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For the better operation of future electronic devices in complex situations, higher requirements of mechanical performance, especially bearing capacity, were put forward to functional composites. Therefore, the mechanical performance enhancement of functional composites had important practical application value. In this work, we reported a short carbon fiber-graphene nanoplatelets-polydimethylsiloxane (SGP)/epoxy acrylic resin (EA resin) composites with integrated thermal conductivity, electromagnetic interference (EMI) shielding, and mechanical performances using a combination method of 3D printing and vacuum impregnation. In the SGP/EA resin composite, EA resin skeleton with different cell shapes was responsible for the bearing capacity of composite samples, while the thermal conductivity and EMI shielding performance were provided by the SGP compound. When the cell shape of skeleton was circular and the filling contents in SGP compound was 15 wt% SCF and 6 wt% GNP, the SGP/EA resin composite presented best combination properties of 323.5 kPa compressive modulus, 2.13 W/(m·K) thermal conductivity, and 45.93 dB EMI shielding performance at 12.4 GHz. This work provided a facile, low-cost, and scalable method to fabricate composite samples with integrated thermal conductivity, EMI shielding, and mechanical performances. These multifunctional composites are highly promising for applications concerning heat dissipation, EMI shielding, and load-bearing devices. [Display omitted] [ABSTRACT FROM AUTHOR]

With the continuous development of modern electronic equipment, thermal management of electronic devices has become the focus of attention due to the energy consumption. As an important part of thermal management system, it is necessary to develop an electrical equipment shell with both superior thermal conductivity and mechanical properties for better thermal management performance. However, it is very difficult to balance the relationship between thermal conductivity and mechanical properties of thermal conductive polymer composites. Increasing filling content of thermal conductive fillers would lead to heavy damage of mechanical properties. In this paper, we construct a bi-continuous structure to solve this problem. The ABS phase provides thermal conductivity enhancement, while the PC phase is responsible for mechanical property maintaining. A highest thermal conductivity of 0.476 W/(m⋅K), 138% higher than that of pure PC, can be obtained after optimum design of formulation and processing conditions. Meanwhile, the mechanical properties of PC/ABS composite are also enhanced comparing with filled-PC. Moreover, the reported PC/ABS composite has excellent electrical insulation and dielectric properties. Overall, our PC/ABS composites with simultaneous enhanced thermal conductivity and mechanical properties are of great prospect as electrical equipment shells for efficient thermal dissipation. [Display omitted] • A bi-continuous structure was built to balance the thermal conductivity and mechanical properties of polymer composites. • A highest thermal conductivity of 0.476 W/(m⋅K) and 48.10 MPa bending strength for PC/ABS composite were obtained. • The reported PC/ABS composite was of great prospect as electrical equipment shells for efficient thermal dissipation. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing, as a layer-to-layer additive manufacturing technology, has received widespread attention for excellent designability. However, as for direct ink writing (DIW), current printing level is difficult to achieve high-precision printing of thermoset composites of different compositions. Therefore, fully 3D printing based on thermoset composites with high designability is proposed. The intralayer and interlayer of structure and materials prepared by this method are designable, and layer thicknesses as well as inter-layer patterns are adjustable. In this work, alumina (Al 2 O 3) and short carbon fiber (SCF) are used as thermally conductive fillers, polydimethylsiloxane (PDMS) is conducted as thermoset matrix. Benefit from the high designability of our method, a series of Al 2 O 3 /SCF/Al 2 O 3 (ASA) and SCF/Al 2 O 3 /SCF (SAS) composite samples with sandwich structures are fabricated and compared. The different materials and structural designs of these composite samples give them completely different properties in terms of thermal, electromagnetic shielding, and mechanical properties, making it possible to create customized designs for different scenarios. Taking thermal management materials (TMMs) as an example, we use this method to prepare ASA and SAS composites with sandwich structure, thermal conductivity of A 40 S 30 A 40 and S 30 A 40 S 30 reached 1.00 W/(m·K) and 1.55 W/(m·K) respectively. In all, customized and multifunctional applications make PDMS composites have a widespread prospect. [Display omitted] [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing is a layered additive manufacturing technology. In common 3D printing methods, direct ink writing (DIW) and fused deposition modeling (FDM) are new extrusion-based technologies. FDM works by melting a hot-melt material and squeezing it out through a tiny nozzle. Conversely, DIW, accurately deposit accurate amount of paste at different distances through the conveying system (extruder). As a unique approach, this technology introduces design freedom, versatility and stability into the printing structure at the same time. In addition, DIW technology is suitable for thermoset 3D printing. The influences of filler orientation in polymer matrix and printing paths on the thermal conductivity (λ) of thermoset 3D printing products are worth studying. Therefore, we built a thermoset 3D printer, and optimized the structure of the nozzle device, effectively improved the printing accuracy. Polydimethylsiloxane (PDMS) and hexagonal boron nitride (h BN) are selected as polymer matrix and thermally conductive filler, respectively. Compared with pure PDMS, the λ value of h BN/PDMS composites increases obviously with increasing h BN content. Meanwhile, the mechanical properties of composites with different printing paths are systematically studied. This designable orientation provides opportunities and challenges for other functional structure design such as hollow structure. [Display omitted] [ABSTRACT FROM AUTHOR]

• The validity of the PDE module-based method for simulating the heat transfer in the riparian zone was verified. • The optimal thermal conductivity empirical model for the flow-heat coupling model of the riparian zone was confirmed. • Sensitivity analysis was used to determine the main factors influencing the riparian temperature and hyporheic exchange rate. Recently, the use of heat as a tracer to evaluate the process of hyporheic exchange in riparian zones has attracted wide attention. A more accurate flow-heat coupling model of riparian zones could help us understand the patterns of water flow and heat transfer in riparian zones and provide a scientific basis for the comprehensive management and efficient utilization of these zones. In this paper, a flow-heat coupling model of a riparian zone based on thermal conductivity empirical models (TCEMs) was built by customizing partial differential equations (PDEs) based on the simulation of soil water flow using porous media and the subsurface flow module in COMSOL. Combined with the data collected from the field heat tracer test in the riparian zone, the flow-heat coupling model of the riparian zone under 12 types of TCEMs was validated and compared. The results show that the use of the PDE module instead of the heat transfer in porous media (HTPM) module is very effective for modeling; the PDE module could basically replace the HTPM module in the heat transfer calculation. The performance of the flow-heat coupling model varies under different types of TCEMs, and the Chung and Horton (1987) model shows better simulation effects, with a root mean square error (RMSE), coefficient of determination (R2), mean absolute error (MAE), and mean relative error (MRE) ranging from 1.37 to 2.48 ℃, 0.73–0.94, 1.06–2.08 ℃, and 11.94–15.79%, respectively. Therefore, this model could better reflect the dynamic temperature variations in the riparian zone. The sensitivity analysis results illustrate that the hydraulic conductivity (K s), van Genuchten parameter (β), volumetric heat capacity of dry solids (C s), and porosity (n) of the flow-heat coupling model greatly influence riparian zone temperature variations, and the parameters β , K s , and residual water content (θ r) significantly affect the lateral hyporheic exchange rate in the riparian zone, of which β has the largest effect. [ABSTRACT FROM AUTHOR]