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In this study, melamine–naphthalene covalent polyamic acid and its metal carboxylate salts were synthesized as building blocks of nanofillers (Nt–Mn–PA–COOM, M = H, Li, Na, and K). The Nt–Mn–PA–COOM nanofillers were added as a dopant to vinyl ester resin at 1–5 wt% and their flame retardancy and thermal properties were evaluated. The flame retardancies of 5 wt% of Nt–Mn–PA–COOK–VE and Nt–Mn–PA–COONa–VE were found to improve the heat release rate by up to 95% and 90%, respectively, in comparison with the pristine vinyl ester (VE) composite. These results demonstrated significant progress in the fireproofing performance of VE composites. The burning times of Nt–Mn–PA–COONa–VE and Nt–Mn–PA–COOK–VE composites were shown to be higher 10.6 min, and 12.1 min, respectively, when compared with the pure VE composite (6.28 min). Also, the burning rates of Nt–Mn–PA–COONa–VE and Nt–Mn–PA–COOK–VE concerning flame retardancies were decreased from 11.92 min to 7.07 and 6.19 min, respectively. The delay in burning time, and the reduction of burning rate clearly refer to the enhancement of flame retardancy behavior of the Nt–Mn–PA–COOM–VE composites. It was found that 5 wt% of nanofiller dopants Nt–Mn–PA–COOM–VE (M = Na, and K) in VE was the ideal loading for considering the integrated perspective for flame retardancy applications. The excellent flame retardancy and thermal performance of the Nt–Mn–PA–COOM–VE (M = Na, and K) composites made them promising candidates for developing novel flame retardancy nanofiller dopants.

Polypropylene (PP) nanocomposite films reinforced with surface-modified nanoclay, maleic anhydride-grafted PP (PP-g-MA), and surfactants, such as cetyl-trimethyl-ammonium bromide (CTAB) and octadecyl-trimethyl-ammonium bromide (ODAB), were fabricated by extrusion, and the effect of surfactant type used for the nanoclay and the take-up speed of extrusion on the mechanical properties and crystallinity of the nanocomposite films were investigated. Multi-scale hybrid composites (MHCs) consisting of plasma-treated plain woven carbon fiber (WCF) and nanocomposite films were manufactured by hot pressing. Flexural and impact tests were performed to measure the mechanical properties at various plasma treatment times. Scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) were used to observe the surface morphology and detect polar functional groups, respectively. Results of XPS analysis showed a considerable increase in the oxygen atomic percentage after plasma treatment. The mechanical properties of the MHCs were greatly affected by the presence of nanoclay in the composite and the plasma treatment. The flexural modulus and strength, impact force, and absorbed impact energy of the MHC specimens treated with plasma (15 s) and reinforced with nanoclay/ODAB(5:1, 1.5 wt%) and PP-g-MA(3 wt%), increased by 69, 87, 49 and 54%, respectively, compared to the neat non-plasma-treated WCF/PP composites.

The development of a flexible electronic skin (e-skin) highly sensitive to multimodal vibrations and a specialized sensing ability is of great interest for a plethora of applications, such as tactile sensors for robots, seismology, healthcare, and wearable electronics. Here, we present an e-skin design characterized by a bioinspired, microhexagonal structure coated with single-walled carbon nanotubes (SWCNTs) using an ultrasonic spray method. We have demonstrated the outstanding performances of the device in terms of the capability to detect both static and dynamic mechanical stimuli including pressure, shear displacement, and bending using the principles of piezoresistivity. Because of the hexagonal microcolumnar array, whose contact area changes according to the mechanical stimuli applied, the interlock-optimized geometry shows an enhanced sensitivity. This produces an improved ability to discriminate the different mechanical stimuli that might be applied. Moreover, we show that our e-skins can detect, discriminate, and monitor various intensities of different external and internal vibrations, which is a useful asset for various applications, such as seismology, smart phones, wearable human skins (voice monitoring), etc.

Highly sensitive and flexible composite sensors with pressure and temperature sensing abilities are of great importance in human motion monitoring, robotic skins, and automobile seats when checking the boarding status. Several studies have been conducted to improve the temperature-pressure sensitivity; however, they require a complex fabrication process for micro-nanostructures, which are material-dependent. Therefore, there is a need to develop the structural designs to improve the sensing abilities. Herein, we demonstrate a flexible composite with an enhanced pressure and temperature sensing performance. Its structural design consists of a multilayered composite construction with an elastic modulus gradient. Controlled stress concentration and distribution induced by a micropatterned structure between the layers improves its pressure and temperature sensing performance. The proposed composite sensor can monitor a wide range of pressure and temperature stimuli and also has potential applications as an automotive seat sensor for simultaneous human temperature detection and occupant weight sensing.

The laser-induced synthesis of nanostructures provides an innovative and unique way to shorten the overall processing time in comparison to traditional methods, while allowing precise control of the growth. This is the novel research to report continuous laser beam-assisted uniform growth of aligned nanowires, nanorods and nanotubes on woven carbon fibers (WCF) within a short period of time. The morphologies of the nanostructures were finely controlled by tuning the laser power, beam speed and exposure time. We compared the nanowire/nanorod growth patterns to those obtained with pulsed laser processed growth. The nanostructured-WCF was then used as an electrode and a woven Kevlar fiber (WKF) sheet as a separator for the fabrication of supercapacitor-type sensors. The supercapacitor displays excellent electrochemical and mechanical performance with outstanding multifunctionality. The self-energized supercapacitor exhibits high sensitivity with good cyclic stability. The device functions very well, with few errors, under various environmental conditions. We believe that our supercapacitor-type sensor will be extremely beneficial for the detection of structural problems in bridges, buildings, aerospace vehicles and automobiles, and facilitate the precise motion control of different types of instruments.

Progresses in sensor and energy technologies have been an important driving force for the rapid development of these industries and have drawn the attention of researchers on environmental concerns. In particular, carbon nanomaterial (carbon nanotubes, graphene, graphite, etc.)-based composites are widely used for sensor and energy harvesting applications owing to their excellent electrical, thermal, and mechanical properties. In this review, we have discussed various aspects of the use of carbon nanocomposites for the development of sensor and energy harvesting devices. These devices have shown outstanding sensing and energy harvesting performances. Various carbon nanomaterial-based composites with sophisticated structural and material designs have been developed to improve their sensing performance for various applications. We have also reviewed recent technological developments in carbon nanocomposite-based energy generators that adopt thermoelectric and triboelectric working mechanisms. Further research on the development of carbon nanocomposites with enhanced sensing and energy harvesting properties will expand the range of their applications to automotive, aerospace, artificial skin, healthcare, and environmental/infrastructure industries.

