Composites Part A: Applied Science and Manufacturing最新文献

The proactive design of tribo-chemistry at friction interface is an effective way to improve the quality of transfer film. Herein, silver served as an assistant in tribo-chemistry, along with graphite incorporated into the short carbon fiber (SCF)/ polytetrafluoroethylene (PTFE)/poly ether ether ketone (PEEK) composite. The lowest wear rate of 3.5 × 10^-7 mm³/Nm was achieved for the composite at a graphite content of 5 wt% and a silver content of 5 wt% (Gr₅Ag₅) under dry friction condition, primarily benefiting from the synergistic interaction of silver and graphite. The transfer of silver and graphite to the friction interface endowed the transfer film with lubricity and load-bearing ability. Crucially, the oxides generated by silver enhanced the strength of the transfer film, and the tribo-chemical reaction involving Ag could increase the bonding of the transfer film to the metal.

Determination of cross-sectional area of glass and carbon fibres is a critical part of mechanical testing of the fibres. The present study focuses on the vibroscope method which is based on frequency measurements of a fibre under tension. Three data analysis procedures, named simple, direct and iterative, are presented, providing estimates of the fibre cross-sectional area with increasing accuracy. The simple procedure underestimates the cross-sectional area with about 0.4 – 2.0 % and 0.4 – 3.7 % for the tested glass fibres and carbon fibres, respectively. The cross-sectional area determined by the direct procedure deviates only marginally from the most accurate cross-sectional area as determined by the iterative procedure. Histograms of cross-sectional areas of glass and carbon fibres are presented to show the large variation of cross-sectional areas between individual fibres. Stress–strain curves of the tensile tested fibres are presented, and the small variation of stress–strain curves between individual fibres contributes to the validation of the vibroscope method.

An understanding of the off-axis mechanical behavior and failure mechanisms of ultra-high molecular weight polyethylene (UHMWPE) cross-ply laminates subjected to quasi-static and dynamic loadings is developed, with focus on the influence of off-axis angle and strain rate. For off-axis tension, UHMWPE laminates exhibit polymer shear response characteristics. An orientation-hardening phenomenon is captured, as fiber rotation leads to local increment of load capacity along the loading orientation. The failure strength presents an evidentially descending trend with off-axis angle from 0° to 45°. A non-monotonic variation of strength with strain rate is further observed: increasing with strain rate up to 500 s⁻¹ but decreasing above, which is attributed to failure mode switching from plastic failure to brittle failure. The Tsai-Wu failure criterion, on homogenized cross-ply laminae, is experimentally modified with rate dependence. Further investigation on detailed information of the unidirectional properties should be conducted with the backing-out scheme to establish unidirectional failure criterion.

Fabrics with passive radiative cooling (PRC) capability possess great values for thermally comfortable clothes and low-carbon economy. However, all-weather thermal management is always hard to achieve due to the undesirable and ceaseless mid-infrared emission of PRC materials under all circumstances. Herein, a dual-mode thermal managing metafabric integrating PRC technology and Joule heating strategy is developed on a sandwiched structure for all-day dressing comfort. The metafabric is prepared by a versatile orthogonal assembly of oriented SEBS microfibers encapsulated with TiO₂ microparticles, thus yielding highly homogeneous porosity in the metafabric with 96 % sunlight reflectivity (0.3–2.5 μm) and an average emissivity of 91 % (atmospheric window). Additionally, printed EGaIn circuits are stably sandwiched in the extremely elastic metafabric to provide low-watt Joule heating ability under large-scale tensile conditions. As a result, a maximum daytime cooling effect of ∼ 13 °C and a nighttime Joule heating performance of ∼ 7°C are delivered by the dual-mode metafabric, offering all-weather thermal management for comfortable and healthy wearing. The straightforward preparation and versatility of this metafabric open a promising avenue for developing advanced thermal regulation materials.

Cellulose foams were used to produce porous epoxy-composites. The influence of fibre wetting by the resins on foam morphology and resulting compression properties was investigated. Impregnated foam morphology determined the composite structures and their mechanical properties. Fibre preforms of various densities (40–80 kg·m⁻³) were prepared by frothing surfactant stabilised fibre suspensions. The preforms, exhibiting compressive strengths of 0.02 MPa, were impregnated with three different resins (a lignin-based resin BLER/MA, and two commercial formulations, A/A and A/XB). Depending on the formation of closed- or open-cell structures in the cured foam composites, compressive strengths of up to 2 MPa (BLER/MA), 33 MPa (A/A), or 23 MPa (A/XB), and compressive moduli of up to 47 MPa (BLER/MA), 468 MPa (A/A), or 379 MPa (A/XB) were obtained. The surface area, fibre coverage homogeneity, and composite morphology were investigated in relation to wetting. A tool kit for fibre foam templated porous composite design is provided.

