor deficient can be readily realized, which helps to maintain high resource utilization. Complex geometries for EMIS can be rapidly and cheaply obtained without molds, which is difficult for traditional processes. These advantages make the 3D-printed CF-reinforced composites competitive with other EMIS materials and traditional processes. [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]

[Display omitted] • A novel dual-channel Schiff-based sensor (FHBS) was well-designed and prepared. • The sensor can be used for Mg2+ and Zn2+ detection. • Theoretical calculations proved that the sensor can effectively bind to Mg2+ and Zn2+. • The sensor was successfully applied in actual water samples and bioimaging. Mg2+ and Zn2+ are essential metal ions for organism growth and development since they participate in various physiological metabolic processes and keep the body functioning normally. Realizing the efficient detection of these two metal ions is therefore crucial. In light of this background, we developed and synthesized a novel Schiff-based dual-channel fluorescein-derived chemo-sensor (FHBS) for the detection of Mg2+ and Zn2+ using theoretical calculations. The optimized experimental findings demonstrated that Mg2+ in DMSO/H 2 O (95/5, v/v, pH = 7.0, Tris-HCl) and Zn2+ in DMF/H 2 O (9/1, v/v, pH = 7.0, Hepes) may selectively elicit responses towards FHBS. Under the aforementioned optimization circumstances, the linear detection range of Mg2+ was from 0.4 to 7.0 μM, and for Zn2+, it was from 0.5 to 10.0 μM. The detection limits for Mg2+ and Zn2+ were calculated to be 0.40 μM and 0.65 μM, respectively. Finally, chemo-sensor (FHBS) was successfully applied in L929 cells and zebrafish live imaging. The experimental results demonstrated that FHBS can accurately detect Mg2+ and Zn2+ in organisms. Additionally, through cytotoxicity experiments, it was proved that the chemical sensor has good safety and biocompatibility. [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 two-dimensional flattened Luneburg lens with an ultra-wide viewing angle has been realized based on a liquid medium approach in our present work. A field-of-view angle up to 180° is achieved over the microwave regime. The transformed lens is realized by using a low-loss liquid medium and a large variation of refractive index from 1 to 4.18 is achieved. The non-resonant property of the liquid ensures a broadband and low-loss performance of the lens from 12.4 GHz to 18 GHz. The high directivity and relatively low loss of the proposed lens were demonstrated by simulation and experimental results. [ABSTRACT FROM AUTHOR]

A vibration energy harvesting generator was studied in the present research using point-defect phononic crystal with piezoelectric material. By removing a rod from a perfect phononic crystal, a resonant cavity was formed. The elastic waves in the range of gap frequencies were all forbidden in any direction, while the waves with resonant frequency were localized and enhanced in the resonant cavity. The collected vibration energy was converted into electric energy by putting a polyvinylidene fluoride film in the middle of the defect. This structure can be used to simultaneously realize both vibration damping and broad-distributed vibration energy harvesting. [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]

Traditional dressings, such as bandages, gauze, and cotton pads stick to new granulation tissue, thereby aggravating wound injury or causing secondary injury during replacement. Microspheres that are biodegradable and adaptable to various wound shapes are a good alternative to traditional dressings. In this work, a novel microsphere was prepared by reverse microemulsion method using sodium alginate and silk peptide (SP) as the aqueous phase. After cross-linking by Ca2+, calcium alginate (CA) and SP composite microspheres called CA/SP were prepared. By adjusting the SP content, the swelling rate of microspheres reached 1050 % and the pore diameter reached 19.59 nm. In addition, the introducing SP provided a stable loading site for thrombin (Th). This platform (called CA/SP@Th)—integrating rapid blood enrichment, calcium release, and Th catalysis—can ensure rapid hemostasis in a variety of bleeding models. Additionally, the SP present in this modality also promoted fibroblast proliferation, this increased the wound closure rate in a total cortex injury mouse model (more than 97 % within 15 days). Therefore, CA/SP@Th can be used as a multifunctional dressing for rapid hemostasis and wound healing. [Display omitted] • Structurally controllable composite microspheres were prepared by reverse microemulsion method. • The composite microspheres are beneficial to maintain the Th activity by forming various hydrogen bonds with it. • The combination of Th and Ca2+ could acutely trigger the coagulation cascade. • The composite dressing can achieve rapid hemostasis and healing of the wound. [ABSTRACT FROM AUTHOR]

Continuous fiber reinforced thermoplastic composites have been widely used in modern aerospace and other high-end manufacturing fields because of their light weight, high strength, fatigue resistance, and corrosion resistance properties. Due to the reinforcement of carbon fiber strands, continuous fiber reinforced thermoplastic composites have good conductivity which makes it a potential material for the preparation of space-borne antennas reflecting surfaces. The reflecting surfaces of common mesh antennas are usually prepared by gold-plated molybdenum wire which is expensive and hard to produce. In this study, the continuous fiber reinforced thermoplastic composites mesh reflecting surfaces are prepared by 3D printing technology. The effect of different mesh shape and mesh size on the electrical properties are investigated systematically. The electrical property of the reflecting surface were tested by waveguide method at the S band with the frequency of 1.9 ~ 2.3GHz. The results show that the reflection loss of the 3D printed continuous fiber reinforced thermoplastic composite mesh reflecting surfaces are lower than 0.25 dB, which can well meet the requirement of space-borne antennas in the S waveband. The reflection loss of the 3D printed continuous fiber reinforced thermoplastic composite mesh reflecting surfaces increases with the increase of mesh size accordingly for both the quadrangular and the triangular mesh reflecting surface. The reflecting property of the mesh reflecting surface tends to be better with a higher surface mass density. The results foresee that the continuous fiber reinforced thermoplastic composites can be used to develop the reflector of large mesh antenna in the future work. [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]

