Composite Substrate Research Articles

ABSTRACTWearable flexible resistive sensors developed with conductive polymer composites (CPCs) have grown rapidly in recent years. However, these sensors suffer from poor breathability, which affects comfort and causes difficulties in balancing sensitivity and response range. In this paper, a composite fibrous membrane substrate was prepared using thermoplastic polyurethane (TPU) and styrene‐butadiene‐styrene (SBS) block copolymer as raw materials by electrostatic spinning. Subsequently, 1D silver nanowires (AgNWs) and 0D silver nanoparticles (AgNps) were loaded onto the surface of the substrate via scraping and magnetron sputtering techniques, respectively, to obtain TPU/SBS/AgNWs/AgNps (TS/Aw/Ap) flexible strain sensors. The TPU/SBS composite fibrous membrane substrate has excellent mechanical properties (tensile strength of 28.86 MPa, elongation at break of 814.61%) and great breathability (> 180 mm/s). The TS/Aw/Ap strain sensor has good sensing performance (GF = 108.85), a response range reaching up to 300%, speedy response functionality (response time: 106.3 ms and recovery time: 147.3 ms), and is able to capture very small deformations (0.1% strain), more than 3000 cycles in long‐term use. There are also many practical applications for the TS/Aw/Ap sensors in human motion detection. The exploration of this sensor may provide a strategy for the further development of wearable devices and flexible electronics.

In this study, a composite substrate with adjustable dielectric properties was prepared, and its promising application in wearable medical device antennas was demonstrated. 3-Methacryloxypropyltrimethoxysilane (KH570) was used to modify titanium dioxide (TiO2) nano-powder, and the modified powder was blended with a mixture of polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE) under the action of anhydrous ethanol. The resulting polymer material had the advantages of hydrophobicity, softness, low loss, and a high dielectric constant. Meanwhile, the effects of the KH570 mass fraction on the microstructure and dielectric properties of TiO2-PTFE-PDMS composites were investigated, and the results showed that when the mass fraction was 5%, the composites exhibited better dielectric properties in the range of 2–12 GHz. Finally, an ultra-wideband antenna with an operating frequency band in the range of 2.37–11.66 GHz was prepared based on this composite substrate. The antenna demonstrated significant potential for future applications in detecting environmental thermal changes due to its special temperature-sensitive linear frequency shift characteristics, and its effect on the human body under bending conditions was studied. In addition, specific absorption rate (SAR) measurements were performed to assess the effects of antenna radiation on the human body in practical applications.

Abstract This study introduces a novel one‐step selective laser reaction pyrolysis (SLRP) method for synthesizing hafnium carbide (HfC), an ultrahigh‐temperature ceramic (UHTC). Unlike conventional methods that involve multiple steps, including crosslinking and pyrolysis, this approach combines both processes into a single laser‐driven step, reducing time and energy consumption. The CO2 infrared (IR) laser (λ = 10.6 µm) used in this technique enables localized heating up to 2000°C within seconds, facilitating the conversion of a liquid polymer precursor into HfC. Material characterization using x‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) confirmed the crystallinity and phase purity of the synthesized HfC powder. To study energy absorption, thermal and photo‐activators were added to the precursor before laser exposure. The thermal activator had a negligible impact on reflectivity but yielded a pure HfC phase, demonstrating the potential for optimized precursor formulations to enhance efficiency without compromising purity. The one‐step process was successfully applied for additive manufacturing, depositing HfC coatings onto carbon–carbon (C/C) composite substrates. This technique eliminates the need for high‐temperature furnaces, enabling rapid fabrication of UHTC components and advancing scalable, energy‐efficient manufacturing. The study highlights its potential for energy, aerospace, and other extreme environment applications.

Abstract The fracture toughness of a ceramic coating is an important parameter for the application of coated components, but it is hard to be measured because the coating is usually too thin to be stripped directly from the substrate and tested as a block material. In this study, an effective technique to determine the fracture toughness of coating was proposed. An analytical relationship among the fracture toughness of the coating, substrate sample, and coated sample were derived, so that the fracture toughness of the coating can be calculated from the measured toughness of the substrate and coated samples. This indirect test is called relative method. By this simple method, the fracture toughness of SiC coatings on graphite substrate and on C/C composite substrate were evaluated respectively based on tests of single edge V‐notched beam method (SEVNB). The results indicate that the relative method is convenient and feasible for evaluating the fracture toughness of ceramic coatings.

