Barium titanate (BT) is a key lead-free piezoelectric ceramic, but conventional forming methods limit its structural design freedom and performance regulation. This work proposes an additive manufacturing route for BT-Al2O3 composites via fused deposition modeling (FDM) with a solution-based PVB/PEG feedstock. The process included filament extrusion, FDM printing, staged debinding, and sintering. Scanning electron microscopy confirmed homogeneous ceramic dispersion and interfacial compatibility, enabling complex architectures. Sintering temperature (1100–1300 ∘C) and Al2O3 particle size (1–100 µ m) significantly influenced microstructure and phase evolution, allowing the piezoelectric coefficient (d33) to be tuned from 14.3 to 96.1 pC/N. Optimized composites sintered at 1200 ∘C with 10 µ m Al2O3 exhibited a compressive strength of 4.16 ± 0.31 MPa and a flexural strength of 0.96 ± 0.23 MPa. A four-sensor-integrated component fabricated via FDM demonstrated the capability of monitoring impact areas. This work establishes a generalized AM strategy for BT-based ceramics with tunable piezoelectric and mechanical properties, offering significant potential for smart ceramic systems.

Dielectric energy storage ceramics with both superior energy storage performance (ESP) and simple chemical compositions are highly in demand for dielectric capacitors practical applications. However, advancing excellent ESP commonly demands highly complex chemical components, which is a challenging task that remains unresolved. Here, via integrating the component engineering and process engineering, we achieve substantially improved energy storage density Wrec (∼9.21 J/cm3) and efficiency η (∼85.4%)under 940 kV/cm in SrTiO3-based ceramic with a simple chemical composition (two doped elements), showcasing tremendous potential for next-generation energy-storage device. The achieved performance merits are credited to multiple synergy effects: local polar structure concomitant with ultrasmall and highly dynamic polar nano-regions, improved electrical homogeneity, reduced grain size, and suppressed oxygen vacancies. Therefore, our proposed approach offers a design freedom to develop high-performance dielectrics with a simple composition for practical implementations of dielectric capacitors.

Thin-walled lenticular deployable composite booms (DCBs) are widely used in space deployable arms that require folding, storage, and load-bearing during deployment. However, space deployable structures have complex multi-directional mechanical performance requirements, which place higher demands on the elastic properties of DCBs in various directions. Therefore, this paper proposes a lattice-based 3D printing strategy to form DCBs, achieving lightweight design while also considering the multi-directional elastic properties of the DCBs. First, the cross-sectional and surface lattice structure of the DCB were designed, and the mechanical behaviors of radial flattening, folding, bending resistance, and axial compression were evaluated using numerical calculations and experimental methods. The study found that the directional elastic properties of the DCB could be adjusted by changing the line spacing (L). Compared to the closed structure, after lattice structuring (when L = 4.8 mm), the folding and bearing stiffness decreased by approximately 90.0 % and 60.0 %, respectively; however, the specific stiffness under loading is still improved. The consistency of the force-displacement curves of the three-point bending test and cantilever beam test before and after the folding cycle of the DCB indicates that both the flattening and folding of the structure are elastic deformations. In summary, lattice-based DCBs are expected to provide new design ideas and solutions for the engineering development of space deployable arms.

The rapid development of smart equipment and emerging energy technologies demands structural components that are lightweight, mechanically robust, energy-dense, and geometrically versatile. Yet load-bearing electrochemical energy-storage devices remain constrained by the challenge of simultaneously improving electrode activity and ion/electron transport while maintaining mechanical robustness. Here, we report a low-cost 3D printing strategy for the integrated fabrication of load-bearing Zn-ion hybrid supercapacitors using functional core-shell continuous carbon fiber prepreg filaments, where "fully 3D-printed" refers to the one-step additive manufacturing of the structural framework (electrodes and electrolyte matrix) followed by necessary post-printing treatments (supercritical foaming and gelation) to activate electrochemical performance. On the electrode side, supercritical fluid-assisted laser-induced graphitization converts continuous carbon fiber bundles into hierarchical porous graphene cathodes, delivering a 2.4-fold increase in areal capacitance over conventional LIG electrodes. On the electrolyte side, a biphasic PP/PVA semi-solid electrolyte is engineered by supercritical foaming to construct interconnected open ion-transport channels, increasing the ionic conductivity from 0.5 to 4.2 mS cm- 1. Together, these designs enable fully 3D-printed continuous fiber devices with integrated mechanical load-bearing and electrochemical energy-storage functions. This work establishes a versatile, cost-effective, and scalable route toward multifunctional structural power sources for next-generation integrated devices.