SiC particles (SiCp) reinforced magnesium matrix composites (MMCs) exhibit elevated specific stiffness. However, the non-uniform distribution of SiCp and the interfacial cracking between the SiCp and Mg matrix compromise the ductility. This paper presents a novel approach to enhance the modulus and ductility of the MMCs by utilizing in-situ synthesized graphene nanoplatelets (GNPs) and MgO nanoparticles (MgO_np). The in-situ reaction of GNPs and MgOnp (GNPs&MgO_np) conducted at a high temperature (720 °C) demonstrates an improvement in the local agglomeration of SiCp compared to the conventional semi-solid temperature (590 °C). Moreover, the GNPs&MgO_np optimized interfacial structure and transferred the load during plastic deformation, inhibiting stress concentration and crack propagation at the interface of SiCp. The ductility and modulus are enhanced by approximately 70 % and 10 % compared to SiCp/Mg-6Zn composites, demonstrating the effectiveness of the strategy employing micro-nano hybrid reinforcement and synergistic enhancement of ductility and modulus.

This paper develops an accurate experimental framework to measure interlaminar strains on laminate free edges. Digital Image Correlation (DIC) is used with an ultra-fine speckle pattern and macro lens to resolve strain fields with a resolution of ∼ 15 µm, allowing for through-thickness deformation and strain mapping. Data analysis techniques are developed to denoise the strain field and discount the effect of random local fibre distribution.

The major application of the framework is to validate numerical predictions, and it is demonstrated on angle-ply laminates over a range of ply orientations. A micropolar-based finite-element approach was compared to both a classical finite-element approach and the DIC-acquired interlaminar strain fields. Key improvements by the results include significantly overcoming the stark inconsistency of classical normal strains, and reducing the discrepancies of shear strains from 30 % to 3 ∼ 10 %. The outcomes can be extended to destructive failure analysis and the free-edge study of various other composite architectures.

Metal-organic framework-based carbon–carbon composite represent a novel class of microwave-absorbing materials (MAMs). However, obtaining lightweight and highly efficient absorbers with a lower filling ratio and larger effective absorption bandwidth (EAB) poses a challenge. In this study, we developed a controllable preparation method for ZIF-67 template polyacrylonitrile-wrapped nanocomposite (ZIF-67@PAN) precursor. This was achieved through radical polymerization of acrylonitrile (AN) initiated by azobisisobutyronitrile (AIBN). Subsequent annealing at high temperatures produced a lightweight nitrogen and oxygen-doped graphite layer-wrapped Co@C smart material (Co@C₁, Co@C₂, and Co@C₃) with tunable microwave absorption properties (MAP). The results demonstrate that Co@C₂ achieved a minimum reflection loss (RL_min) value of −50.20 dB at a thickness of 2.0 mm with an EAB of 6.1 only at a filler content of only 13 %. Therefore, this work offers a controllable preparation method and introduces a simple and facile approach for creating efficient, lightweight micro and nano-sized microwave-absorbing materials.

Carbon phenolic composites are used as thermal protection systems (TPS) materials on space capsules to protect them from the hot aerothermal environment. The phenolic resin in the composite material decomposes (pyrolyzes) at low temperatures resulting in a pyrolysis front within the material. The detection of the pyrolysis front after exposure to heat has historically been achieved by physically sectioning cross-sections of the material. We combine the phase contrast retrieval method to reconstruct x-ray computed tomography scans along with image convolution to identify the pyrolysis front in carbon phenolic composites. Unlike the standard filtered back projection method that captures only the carbon phase, the phase contrast retrieval method uses both the attenuation coefficients and refractive indices to illuminate all three phases (carbon, resin, and voids) of carbon phenolic composites. Image convolution is applied on scans reconstructed using the phase contrast retrieval method to develop a density map of the composite to locate the pyrolysis front. The analysis is performed on a sample of phenolic impregnated carbon ablator that was tested in an arc-jet facility. For the sample analyzed, the depth of the pyrolysis front from the surface of the sample is calculated to be 2.150 ± 0.148 mm. Although the proposed approach is applied to detect the pyrolysis front, the tools can be used to illuminate the structure of any carbon phenolic composite, and we propose the use of the phase contrast retrieval method as a methodological standard to analyze carbon phenolic composites used on space capsules.

Novel composite filaments are developed by mixing PLA, TPU, and Nd-Fe-B components and utilizing melt extrusion for 4D printing. The results reveal that the Nd-Fe-B magnetic particles are uniformly dispersed in the PLA/TPU polymer matrix, and the composite filaments meet the requirements of high-precision printing. Increasing the proportion of Nd-Fe-B magnetic particles in the composite contributes to higher remanence, coercivity, and magnetic energy product for the printed magnets. Under the 70 °C thermal stimulus, it has a high shape fixed ratio (>99 %), a high shape recovery ratio (>90 %), and a rapid response time (≤6.55 s). The magnetic particles accelerate the shape recovery process. Moreover, the petal-like structure and the hollow ball structure are designed and printed. After deformation, each structure can nearly fully recover its initial shape. This recovery is achieved through a non-contact stimulus response based on ’thermal-magnetic’ coupling. The grippers printed by the developed composite show comprehensive properties of shape memory and magnetically controlled smart gripping.