In this study, we propose analytical and experimental methods to predict and detect deformation and interlaminar crack propagation in carbon fiber-reinforced plastics (CFRPs) based on electrical resistance measurement. The electromechanical behavior of CFRP was investigated from the elastic region to crack propagation. The CFRPs were subjected to tensile, three-point bending, and Mode I dual cantilever beam loads, and the signature electromechanical response was correlated to subsequent deformations and crack propagation. The self-sensing investigation was extended to different fiber combinations and electrode placement schemes to obtain customized sensitivity. The experimental results were verified through finite element analysis . In parallel, equivalent electrical circuit modelling was conducted to obtain the “resistor components” that exist in a CFRP and predict the electromechanical behavior under various mechanical loads.

Fiber laser cutting of CFRP sheets was investigated using a 2 kW multi-mode fiber laser, focusing on how the cut quality factors, such as kerf width, kerf depth, matrix evaporation width, matrix recession width, kerf taper angle, matrix damage zone, and cut surface morphology, change as laser power, laser scanning speed, and the number of laser passes are varied. By designing a systematic experiment on a large process window, several important parameters for kerf width, kerf depth, matrix evaporation width, and matrix recession width were identified, and using them, it was verified that the beam scanning speed is a dominant factor for minimizing thermal damages. Also, circular rings were observed in each carbon fiber at the cut surfaces, and it looked as if they were generated when each fiber was thermally fused in the radial direction. A larger number of laser passes was found to contribute to a smooth surface morphology, because of the formation of highly-fused surfaces, which prevents fiber delamination and pull-outs. Optimum process conditions were also identified by comparing various cut quality factors.

Structural supercapacitors provide a variety of opportunities for woven carbon fibers in portable electronics, hybrid automobiles and aerospace applications. We describe herein the synthesis of bimetallic Cu-Co selenide nanowires based on woven carbon fibers, and their use as electrodes in supercapacitors. Woven Kevlar fiber is used as separator for the electrodes and a polyester resin with an ionic liquid and lithium salt is used as solid polymer electrolyte. The supercapacitors exhibit efficient energy storage and significant enhancements in mechanical strength (89.38%) and modulus (70.41%) over those of bare woven carbon fiber base supercapacitors. The specific capacitance of these supercapacitors increases from 0.197 F g−1 to 28.63 F g−1 after the growth of nanowires, with accordingly high energy density (191.64 mW h kg−1) and power density (36.65 W kg−1). In situ mechano-electrochemical tests of these supercapacitors yield excellent capacitance retention (77.3%) at the mechanical failure point (481.29 MPa).

Zinc oxide nanorod (ZnO NR)-grown woven carbon fiber/polyamide 6 composites were fabricated using hydrothermal synthesis and thermoplastic resin transfer molding. The in-situ polymerization of e-caprolactam, which exhibits extremely low viscosity and high reaction speed, enabled excellent penetration of the resin into the densely grown ZnO forest on the carbon fibers. This further increased the mechanical interlocking and chemical interaction between the fiber and resin, leading to enhanced interfacial bonding. By increasing the number of oxygen functional groups and the surface roughness of the fiber surfaces through an atmospheric plasma treatment, the ZnO NRs were observed to grow even with very low growth-solution concentrations (20 mM), fewer seed cycles (4), and a short hydrothermal treatment time (4 h). By using the plasma-treated carbon fibers for ZnO NR growth, the impact resistance and in-plane shear strength were enhanced by up to 72 and 50%, respectively, as compared to carbon fiber composites without ZnO NRs, while the use of ZnO precursors and growth time was minimized.

Nylon 6,6 nanocomposites containing well-dispersed graphene oxide (GO) and carbon nanotubes (CNTs) were successfully fabricated via in situ interfacial polymerization between two immiscible phases: organic phase assisted by poly(vinylpyrrolidone, PVP) surfactant containing adipoyl chloride with dispersion of GO and CNTs; aqueous phase containing hexamethylenediamine. Prior to polymerization, GO was functionalized with thionyl chloride, resulting in acyl-chloride-functionalized GO (AGO). The effect of incorporation of AGO and PVP on the state of dispersion was investigated. It was observed that the addition of AGO and PVP reduced particle flocculation, leading to a well-dispersed suspension as verified using dispersion stability measurement and UV–Vis spectroscopy. The interfacial interaction between the carbon nano-fillers and nylon 6,6 chain can be induced via hydrogen and covalent bonding between them. Thermal analyses revealed nuclei crystallization in nylon 6,6 nanocomposites was promoted by the strong nucleating behavior of AGO, and the thermal stability was improved. Tensile tests of the composite films (nylon 6,6/AGO, CNT) showed increases of 122 and 152%, respectively, in the tensile strength and modulus as compared to the neat polymer. This suggests that the interfacial interaction between nylon 6,6 and AGO/CNT contributes to enhanced load transfer in nanocomposites, thus enhancing the mechanical properties of the nanocomposites.

Thermotherapy is a widespread technique that provides relief for muscle spasms and joint injuries. A great deal of energy is used to heat the surrounding environment, and heat emitted by the human body is wasted on our surroundings. Herein, a woven Kevlar fiber (WKF)-based personal thermal management device was fabricated by directly growing vertical copper-nickel (Cu-Ni) nanowires (NWs) on the WKF surface using a hydrothermal method. The treated WKF was combined with reduced graphene oxide (rGO) dispersed in polydimethylsiloxane (PDMS) to form composites using vacuum-assisted resin transfer molding (VARTM). This WKF-based personal thermal management system contained a conductive network of metallic NWs and rGO that promoted effective Joule heating and reflected back the infrared (IR) radiation emitted by the human body. It thus behaved as a type of thermal insulation. The Cu-Ni NWs were synthesized with a tunable Ni layer on Cu core NWs to enhance the oxidation resistance of the Cu NWs. The combined effect of the NW networks and rGO enabled a surface temperature of 70 °C to be attained on application of 1.5 V to the composites. The Cu3Ni1-WKF/PDMS provided 43% more thermal insulation and higher IR reflectance than bare WKF/PDMS. The absorbed impact energy and tensile strength was highest for the Cu1Ni3- and rGO-integrated WKF/PDMS samples. Those Cu-Ni NWs having higher Ni contents displayed better mechanical properties and those with higher Cu contents showed higher Joule heating performance and IR reflectivity at a given rGO loading. The composite shows sufficient breathability and very high durability. The high flexibility of the composites and their ability to generate sufficient heat during various human motions ensures their suitability for wearable applications.

