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This paper studies the pyrolysis mechanisms of Nomex insulation paper in nitrogen and air atmospheres. The Nomex insulation paper is composed of 93% poly (m-phenylene isophthalamide) (PMIA) fibers and 7% inorganic substances based on elemental analysis. Using the thermogravimetry, it is found that the pyrolysis behaviors in nitrogen and air are similar below 770 K, with large discrepancies identified in the temperature range of 770–1073 K. The peak mass loss rate in air is 9 times higher than that in nitrogen. The kinetic analysis shows that the average activation energy (E ) in air is lower than that in nitrogen by 32% when the temperature is higher than 770 K, indicating a lower thermal stability. The PMIA fibers are found decomposing more seriously in air using SEM. Below 770 K, the functional groups of two atmospheres are mainly produced by the breakage of amide bonds and formation of aromatic nitrile. Unlike nitrogen, the organic substances in the solid residue are mostly oxidized at 1073 K in air. Consequently, the maximum productions of H2O, CO2 and CO in air are nearly 5 times higher than those of nitrogen, and the HCN generated during pyrolysis is further oxidized to NOx in air. Combining with the results of Py-GC/MS, it is inferred that the small molecules generated by the degradation of PMIA molecular chains, especially the benzene rings, will experience oxidization reactions in air atmosphere, with large amounts of H2O, CO2, CO and NOx produced. [ABSTRACT FROM AUTHOR]

Lead‐free halide perovskites possess excellent photoelectric properties, making them widely used in the photoelectric fields. Herein, lead‐free double perovskite crystals (PCs) doped with manganese (Cs2NaInCl6:Mn2+) are successfully prepared by the more energy‐efficient crystallization method. The crystals emit bright orange‐red light under the ultraviolet (UV) lamp, showing unique optical properties. They have the highest photoluminescence quantum yield of 42.91%. The white light‐emitting diodes (LEDs) are fabricated using these perovskite crystals, which show a color rendering index of 92 and external quantum efficiency (EQE) as high as 16.3%. Furtherly, perovskite‐modified fiber paper made of aramid chopped fibers (ACFs) and polyphenylene sulfide (PPS) exhibited fluorescent properties under different conditions. This paper combines fiber composite technology with PPS fiber filter bags, which are widely used in environmental protection, for the first time and demonstrates functional fiber filter bags with fluorescent characteristics. This filter bag provides an idea for the automatic detection of industrial filtration. Meanwhile, after being exposed to industrial waste gas for 60 h, the filter bag can maintain superior fluorescence performance. In this study, lead‐free double perovskites are synthesized using an efficient method for preparing high‐performance LEDs and high‐stability fluorescent fibers. Concurrently, the application of perovskites in environmental protection is expanded. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of a study that was conducted to evaluate the performance of field-produced aramid fiber-reinforced asphalt mixtures used for resurfacing applications and compare it to that of polymer-modified asphalt mixtures. Twelve test sections were constructed as part of resurfacing projects in Ohio. Two aramid fibers from different sources were used in these projects. During the construction of the test sections, loose asphalt mixtures were collected and were used to prepare samples. Different tests were conducted on the prepared samples. These included the following: semicircular bend and indirect tensile asphalt cracking to evaluate the cracking resistance of prepared samples, the asphalt concrete cracking device test to evaluate the low-temperature cracking resistance of prepared samples, and the Hamburg wheel tracking test to evaluate the resistance of samples to rutting and moisture damage. Results indicated that the effects of the addition of aramid fiber to asphalt mixture vary depending on the type of aramid fiber and mixture properties. In general, Fiber A and Fiber B significantly improved the cracking resistance of mixtures with PG 64-22. Furthermore, mixtures with PG 64-22 binder and aramid fibers had similar or higher cracking resistance as compared to those with PG 70-22M asphalt mixture. The addition of fibers improved the resistance of reinforced mixtures to rutting and moisture damage. The fibers slightly improved the low-temperature cracking resistance of asphalt mixtures. Statistical analysis of testing results indicated that the properties related to the cracking resistance of the fiber mixtures did not significantly change during production. [ABSTRACT FROM AUTHOR]

