Search Results (86)

To address the challenges of concrete construction in polar regions, this study investigates the feasibility of fabricating cement-based materials under severely low temperatures using electric-induced heating curing methods. Cement mortars incorporating fly ash (FA-CM), ground granulated blast furnace slag (GGBS-CM), and metakaolin (MK-CM) were cured at environmental temperatures of −20 °C, −40 °C, and −60 °C. The optimal carbon fiber (CF) contents were determined using the initial electric resistivity to ensure a consistent electric-induced heating curing process. The thermal profiles during curing were monitored, and mechanical strength development was systematically evaluated. Hydration characteristics were elucidated through thermogravimetric analysis (TG), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) to identify phase compositions and reaction products. Results demonstrate that electric-induced heating effectively mitigates the adverse effect caused by the ultra-low temperature constraints, with distinct differences in the strength performance and hydration kinetics among supplementary cementitious materials. MK-CM exhibited superior early strength development with strength increasing rates above 10% compared to the Ref. specimen, which was attributed to the accelerated pozzolanic reactions. Microstructural analyses further verified the macroscopic strength test results that showed that electric-induced heating curing can effectively promote the performance development even under severely cold environments with a higher hydration degree and refined micro-pore structure. This work proposes a viable strategy for polar construction applications. Full article

Hybrid fiber-reinforced polymer-laminated composites are often used under icy conditions (such as for reinforcing parts in aircraft frames and bridge beams), where there is an urgent demand for deicing. In this paper, besides the different mechanical properties of laminates along the longitudinal carbon fiber (CF) and glass fiber (GF) directions, the anisotropic electrothermal behavior of a hybrid glass/carbon fiber-reinforced epoxy (GCF/EP) is also investigated, as well as its deicing performance and self-repairing capability. The surface equilibrium temperature of GCF/EP composites can conveniently be adjusted by tuning the current magnitude and its flow direction. Compared to the longitudinal CF direction of the GCF/EP, where 0.3 A was loaded to achieve a surface equilibrium temperature of 122.8 °C, a much weaker current (0.03 A) was needed to load along the longitudinal GF direction to reach almost the same temperature. However, besides the higher flexural strength and fast temperature response, along the longitudinal CF direction, the GCF/EP exhibited excellent deicing performance, including a shorter time and larger energy efficiency. Furthermore, the self-repairing ability of the GCF/EP and its effect on the deicing performance of the composite were characterized. Studying the Joule heating effect of GCF/EP composite laminates and their corresponding deicing performance lays the foundation for their design and practical application in icy environments. Full article

With the growing integration of electronic systems into modern infrastructure, the need for effective electromagnetic interference (EMI) shielding materials has intensified. This study explores the development of electroless Ni-plated fiber composites and systematically investigates the effects of post-heat treatment on their electrical, structural, and interfacial performance. Both carbon fibers (CFs) and glass fibers (GFs) were employed as reinforcing substrates, chosen for their distinct mechanical and thermal characteristics. Ni plating enhanced the electrical conductivity of both fibers, and heat treatment facilitated phase transformations from amorphous to crystalline Ni₃P and Ni₂P, leading to improved EMI shielding effectiveness (EMI-SE). NGF-based composites achieved up to a 169% increase in conductivity and a 116% enhancement in EMI-SE after treatment at 400 °C, while NCF-based composites treated at 800 °C attained superior conductivity and shielding performance. However, thermal degradation and reduced interfacial shear strength (IFSS) were observed, particularly in GF-based systems. The findings highlight the importance of material-specific thermal processing to balance functional performance and structural reliability. This study provides critical insights for designing fiber-reinforced composites with optimized EMI shielding properties for application-driven use in next-generation construction materials and intelligent infrastructure. Full article

Additive manufacturing (AM) is one of the most frequently used technologies to produce complex configuration products. Moreover, AM is very well known as a technology which is characterized by a low amount of generated waste and the potential to be called zero-waste technology. As is known, there are seven main groups of technologies described in the ISO/ASTM 52900 standard that allow the use of very different materials from polymers to metals, ceramics, and composites. However, the increased utilization of additively manufactured composites for different applications requires a deeper analysis of production processes and materials’ characteristics. Various AM technologies can be used to produce complex composite structures reinforced with short fibers; however, only material extrusion (MEX)-based technology is used for the production of composites reinforced with continuous fibers (CFs). At this time, five different methods exist to produce CF-reinforced composite structures. This study focuses on co-extrusion with the towpreg method. Because of the complexity and layer-by-layer nature of the process, defects can occur during production, such as poor interlayer adhesion, increased porosity, insufficient impregnation, and others. To eliminate or minimize defects’ influence on mechanical properties and structural integrity of additively manufactured structures, a hypothesis was proposed involving heat treatment. Carbon fiber’s conductive properties can be used to heal the composite structures, by heating them up through the application of electric current. In this research article, an experimental evaluation of conditions for additively manufactured composites with continuous carbon fiber reinforcement for self-healing processes is presented. Mechanical testing was conducted to check the influence of heat treatment on the flexural properties of the composite samples. Full article