We report an experimental study on improvement of mechanical properties of a multiscale hybrid composite consisting of in-situ polymerized polyamide-6 and zinc oxide nanorod(ZnO NR)-grown woven carbon fiber (WCF) coated with carbon nanotube(CNT)-modified silane. The ZnO growth process and silane coating process were performed on the fiber surface, and then the composite was fabricated by ultra-fast (

High-speed molding of continuous carbon fiber-reinforced composites was carried out by thermoplastic resin transfer molding using a very-low-viscosity thermoplastic monomer. After dispersing 0.1 wt.% of various nanomaterials in e-caprolactam, a monomer of anionic polymerized polyamide 6 (A-PA6), the processing temperature and catalyst-activator contents were optimized based on the polymerization induction time required for resin injection in the mold. Additionally, the dispersion stability, solidification time, monomer conversion, crystallinity and mechanical properties of the composites were evaluated. Higher dispersion stability of the nanomaterials in A-PA6 resulted in a significantly shortened process cycle time – on the order of seconds –and higher crystallinity in the composite. In addition, carbon fibers treated with atmospheric plasma were used to increase the rate of resin impregnation into fibers. These factors not only increased composite fabrication productivity but also enhanced its mechanical properties.

Various morphologies of α-MnO2 nanostructures were synthesized on the surface of woven Kevlar fiber (WKF) by hydrothermal method under different reaction conditions. Reduced graphene oxide-polyaniline nanofiber (RGO-PANI) arrays were synthesized by an in situ dilute polymerization technique and then dispersed within polyester (PES) resin. High-performance composites based on α-MnO2-grown WKF and RGO-PANI array-dispersed PES were fabricated with effective microwave-absorbing and mechanical properties by vacuum-assisted resin transfer molding (VARTM). WKF/MnO2 nanofibers/PES/PANI-RGO (2%) composites showed superior electromagnetic parameters in the frequency range of 1–18 GHz. The reflection loss (RL) of WKF/MnO2 nanofibers/PES/PANI-RGO (2.0%) was −36.5 dB at an absorbing frequency of 11.8 GHz, which has not been reported before. A higher tensile strength (160.12%), modulus (104.43%), and absorbed impact energy (207%) were observed for α-MnO2 nanofibers, compared with other morphologies of α-MnO2-incorporated WKF composites and the properties were enhanced with an increased percentage of PANI-RGO.

Ag/AgCl/V2O5 nanocatalysts with one dimensional (1D) architecture was synthesized in carboxylic acid functionalized multi-walled carbon nanotubes for methylene blue dye degradation. The growth of uniformly distributed nanoparticles along the carbon-nanotubes was revealed from high resolution transmission electron microscopy and atomic force microscopy analyses. Raman spectroscopy and transmission electron microscopy analyses also confirmed for the creation of defects in the multi-walled carbon nanotube. The hybrid nanocomposite appeared as a suitable photocatalyst for degradation of methylene blue dye absorbing the light in the visible range of solar spectrum. The presence of interactions within the nanoparticles and with the nanotubes was believed to enhance the photo-oxidation process. The creation of defects in the carbon nanotube on modification with Ag/AgCl/V2O5 improved the photocatalytic activity by enhancing the photoelectron transfer process. About ∼90% of the total organic carbon of the dye molecule was found to decompose into CO2, H2O and inorganic ions within 25 min under sunlight.

An effective analytical modeling method to predict the thermal conductivity of a multiscale hybrid composite, consisting of nano-sized filler, micron-scale continuous fiber and polymer matrix, has been proposed. The method combines the modified Mori-Tanaka method and woven fiber composite modeling, which are used to predict the thermal conductivities of carbon nanotube(CNT)/polymer composites and CNT/woven fiber/polymer multiscale composites, respectively. The thermal-electrical circuit analogy was applied to the unit cell of a multiscale woven fiber composite, which allowed predictions of conductivities in both in-plane and through-thickness directions. The experimental validations on woven fiber composites and multiscale composites revealed that thermal conductivity predictions based on the proposed modeling approaches agreed well with the experimental results, taking into account the effects of CNT content, fiber volume fraction, constituent conductivities, and fiber undulation.

Carbon fiber-reinforced plastics (CFRPs) made of uni-directional carbon fibers (UDCFs) are used in various applications such as construction, aerospace, and automobiles. Therefore, their structural health monitoring (SHM) and non-destructive evaluation (NDE) are important to ensure safety during operation. While there is literature on self-sensing of CFRPs to realize various properties, there is no information on their impact self-sensing properties. Therefore, in this study, CFRPs in several orientations were investigated in terms of their mechanical fracture and electromechanical behavior. Changes in their electrical resistance due to impact damage can be utilized for SHM using the corresponding electrically equivalent circuit models. The circuit models constructed consisted of electrical resistors that described the UDCFs. In addition to converting CFRPs into 2D circuits, 3D electrical routes between electrodes were proposed for NDE. Calculating the detour length of the electrical routes using the proposed models helps in assessing the severity of the impact damage. Therefore, the models for CFRPs developed in this study not only provide support for SHM but also for NDE using electrical resistance.

In this study, the interfacial bonding of carbon fiber (CF)/polyamide 6 (PA 6) composites is enhanced through the application of a mixture composed of a PA sizing agent and a reduced graphene oxide (RGO) coating onto a CF surface. RGO is introduced from shellac as a biodegradable polymer through an annealing process that is simple, eco-friendly, and inexpensive, resulting in shellac-derived RGO (SRGO) on the CF surface with strong bonding. Furthermore, it can be concluded that the reinforced interphase between the fiber and matrix by subsequent sizing treatment leads to complex physical and chemical bonding mechanisms. The chemical relationship between the sizing agent and SRGO was investigated using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis, differential scanning calorimetry, and thermogravimetric analysis. By modifying the sizing agent and mixture coating, the interlaminar shear strength increased by up to 70.7% for the CF/PA6 composites compared to those obtained without modification. Furthermore, the flexural strength and modulus of the mixture of the modified composites increased by 73% and 84%, respectively. Finally, the storage modulus and absorbed impact energy increased by 200% and 73.3%, respectively. These results suggest an improvement in the interfacial bonding of the composites upon the application of a mixture of PA sizing agent and SRGO coating.