A multi‐stage fiber spreading process for the preparation of high‐performance continuous aramid fiber reinforced nylon 12 (CAF/PA12) composites was proposed in this paper. The effects of spreading rod crown radius, spreading rod axis height and traction speed on fiber impregnation effect and filaments properties were investigated. The fiber volume fraction of the prepared filament was approximately 30%. And the maximum tensile strength and modulus of the filaments were 839.89 MPa and 41.35 GPa, which were 34.36% and 34.30% higher than unspreading filaments, respectively. The influences of printing process parameters such as printing temperature, the combination of layer thickness and printing spacing on the transverse tensile properties of the specimens were studied. Printed specimens reached a transverse tensile strength and tensile modulus of 13.988 MPa and 1.293 GPa, respectively. The influences on low velocity impact properties of the specimens were also investigated in terms of impact energy and printing stacking sequences. Results revealed that the impact threshold energy of orthotropic ([0/90/0/90]2) specimens was 50 J. Quasi‐isotropic ([0/45/90/−45]2) specimens exhibited the superior impact resistance with an impact load of 4.939 kN. Macro‐ and micro‐matrix crack, surface buckling, fiber fracture and delamination were the main failure modes of the specimens. Highlights: A novel thermoplastic composite filament forming process was proposed, and the filament forming equipment was designed and manufactured.Continuous aramid fiber‐reinforced PA12 filaments with about 30% fiber content were prepared by orthogonal tests under different forming process conditions, which showed maximum tensile properties of 839.89 MPa and 41.35 GPa, respectively.Spreading multiplication was positively related to filament tensile properties, which was major affected by the axial height of the spreading rod.Transverse tensile strength (13.988 MPa tensile strength and 1.293 GPa tensile modulus) of printed specimens was investigated under different printing parameters.Fiber orientation had a significant effect on the low‐velocity impact properties. Micro‐ and macro‐matrix crack, surface buckling, fiber fracture and delamination were the main failure modes of the low‐velocity impact specimens. [ABSTRACT FROM AUTHOR]

Carbamate is a key structural motif in the development of fungicidal compounds, which is still promising and robust in the discovery of green pesticides. Herein, we report the synthesis and evaluation of the fungicidal activity of 35 carbamate derivatives, among which 19 compounds were synthesized in our previous report. These derivatives were synthesized from aromatic amides in a single step, which was a green oxidation process for Hofmann rearrangement using oxone, KCl and NaOH. Their chemical structures were characterized by 1H NMR, 13C NMR and high-resolution mass spectrometry. Their antifungal activity was tested against seven plant fungal pathogens. Many of the compounds exhibited good antifungal activity in vitro (inhibitory rate > 60% at 50 μg/mL). Compound 1ag exhibited excellent broad-spectrum antifungal activities with inhibition rates close to or higher than 70% at 50 μg/mL. Notably, compound 1af demonstrated the most potent inhibition against F. graminearum, with an EC50 value of 12.50 μg/mL, while compound 1z was the most promising candidate fungicide against F. oxysporum (EC50 = 16.65 μg/mL). The structure–activity relationships are also discussed in this paper. These results suggest that the N-aryl carbamate derivatives secured by our green protocol warrant further investigation as potential lead compounds for novel antifungal agents. [ABSTRACT FROM AUTHOR]