A modular design method is introduced to design an acoustic metamaterial based on nested Helmholtz resonators that target low‐frequency sound attenuation. The method combines a performance evaluation using finite element methods with structural evolution, and uses a genetic algorithm to optimize the acoustic metamaterial to attain the desired properties. Both the simulated and experimental results demonstrate the noise attenuation property of the optimized acoustic metamaterials. The modular design method proposed by this study may potentially design acoustic metamaterials for practical sound attenuation applications in industries by considering different environments and constraints. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to present a novel and effective fabricating method of 3D ceramic photonic crystals with diamond structure. Design/methodology/approach – The reverse diamond-structure resin molds are fabricated by stereolithography (SL), then ceramic slurry is prepared and injected into the molds under vacuum condition. Subsequently, ceramic photonic crystals are obtained after vacuum freeze-drying and sintering. Findings – The combination of SL, gel-casting and freeze-drying could be used to fabricate the 3D ceramic photonic crystals with diamond structure which have intact structure and minimal shrinkage. The samples have been tested and the experimental results indicate that their band gap is in the range of 10.14-12.20 GHz, consistent with the simulation results. Research limitations/implications – The influence of fabrication process on the photonic band gap needs further study. Originality/value – This paper presents a novel fabricating method of 3D diamond-structure ceramic photonic crystals based on SL, gel-casting and freeze-drying. The method fabricates complex ceramic photonic crystals with high accuracy and helps further research in this field. [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]

We have proposed a new method to achieve gradient refractive-index (GRIN) optics via a compound liquid medium. By adjusting the composition of the liquid medium, the refractive index of the compound liquid was tuned in a very broad range from 1.58 to 5.15. The liquid medium also exhibited weak frequency dependence. Based on these properties, we designed a liquid GRIN planar lens and experimentally demonstrated the feasibility of this approach. The beam deflection of the lens was controlled by adjusting the distribution of the refractive-index of the lens. By changing the composition of the compound liquids in different cells of the lens framework, different spatial gradually varied refractive index profiles have been achieved. The proposed liquid planar lens has shown a good directive property at different receiving angles and demonstrated a broadband performance between 12 GHz and 15 GHz. This method results in a rapid and flexible realization of gradient refractive index structures by using liquid medium. [ABSTRACT FROM AUTHOR]

4D printing, which is the combination of 3D printing technology and printable smart materials, provides the potential of automating actuation devices. In this paper, we have used a modified-fused deposition modelling 3D printing technology to fabricate a double-layer laminate smart material, which can be activated by temperature directly or by an electric circuit indirectly. A double-layer laminate mathematical model has been developed to describe the bending behaviour caused by the mismatch strain between the surface layer and the basal layer. The electrocaloric deformation testings were performed to find the different bending rules of this low-cost printed active composite in different physical states. The considerable maximal deformation values and deformation force (7 mm and 100 mN for these carbon fibre (CF)/polylactic acid specimens, and 10 mm and 200 mN for these CF/polyether-ether-ketone specimens in the paper) provide this double-layer smart material and 4D printing method the prospective to be applied in biomimetic sensors, actuators, transducers, and artificial muscles. [ABSTRACT FROM PUBLISHER]

In the post-epidemic era, people's lives are gradually returning to normal, and travel is gradually resuming. The safe evacuation of cross-regional travelers in railway station has also attracted more and more attention, especially the evacuation behavior of college students in railway station. In this paper, considering the pedestrian dynamics mechanism in the emergency evacuation process during the COVID-19 normalized epidemic prevention and control, an Agent-based social force model was established to simulate the activities of college students in railway station. Combined with the virus infection transmission model, Monte Carlo simulation was used to calculate the total exposure time and the number of high-risk exposed people in the railway station evacuation process. In addition, sensitivity analysis was conducted on the total exposure time and the number of high-risk exposed people under 180 combinations of the number of initial infections, social distance, and the proportion of people wearing masks incorrectly. The results show that with the increase of social distances, the total exposure time and the number of high-risk exposures do not always decrease, but increase in some cases. The presence or absence of obstacles in the evacuation scene has no significant difference in the effects on total exposure time and the number of high-risk exposures. During the evacuation behavior of college students in railway station, choosing the appropriate number of lines can effectively reduce the total exposure time and the number of high-risk exposures. Finally, some policy suggestions are proposed to reduce the risk of virus transmission in the railway station evacuation process, such as choosing dynamic and reasonable social distance and the number of queues, and reducing obstacles. • Social force model and the virus transmission model are established to exposed the risk of virus transmission in the evacuation of college students in railway station using actual arrival data of students returning to school in Tianjin, China. • Influence parameters (the number of initial infections, social distance, and the proportion of people wearing masks incorrectly) and different scenarios (the presence or absence of obstacles and the number of lines) are analyzed to explore their influence on total exposure time and the number of high-risk exposures. • Relevant policies are proposed based on experimental results, including choosing dynamic and reasonable social distance and the number of queues, and reducing obstacles. [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]