Continuous-fiber fused filament fabrication (FFF) enables local reinforcement of polymer composites, but the effect of fiber deposition strategy on transverse compressive response remains insufficiently quantified. This work investigates cylindrical Onyx specimens reinforced with continuous carbon fiber layers printed with two deposition patterns: isotropic (0°/45°/90°/135°) and concentric. The fraction of reinforced layers was varied from 10% to 100%, and Onyx-only specimens were tested as a reference. Unlike previous studies on compression properties, this work integrates compression tests with transverse-strain measurements and X-ray CT inspection of both untested and failed specimens to directly relate nominal print settings to the effective as-built fiber architecture, porosity, and damage mechanisms. Increasing the reinforced-layer fraction increased stiffness and maximum compressive stress, while reducing lateral expansion relative to Onyx-only specimens. Although concentric paths deposited a higher effective fiber volume, isotropic paths provided higher stiffness and strength efficiency. Both layouts showed a change in transverse-strain response at approximately 2–3%, consistent with the onset of carbon-fiber damage at the structural scale. CT and SEM observations revealed pattern-dependent fracture mechanisms: concentric specimens failed through circumferential fiber breakage and tortuous crack propagation, whereas isotropic specimens showed inclined d shear-like fracture and interlaminar delamination. Linear regressions described the dependence of maximum compressive stress on effective fiber volume fraction for the two patterns. The results support deposition-pattern selection for compressively loaded continuous-fiber FFF components, especially where stiffness, strength and lateral expansion constraints must be balanced.
2.5D woven variable thickness composites have been gradually applied in aerospace power plants, and their high-temperature strength failure characteristics have become a key constraint for the engineering application of such materials. In this study, a high-temperature quasi-static tension test scheme for outer reduction yarn woven composites (ORYWC) is designed, and the digital image correlation (DIC) system is employed to segmentally measure the average stiffness of each part of the structure. Based on the strength data from the aforementioned tests, two loading interruption points are set to conduct high-temperature interrupted tension tests, and the X-ray micro-computed tomography (Micro-CT) is combined to characterize the damage evolution of material components during the loading process. The results indicate that the average tension stiffness of each part of the structure shows little difference; the structural strength at 223 °C decreases by approximately 18% compared with that at room temperature; at 75% of the ultimate stress, the detectable damage is mainly concentrated in the surface yarn-reduced region. Based on Micro-CT images under different interrupted loading conditions, the damage evolution of material components follows the characteristic of matrix cracking prior to fiber fracture.
High-frequency electronic packaging for 5G and 6G technologies demands substrate materials with high thermal conductivity and low dielectric loss. Traditional blending induces horizontal filler alignment, disrupting through-plane thermal pathways and provoking severe phonon scattering. To overcome this, an interconnected three-dimensional (3D) sponge-like framework was fabricated via a water-based gel-casting strategy. Using a dual-additive system, regulating the hexagonal boron nitride (h-BN) concentration creates spatial confinement, suppressing the preferential orientation of the anisotropic flakes. The resulting polysilylaryl-enyne (PSAE) composite achieves a high through-plane thermal conductivity of 2.99 W∙m-1∙K-1. Finite element method (FEM) simulations demonstrate that this continuous network effectively minimizes interfacial thermal resistance. Furthermore, the composite exhibits a low dielectric constant of 2.88 at 10 GHz and maintains a stable dielectric property across the 0.2 to 1.7 THz range. Electric field simulations confirm that these continuous parallel pathways homogenize the internal electric field. Overall, the optimized 3D architecture simultaneously enhances thermal transport while maintaining low dielectric constant and loss, demonstrating its potential for high-frequency electronic substrate applications.
Epidermal-like stretchable pressure sensors are essential for detecting physical interactions within dynamic biological tissues, prosthetics, and robotic systems. However, their pressure sensing accuracy is consistently compromised by interference from lateral strain. This study presents a magnetically oriented gradient-modulus pressure sensor designed to overcome this limitation. By leveraging a structure with distinct modulus differences along both the in-plane and normal directions, the sensor achieves both strain insensitivity and a graded, high-sensitivity response to pressure. Customizable elastomer modulus is achieved by adjusting Ni particle content. Tensile deformation of the elastic mesh induces minimal effect on the rigid sensing units, conferring excellent strain insensitivity. Furthermore, a graded pressure response is engineered through systematic modulus variations, enabling the sensing units to exhibit high sensitivity (0.0174 kPa-1) over a broad detection range (0-100 kPa). A 4×4 sensor array was fabricated, successfully demonstrating its capability for biophysical signal detection and object recognition, thereby highlighting its potential for practical applications.