Rubber is widely applied in the field of electrical engineering due to its high elasticity. However, its poor thermal conductivity can cause localized overheating and eventual failure. This issue can be addressed through adding fillers with high thermal conductivity. In this study, natural rubber is selected as the matrix, while braided carbon fiber (B-CF), known for its excellent thermal conductivity, serves as the reinforcing phase. This research defines cubic Bessel curves, establishes a curvilinear coordinate system, and examines the orthogonal anisotropic thermal conductivity of B-CF bundles. It has been verified that eight cycles of fiber accurately represent the finite element simulation model. Based on this, the impact of the cross-sectional shape and area of the fiber bundle on heat dissipation was studied. The results show that the cross-sectional shape has minimal impact on heat dissipation, with temperature differences between the heat source center and the end of the cross-section line remaining within 1 °C. In contrast, the cross-sectional area significantly affects the reduction of the temperature, achieving reductions of up to 32.6% at the heat source center and 40.4% at the opposite side, respectively. This study provides valuable guidance for improving the thermal performance of braided fiber-reinforced rubber products. Full article

This study aims to develop an electrically heated sidewalk system to efficiently clear ice and snow from pedestrian walkways, ensuring safety and minimizing environmental impact during winter. While extensive research has been conducted on heated pavement and slab systems for vehicles and aircraft, there is a notable gap in studies focusing on heated sidewalk systems for pedestrians, which are unique due to their disjointed configurations. Concrete mixtures containing 2.2% carbon fibers (CFs) and 0.5% carbon nanotubes (CNTs) by cement weight were used to cast the electrically heated concrete side blocks. No. 3 structural rebars served as electrodes to physically connect the side blocks and distribute electrical power to them. A laboratory-scale prototype, consisting of a 5 × 5 block array (750 mm × 750 mm), was constructed to evaluate heating performance. The surface and internal temperatures were measured using an infrared camera and thermocouples, respectively, while consistently powering the prototype with a power supply. The blocks were connected in a parallel electrical configuration to operate the system at low voltage levels. The results indicated a surface temperature increase of 16–20 °C over two hours with a power density ranging from 620 to 830 W/m², which was sufficient for deicing pedestrian walkways. Full article

This study investigated silicone composites with distributed boron nitride platelets and carbon microfibers that are oriented electrically. The process involved homogenizing and dispersing nano/microparticles in the liquid polymer, aligning the particles with DC and AC electric fields, and curing the composite with IR radiation to trap particles within chains. This innovative concept utilized two fields to align particles, improving the even distribution of carbon microfibers among BN in the chains. Based on SEM images, the chains are uniformly distributed on the surface of the sample, fully formed and mature, but their architecture critically depends on composition. The physical and electrical characteristics of composites were extensively studied with regard to the composition and orientation of particles. The higher the concentration of BN platelets, the greater the enhancement of dielectric permittivity, but the effect decreases gradually after reaching a concentration of 15%. The impact of incorporating carbon microfibers into the dielectric permittivity of composites is clearly beneficial, especially when the BN content surpasses 12%. Thermal conductivity showed a significant improvement in all samples with aligned particles, regardless of their composition. For homogeneous materials, the thermal conductivity is significantly enhanced by the inclusion of carbon microfibers, particularly when the boron nitride content exceeds 12%. The biggest increase happened when carbon microfibers were added at a rate of 2%, while the BN content surpassed 15.5%. The thermal conductivity of composites is greatly improved by adding carbon microfibers when oriented particles are present, even at BN content over 12%. When the BN content surpasses 15.5%, the effect diminishes as the fibers within chains are only partly vertically oriented, with BN platelets prioritizing vertical alignment. The outcomes of this study showed improved results for composites with BN platelets and carbon microfibers compared to prior findings in the literature, all while utilizing a more straightforward approach for processing the polymer matrix and aligning particles. In contrast to current technologies, utilizing homologous materials with uniformly dispersed particles, the presented technology reduces ingredient consumption by 5–10 times due to the arrangement in chains, which enhances heat transfer efficiency in the desired direction. The present technology can be used in a variety of industrial settings, accommodating different ingredients and film thicknesses, and can be customized for various applications in electronics thermal management. Full article