In laser drilling, precise parameter optimization is essential to achieving the desired hole characteristics. This study investigates the influence of the pulse width and pulse spacing on the machined hole geometry and proposes an artificial intelligence-based framework to predict hole shapes in multilayer composite substrates. The distribution of hole diameters resulting from CO2 laser machining was evaluated via response surface methodology, considering variations in the pulse width and irradiation time. The results demonstrated a strong dependency of the hole diameters on the laser conditions and revealed significant autocorrelation among the machined-hole parameters.

Abstract The effect of 200 days of cyclic weathering test (CWT) and 1,000 h of salt spray test (SST) on the performance of polyurethane (PU) coating was investigated. A 200 μm coating was applied to a composite and cured before CWT and SST ageing studies. CWT was conducted in ten cycles (each cycle: −40°C for 5 days, 70°C for 5 days, 40°C and 90% RH for 5 days, and salt fog for 5 days). Initial water immersion tests concluded that the coated specimens have 37% less water absorption than uncoated specimens. The degradation behaviour of the coating was evaluated by measuring pull-off adhesion strength, critical load from the scratch test, and wear depth from the pin-on-disk test. Similarly, the surface characteristics of the coating were studied by SEM, gloss value, and contact angle. CWT ageing caused a decrease in gloss value (93–78 GU), pigment content (18–8 wt%), contact angle (92–70°), and an increase in wear depth at 20 N of applied load (45–200 µm). Similarly ageing also decreased the pull-off adhesion strength to 6.77 MPa (CWT) and 7.93 MPa (SST). CWT and SST also decreased the thermal stability by 11–13°C, considering 5 wt% loss and tensile strength of the coating from 42 to 29 MPa. The damage to the composite substrate was not significant due to prolonged exposure periods under CWT and SST, though the damage was noted in PU coating, like increased surface roughness and wear depth.

The silicon carbide (SiC) composite substrate, fabricated using crystal-ion-slicing (CIS) technology, exhibits outstanding performance and has potential applications in many fields. However, the damage caused by H+ implantation is the main factor that limits the performance of the materials. In this study, the longitudinal distribution of defects and lattice stress, the crystal cleavage behavior in the H+ accumulation region, and the damage recovery effect in different depths of the H+ penetration region were studied by deep ultraviolet Raman spectroscopy and x-ray diffraction combined with Ar+ etching. The results indicate that in addition to the H+ accumulation region, the H+ penetration region also exhibits a relatively high defect density and lattice stress in the implanted 4H-SiC. After annealing, in the H+ penetration region, the repair effect is more pronounced near the surface, while near the H+ accumulation region, the damage recovery is less effective, and significant damage remains. Therefore, in the post-treatment process of thin films, it is essential to focus not only on the residual defects from crystal cleavage but also on the regions of high-density damage at a certain depth below the film surface. This study offers new insights for defect analysis in single-crystal thin films fabricated using CIS technology and provides a basis for their treatment and repair.

Abstract Stretchable electronics that are directly mounted on the skin surface can offer valuable electrophysiology information for health conditions monitoring. The rough skin surface can excrete sweat to regulate body temperature, covering the skin with impermeability substrates results in uncomfortable sensations, reducing the adhesion force, and leading to subsequent skin irritation within hours to days. Strain concentration also occurs at the rigid region interface due to the modulus differences, leading to crack issues. The approach utilizes mushroom-shaped tips, and clingfish-inspired microgrooves do not have enough permeability performance, so additional medical adhesive film is required to stabilize the electrophysiological signals. In this work, a new stretchable bi-layer substrate with laser-ablated vias is developed for the ECG sensing patch. The adhesive bottom layer offers biocompatible adhesion to the skin surface, while the top layer is used to adjust the initial Young’s modulus of the substrate. By designing the vias in the composite substrate, the effective Young’s modulus of the substrate with vias region can be reduced to 1.1 MPa, the elongation, and the permeability improved to more than 5 and 10 times, respectively, and strain concentration at the sensing electrode interface can also be suppressed. The fabricated ECG sensing patch has reliable contact with the skin surface during the test after normal and vigorous activities.