A novel sandwich-structured composite comprising a three-dimensionally (3D) printed core and a woven carbon fiber/polyamide-6 facesheet was fabricated and characterized. By using selective laser sintering, which is a 3D printing technology, a structurally reinforced honeycomb-truss hybrid core was produced, which had superior compressive stiffness in various directions compared with conventional honeycomb cores. The interface between the core and the facesheet was enhanced by laser power control during the sintering as well as plasma surface treatment. The sandwich composite was produced by the reactive thermoplastic resin transfer molding (T-RTM) technique using anionic polymerization of e-caprolactam, which has an ultra-low viscosity in the molten state. This in-situ polymerization not only enabled manufacturing process simplification by combining fabrication and bonding processes of the facesheet, but also provided excellent resin impregnation into the fiber fabrics and core surface. Therefore, the 3D printing technology, interfacial strengthening techniques, and T-RTM process induced synergistic effects on mechanical properties of the sandwich composite by forming structural reinforcement and strong mechanical and chemical interactions. The edgewise compressive properties of the hybrid core were significantly better than those of a normal honeycomb core. In addition, the interlaminar fracture toughness, impact energy absorption, and penetration limit of the sandwich composite consisting of the structurally and interfacially strengthened hybrid core increased by 76, 77, and 125%, respectively, compared to those of a nonreinforced sandwich composite.

Personal thermoregulation is a major goal in the development of smart, wearable devices, regardless of climate conditions, and can reduce the demand for power from external sources. An immense amount of energy is consumed for heating indoor environments in cold weather, while body heat is continually radiated into the surroundings. Maintaining comfortable personal thermal conditions while outdoors in the summer is also challenging. Here, we have developed a novel personal thermoregulatory (PTM) device inspired by the thermoregulation mechanism of endotherms. The PTM device features a smart heating/cooling mechanism that responds to changing climatic conditions. The devices were fabricated with woven Kevlar fiber (WKF) containing perpendicularly grown silver nanoparticle-decorated branched cobalt molybdenum phosphide nanowires (Ag@CoxMo1-xP). These fibers were spin-coated with reduced graphene oxide (rGO) dispersed in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) or PEDOT:PSS/poly(N-isopropylacrylamide) (PNIPAM). Ag@CoxMo1-xP coupled with rGO promoted efficient Joule heating, attaining 76 °C at 2.1 V, in WKF/PEDOT:PSS. Ag@CoxMo1-xP incorporated into WKF/PEDOT:PSS showed higher infrared (IR) reflectance (97.9%) and thermal insulation (52.1%) than bare WKF/PEDOT:PSS. However, IR transmittance increased, and thermal insulation decreased, with increasing surrounding temperature when Ag@CoxMo1-xP were incorporated into a PNIPAM composite. All of the Ag@CoxMo1-xP and rGO-loaded composites exhibited remarkable durability, flexibility, and air permeability, with increased impact resistance (162.2%) and tensile strength (94.9%). The Ag@CoxMo1-xP device fabricated without PNIPAM functioned as a wearable heater and, when doped with PNIPAM, provided a passive heating/cooling effect depending on the environmental temperature. Thus, our PTM devices could help to mitigate the world energy crisis by helping the wearer maintain to a comfortable personal environment while minimizing household energy consumption.

A novel multifunctional composite has been developed with functions of a supercapacitor and structural health monitoring sensor. The need for energy efficiency, lightweightness, and safety motivated the study for the multifunctional composite. The electrical energy storage was realized by nickel-cobaltite-grown conductive uni-directional carbon fibers (UDCFs), an aramid fiber, and an ionic liquid with a lithium-based salt as electrodes, a separator, and an electrolyte of the supercapacitor, respectively. The structural health monitoring sensor was enabled using the electrical resistance changes of the composite under mechanical loading. These functions can be utilized for the structural supercapacitor and self-sensing structure. Hence, the composite is called a 2-in-1 multifunctional composite. The nickel cobaltite nanowire and ionic liquid exhibited promising energy storage capacitance (37.43 F g−1) as a structural supercapacitor. Moreover, its energy density and power density were 176.37 mWh kg−1 and 36.96 W kg−1, respectively. The UDCF exhibited a clear electromechanical behavior. Therefore, the electrical resistance of the composite indicates an applied mechanical deformation, similar to that observed in a deformation sensor. The difference in electromechanical sensitivity with respect to the loading direction was investigated considering the orthotropic composition of the composite. The developed 2-in-1 multifunctional composite exhibits advantages of lightweightness, high energy storage, self-sensing, and facile engineering design and, thus, can be applied in various fields such as automobiles, aerospace, civil infrastructure, and industrial plants.

We propose the probabilistic sensing cloud method for non-destructive self-sensing impact localization in carbon fiber reinforced plastics (CFRPs) with optimized electrode arrays. Electrical resistance was measured between various electrode sets to identify the potential damage area. Subsequently, overlapped probabilistic clouds helped localize the damaged location, which was verified by our experimental results. The proposed technique was optimized by investigating the inter-electrode distance, finite element analysis of electrical current density, and cloud shaping in terms of the resistance change. Pre-existing techniques such as eddy current sensing, fiber Bragg grating sensing, and lead zirconate titanate sensing are limited to schedule-based inspection or sparse sensing units holding blind spots. However, the proposed method is an in situ real-time condition-based self-sensing method that requires no additional sensors and fewer electrodes. Furthermore, the noise and error components for the structure were significantly lower than in ordinary piezoresistive self-sensing systems. Therefore, probabilistic sensing cloud method can enhance efficient structural health monitoring of CFRPs with electrode distance optimization and can reduce data complexity induced by structural complexity.

