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The emergence of multi-material extrusion systems has opened up new possibilities for 3D printing, spurring research on the combination of diverse materials and structures to enhance part quality and performance. In this work, a nested-screw coaxial co-extrusion 3D printing mechanism was designed for hybrid coaxial structures to address the viscosity matching limitation that is present in traditional coaxial extrusion. The high-viscosity shell material, with 3 wt% added carbon fiber, can be extruded and printed at room temperature. This suggests that the nested-screw can be used to adjust the high viscosity difference between the core and shell materials for co-extrusion. A model for coaxial extrusion was developed to establish appropriate printing parameters for the hybrid integration of materials and structures in coaxial designs. The resulting model for determining the printing parameters of the C-S structure improves dimensional stability and print repeatability. The coaxial printing was also employed to validate the bionic coaxial structure of antlers. The influence of the core-shell material and structure combinations on strength and toughness was thoroughly examined, enabling the optimization of structures with superior strength-toughness combinations. The comparative truss structure tests demonstrated that the core-shell structure enhanced damage absorption by 30.1 % compared to a single-structure design. This confirms the adjustability of mechanical properties in printed systems through a combination of hybrid materials and structure.

To improve the bending and interlayer properties of hybrid-fiber-reinforced composites (HFRCs), a functionally graded hybrid (FGH) strategy is proposed inspired by the graded structure of bamboo. Specimens were prepared by utilizing the continuous-fiber 3D-printing manufacturing process, achieving graded changes in the fiber content and properties of the composites between and within layers. The differences in the mechanical properties and failure mechanisms of traditional interlayer HFRCs (IHFRCs) and functionally graded HFRCs (FGHFRCs) were comparatively analyzed. The mechanical-property test results demonstrated that the FGH strategy can further improve the mechanical properties of HFRCs. Compared with those of the IHFRCs, the bending strength and interlayer shear strength of the FGHFRCs increased by a maximum of 25.95 % and 41.20 %, respectively. Macro-micro fracture morphology analysis revealed that the interlayer hybrid led to a risk of delamination failure. However, the FGH effectively reduced the interlayer performance differences, changed the direction of crack propagation along the interlayer, and effectively suppressed the generation of delamination damage, which was conducive to further improving the properties of HFRCs. Owing to their enhanced properties and positive hybrid effect, the manufacturing process and the FGH strategy have considerable potential in engineering applications.

Carbon-fiber-reinforced polymer (CFRP) composites have received extensive attention in aerospace, weapon equipment, communication electronics, transportation and other fields. The improved compression-molding process is one of the most advantageous processes for preparing CFRP composites. It is important to understand the effects of molding process parameters, in particular temperature parameters, on the preparation of an ideal composite. This paper addresses the effect of the no-pressure curing temperature on the two-dimensional woven CFRP (2D-CFRP) bending property of the improved compression-molding process. 2D-T700/E44 composites were prepared under no-pressure curing temperatures of 80, 90, 100, 110, 120 and 130°C. The effect law and influence mechanism of the temperature parameter on the microstructure and bending property of composites were summarized. The results show that excessively high or low no-pressure curing temperatures are unfavorable for the preparation of 2D-T700/E44 composites. When the temperature is 110°C, the impregnation effect of the resin is ideal, and the defects are effectively controlled. The fracture morphology is reasonable, and the performance is greatly improved, so the bending strength reaches 860 MPa.

While 4D printing technology can effectively simplify the manufacturing process of complex spatially deployable structures and improve material utilization, its sustainable development still faces challenges due to the inferior mechanical load bearing properties of the printed materials. In this study, continuous fiber-reinforced thermosetting shape memory polymer (CF/Ts-SMP) 4D printing technology was employed to attain superior load bearing and shape memory functions of structures. The mechanism of Ts-SMP cross-linking degree on the printing rheological, thermomechanical, mechanical load bearing and shape memory properties of composites was investigated. With 5 % curing agent content, the 4D printed CF/Ts-SMP composites was in moderate cross-linking degree and showed superior overall mechanical and shape memory properties, with a bending strength of 806.38 MPa, a flexural modulus of 47.2 GPa, a shape fixation ratio of 98.46 %, and a shape recovery ratio of 99.01 %. Based on this, complex sandwich pod structure was further printed, which have potential future applications in the fields of space-deployable structural hinges and robot deformable joints.