This paper presents the development, characterization, and testing of PP/PE-g-MA composites with 10 and 15 wt% surface-modified aramid fibers, and aluminum-based pigment, as covers for a small drone body for collision protection. The successful fiber surface modification with SiO2 by the sol–gel method using TEOS was confirmed by FTIR, SEM, and EDS analyses. The composites were characterized by FTIR and SEM analyses and surface energy and water contact angle measurements and tested in terms of tensile, flexural, impact, and thermal properties. The materials exhibited hydrophobic character and compact and uniform morphostructures, with increased surface energy with fiber content owed to improved adhesion between modified fibers and the matrix. Compared to the control sample, composites with modified fibers showed an increase by 20% in tensile strength, and 36–52% in the modulus, and an increase by 26–33% in flexural strength and 30–47% in the modulus, with higher values at room temperature. Impact resistance of modified fiber composites showed an increase by 20–40% compared to the control sample, due to improved interaction between SiO2-modified fibers and maleic anhydride, which inhibits crack formation, allowing higher energies' absorption. The composites were vacuum-thermoformed on 3D-printed molds as a two-part cover for the body of a drone, successfully withstanding the flight test. [ABSTRACT FROM AUTHOR]

The paper presents a study on composites based on 50:50 (PP:LLPE‐g‐MA) reinforced with 0.5, 1, and 2 wt% aramid fibers unmodified/modified with TiO2, processed by melt compounding. Micronic aramid fibers were acetone washed to remove impurities and treated with Ti(IV)isopropoxide precursor via sol–gel method, adding microcellulose for TiO2 particle dimension control. Composites were hot‐pressed into 4 mm‐thick plates for sampling and 0.5 mm‐thick sheets for thermoforming. All composites were successfully thermoformed, fibers‐based samples showing improved thermoforming ability without wrinkling. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy dispersive X‐ray spectroscopy (EDS) analysis confirmed the formation of TiO2 particles on the fiber surface. Optical microscopy, SEM and FTIR analysis exhibit the fibers' strong embedment into the matrix due to physical interlocking, generating surface defect reduction. Water absorption decreased from 0.195% (control) to 0.075 and 0% for 1 TiO2 and 2 TiO2 samples, due to material compactization. Contact angles increased from 95.18° (Control) to 108° (1 TiO2) and 112.89° (2 TiO2). The highest flexural strength and modulus were exhibited by 1 TiO2 sample that increased by 44.88% and 47.6% compared to the control sample, due to higher intrinsic rigidity of fibers and TiO2 modifying surface rugosity and phase interaction. The impact strength of the control sample improved by 139% compared to PP due to brittleness reduction, 1 TiO2 by 209% compared to PP, 29% compared to the control sample. The results and excellent thermoformability recommend the materials for encapsulation of electronic/expensive parts in automotive or drone applications, offering viable, facile, rapid, and cost‐effective solutions to easily replace damaged parts. Highlights: Aramid fibers were successfully modified using isopropoxide precursor;Strong embedment of fibers in the polymer diminishes crack propagation/damage;Improved impact and bending properties and water contact angle;The composites showed a high ability to thermoform into complex shapes;Potential to replace non‐reusable materials as encapsulation solutions. [ABSTRACT FROM AUTHOR]