In the past decade, 4D printing has received attention in the aerospace, automotive, robotics, and biomedical fields due to its lightweight structure and high productivity. Combining stimulus-responsive materials with 3D printing technology, which enables controllable changes in shape and mechanical properties, is a new technology for building smart bearing structures. A multilayer smart truss structural component with self-sensing function is designed, and an internal stress calibration strategy is established to better adapt to asymmetric loads. A material system consisting of continuous carbon fibers and polylactic acid was constructed, and an isosceles trapezoidal structure was chosen as the basic configuration of the smart component. The self-inductive properties are described by analyzing the relationship between the pressure applied to the specimen and the change in the specimen’s own resistance. Load-carrying capacity is realized by electrically heating the continuous carbon fibers in the component. Thermal deformation calibrates internal stress and enhances the load-carrying ability of the component over 50%. The experimental results demonstrate that the truss structure designed in this paper has strong self-induction, self-driving ability, and asymmetric load adaptation ability at the same time. This verifies that the 4D-printed smart component can be used as a load-carrying element, which broadens the application scope of smart components. Full article

The development of electric resistance is a key factor affecting the performance of conductive concrete, especially the electrical–thermal performance. In this work, the effects of different influencing factors (including the water-to-binder ratio, coarse aggregate content and carbon fiber (CF) content) on the electric resistance of conductive concrete were systematically investigated. At the same time, ohmic heating (OH) curing was applied to fabricate CF-reinforced conductive concrete (CFRCC) under a negative temperature environment at −20 °C. The effects of different factors on the electrothermal properties (curing temperature and conductive stability) of the samples were studied. The mechanical strengths of the CFRCC cured by different curing conditions were also tested, and the feasibility of OH curing for preparing CFRCC in a negative-temperature environment was verified at various electric powers. This work aims to give new insights into the effects of multiple factors on the performance of CFRCC for improved concrete construction in winter. Full article

In response to the growing demand for lightweight yet robust materials in electric vehicle (EV) battery casings, this study introduces an advanced carbon fiber-reinforced composite (CFRC). This novel material is engineered to address critical aspects of EV battery casing requirements, including mechanical strength, electromagnetic interference (EMI) shielding, and thermal management. The research strategically combines carbon composite components with copper-plated polyester non-woven fabric (CFRC/Cu) and melamine foam board (CFRC/Me) into a sandwich-structure composite plus a series of composites with graphite particle-integrated matrix resin (CFRC+Gr). Dynamic mechanical analysis (DMA) revealed that the inclusion of copper-plated fabric significantly enhanced the stiffness, and the specific tensile strength of the new composites reached 346.8 MPa/(g/cm³), which was higher than that of other metal materials used for EV battery casings. The new developed composites had excellent EMI shielding properties, with the highest shielding effectives of 88.27 dB from 30 MHz to 3 GHz. Furthermore, after integrating the graphite particles, the peak temperature of all composites via Joule heating was increased. The CFRC+Gr/Me reached 68.3 °C under a 5 V DC power supply after 180 s. This research presents a comprehensive and innovative approach that adeptly balances mechanical, electromagnetic, and thermal requirements for EV battery casings. Full article

Diglycidylether of vanillyl alcohol (DGEVA), in combination with mechanically recycled carbon fibers (RCFs), was used to make, via Radical-Induced Cationic Frontal Photopolymerization (RICFP), fully sustainable and bio-based conductive composites with good electrical conductivity and consequent Joule effect proprieties. Three different fiber lengths, using three different sieve sizes during the mechanical recycling process (0.2, 0.5, and 2.0 mm), were used in five different amounts (ranging from 1 to 25 phr). The samples were first characterized by dynamic mechanical thermal analysis (DMTA), followed byelectrical conductivity and Joule heating tests. More specifically, the mechanical properties of the composites increased when increasing fiber content. Furthermore, the composites obtained with the longest fibers showed the highest electrical conductivity, reaching a maximum of 11 S/m, due to their higher aspect ratio. In this context, the temperature reached by Joule effect was directly related to the electrical conductivity, and was able to reach an average and maximum temperatures of 80 °C and 120 °C, respectively, just by applying 6 V. Full article

This study examined spatial and temporal thermal performance and energy consumption. The temperature distribution in the running period was monitored in test rooms with integrated electric- and hot water-heated floors. The short- and long-term energy consumption of the two heating systems were recorded and compared. The results indicated that the integrated electric heating system generated higher temperatures for indoor air and on the exterior surface of the wooden floor than the hot water heating system; meanwhile, the difference in the mean temperatures of the exterior and rear surfaces of the electric-heated floor was 2.44 °C, while that of the hot water-heated test room was 13.25 °C. The efficient structure of the integrated electric heating system saved 22.97% energy compared to the hot water system after short-term (7 h) charging and reaching a dynamic balance, and it efficiently increased the energy utilization rate to 11.81%. After long-term charging, the daily energy consumption of the integrated electric heating system consumed much less energy than the hot water system every month. The integrated electric heating system saved 62.55% and 34.30% of energy in May and January, respectively, and consumed less than half of the energy the hot water system consumed in the less cold months. Therefore, a high-efficiency and energy-saving integrated electric-heated floor could be a potential indoor heating solution. Full article