Purpose This study aims to enhance U-turn precision in robotic three-dimensional (3D) printing of continuous fiber reinforced thermoplastics for near-net-shape manufacturing by analyzing fiber bundle shifting and width variation to optimize process parameters. Design/methodology/approach A six-axis robotic fused filament fabrication system was developed with a preprinting tool center point calibration method that reduced X-direction deviations by 80% (280 -> 32 mu m). L9(3(4))orthogonal experiments evaluated printing speed (120-240 mm/min), turning radius (0.5-1.5 mm), feeding ratio (40%-60%) and retraction control. Findings Turning radius significantly impacted accuracy (p < 0.1). Optimal parameters (1.5 mm radius, 120 mm/min speed, 60% feeding, enabled retraction) achieved 244 m shifting and 0.19% width error. Specimens showed 167.9 mu m (flat) and 89.6 mu m (curved) average accuracy, with edge deviations reaching +/- 1.78 mm. Originality/value This study provides practical solutions for high-precision continuous fiber reinforced thermoplastic composites manufacturing and establishes a framework for optimizing robotic 3D printing in aerospace and automotive applications, while guiding future thermal and extrusion research.

Traditional rigid mechanisms used in airfoils often result in gaps and bulges, adversely affecting the aircraft's performance and economy while the continuous variant wing has significant advantages in flight speed and economy due to its aerodynamic shape. However, current research on variant wings focuses more on the design of special deformation mechanisms, without applying metamaterials to the filling structure inside the wing, thus fully leveraging the advantages of metamaterials in the deformation process. To overcome this limitation, this paper presents the design and analysis of a novel spanwise differential variable camber morphing wings device for aircraft applications. The proposed design integrates both rigid and flexible materials in the wing morphing structure. The device is developed based on chiral metamaterials using 3D printing technology. Finite element analysis is utilized to establish the theoretical relationship between the rotation of the steering engines and the resulting wing deflection. Experimental measurements of deflection angles are obtained through the use of scale plates. Comparing the experimental results with the theoretical predictions, a close correlation is observed, validating the effectiveness of the proposed design. This paper provides a new method for the design of flexible variant wings, fully utilizing the advantages of chiral metamaterial structures in the deformation process, and innovatively proposing a new method of filling chiral structures into variant wing structures.

To enhance both the mechanical properties and electromagnetic wave absorption performance of lightweight lattice structures, this study proposes a functional Z-pins reinforcement approach. Carbon fiber reinforced composite prepreg filaments are arranged in a pyramidal configuration and embedded within the interior of a 3D-printed lattice structure, thereby activating the spoof surface plasmon polariton (SSPP) mode inherent to the design. Simulation and experimental findings indicate that, when the incident angles reach up to 70 degrees, the absorption performance is significantly improved, and the absorptivity remains above 80 % within the frequency range of 12.5-18 GHz. Furthermore, by incorporating carbon fiber composite filaments in the vertical direction, the compressive strength of the lattice structure increases by approximately 14 % compared to a pure resin-based counterpart. Owing to its superior mechanical integrity and electromagnetic absorption capabilities, the proposed lightweight lattice structure exhibits strong potential for multifunctional applications intelattice loadbearing and wave-absorbing functionalities.