A self-powered biosensor with cascade amplification capability facilitates ultra-sensitive detection of microRNA biomarkers.

Modification of thin film composite membranes substrate by graphene oxide nanosheets and carbon nanotubes for forward osmosis desalination

Co/Zn ZIFs with MXene and MWCNTs nanocomposites for electro-detection of nitrite ions: Effect of composite substrate

Surface-enhanced Raman scattering probes based on sea urchin-like Bi2S3@Co3O4 composite for the detection of dopamine during neural stem cell differentiation.

The mechanical response of monolithic CuZr metallic glass (MG) and MG/Cu composite substrates under high-velocity impact was investigated using molecular dynamics simulations, with variations in impact velocity and initial temperature. Higher impact velocities resulted in deeper penetration and increased plastic deformation, with the monolithic MG exhibiting greater energy absorption and slightly more extensive projectile fragmentation. The MG/Cu composite displayed enhanced plastic deformation, attributed to the higher stiffness of the crystalline Cu phase, which promoted plasticity in the amorphous matrix. Temperature effects were more pronounced in the composite, where elevated temperatures enhanced strain localization and atomic mobility in the glassy phase. This was supported by a decrease in dislocation density and the population of hexagonal close-packed (HCP) atoms with increasing temperature, indicating a shift in plastic activity toward the amorphous matrix. These findings provide insights into the interplay between impact velocity, temperature, and material composition, contributing to a deeper understanding of MG-based composite behavior under extreme loading conditions.

New dual-curing resin cements are constantly launched into the market to improve the bond strength between dentine and indirect restorations when light irradiation is limited by the restoration material. The present study evaluated the microshear bond strength (μSBS) of two dual-cured resin cements, Estecem II Plus (EP) and Variolink Esthetic DC (VAR), when resin composite or dentine substrates were conditioned with their corresponding universal adhesives, Tokuyama Universal Bond II (TUB) and Adhese Universal DC (ADH). The experimental groups (n = 20) were (1) TUB/EP light-cured, (2) TUB/EP self-cured, (3) ADH/VAR light-cured, and (4) ADH/VAR self-cured. A μSBS test was performed after 24 h (T0) or after thermocycling (TC), and failure modes were assessed. Data analysis was performed using three-way ANOVA and Tukey tests (p < 0.05). In composite, TUB/EP self-cured demonstrated the highest μSBS at T0 and TC. After TC, TUB/EP self-cured and ADH/VAR light-cured remained stable (p > 0.05). In dentine, TUB/EP light-cured was statistically superior to TUB/EP self-cured and ADH/VAR self-cured at T0. Thermocycling decreased the μSBS of light-curing groups. TUB/EP achieved optimal μSBS when the manufacturer's instructions were followed and the adhesive was self-cured, irrespective of the bonding substrate. However, ADH/VAR was more dependent on the type of bonding substrate than on the curing mode of the resin cement.

Surface-enhanced Raman scattering (SERS) is extensively employed for detecting organics, where its sensitivity and selectivity are strongly influenced by the properties of the SERS substrates. In this work, a simple hydrothermal synthesis followed by a subsequent reduction was used to prepare Au-CeO2 composite nanocubes as a new SERS substrate, in which the side length of the CeO2 cubes was 20~30 nm and the diameter of the Au nanoparticles was 5~25 nm. Using methylene blue (MB) and crystal violet (CV) as probe molecules, the lowest detection limit (LDL) of methylene blue (MB) on the Au-CeO2 composite nanocubes substrate was 10−7 M, and the maximum SERS enhancement factor (EF) was 2.6 × 105. As a result, the lowest detection limit (LDL) of crystal violet (CV) was 10−7 M, and the maximum enhancement factor (EF) was 3.7 × 104. The above results proved that the Au-CeO2 composite nanocubes had a quite good Raman enhancement effect, which could be used as a SERS substrate. Finally, a Raman enhancement mechanism is proposed for the Au-CeO2 nanucubes.