A low-power-consuming, self-powered wearable personal thermal management (PTM) device could minimize our reliability on external power sources. Herein, we describe the fabrication of a self-powered PTM device providing thermotherapy that can be wirelessly heated, with warmth preservation and heat produced via the triboelectric effect. Initially, ferromagnetic porous spongy FexCo1−xP nanostructures were synthesized uniformly over the surface of woven Kevlar fiber (WKF). Synthesized MXene was then dispersed in polydimethylsiloxane (PDMS) and prepared as a composite with WKF/FexCo1−xP. The combined effect of MXene and FexCo1−xP resulted in very effective Joule heating (74 °C at 3 V), and the ferromagnetic behavior of the composite induced wireless heating. The dense interrelated porous structure created by MXene incorporation helped to maintain body warmth (an enhancement of 40.1% compared with bare WKF/PDMS) by reflecting almost all of the infrared radiation (97.7%) back to the body. The composite also exhibited high impact resistance (131.4% compared with WKF/PDMS) for use as smart body armor. Additionally, the PTM device exhibited a maximum power density of 1.3 mW cm−2 at a low impact frequency of 5 Hz and was capable of harvesting energy from human motion and wind, indicating a potential self-heating ability of the PTM composite.

Thermoplastic composites are rapidly emerging as alternative materials for auto parts owing to recyclability as well as excellent stiffness- and strength-to weight ratios. In this study, an optimal stacking sequence using twill-weave carbon fiber-reinforced polypropylene (CF/PP) prepregs and random fiber-reinforced polypropylene (RFP) sheets were investigated for the fabrication of an automobile fender. The lamination consisting of CF/PP only incurred imperfect resin impregnation. RFP insertion between CF/PP layers improved the resin impregnation. The hybrid stacking sequence not only reduced internal void contents but also increased the flexural and impact strength of the composite laminate. Using the optimal stacking sequence, a real-scale composite fender was fabricated and impact tests were performed. The test results were compared with the ones from an existing steel fender. In case of the steel fender, permanent deformation was observed even in one attempt, while no visible damage was found from the composite fender even after five consecutive impact tests.

Well-aligned NiCo2S4 nanowires, synthesized hydrothermally on the surface of woven Kevlar fiber (WKF), were used to fabricate composites with reduced graphene oxide (rGO) dispersed in polyester resin (PES) by means of vacuum-assisted resin transfer molding. The NiCo2S4 nanowires were synthesized with three precursor concentrations. Nanowire growth was characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Hierarchical and high growth density of the nanowires led to exceptional mechanical properties of the composites. Compared with bare WKF/PES, the tensile strength and absorbed impact energy were enhanced by 96.2% and 92.3%, respectively, for WKF/NiCo2S4/rGO (1.5%)/PES. The synergistic effect of NiCo2S4 nanowires and rGO in the fabricated composites improved the electrical conductivity of insulating WKF/PES composites, reducing the resistance to ∼103 Ω. Joule heating performance depended strongly on the precursor concent...

Structural supercapacitors can be considered as next-generation energy storage devices that have significant simultaneous performance characteristics in both structural applications and battery-like functions. In this study, we report the development of novel structural supercapacitors for the first time based on ZnO nanotubes, grown on woven carbon fiber electrodes, with a glass fiber separator. A solid polymer electrolyte is developed by mixing an ionic liquid (EMIMBF4), a lithium salt (LiTf), and polyaniline nanofiber with a polyester resin matrix. The supercapacitor is fabricated by a vacuum-assisted resin transfer molding process that is both effective and eco-friendly. The specific capacitance of the supercapacitor enhances to 18.8 F g−1, versus 0.2 F g−1 for a bare carbon-fiber supercapacitor. Large increases in energy (156.2 mW h kg−1) and power density (19.87 W kg−1) are also achieved, with exceptional tensile strength (325 MPa) and modulus (21 GPa) values. The device demonstrates strong multifunctional performance so that it can be used confidently for energy storage in electric vehicles and unmanned aerial vehicles, and in the aerospace industry generally.

Solid-state grinding of palladium and copper salts allowed the growth of palladium/copper oxide interface at the zeolite-Y surface. The hybrid nanostructured material was used as reusable heterogeneous catalyst for selective oxidation of various benzyl alcohols. The large surface area provided by the zeolite-Y matrix highly influenced the catalytic activity, as well as the recyclability of the synthesized catalyst. Impregnation of PdO-CuO nanoparticles on zeolite crystallite leads to the generation of mesoporous channel that probably prevented the leaching of the metal-oxide nanoparticles and endorsed high mass transfer. Formation of mesoporous channel at the external surface of zeolite-Y was evident from transmission electron microscopy and surface area analysis. PdO-CuO nanoparticles were found to be within the range of 2–5 nm. The surface area of PdO-CuO-Y catalyst was found to be much lower than parent zeolite-Y. The decrease in surface area as well as the presence of hysteresis loop in the N2-adsoprt...

Bioinspired dry adhesives with protruding tips offer strong, repeatable, and reversible adhesion both in normal and shear directions owing to the presence of a thin spatulate layer. However, the temperature range in which they can be used is limited because most of them are made of polymeric materials that have inherently poor thermomechanical stability. Here, we report a nanocomposite dry adhesive as a high-temperature reversible adhesive with high pull-off strength. The nanocomposite dry adhesive is fabricated by a replica-molding technique with polydimethylsiloxane (PDMS) enforced with multiwalled carbon nanotubes (MWCNTs) of different concentrations. The MWCNT/PDMS composite adhesives exhibit remarkably better thermal stability than pristine PDMS adhesives owing to the excellent thermal and mechanical properties of the MWCNTs in the composite. Furthermore, the nanocomposite adhesives have a high adhesion strength even when they are thermally annealed at high temperatures of up to 350 °C, demonstrating a strong potential as a versatile high-temperature reversible adhesive.

In this paper, recent technology for wearables to detect electrolyte of sweat and biocompatible smart materials for additive manufacturing (AM) have been surveyed. The challenges and gaps toward successful realization of functional wearable devices as a kit to test biomarkers were, then, discussed. While wearable devices sensing physical conditions of users are popular in a consumer market, wearable devices to detect chemical components of human sweat have little studied due to several limitations such as contacting human skin and controlling ambient parameters etc. AM technology makes innovative products realized, differing from conventional fabrication and design methodologies due to unlimited design freedom for manufacturing and material selections. We investigate the potentials of AM to be applied for wearable devices, although detecting chemical biofluids requires wider and deeper researches on the development of advanced materials and AM process.