Aiming at the contradiction between load-bearing and folding of traditional thin-walled lenticular deployable composite booms (DCBs) and insufficient radial load-bearing of lattice-based DCBs, this paper proposes a flexible strip-regulated 3D printed lattice-based DCBs design. Geometric parameters are determined via design, and specimens are fabricated by dual-nozzle FDM 3D printing and compression-molded curved forming. Through radial compression experiments, finite element simulations, and theoretical modeling, the regulation laws of flexible strip number and pre-tension on mechanical properties are studied, with folding-unfolding cyclic tests verifying reliability. Results show that 3 and 5 flexible strips increase radial stiffness by 255.0 % and 375.0 % respectively, without raising the maximum folding stress, and enhance elastic strain energy by 17.9 % and 29.8 %; pre-tension improves load-bearing, and increasing cross-sectional height from 40.0 mm to 50.0 mm boosts radial stiffness by 52.1 % and elastic strain energy by 50.7 % with stable folding stress. An analytical model for radial compression force is established based on Kagome lattice homogenization and moment equilibrium, with a relative error < 5.0 % vs FEA results; cyclic tests show no obvious degradation, demonstrating excellent stability. This strategy achieves synergistic improvement of radial load-bearing and folding, offering a new approach for high-load, high-folding-ratio space deployable composite booms.

To address the long-standing trade-off between heating efficiency and mechanical performance in electrothermally driven 4D printing of continuous carbon fiber-reinforced composites (CFRCs), we propose a dual-process hybrid printing strategy that integrates Electric-Field-Driven Microscale 3D Printing with Fused Deposition Modeling. This approach enables the seamless incorporation of continuous carbon fiber structural layers and silver-paste microcircuits, yielding embedded microcircuit CFRCs (EM-CFRCs). The embedded microcircuits significantly enhance electrothermal heating efficiency while maintaining the intrinsic strength of CFRCs. Experimental results show that EM-CFRCs achieve a heating rate of 5.9 degrees C/s, representing a 118.5 % improvement compared with conventional CFRCs, while the tensile modulus and structural stiffness remain nearly unchanged (increased by 1.5 %). We develop a predictive model based on multilayer beam theory that accurately captures the electrothermally induced deformation behavior and underlying mechanisms. Finally, we fabricate 4D-printed origami structures with complex geometries that demonstrate rapid actuation. These results highlight the potential of EM-CFRCs for aerospace deployable structures (e.g., solar sails), intelligent morphing components, and other advanced functional devices.

Optimizing 3D printing deposition paths is essential for continuous fiber reinforced thermoplastic composites under complex multi-mode loading in lightweight transportation structures. Existing principal stress method (PSM) toolpaths can align fibers with stress trajectories, but may leave unfilled regions and non-uniform spacing when stress fields diverge or converge in complex geometries. To address this limitation, this study develops a contour modulating principal stress method (CM-PSM) for multi-mode loading scenarios. CM-PSM couples seed-path extraction, bidirectional equidistant offsetting, and angular-deviation control to increase path coverage while constraining the mismatch between the deposited fiber direction and the first principal stress direction. The generated paths further enable partitioned equivalent modeling for finite element evaluation. Using a full-scale suspension control arm, the method is evaluated under acceleration and deceleration loads through layup optimization, simulation, fabrication, CT inspection, and quasi-static testing. CM-PSM increases the fiber volume fraction from 13% for conventional PSM paths to 40%, close to the 41% theoretical upper limit set by the prepreg filament. Relative to the 0° unidirectional composite laminate baseline, the optimized design reduced the maximum principal stress by 52% and increased the weighted safety factor by 121%; relative to the stainless steel benchmark, it achieved a 60% weight reduction. Simulation–test displacement differences of 13.4% and 2.9% under the two loading cases indicate that the partitioned equivalent model captures the global quasi-static response within the tested small-deformation range. These results demonstrate a manufacturable and simulation-compatible method for stress-guided continuous-fiber toolpath generation in complex composite components under multi-mode loading.