Phase change composites (PCCs) must combine latent-heat buffering with direction-specific heat transport for advanced thermal management, yet the preferred heat flow direction in anisotropic PCCs is typically imposed by external alignment fields, templates, or processing geometry, making directional redesign dependent on the changes in fabrication conditions. Herein, we design composition-programmable graphitized carbon networks in paraffin wax-based PCCs to tune the preferred heat conduction direction. The conduction networks integrate one-dimensional carbon fiber (CF) backbones with two-dimensional graphene-derived bridges. By regulating the concentration of graphene oxide (GO) and the loading of CFs, the relative dominance of conductive components can be tuned to reconstruct heat transfer pathways without changing the fabrication route. Increasing the GO concentration at a low CF loading can generate a vertically aligned network, and its paraffin wax composite exhibits a through-plane thermal conductivity of 11.7 W m-1 K-1; whereas, increasing the CF loading at a high GO concentration can redirect the heat transport toward the in-plane direction, endowing the paraffin wax composite with an in-plane thermal conductivity of 9.3 W m-1 K-1. Besides, the resultant PCC retains high melting enthalpy, satisfactory shape stability, and cycling durability. As a thermal interface material for high-power LEDs, it can decrease the operating temperature by 25.6 °C and increase the equivalent heat-transfer coefficient by 184%. This work demonstrates the effective tuning of heat transfer pathways in PCCs by compositional regulation of thermally conductive networks.
Oxide ceramic aerogels have shown great potential as thermal insulation materials in the aerospace field due to their high-temperature resistance, oxidation resistance, ultra-lightweight, and corrosion resistance. However, conventional oxide ceramic aerogels suffer from insufficient mechanical properties due to their intrinsic brittleness and weak neck connections between particles, as well as deteriorated thermal insulation at high temperatures caused by poor extinction performance, which limits their further applications. In this work, a facile reinforcement strategy is proposed, in which PCS is pyrolyzed in situ to generate SiC, enabling the fabrication of high-strength SiC-ZrO2 composite ceramic aerogels (denoted as SZA). The PCS-derived SiC phase forms shell-like coating regions around the rigid and brittle ZrO2 particles to enlarge the interparticle contact area, while its continuous distribution strengthens the connections between adjacent particles, which can efficiently dissipate the external compressive stress, mitigate brittle fracture at the ZrO2 interparticle necks, and regulate the pore structure. Meanwhile, the introduction of the SiC phase also significantly increases the effective extinction coefficient (e*) of the composites, thereby reducing radiative heat transfer. The results demonstrate that the SZA possesses a high compressive strength (4.71 MPa) and a low thermal conductivity (0.0383 W m−1 K−1 at 25 °C and 0.0655 W m−1 K−1 at 1000 °C). These findings demonstrate the potential of the reinforcement strategy based on the in situ pyrolysis of PCS to generate SiC for developing mechanically robust and thermally insulating ceramic aerogels.
Porous titanium alloy implants reduce stiffness mismatch with bone, but high porosity promotes local stress concentration, pore-wall buckling, and unstable collapse. Inspired by natural antler's irregular microporous network, we developed an antler-inspired Ti6Al4V/ultra-high molecular weight polyethylene (UHMWPE) interpenetrating scaffold for direction-dependent load bearing and energy absorption. Count Density and Scale Factor were parameterized to control pore diameter, relative density, and specific surface area. Ti6Al4V skeletons were fabricated by laser powder bed fusion and infiltrated with UHMWPE by hot compression molding. Microscopy and elemental mapping showed local UHMWPE infiltration, while Micro-CT demonstrated 93.7% mean filling fidelity and volumetric continuity across the Ti pore network, forming a continuous hard–soft interpenetrating structure. Compression tests revealed pronounced loading-direction dependence. Under longitudinal loading, UHMWPE minimally affected initial modulus and 0.2% yield strength but improved post-yield stability and energy absorption (EA), increasing EA by up to 109% in the P80 group. Under transverse loading, UHMWPE supported pore walls and shared load, increasing yield strength by up to 117%, EA by 182%, and specific energy absorption by 73% in high-porosity groups. Gibson–Ashby analysis showed lower density-sensitivity exponents for transverse composites than for Ti scaffolds, indicating slower performance degradation at low density. Finite element simulations confirmed that UHMWPE suppressed local stress concentration and promoted progressive deformation under transverse loading. These findings establish a direction-dependent design strategy for candidate low-modulus orthopedic scaffolds with enhanced energy absorption, although biological safety and long-term performance require validation before clinical application.