For the remote sensing satellite with an unbalanced rotating payload suspended by an Active Magnetic Bearing (AMB), this paper proposes a payload-oriented control scheme where the high-precision payload attitude control is dominating. Firstly, to suppress the disturbances induced by payload inertia uncertainties and state measurement errors, an integrated framework of parameter identification and nonlinear predictive filtering is proposed to estimate payload inertia parameters and system states from multi-timescale, noise- and drift-contaminated measurement data, breaking the mutual constraint between identification and filter. Secondly, based on the estimation results, the control law and bearing electromagnetic force allocation strategy of the payload-oriented scheme are provided, so that the payload tracks the desired motion and the satellite platform follows payload to prevent the air gap of AMB from exceeding the safety threshold. Finally, the simulations are carried out to verify the advantages of the proposed control scheme in enhancing the payload control precision and isolating the platform vibration.

Continuous fiber-reinforced composite (CFRC) 3D printing provides attractive solutions for integrated fabrication of all-composite honeycomb sandwich structures. However, weak matrix strength and insufficient interlayer bonding degrade the performance of 3D-printed thermoplastic honeycomb sandwich structures. The curing-mold-dependent thermoset honeycomb sandwich structures are challenging to fabricate integrally by 3D printing. This study addressed these issues by filling the honeycomb cells with lightweight polymethacrylate (PMI) foam during 3D printing, achieving co-curing support and enhanced performance of the integrally 3D-printed honeycomb sandwich structures. The novel foam-reinforced structure was studied using three-point bending tests and compared to the foam-free bonding-based structure. With a minor weight gain (9.48 %), the PMI foam reinforcement increased the peak load capacity of the honeycomb sandwich structure by 198.31 % (4.32 kN). The specific bending stiffness and the specific core shear strength were increased by 49.32 % and 165.69 %, respectively. Finally, the failure flow maps and stress state were analyzed to reveal structural failure modes and PMI foam reinforcing mechanisms.

Maximizing the structural efficiency of composite materials is often limited by the minimum turning radius of fibers in composite manufacturing. Neglected defects, such as local fiber buckling, become more pronounced in regions with a large curvature, leading to reduced load-carrying capabilities and a deviation from the target design specifications. This study introduces “hammered printing” as a novel approach for achieving a large curvature of the fiber path in composite manufacturing. By utilizing the transition of the modulus with temperature of a thermoset epoxy pre-polymer, the proposed hammered printing technique generates a unique pressure effect that improves adhesion between the fiber tow and the substrate. This enables the production of accurate and uniform composite structures with a minimum curvature radius of 2mm, while reducing the occurrence of wrinkling and bending deformations. A continuous fiber path with a small radius (2mm) for open-hole plates was accurately printed using this printing pattern. Compared with conventional laminates and drilled composites, the obtained printed samples exhibit 75.3% and 28.8% increments in the tensile and bearing strengths, respectively, indicating that this continuous small-radius fiber path can effectively retain the strength and safety of fastened composite parts. Finally, comparisons indicate the great potential of the proposed technique as a large-curvature-path and high-performance manufacturing alternative for the cutout of composite assemblies in the aerospace and related engineering industries.

Three‐dimensional carbon fiber reinforced resin matrix composite can effectively overcome the defects of traditional composite in the interlayer strength and stiffness, and has been widely used. Herein, the threshold infiltration pressure of resin in three‐dimensional carbon fiber preform is respectively calculated as 0.170 and 0.973 MPa from the perspective of statics and dynamics. The static calculation ignores the additional pressure caused by the viscous resistance of the resin during the infiltration process, which deviated greatly from the actual value. Therefore, the dynamics calculation value is used as a reference to extrusion pressure in the experiment. The composites with extrusion pressure of 1, 2, 3, 4, and 5 MPa are prepared by vacuum infiltration hot pressing process. Through the study of the infiltration microstructure and bending fracture morphology of the composite, it is found that when the extrusion pressure is 3 MPa, the preparation effect is the best. At this time, the bending strength of the composite is 540 MPa, which is 92.86% and 71.43% higher than that at 1 and 5 MPa, respectively. It is indicated that the extrusion pressure is a key parameter in the composite preparation process and needs to be selected reasonably. The threshold infiltration pressure of resin in 3D carbon fiber preform is respectively calculated from the perspective of statics and dynamics. The dynamics calculation value is more suitably used as a reference to extrusion pressure in the experiment. On this basis, the influence mechanism of different extrusion pressures on the infiltration effect and bending strength of composite is demonstrated.