The addition of fibers to asphalt mixtures has the potential to improve the resistance of asphalt mixtures to cracking and permanent deformation (rutting). However, the state (distribution) of fibers in the asphalt mix is critical parameter in determining performance enhancement. This study evaluated the impact of different laboratory mixing methods (mainly Hobart and bucket) on fiber distribution and selected a method comparable to plant-produced fiber-reinforced mixes. The laboratory performance of plant-mixed lab-compacted (PMLC) and lab-mixed lab-compacted (LMLC) fiber-reinforced mixtures was compared. Four types of laboratory and plant mixtures [unreinforced, polyolefin and aramid (PFA) fibers at 0.05% dosage, and Sasobit-coated aramid (SCA) fibers at 0.01% and 0.02% dosages] were produced to compare the laboratory performance of asphalt mixtures. The cracking resistance [evaluated using indirect tensile strength (ITS) and semicircular bend (SCB) tests], rutting susceptibility [evaluated using flow number (FN) and the Hamburg wheel tracking test (HWTT)], durability (evaluated using Cantabro loss), and fatigue (evaluated using a uniaxial fatigue test) performance of control and fiber-reinforced asphalt mixtures were evaluated. Among laboratory mixing methods, a bucket mixer was selected to produce LMLC samples because it produced the maximum fiber distribution (87% of fibers in the individual state). Laboratory performance testing results showed that PFA-reinforced mixtures enhanced the rutting performance regardless of mixing method. The mixtures with PFA 0.05% and SCA 0.01% fibers were highly durable and had better dynamic modulus (|E*|) at low frequency and high temperature. Cracking performance was improved with the addition of SCA fibers into the mix; however, fiber-reinforced mixes (PFA 0.05% and SCA 0.01%) had higher fatigue damage tolerance, except SCA 0.02% reinforced mix. The laboratory bucket mixing method is representative of plant-produced fiber-reinforced mixtures, and laboratory performance results were consistent for laboratory bucket and plant produced mixtures. This paper showcases laboratory mixing method equivalent to fiber distribution that produce fiber-reinforced asphalt mixtures comparable to those produced at an asphalt plant. Different laboratory mixing equipment, including Hobart and bucket mixers, was used to produce fiber-reinforced asphalt mixtures in the laboratory. Aramid fibers were added into these mixers after separation by hand. In addition, the same fiber-reinforced mixtures were produced at a batch plant for comparison purpose. Fibers and binder were extracted from all mixtures and individual fibers (indicating better fiber distribution) were quantified. According to the results, the use of a bucket mixer led to better fiber distribution within the produced asphalt mixtures than did a Hobart mixer. Laboratory performance comparison results showed that the mixes produced using the bucket mixer had identical results to plant-produced mixtures. Hence, using a bucket mixer and introducing aramid fibers after hand separation is an effective way to produce plant-representative fiber-reinforced asphalt mixtures. This is a major step toward designing and producing fiber-reinforced asphalt mixtures and enhancing the cracking performance of asphalt mixtures. [ABSTRACT FROM AUTHOR]

In general, the majority of fiber-reinforced polymer composites (FRPs) used in structural applications comprise carbon, glass, and aramid fibers reinforced with epoxy resin, with the occasional utilization of polyester and vinyl ester resins. This study aims to assess the feasibility of utilizing recyclable and sustainable materials to create a resilient composite suitable for structural applications, particularly in scenarios involving low-velocity and high-velocity impact (LVI, HVI) loading. The paper presents a comparative analysis of the performance of E-glass, aramid, and eco-friendly basalt-reinforcing fabrics as reinforcement fibers in both thermosetting (epoxy) and recyclable thermoplastic (Elium©) resins. Given the limited research on Elium composites, especially those incorporating basalt-reinforcing fiber, there is an urgent need to expand the databases of fundamental mechanical properties for these diverse composites. This necessity is exacerbated by the scarcity of the literature regarding their performance under low- and high-velocity impact loadings. The results of this study will demonstrate the potential of basalt-reinforced Elium composite as an effective recyclable and environmentally friendly structural material system for both static and dynamic loading conditions. [ABSTRACT FROM AUTHOR]

Resin mineral composites (RMC) have attracted a great deal of attention in ultra-precision machining because of their excellent vibration-dampening properties; however, their poor mechanical properties limit their wide applications. Adding reinforcing fibers is an effective way to improve the mechanical properties of RMC. This paper systematically studies the effect of aramid fibers as reinforcing components on the mechanical and thermal expansion properties of RMC. Results show that the mechanical strength of RMC can be effectively improved by a suitable selection of surface treatment methods and parameters. The mechanical strength of RMC reached its maximum value when the ultrasonic power was 200 W and the treatment time was 6 min; the mechanical strength of RMC reached its maximum value when the concentration of phosphoric acid oxidation was 20 wt % and the treatment time was 2 h. This study investigates the effect of different surface treatments on aramid fibers on the mechanical properties of resin mineral composites, optimizes the aramid fiber surface treatment parameters, enhances the mechanical properties of resin mineral composites, and extends the applications of resin mineral composites in high-speed processing and ultra-precision processing. [ABSTRACT FROM AUTHOR]