Mitigating the corrosion-induced degradation of marine infrastructure in high-salinity and high-humidity environments remains a major challenge, particularly when conventional polymer barrier coatings suffer irreversible failure after mechanical damage. Herein, a multifunctional nanocomposite coating was developed by integrating 2-mercaptobenzimidazole (MBI) loaded, mussel-inspired polydopamine (PDA)-modified zirconium phosphate nanosheets (mZrP@MBI) into a polyurea (PUA) network containing exchangeable disulfide bonds. The resulting coating combines passive barrier protection, active interfacial inhibition, and thermally assisted self-healing. The well-dispersed mZrP@MBI nanosheets construct tortuous diffusion pathways, effectively retarding the penetration of H2O, O2, and Cl−. Meanwhile, the loaded MBI molecules can migrate/release toward corrosion-active interfaces and coordinate with iron species, thereby establishing a corrosion-inhibiting interfacial layer. In addition, dynamic disulfide bonds enable the PUA matrix to repair localized mechanical damage under thermal treatment. The low-frequency impedance modulus of PUA/mZrP@MBI remained in the 108 Ω cm2 range after 30-day of exposure to 3.5 wt% NaCl solution, demonstrating its durable protective capability. Furthermore, the coating achieved a tensile healing efficiency of 96.1% and retained an electrochemical anti-corrosion healing efficiency of 87.8% after scratch-healing treatment. This work provides a feasible strategy for designing durable smart protective coatings for marine infrastructure.
The increasing use of multispectral detection requires protective materials that combine vegetation-matching optical response with microwave attenuation. Herein, SiCw /CoAl2O4 (SC) composite fibrous membranes were prepared by electrospinning and calcination. CoAl2O4 provided a stable green color and Vis–NIR reflectance behavior close to natural leaves, while SiCw introduced dielectric loss and conductive pathways for microwave dissipation. The SiCw /CoAl2O4 heterointerfaces further promoted interfacial polarization, and the interwoven fibrous network assisted wave scattering and propagation. By optimizing the SiCw loading and calcination temperature, S15T800 achieved the best overall performance, with a minimum reflection loss of -56.60 dB and an effective absorption bandwidth of 7.12 GHz at 1.9 mm. RCS simulations also showed an RCS reduction of 18.69 dB·m2. This work offers a feasible route for designing lightweight multispectral-compatible microwave absorbing membranes.
The practical application of carbon fiber-reinforced epoxy resin composites (CFRPs) is hindered by weak fiber-matrix interfacial adhesion and the inherent flammability of epoxy resins. In this study, a multifunctional integrated interface was innovatively constructed on the carbon fiber surface via electrostatic self-assembly of polyhedral oligomeric silsesquioxane based nanocomponents (PPI) and MXene nanosheets. This mild modification strategy preserves the intrinsic tensile strength of the fibers while significantly enhancing surface wettability and surface energy. The resulting PPI-MXene hybrid interface substantially improves interfacial adhesion, achieving a 43.9% increase in interfacial shear strength compared to unmodified CFRPs. The optimal composite, 5-MPCF/EP, exhibits outstanding mechanical performance, with interlaminar shear strength, flexural strength, and unnotched impact strength increased by 30.9%, 30.1%, and 50.6%, respectively. Moreover, the integrated interface endows the composites with exceptional flame retardancy, achieving a UL-94 V-0 rating and a limiting oxygen index of 35.4%. Cone calorimetry tests reveal significant reductions in peak heat release rate (53.4%), total heat release (33.2%), and carbon monoxide production (76.9%). The synergistic flame-retardant mechanism involves physical barrier formation, radical scavenging, catalytic carbonization, and thermal reflection. This work overcomes the longstanding trade-off between flame retardancy and mechanical properties in CFRPs, offering a promising strategy for developing high-performance, fire-safe composites.