In response to the shortcomings of traditional surface-enhanced Raman spectroscopy (SERS) substrates, such as short shelf life, poor uniformity, and low selectivity, this study innovatively proposed a three-dimensional composite substrate of CNTs/Ag/AgNWs/SiO2. This substrate demonstrates excellent SERS enhancement effects, with a detection limit of 10-12 mol/L for the probe molecule Rhodamine 6G (R6G) and an enhancement factor (EF) of 8.947 × 108. Further experiments confirmed the substrate's superior uniformity and stability. The enhancement mechanism was investigated using both experimental methods and the Finite Difference Time Domain (FDTD) approach. When commonly used pesticide thiram was used as the target analyte, the detection limit of the substrate reached 0.1 mg/L, which is significantly lower than the pesticide residue standards of China and the European Union. Additionally, the genetic algorithm (GA)-optimized Back Propagation (BP) neural network was introduced for the quantitative analysis of thiram concentrations. The experimental results indicated that the GA-BP algorithm achieved the training prediction accuracy of 92.5% for thiram, demonstrating good network performance. This method shows good selectivity and has broad application prospects in the detection of toxic chemicals, environmental pollutants, and food additives.

Abstrak Teknologi Microstrip saat ini pada umumnya menggunakan material substrat dari fiberglass – epoxy atau FR4, fiberglass – epoxy mempunyai kerapatan yang kurang sehingga akan menyebabkan pelemahan sedangkan substrat dengan material alumina mempunyai harga yang mahal, sulit diperoleh dan proses fabrikasi yang sulit sehingga biaya pembuatan mahal dan pemasangannya sulit. Substrat Limbah Serat Rami Komposit mempunyai karakter yang saling memperbaiki sifat elektrik, mekanik maupun kimia sehingga mempunyai kerapatan molekul yang sangat tinggi sehingga kebocoran dan pelemahan sangat kecil, fabrikasi relatif mudah, dan biaya pembuatan lebih murah. Tujuan penelitian ini adalah untuk merancang suatu antena larik Microstrip Multiple Array menggunakan material substrat yang presisi dan mampu dioperasikan pada frekuensi gelombang mikro dan pada daerah yang kondisi cuacanya ekstrim. Prinsip dasar antena ini adalah resonansi sehingga dapat dikembangkan untuk mengakomodir Untuk FCC (Flight Communication Control) Pada Sistem Penerbangan Pesawat. Pada penelitian ini akan dirancang antena Microstrip Multiple Array bentuk directional menggunakan substrat Substrat Limbah Serat Rami Komposite yang merupakan pengembangan dari antena mikrostrip hasil penelitian sebelumnya. Kata kunci : Antena, Microstrip, Komposite , CST, Flight Communication Control, CST, Flight Communication Control. Abstract Current Microstrip technology generally uses fiberglass-epoxy or FR4 substrate materials, fiberglassepoxy has a low density so that it will cause weakening while substrates with alumina materials are expensive, difficult to obtain and difficult to fabricate so that manufacturing costs are expensive and installation is difficult. Substrate Waste Fiber Composite has a character that mutually improves electrical, mechanical and chemical properties so that it has a very high molecular density so that leakage and weakening are very small, fabrication is relatively easy, and manufacturing costs are cheaper. The purpose of this study is to design a Microstrip Multiple Array antenna using a precise substrate material and can be operated at microwave frequencies and in areas with extreme weather conditions. The basic principle of this antenna is resonance so that it can be developed to accommodate FCC (Flight Communication Control) in the Aircraft Flight System. In this study, a directional Microstrip Multiple Array antenna will be designed using a Composite Fiber Waste Substrate substrate which is a development of the microstrip antenna from previous research. Kata kunci : Antenna, Microstrip, Composite, CST, Flight Communication Control. CST, Flight Communication Control.

