Composites Communications最新文献

3D printing via material extrusion is capable of using polymeric materials for a large range of applications. They are generally used, however, for prototyping as opposed to creating functional parts due to their lower mechanical properties in comparison to other materials, such as metals or epoxies, and processing methods, such as compression molding or injection molding. Carbon fiber, glass fiber, and kevlar have been used as reinforcement materials with very positive results in terms of creating functional parts. However, little focus has been placed on metallic wire reinforcement. In this investigation, a novel strategy to manufacture continuous metallic wire-reinforced polymer–matrix composites with increased mechanical properties by material extrusion is presented. A customized multimaterial 3D printer was built and used to fabricate coupons of unidirectionally reinforced Al wire/PLA matrix composites with either 15% or 25% wire volume fraction. The microstructure of the composites was analyzed to understand the formation of porosity during processing. These results also showed the potential of the manufacturing technique to precisely control the wire location and orientation. Incorporation of a volume fraction 25% of Al wires led to a 600% increase in elastic modulus and a 63% increase in tensile strength compared to pure PLA. These results indicate an efficient load transfer between the polymer matrix and the incorporated wires, despite exhibiting a relatively low interface strength. Overall, the novel strategy opens the possibility to manufacture high volume fraction composite laminates of thermoplastic polymers reinforced with metallic wires by material extrusion.

The layered structure of two-dimensional transition metal carbides/nitrides (MXenes) is potentially conducive to efficient electromagnetic wave absorption (EWA). However, Ti₃C₂T_x MXene typically encounters challenges with a narrow effective absorption bandwidth (EAB) due to impedance mismatch caused by its inherent high conductivity. This study employed γ-radiation to induce the in-situ formation of TiC/MXene nanocomposites for EWA. The radiation preparation process is carried out under reducing conditions at ambient temperature and pressure, effectively minimizing the risk of MXene oxidation while preserving its original layered structure. The resultant intercalated structure, featuring in-situ formed TiC nanoparticles embedded within the Ti₃C₂T_x MXene layers, facilitates the integration of layered conductive networks with abundant spatial gaps and multiple heterojunction interfaces. Leveraging these structural and chemical advantages, the composite demonstrates enhanced EWA capabilities. At a 50 wt% irradiated MXene loading, the material achieves an EAB of 6.08 GHz at 1.55 mm thickness and a minimum reflection loss (RL_min) of −51.1 dB at 3.95 mm. Compared to conventional composite fabrication methods, γ-radiation offers a more environmentally sustainable, efficient, and scalable approach. This research opens up a new avenue for exploiting the MXene family in EWA applications.

Conventional graphite flakes (GFs)/Cu composites suffer from severe anisotropy in terms of their thermal conductivity (TC) and coefficient of thermal expansion (CTE) between the in-plane and through-plane directions, which as thermal management materials (TMMs) play crucial roles in the overall heat dissipation performance of electronic components. To address this issue, a radial structural design for the reinforcement phase of GFs was developed. In this study, conventional stacked structured GFs/Cu composites and newly designed radial structured GFs/Cu composites were prepared by electroless plating of Cu on the surface of GFs followed by fast hot-pressing technology. The GFs content was varied from 30 to 70 vol%. The spatial orientation of the GFs was determined via X-ray computed tomography. For the radial structured GFs/Cu composites, the CTE were 11.52 and 14.42 ppm K⁻¹ in the in-plane direction through-plane direction when the GFs content was 50 vol%, and the TC reached maximum values of 681 and 590 W m⁻¹ K⁻¹ in the in-plane direction and through-plane direction when the GFs content was 50 vol%. The TC in the through-plane direction was nine times greater than that of the stacked structured GFs/Cu composites (65 W m⁻¹ K⁻¹) at the same GFs content, demonstrating overall isotropy. Although radial structured GFs/Cu composites have more defects that can affect their thermal properties due to process factors, they have better heat dissipation abilities in practical applications; this indicates their great potential as a new generation of TMMs.

Compared to the isotropic dielectric elastomer (DE), uniaxial fiber reinforced DEs have larger deformation capabilities in specific directions, showing great application prospects. However, there are still significant challenges in achieving self-sensing without introducing additional sensing components. Inspired by the control method of biological muscles, in this article, we used carbon nanotube (CNT) fibers as reinforcing fibers that resistance changes are highly sensitive to tensile strain and exhibit a linear relationship within a small strain range. Based on the developed uniaxial reinforced strain behavior model of DEs, a shear lag model was adopted to introduce an interface transition layer between the DEs and CNT fiber to consider the strain difference caused by the difference in elastic modulus. The relationship between CNT fiber strain and DE strain was established, and the influence of CNT fiber mechanical properties on self-sensing performance was explored. The verification results under 0.05 Hz, 20 kV/mm signals show that the model has 4 % error, providing new ideas for the self-sensing function of uniaxial fiber reinforced DEs.

Thermally conductive composites rely on efficient heat transfer networks. Here, we employ polyethyleneimine to modify 1D boron nitride nanotubes (BNNTs) and 2D boron nitride nanosheets (BNNSs) to improve their dispersion while enhancing the interfacial interaction between them and the matrix through amide bonds, hydrogen bonds, and Lewis acid-base interactions, thereby reducing interfacial thermal resistance. Moreover, the introduction of 1D BNNTs bridges 2D BNNSs, boosting the thermal conductivity network. This resulted in an enhanced thermal conductivity of the composite film by 17.8 %, reaching 28.71 W/(m·K) at a 30 wt% filler content. Coupled with satisfactory mechanical strength and thermal stability, this heat dissipation capability is highly valuable for applications.