A facile and simple methodology was adopted for the trapping of highly crystalline AgCl and Ag/AgCl nanoparticles (NPs) into the interlayer spacings of vanadium oxides (VOx). Self-organization of AgCl and Ag/AgCl-NPs on VOx was found to be governed by the nature of the dicarboxylic acids used during the synthesis of the nanocomposites. A “fractal-like” morphology of the AgCl@VOx nanocomposite was achieved in the presence of cis-1,2 cyclohexanedicarboxylic acid. Heating of the AgCl@VOx nanocomposite above 68 °C resulted in the growth of polydispersed and ultrafine (3–4 nm) Ag/AgCl-NPs and its self-organization into monolayer formation on a partly crystalline VOx matrix. Change in the conformation of the dicarboxylic acid to the trans-isomer resulted in the formation of a ‘rod-like’ structure of Ag/AgCl-NPs on a highly crystalline VOx matrix. The band gaps of the nanocomposites were within the range of 1.8 to 2.9 eV. Because of such a low band gap, the synthesized nanocomposites were found to be highly active toward the photooxidation of methylene (MB) and methyl orange (MO) under sunlight.

The main purpose of the present work is to demonstrate mechanical performance of a wet-compression-molding (WCM) composite product through conventional compressive-strength-after-impact (CSAI) analysis. Biaxial non-crimp fabric (NCF) is utilized to manufacture laminated composite panels. Specimens are cut from the panels and tested to characterize fundamental mechanical properties of the NCF composite. The volume fractions of fibers and voids are also measured to evaluate the quality of the WCM product. Impact tests are carried out to examine impact resistance of the composite structure. Numerous impact characteristics at various energy levels are quantitatively measured. Internal failure patterns and damage extent are revealed via X-ray CT. Compression tests on the impacted plates are followed to evaluate structural integrity and damage tolerance (SIDT). 3D DIC technique is employed and distinct buckling responses dependent on impact energy levels are successfully visualized. Experimental results are showing a promising potential of the WCM process as one of the alternatives to the conventional autoclave-based fabrication method.

Filtration of nanofillers into porous fabric media is still an issue during the preparation of advanced fiber-reinforced composites. The assessment of resin/multiwall carbon nanotube (MWCNT) flow, MWCNT filtration, and the cure monitoring of glass fiber/carbon nanotube-polyester composites by means of the measurement of the electrical resistance was introduced. The vacuum-assisted resin transfer molding technique was used. The electrical resistances measured over the span of a composite were qualitatively correlated with MWCNT flow and the degree of MWCNT filtration. It was found that while the complexity of the fabrics could likely introduce preferential deposition of MWCNTs, their filtration is mainly affected by their dispersion state in the resin suspension. Relationships among critical parameters such as the lengths and diameters of MWCNTs, the inter- and intra-tow dimensions of glass fabrics, the dispersion level of MWCNTs, and the viscosity of nanocomposite samples are discussed and correlated to the filtration, cure, and flow phenomena. We showed that our method can also serve as an early warning to obviate defects in the resulting composite.

Nanofluids (NFs) are highly promising liquids for critical heat flux (CHF) enhancement in pool boiling, due to their environmental friendliness, easy chemical modification, tunability, low cost, and high thermal conductivity (TC). NFs based on CuO nanoparticles (NPs) are moderately good for CHF applications, but have low TC compared with other metal-oxide NFs. The development of ecofriendly NFs with enhanced thermal transfer properties is essential. In this study, we engineered a highly efficient, soft, hydrophilic CuO–chitosan (CS) NF template, the first of its kind. CS is a low-cost, naturally abundant, raw material, with hydroxyl, amine, and amide functional groups. When combined with CuO NPs, the CS functional groups create strong CuO–CS nanocomposites (CuO–CS NCs). In this research, 0.003, 0.006, 0.03 and 0.06-wt% CuO–CS NFs were produced by dissolving various concentrations of the CuO–CS NC in deionized water. A nichrome wire was coated with the NF samples during pool boiling experiments. The 0.06-wt% CuO–CS NF showed the highest CHF value, approaching 79%, which is much higher than that of pristine CuO NPs (28%). The chemical structure and crystallinity of the CuO–CS NCs were investigated using Fourier-transform infrared and X-ray photoelectron spectroscopy and X-ray diffraction; zeta potential and zeta size analyses were used to determine their charge, shape, and size. Atomic force microscopy, field-emission scanning electron microscopy, and transmission electron microscopy of the CuO–CS NC-coated nichrome wire after pool boiling experiments revealed a rough surface with high wettability and a low contact angle (42° for the 0.06-wt% CuO–CS NF sample), due to the formation of a nanoporous, soft template on the wire surface. We also demonstrated a method for in situ production of a naturally available, sustainably green, biodegradable raw material. The robust CuO–CS NF introduced here is expected to enhance pool boiling CHF, even at the lowest concentrations (0.003 wt%) required for practical applications.

Polyamide 6 composite fibers containing various kinds of pristine graphene nanoplatelets [P-graphene nanoplatelets (GnPs): P-M5 and P-C750] as well as oxidized GnPs (acid-M5, acid-C750) were prepared via melt spinning. Both P-GnPs and acid-GnPs were used as reinforcements to enhance the thermomechanical properties of the composite fibers. GnPs were dispersed in the polymer matrix via solution mixing followed by coagulation. Composite fibers were melt-spun using a plunger-type extrusion system, followed by stretching to the maximum draw ratio using a Godet setup. The tensile and dynamic mechanical properties of the composite fibers were tested, as well as the thermal properties. The results showed considerable enhancements in the mechanical and thermal properties of the polyamide 6 fibers due to loading with 0.5–5 wt% GnP, and the composite fibers containing 1 wt% of acid-C750 exhibited an increase of up to 76% in the tensile strength compared to that of the neat polyimide 6 fibers. Dynamic mechanical analysis, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy were carried out to investigate the effects of the crystallinity, crystallization kinetics, and interfacial bonding on the tensile properties of the polyamide 6 composite fibers.

Novel structural supercapacitors based on CuO nanowires and woven carbon fiber (WCF) has been developed for the first time employing vacuum assisted resin transfer molding (VARTM) process. The growth of CuO nanowires on WCF is an efficient process and can be used in structural capacitors which can trigger the electric vehicle industries toward a new direction. The specific surface area of the carbon fiber was enhanced by NaOH etching (41.36 m2 g−1) and by growing CuO nanowires (132.85 m2 g−1) on the surface of the WCF. The specific capacitance of the CuO–WCF based supercapacitor was 2.48 F g−1, compared with 0.16 F g−1 for the bare WCF-based supercapacitor. The usage of ionic liquid and lithium salt improved the capacitance to 5.40 and 6.75 F g−1 with lowest ESR and Rp values of 133 and 1240 Ω along with improving mechanical properties within an acceptable range. The energy and power densities were also increased up to 106.04 mW h kg−1 and 12.57 W kg−1. Thus, this study demonstrated that growing CuO nanowires on the surface of WCF is a novel approach to improve multifunctionality that could be exploited in diverse applications such as electric cars, unmanned aerial vehicles (UAVs), and portable electronic devices.