Epoxy vitrimers, distinguished by their unique combination of the mechanical strength typical of thermosets with the reprocessability of thermoplastics, represent a promising class of materials for advanced technological applications. To optimize their performance in high-demand environments, surface functionalization of vitrimers and vitrimeric composites is crucial to enhance their durability and reliability in harsh conditions. This research work aims at studying the feasibility of metallising vitrimer-based components through cold spray technology. Aluminium coatings were applied under varying process parameters, inlet gas temperature (T = 150 –450 °C) and standoff distance (SoD = 70 mm–100 mm), to evaluate their impact on deposition quality and substrate behaviour. The deposition processes were performed on non-reinforced vitrimeric substrates as well as on vitrimeric matrix substrates reinforced with carbon fibre fabric. The results suggest that successful metallization occurs when the substrate temperature exceeds the topology freezing transition temperature (Tv ≈ 170 °C), enabling the ductile behaviour necessary for effective adhesion. At T = 300 °C and SoD = 100 mm, pure vitrimer coatings exhibited an average thickness of 50 ± 10 µm with minimal substrate deformation (grooves < 4% of panel thickness), while lower temperatures (T = 150 °C) resulted in brittle fracture and poor adhesion. Surface roughness increased from Sa = 0.15 ± 0.05 µm for uncoated substrates to Sa = 6.59 µm after coating. In contrast, composite substrates demonstrated enhanced stability due to fibre reinforcement, which constrained excessive substrate flow. At the best process conditions (T = 300 °C and SoD = 100 mm), composite panels achieved homogeneous coatings with Sa = 4.513 µm. However, excessive temperatures (T = 450 °C) led to substrate erosion and fibre damage in both pure vitrimer and composite panels.

Abstract In this work, a novel self‐healing epoxy system has been developed to address the challenge of repairing glass fiber‐reinforced composites, which are widely utilized in aerospace, automotive, marine, and wind turbine applications due to their superior physical and mechanical properties. Damage to these composites can lead to compromised performance and costly repairs. The objective of this study is to offer an efficient repair method that eliminates the need for external interventions. This self‐healing system is created by incorporating microcapsules composed of a solidified epoxy resin shell and a liquid epoxy resin core. The chemical composition of the microcapsule walls is tailored to match the composite substrate, ensuring precise delivery of the repair agent into the damaged regions. The microcapsules are seamlessly integrated into the resin matrix during the fabrication process, with no extraneous components, ensuring compatibility. Rigorous testing, including mechanical and thermal stress assessments, demonstrated that the system successfully initiates self‐repair without affecting the structural integrity of the composite. The results showed that incorporating 15 wt% microcapsules optimized self‐healing and mechanical strength, restoring 90% of flexural strength. The system reduced damage propagation under thermal and mechanical loading, enhancing repair efficiency. This study advances self‐healing materials for aerospace and automotive applications, improving composite durability and reliability.Highlights Novel self‐healing epoxy system developed for composites. Microcapsules deliver repair agents precisely to damage sites. Testing shows effective restoration of mechanical properties. No external interventions are needed for self‐repair functionality. Compatible with glass fiber‐reinforced composite substrates.

Abstract Rare earth silicates are promising thermal/environmental barrier coatings (T/EBC) materials facing silicon‐based ceramic matrix composite substrates and have attracted much attention due to the severe CMAS (CaO–MgO–Al2O3–SiO2) corrosion. Understanding the mechanism of thermal conductivity and oxygen vacancy behavior of their CMAS corrosion products is crucial to evaluate the performance of coatings in post‐service stage. In this work, thermal conductivity as well as the stability and migration behaviors of oxygen vacancy of these seven CMAS corrosion products are studied using first‐principles calculations. Analysis of their phonon behaviors indicates that low‐frequency phonons play an essential role in heat conduction due to their long phonon relaxation times. The predominant oxygen vacancy configurations for these seven products are determined and their temperature dependent concentrations are predicted according to the calculated formation energies. α‐CaSiO3 with low thermal conductivity and high migration energy barriers is suggested to be the potential corrosion product of T/EBC with excellent service performance. These discoveries do not only provide insights into the thermal conductivity and oxygen vacancy behavior of corrosion products, but also are expected to suggest their potential application as advanced T/EBC materials.