This paper aims to improve the deicing performance and energy utilization of bridge pylon crossbeams with built-in carbon fiber electric heating (BPB–CFEH). Therefore, a three-dimensional thermal transfer model of BPB–CFEH with one arrangement is established. Two ice-melting regions and two ice-melting stages were set up according to the characteristics of the icing of the crossbeam. The effects of wind speed and ambient temperature on the paving power required to reach the complete melting of the icicles within 8 h were analyzed. The effects of the laying spacing and rated voltage of the carbon fiber heating cable on the melting ice sheet and the thermal exchange of the two regions of the icicle after heating for 8 h were compared. Additionally, its effect on energy utilization of the process from the ice sheet melting stage to the ice column melting stage was analyzed. Ice-melting experiments verified the applicability and reasonableness of the simulated ice-melting calculation formula. The results show that under ambient temperature of −10 °C and wind speed of 4.5–13.5 m/s, the proposed paving power is 817.5–2248.12 W/m². Increasing the rated voltage and shortening the spacing increases the thermal exchange capacity of the two melting regions. The shortening of the spacing improves the energy utilization rate of the melting stage of the ice sheet to the melting stage of the icicle processes. The difference between the melting time obtained from the formula proposed by numerical simulation and the melting time obtained from indoor tests is about 10 min. This study provides a design basis for the electrothermal ice melting of bridge pylon crossbeams. Full article

The escalating thermal power density in electronic devices necessitates advanced thermal management technologies. Polymer-based materials, prized for their electrical insulation, flexibility, light weight, and strength, are extensively used in this field. However, the inherent low thermal conductivity of polymers requires enhancement for effective heat dissipation. This work proposes a novel paradigm, emphasizing ordered structures with functional units, to create triple-level, ordered, low-filler loading of multi-walled carbon nanotube (MWCNT)/poly(vinyl alcohol)(PVA) nanofibrous films. By addressing interfacial thermal resistance through –OH groups, the coupling between polymer and MWCNT is strengthened. The triple-level ordered structure comprises aligned PVA chains, aligned MWCNTs, and aligned MWCNT/PVA composite fibers. Focusing on the filler’s impact on thermal conductivity and chain orientation, the thermal transport mechanisms have been elucidated level by level. Our MWCNT/PVA composite, with lower filler loadings (10 wt.%), achieves a remarkable TC exceeding 35.4 W/(m·K), surpassing other PVA composites with filler loading below 50 wt.%. Full article

Copper-based materials have long been used for their outstanding thermal and electrical conductivities in various applications, such as heat exchangers, induction heat coils, cooling channels, radiators, and electronic connectors. The development of advanced copper alloys has broadened their utilization to include structural applications in harsh service conditions found in industries like oil and gas, marine, power plants, and water treatment, where good corrosion resistance and a combination of high strength, wear, and fatigue tolerance are critical. These advanced multi-component structures often have complex designs and intricate geometries, requiring extensive metallurgical processing routes and the joining of the individual components into a final structure. Additive manufacturing (AM) has revolutionized the way complex structures are designed and manufactured. It has reduced the processing steps, assemblies, and tooling while also eliminating the need for joining processes. However, the high thermal conductivity of copper and its high reflectivity to near-infrared radiation present challenges in the production of copper alloys using fusion-based AM processes, especially with Yb-fiber laser-based techniques. To overcome these difficulties, various solutions have been proposed, such as the use of high-power, low-wavelength laser sources, preheating the build chamber, employing low thermal conductivity building platforms, and adding alloying elements or composite particles to the feedstock material. This article systematically reviews different aspects of AM processing of common industrial copper alloys and composites, including copper-chrome, copper-nickel, tin-bronze, nickel-aluminum bronze, copper-carbon composites, copper-ceramic composites, and copper-metal composites. It focuses on the state-of-the-art AM techniques employed for processing different copper-based materials and the associated technological and metallurgical challenges, optimized processing variables, the impact of post-printing heat treatments, the resulting microstructural features, physical properties, mechanical performance, and corrosion response of the AM-fabricated parts. Where applicable, a comprehensive comparison of the results with those of their conventionally fabricated counterparts is provided. Full article