The electric heating and piezoresistive characteristics of CuO–woven carbon fiber (CuO–WCF) composite laminates were experimentally evaluated. Hybrid CuO–WCF composites were fabricated via a two-step seed-mediated hydrothermal method. The interlaminar interface between two plies of hybrid CuO–WCF/vinyl ester composite laminae was influenced by interlocked fiber–fiber cross-linking structures with CuO NRs and acted as electric heating and resistance elements. The contribution of CuO NRs (10–110 mM) to the interlaminar interface was determined by measuring the temperature profile, in order to investigate the electrical resistive heating behavior. At higher concentration of CuO NRs growth in the interlaminar region applied by 3 A, the average temperature reached to 83.55 °C at the interface area 50 × 50 mm 2 and the heating efficiency was 0.133 W/°C owing to radiation and convection given by 10.5 W (3 A, 3.5 V). To investigate the piezoresistive response, the through-thickness gauge factor was observed at 0.312 during Joule heating applied by 2 A, compared with 0.639 at an ambient air temperature for CuO 110 mM concentration. The morphology and crystallinity of CuO NRs were investigated using scanning electron microscopy and X-ray diffraction analyses, respectively. The temperature dependence of hybrid CuO–WCF composite laminates’ storage moduli were analyzed using a dynamic mechanical analyzer. These characterizations showed that the interlaminar interface, combined with the high specific surface area of CuO NRs, provided the electron traps for electrical conduction around multiple WCF junctions and adjacent cross-linked laminae.

Iron-carbon nanotube (Fe-CNT) nanostructures were synthesized in 15–30 s through the microwave irradiation of woven Kevlar ® fibers (WKFs) deposited with either polypyrrole (PPy) or polypyrrole/graphene oxide (GO). Microwave-induced growth of Fe-CNT on the base fibers is a simple technique and has not been previously reported using WKF as a substrate. This method of forming composites avoids the difficulties associated with obtaining a homogeneous dispersion of CNT in a surrounding matrix material. Iron-decorated CNTs were synthesized on WKF and polyester resin (PES) via vacuum-assisted resin transfer molding. Substantial improvements in tensile strength (upto 122.57%) and moduli (upto 89.82%) were observed for Fe-CNTs grown on the WKF/PES composites. The impact response and in-plane shear strength were also significantly enhanced compared to bare WKF/PES composites. In situ polymerization of pyrrole on WKF altered the electrically insulating behavior of Kevlar, creating a conductive material. Fe-CNT/PPy-coated WKF/PES exhibited the highest electrical conductivity. This proposed approach for growing Fe-CNTs constitutes a novel and economical means of developing high-performance WKF/CNT composites with enhanced mechanical properties and electrical conductivity.

We report a method to monitor the manufacturing process of hierarchical micro-/nano-composites that uses integrated and percolated multi-walled carbon nanotube (MWCNT) networks with the aim of reducing part-to-part variability. Composites were fabricated by VARTM. Fiber textiles were spray-coated with MWCNTs, electrodes were embedded prior to vacuum bagging. In situ process monitoring was achieved by measurement of the electrical resistance of electrode pairs. The effects of MWCNT density and length on the ability to monitor the manufacturing process were evaluated. Experiments showed that monitoring the changes in resistance between electrode pairs on the conductive MWCNT network allowed various events during the manufacturing process, including part infusion, onset of crosslinking, and gel point of the resin, which are necessary for accurate evaluation of part quality. Our simple yet effective method to monitor the manufacturing processes and predict the final-part quality of multiscale composites can be integrated into existing processes with minimal modifications.

We have fabricated two types of multifunctional composites, carbon nanotube (CNT)/glass fiber (GF)/epoxy composites and carbon fiber (CF)/epoxy composites, and evaluated thermoelectric properties of the composites for applications as n/p type thermoelectric materials as well as load carrying structural composites. Several test samples of CNT/GF/epoxy composites with various CNT concentrations were fabricated using a three-roll mill and hand-layup process on a hot plate, while CF/epoxy composite samples were manufactured using a hand-layup process. Experimental results demonstrated that the electrical resistivity of the CNT/GF/epoxy composite (multiscale composite) samples decreased as the CNT concentration increased. In-plane samples showed higher electrical and thermal conductivities due to partial alignment of CNTs in the multiscale composites and continuity of carbon fibers in CF/epoxy composites. Generally, CF/epoxy composites had better electrical and thermal conductivities than those of multiscale composites. In the Seebeck coefficient test, the multiscale composites showed n-type thermoelectric behavior, whereas the CF/epoxy composites showed p-type behavior. When temperature gradients were applied to closed circuits comprised of multiscale composites and CF/epoxy composites as n-type and p-type materials, respectively, an electric current was successfully generated.

The resistive heating and thermoelectric characteristics of discontinuous carbon fiber-epoxy composites are explored experimentally and numerically. Composite samples with different carbon fiber concentrations (1, 3, and 5 wt.%) were manufactured using sonication and cast molding. DC current was applied, and the temperature distributions on the surfaces of the samples were assessed visually and quantitatively using an infrared camera. The resistive heating mechanism was investigated in conjunction with applied voltage and carbon fiber loading. Experimental results show that resistive heating efficiency increased proportionately with applied voltage and carbon fiber content, and this was confirmed by numerical simulations of fiber contacts at various fiber volume fractions using representative volume elements. In parallel, the thermoelectric behavior of composites was characterized using a specially designed and fabricated test setup. The discontinuous carbon fiber-epoxy composites showed p-type thermoelectric behavior, and the generated voltage and Seebeck coefficient increased with increasing applied temperature and temperature difference.