The cutting properties of the particles of aluminum-based silicon carbide (SiCp/Al) and the base material are so disparate that it is challenging to ensure the surface quality of machining. The cutting force significantly influences the quality of the machined surface. Therefore, real-time cutting force prediction is paramount for ensuring the workpiece's desired surface quality. This paper presents a 3D ultrasonic milling force model, established from four aspects: cutting formation force, extrusion friction force, SiC particle crushing force, and ultrasonic impact force. The model is based on the ultrasonic action of the cutting process and the unique removal characteristics of the material. A 3D ultrasonic milling system was constructed to experimentally verify the milling force model. The effects of each parameter on the milling force were analyzed through orthogonal experiments, which resulted in the effects of depth of cut, rotational speed, volume fraction, ultrasonic amplitude, and feed rate. The ultrasonic amplitude, feed rate, and other factors were found to influence the milling force to varying degrees. The milling force was observed to be 42.47 %, 22.37 %, 10.85 %, 12.67 %, and 11.64 % affected by the factors mentioned above, respectively. The single-factor experiment was conducted to analyze the cutting force at different machining parameters. The experimental results and the MATLAB numerical simulation results exhibited a similar trend of change. The maximum absolute error between the two was 12.71 %, with an average absolute error of 3.735 %.

In this paper, a systematic evaluation of the freeze-thaw (F-T) resistance of concrete containing waste rubber (WR) and/or waste glass (WG) was performed. Fine aggregates were replaced separately with crumb rubber (CR), glass powder (GP) and a mixture of both, and substitution rates varied from 0 to 15 % by volume. All mixtures were subjected to 25, 50, 75 and 100 F-T cycles, respectively. After reaching the desired number of F-T cycles, changes in the appearance, mass, dynamic modulus, degree of internal damage, and compressive strength of the degraded mixtures relative to the pre-freeze-thaw (Pre-F-T) condition were observed or measured. Results indicated that compared with plain concrete, rubberized concrete had superior F-T resistance but lower Pre-F-T strength. Although glass concrete may be less impressive than rubberized concrete in F-T resistance, it offered better mechanical strength and a denser microstructure. However, the incorporation of GP failed to mitigate the apparent damage and mass loss of concrete in F-T environments. Besides, the long-term F-T durability of glass concrete may be questioned, as evidenced by a sharp deterioration in nearly all of its parameters during 75–100 F-T cycles. For the combined mixtures, 15 % CR and 10 % GP have been proved to be a reasonable combination for maximizing the F-T resistance of concrete. Finally, scanning electron microscopy (SEM) was employed to reveal the mechanisms of CR and GP action in F-T environments at the microscopic level. In summary, CR and GP are materials worth considering in concrete preparation to improve its F-T resistance.

By combining the Re-entrant (RE) cell with the hexagonal (HE) cell, this study proposes a novel three-dimensional honeycomb called Re-entrant-hexagonal-coupling (RHC) honeycomb to improve the strength of a single structure. The deformation modes and the strength of the honeycomb are comprehensively investigated through experimental and numerical methods. Results indicate that the deformation of the RHC honeycomb exhibits a clear coupling effect due to the opposite deformation of the RE and HE honeycombs, resulting in a quasi-zero Poisson's ratio mode and a significant strength enhancement. The coupling-induced enhancement (CIE) of the RHC honeycomb remains consistently higher than 0.585, demonstrating clear superiority over the other two comparative honeycombs. Besides, adjusting the thickness ratio can effectively balance the coupling effect and auxetic effect, thereby enhancing the specific energy absorption at a given relative density. This study offers valuable guidance for the design and research of such coupling auxetic honeycomb structures, warranting further attention.

Flexible piezoelectric nanogenerators (PENGs), as a promising sustainable power source in smart electronics, have attracted much attention for their potential applications in the Internet of Things. In this paper, poly(vinylidene fluoride) (PVDF) fibers with core-sheath hollow porous structure were prepared by coaxial wet spinning process, serving as the dielectric layer, which were perfused internally by liquid metal (LM) as the inner electrode layer and wrapped outside by copper-silver nanoparticles (Cu@AgNP) as the outer electrode layer, thus constructing high-performance PVDF/LM/Cu@AgNP composite fibers. The composite PVDF fibers have a layered pore structure and arbitrarily deformable LM electrodes, which can significantly reduce the effective electric constant and thus enhance the piezoelectric properties. The results reveal that PVDF/LM/Cu@AgNP-PENG yields an optimal voltage output of 410 mV, providing a clear advantage over PENG by using alternative fibers. Moreover, the PVDF/LM/Cu@AgNP-PENG shows an excellent charging capability for energy storage devices, being able to charge 1 μF capacitors to 10 V within 30 s and directly power commercial LEDs. This study demonstrates the significant potential for utilizing composite PVDF piezoelectric fibers in flexible wearable electronic devices.

In this study, the issue of random fiber strength resulting from initial fiber defects and matrix pore defects in the strength response of C/C composite materials is addressed. A method for generating random numbers following the Weibull distribution is proposed and an improved random sequence adsorption (RSA) algorithm is employed to describe pore defects in the matrix, ultimately leading to the development of a representative volume element (RVE) model for C/C composite materials. The influence of fiber strength distribution and pore defects on the mechanical properties of unidirectional C/C (UD-C/C) composite materials is analyzed. This study offers a new approach to investigate the mechanical behavior of C/C composite materials, taking into account both fiber initial defects and pore defects.