3D printing of continuous fiber-reinforced thermoplastic composites (CFRTPCs) enables the fabrication of highperformance complex structures, yet warpage induced by residual-stress release remains an obstacle to dimensional accuracy. Existing studies in conventional composites, automated fiber placement/tape laying, and neat-resin 3D printing have generally attributed this problem to non-uniform thermal shrinkage; however, this explanation fails to reveal the origin and evolution of residual stress in 3D-printed continuous-fiber systems. Here, using multi-scale characterization including computed tomography (CT), morphology scanning, in situ Raman stress measurements, and oil-bath thermal treatment, we investigate the generation of residual-stress differences and warpage during CFRTPC printing. The results show that fiber residual-stress differences originate from nozzle-induced bending and subsequently undergo staged evolution during the resin cooling window and constraint-locking process. After detachment from the substrate, the printed tape undergoes time-dependent deformation jointly driven by resin viscoelasticity and the release of fiber stress differences. In this process, the resin mainly provides a transient constraint that can be weakened by post-treatment, whereas the final warpage level is governed by through-thickness fiber residual-stress differences that cannot be eliminated by posttreatment. On this basis, we establish a four-stage coupled evolution model of fiber-resin residual-stress differences, comprising heating deposition, cooling solidification, constraint locking, and residual-stress balancing. Furthermore, a synergistic process-control strategy designed around the dominant factors in different stages reduces the dimensional error from 5.0% to 0.6%, corresponding to an 8.3-fold improvement in dimensional accuracy. This work provides a mechanism-driven framework and an engineering route for high-precision 3D printing of continuous fiber-reinforced composites.

The detection and repair of delamination damage are of great significance for enhancing the practicality and intelligence of printed composites. In this study, a unique microscopic conductive network was constructed using chopped and continuous carbon fibers as hybrid fiber-reinforced phases. This design improved the electrical conductivity in the layer thickness direction of 3D-printed composites by approximately 165 %. Leveraging the reinforcing effect of short carbon fibers, a self-detection method for delamination damage was developed, with its sensitivity enhanced by approximately 8 times compared to conventional methods. By utilizing the Joule heating effect of ply thickness resistance, an efficient interlaminar strengthening method was established, achieving a typical repair time of approximately 60 s. Furthermore, a self-repairing approach for delamination damage was proposed, enabling an Interlaminar Shear Strength (ILSS) recovery rate exceeding 100 %. Temperature distribution analysis via thermal cloud maps confirmed that high temperatures were concentrated in the damaged layers. In summary, without embedding sensors, heating wires, or conductive films, the intrinsic layerthickness conductivity of hybrid fiber-reinforced composites can be utilized to achieve highly sensitive sensing and rapid, effective repair of delamination damage, offering a practical and intelligent solution for composite structures.

Continuous fiber composite three-dimensional (3D) printing technology enables the production of lightweight, complex 3D composite parts with functional integration and other significant advantages. However, in high-end applications, scenarios such as aerospace and energy delivery the performance stability of materials in long-term service environments is critical. The poor performance and instability of the existing 3D printing of fiber composite materials, particularly fiber-reinforced thermoplastic materials, caused by the various defects introduced in the printing process, has become the main challenge. This paper focuses on high-performance continuous fiber-reinforced thermoplastic composites. It reviews various defects in the printing process and discusses their mechanisms, effects on properties and possible elimination measures. Printing defects are categorized into two types based on their primary components: polymer defects and fiber-related defects. This paper also discusses two types of defects: defects in turning zones and defects on surfaces, which are classified based on their location. In addition, this paper summarizes the existing defect elimination methods and research progress. It also suggests the direction of future development, emphasizing that understanding the mechanisms and addressing irremovable defects are crucial for advancing high-performance 3D printing technology.