Woven carbon fiber (WCF)-based polyester composites were developed via a vacuum-assisted resin transfer molding (VARTM) process in combination with CuO and graphene oxide (GO). The interlaminar resistive heating behavior and allied mechanical properties of the composites were investigated. The CuO nanoparticles were synthesized from copper nitrate and hexamethylenetetramine precursors using traditional microwave green synthesis, while the GO was synthesized by slight modification of Hummer’s method. The nanoparticle shapes and sizes were assessed via scanning electron microscopy, and the nanoparticle distributions in the composites and their chemical interactions were examined using X-ray diffraction and Fourier transform infrared spectroscopy. It was found that the composite strengths and moduli were enhanced by up to 61.2% and 57.5%, whereas the interfacial shear strength was enhanced by 89.9%. A composite filled with 120-mM CuO and 1.2-phr GO exhibited maximum performance as regards mechanical and resistive heating. Impact resistance measurements were conducted at 3-J penetration energy, and a 154.2% increase in nanofiller content was achieved. The addition of CuO nanoparticles increased the interlaminar resistive heating of the composite and, at 120-mM concentration, a 78.9% increment in the average temperature was attained. The presence of nanoparticles in the interlaminar region also decelerated the cooling process.

Polyamide 66 (PA66)/carbon fiber (CF) composites with acyl chloride-functionalized GO (AGO) and carbon nanotubes (CNTs) as hybrid fillers were prepared through in situ interfacial polymerization. The optimal ratio of AGO to CNTs in terms of hydrogen bonding in the composites was determined to be 2:1 via thermochemical analyses of the as-prepared PA66/AGO-CNT composites. The optimized hybrid filler-reinforced PA66/CF composites showed improvements in the interfacial shear strength, tensile strengh and storage modulus by 160, 136 and 300%, respectively, compared to the control sample, as well as high damping properties due to an enhanced transcrystalline interphase. The superior interfacial bonding between CF and PA66 is attributed to hydrogen bonding, enhanced dispersion, and the mechanical interlocking effect induced by AGO-CNT hybrids, which lead to effective energy absorption and load transfer.

In this study, carbon fiber (CF) composites were prepared by synthesizing thermally reduced graphene oxide (TRGO) directly on the surface of CFs in order to reinforce the interface between the CFs and the matrix. The conformal and robust coating of TRGO on the CF surface is achieved by the direct conversion of shellac, a low-cost natural polymer, to TRGO via single-step low-temperature (400–700 °C) annealing. X-ray photoelectron spectroscopy, Raman analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, contact angle measurement, and energy dispersive spectrometry results confirmed the synthesis of high-quality TRGO, which prompted hydrogen bonding and mechanical interlocking at the composite interfaces. The CF-TRGO composites showed 60 and 152% higher interlaminar shear strength (ILSS) and flexural strength, respectively than the untreated CF composites. The fracture surface analysis by SEM further reveals that the interfacial bonding between the matrix and the CFs increased significantly with TRGO coating.

A triboelectric nanogenerator (TENG) is an excellent tool for clean energy harvesting. Herein, we describe the development of a woven carbon fiber (WCF)-based multifunctional TENG-cum-structural supercapacitor and its connection via a rectifier so that the energy generated by the TENG is stored in the supercapacitor. The effectiveness of the WCF electrode was enhanced by growing P-doped Cu–Mn selenide nanowires on the surface. The polyester-based outer surface of the supercapacitor served as the positive electrode for the TENG and the polydimethylsiloxane-coated nanowire-WCF was the negative electrode. The integrated TENG generated 7.4 W m–2 of power, while the supercapacitor displayed energy and power densities of 97.21 Wh kg–1 and 54.25 W kg–1, respectively. The device retained excellent mechanical properties (strength: 583.11 MPa; modulus: 37.52 GPa; impact resistance: 69.91 J) after exposure to various outdoor environmental conditions. This type of device could mitigate the future energy demands of self-charging automobiles, electronics, and various outdoor applications.

In situ monitoring of resin flow, impregnation of carbon fiber fabrics, and curing during composite manufacturing are very important for determining the quality of composite parts. In conventional methods, sensors, such as optical fibers and strain gages, are bonded to or embedded in the composites for measuring the changes in mechanical and chemical properties. Although they can detect resin curing behavior and impregnation of carbon fibers, they may adversely affect the manufacturing process or structural integrity of the composites. In this study, carbon fiber itself was used as a sensor that minimizes the degradation of mechanical properties and increases the efficiency of monitoring the manufacturing process. The change in the electrical resistance of carbon fiber fabrics was monitored during the various manufacturing processes when the resin flowed through the carbon fiber fabric and curing progressed. The effectiveness of this monitoring method was confirmed, and it is expected to be applicable in monitoring the quality of the finished composite parts.

We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90–100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.

Measuring shear displacement and pressure simultaneously is essential for various applications, such as tactile sensors for robotic finger tips, shoe soles for gait monitoring, etc. We present a simple means of transducing shear displacement and pressure change to flexible composite sensor. The presented sensor consists of an array of cylindrical pillars standing on a flat substrate, which is composed of carbon nanotubes (CNTs) and polydimethylsiloxane. The sensing mechanism is based on changing CNT network in pillar and flat structure under shear and pressure. When a shear displacement change occurs in the pillar array, which transfers shear and pressure to flat structure in the sample, the CNT network in the sample is changed due to bending of the pillars. Under pressure, the load is transferred from the pillar array to flat structure inducing changes in relative resistance. Load transfer through this hierarchical structure enabled measurement of shear displacement and pressure up to 5 mm and 1200 kPa, respectively. Therefore, it shows great potential applications in monitoring or even recognizing various human physiological activities.

We investigated the tailored electromagnetic interference shielding effectiveness (EMI SE) of polyester-matrix composites consisting of glass fiber textiles coated with multiwalled carbon nanotubes (MWCNTs) and exfoliated graphite nanoplatelets (xGnPs). The effects of various combinations of material parameters, including MWCNT length, xGnP size, MWCNT:xGnP weight ratio, host-substrate surface configuration of carbon nanomaterials (CNMs), and their amount coated per unit area, on the EMI SE were studied. The shielding mechanisms, namely, absorption, reflection, and multiple reflections, are discussed based on the underlying governing physics. EMI SE measurements showed that coating glass fibers with hybrid MWCNTs/xGnPs at 8/2 ratio yields EMI SEs higher than those of composites containing the same content of a single-type of CNM, ranging from 56.8 dB at 30 MHz to 35.3 dB at 1.5 GHz. Morphological studies showed that, upon placement on glass fiber surfaces, 1D fiber-like MWCNTs serve as interconnects that bridge the randomly oriented 2D platelet-like xGnPs to form an efficient plane shield of electromagnetic waves.