Curvilinear fiber reinforced variable stiffness structures (CFRVSSs) can be designed by adjusting the local fiber orientation and content to maximize the performance advantages of continuous fibers, which have potential application prospects in aerospace and other fields. The continuous fiber reinforced composites (CFRCs) 3D printing process can accurately regulate the fiber content and fiber orientation by planning the printing path and designing the process parameters, which provides the possibility of integrated mold-free fabrication of CFRVSSs. In recent years, it has become a research hotspot. Therefore, the current state of research on the 3D printing of CFRVSSs is reviewed in this paper. First, the modeling methods of the 3D printing of CFRVSSs are introduced. Then the main design methods of CFRVSSs are summarized, the 3D printing process of CFRVSSs and the optimization of their forming defects are introduced, and research work on 4D printing of advanced composite variable stiffness smart structures is summarized. Finally, the future research directions are presented to guide the development and application of 3D printing of CFRVSSs.

Continuous fiber-reinforced thermoplastic composites are widely used in aviation, aerospace, and automotive applications due to the high specific strength, modulus, and design flexibility. However, their properties are susceptible to damage in extreme environments. This study investigates the microscopic property changes of 3D printing thermoplastic composites in service environments with freeze-thaw cycling. we have established the relationship between interfacial crack damage in composites and the mechanical properties of sub-mm-scale prepreg fibers through experiment and simulation. By analysis of grayscale of AFM modulus map, the interfacial crack (interfacial porosity) size evolution law at the fiber-resin matrix interface was investigated. At the micro-scale, the degree of damage at the interface is strongly correlated with the shear properties of the interface, which were derived from micro-debonding experiments. At the sub-mm-scale, the mechanical properties of flexural and axial compressive strengths are sensitive to the extent of interfacial crack damage, as numerical simulation results have also predicted. Conversely, axial tensile strength is minimally affected. Furthermore, it was found that the mechanical properties of the prepreg filaments decreased significantly after re-absorption of water after freeze-thaw cycling, especially the flexural and axial compression properties decreased by 73.2 % and 92.8 %, respectively. Therefore, this paper designed carbon fiber/polyamide-covered-polypropylene (CF/PA-PP) water-resistant prepreg filaments with core-shell structure to reduce water absorption. The core-shell CF/PA-PP filament's mechanics are comparable to those of the CF/PA filament, with strengths of 2010.2 MPa, 1081.2 MPa, and 427.0 MPa, and it has reduced water absorption from 6.8 % to 0.4 %, demonstrating its promising application in the field of 3D printing of water-resistant thermoplastic composites.

3D printing of continuous fiber-reinforced thermoplastic composites (CFRTPCs) is a promising manufacturing technology. However, deformation caused by the release of residual stresses in printed parts remains unavoidable, and there is a lack of accurate and comprehensive measurements or models addressing the microscopic factors behind their formation. This paper presents in-situ measurements of process parameters related to residual stress formation, including temperature gradients, printing force fields, and deformation of printed samples. As temperature is a key factor contributing to residual stresses, this study introduces an in-situ microscale characterization method for the printing temperature field using temperature-sensitive prepreg filaments. The method enables accurate measurement of the full life cycle temperature data across different microscopic regions of the prepreg filament during printing. Using the measured data, including temperature, printing pressure, and tension force, this paper proposes a multi-scale process modeling method referred to as the "extrusion process-printing process combination". This model simulates the temperature field distribution during the extrusion process, as well as the residual stress and deformation during the printing process. Simulation results were validated by experiments, with an error margin of less than 5 %. Using this model, the preliminary process optimization for reducing the residual stress was carried out. In addition, the effects of various process parameters on the temperature gradient during printing and the deformation of printed samples were analyzed. The results show that by optimizing the printing process, it is expected to reduce the generation of residual stresses in composite printed products.

The integrated manufacturing of continuous fibers and resin matrix improves the mechanical properties of composite materials. Multi-material 3D printing technology provides a new technological means to realize the performance adjusting of composite materials. In the paper, a mesoscopic soft-hard dual-material strategy was proposed to strengthen the mechanical properties of composite structures. Tensile, impact, and interlayer shear properties of 3D printed continuous fiber reinforced composite were investigated experimentally. Results showed that the introduction of soft materials significantly affects these mechanical properties. Tensile modulus of sample has little change, being 42.44 GPa and 45.52 GPa before and after adjusting respectively. Tensile strength after adjuting was 1365.67 MPa, which was 46.25 % higher than that of PA-CCF composite. Impact strength increased from 30.26 kJ/m2 to 39.47 kJ/m2, which was 30.44 % higher than that before adjustment. Interlayer shear strength was 29.79 MPa and nonlinear deformation occurred, indicating that interlayer shear strength was sensitive to the introduction of soft materials. In addition, the distribution of soft-hard materials in the test specimen was characterized by microstructure. The failure mode of three types of samples was observed to explain the mechanism of mechanical properties change. The work can provide a reference for the performance adjusting of 3D printing soft-hard multi-material composite structures.

Poor interlaminar performance is still the major problem for 3D printing of continuous fiber-reinforced thermoplastic composites, especially when the fiber content is over 50 %. In this work, an ultrasound and plasmaassisted 3D printing method was proposed towards the synergistic interlaminar strengthening. Fiber-matrix interface defects at the interlaminar zone were identified by a comparison study, which are the causes behind the poor interlaminar properties for high fiber content composites. Experimental and modeling approaches were used to study the effects of printing and strengthening parameters on interlaminar properties. The physical and chemical effects of ultrasound and plasma on material microstructure was investigated and a synergistic effect model was presented. The proposed synergistic strengthening method can greatly reduce the porosity, from 14 % to 3 %, enhance interlayer bonding strength, and result in a 54.17 % increase in interlaminar shear strength. Better interlaminar properties have positive implications for other mechanical properties, e.g. the tensile strength and modulus can reach approximately 1254 MPa and 89 GPa, respectively.

Carbon fiber reinforced polymer (CFRP) tube is utilized in large aperture deployable space antennas for its superior material properties. Impact damages on CFRP tube can significantly impair the load-bearing capacity of the tubes. Efficient and convenient non-destructive evaluation method of impact damage in CFRP tubes is essential. This study develops a high-frequency eddy current testing (HF ECT) finite element analysis method that accounts for both the dielectric properties and anisotropic conductivity of CFRP, and establishes a fiber bundle model that explains the operating mechanism of displacement current and eddy currents in CFRP, offering guidance for predicting HF ECT signals in CFRP. A high signal-to-noise ratio mutual differential Bobbin probe is developed specifically for detecting impact damage in CFRP tubes. A HF ECT experiment system is constructed and validated using impact damages induced by a force hammer, demonstrating the effectiveness of method and probe, and the invisible impact defect is detected successfully.

The microstructure and mechanical properties of the (Fe35Ni35Cr20Mn10)100-xAlx (X = 0, 2.91, 4.76, 6.54, 8.26, 9.91, at%) high-entropy alloys (HEAs) with varying Al content were investigated through microstructure observation and tensile testing. The phase structure of the prepared HEAs changes gradually from a single facecentered cubic phase structure to a combination of face-centered cubic and body-centered cubic phase structures with an increase in aluminum content. The volume fraction of the body-centered cubic phase increases gradually as well, being rich in Ni and Al elements and having a coherent relationship with the face-centered cubic phase of the matrix. With increasing Al content, both the microhardness and tensile strength of the (Fe35Ni35Cr20Mn10)100-xAlx HEAs also increase gradually. At an aluminum content of 8.26 %, specifically for (Fe35Ni35Cr20Mn10)91.74Al8.26 HEA has higher tensile strength and yield strength at approximately 926 MPa and 867 MPa respectively; while maintaining an elongation after fracture at about 11 %. The main reason for its strength improvement is attributed to dislocation proliferation along with hindrance from second-phase bodycentered cubic structure relative to dislocations during tension process; whereas maintaining higher elongation is mainly due to congruent relationship between second-phase and matrix phases allowing some dislocations slip through congruent interface.