The paper investigates the normal interaction between the steel striker, carbon fiber and aramid fiber reinforced plastic plates at a speed ranging from 166.6 to 184.2 m/s. A series of physical and numerical experiments with impact load is conducted to design a mathematical model and numerical algorithm for the composite plate. The behavior and fracture of composites are described by the elastic-brittle model accounting for their different compressive and tensile strengths. The numerical simulation utilizes the finite element method in the EFES software developed by the authors. [ABSTRACT FROM AUTHOR]

Currently, fiber-reinforced polymer composites (FRPs) used for demanding structural applications predominantly utilize carbon, glass, and aramid fibers embedded in epoxy resin, albeit occasionally polyester and vinyl ester resins are also used. This study investigates the feasibility of employing recyclable and sustainable materials to formulate a composite suitable for load-bearing structural applications, particularly in scenarios involving low-velocity and high-velocity impacts (LVIs and HVIs, respectively). The paper presents a comparative analysis of the performance of basalt–Elium, a fully recyclable, sustainable, and environmentally friendly composite, with an epoxy-based counterpart. Moreover, an accurate and reliable numerical model has been developed and introduced through which the response of these composites can be examined efficiently and accurately under various loading states. The results of this investigation demonstrate the viability of the basalt–elium composite as a fully recyclable and sustainable material for crafting efficient and lightweight composites. Additionally, the accurately developed finite element model presented here can be used to assess the influence of several parameters on the composite, thereby optimizing it for a given situation. [ABSTRACT FROM AUTHOR]

This study investigated the high‐velocity impact behavior of composite plates with different hybrid ratios and structural configurations through experimental and numerical simulation studies. The results showed that the critical penetration velocity of the composite plate generally increases with an increase in the volume fraction of aramid fibers. The high‐velocity impact finite element model developed in this study accurately simulated the high‐velocity impact behavior of laminated fiber composite plates with various hybrid ratios and different structures. The impact failure patterns of the plates were analyzed, and it was observed that the carbon fibers on the back face were prone to tensile fracture, followed by the gradual fracture of aramid fibers. The numerical simulation results show significant differences in residual impact velocity and energy absorption when impacted from different sides and the impact from the aramid side resulted in better energy absorption, which is contrary to the findings in many existing research papers. These findings provide valuable insights into the impact resistance of composite materials and can guide the design and development of high‐performance composite structures for aero‐engine case designing. Highlights: The high‐velocity impact behavior of C/K fiber epoxy resin matrix composite laminates are studied.The critical penetration velocity increases with the increase of aramid fiber volume fraction.The laminate absorbs most of the impact energy during the instantaneous impact time.Energy absorption ability is better when the impact surface is aramid fibers.Carbon fibers on the back side of the laminate are more prone to tensile fracture. [ABSTRACT FROM AUTHOR]

The recent advancements in communication technology have facilitated the widespread deployment of electronic communication equipment globally, resulting in the pervasive presence of electromagnetic pollution. Consequently, there is an urgent necessity to develop a thin, lightweight, efficient, and durable electromagnetic interference (EMI) shielding material capable of withstanding severe environmental conditions. In this paper, we propose an innovative and scalable method for preparing EMI shielding films with a tunable sandwich structure. The film possesses a nylon mesh (NM) backbone, with AgNWs serving as the shielding coating and aramid nanofibers (ANFs) acting as the cladding layer. The prepared film was thin and flexible, with a thickness of only 0.13 mm. AgNWs can easily form a conductive network structure, and when the minimum addition amount was 0.2 mg/cm2, the EMI SE value reached 28.7 dB, effectively shielding 99.884% of electromagnetic waves and thereby meeting the commercial shielding requirement of 20 dB. With an increase in dosage up to 1.0 mg/cm2, the EMI SE value further improved to reach 50.6 dB. The NAAANF film demonstrated remarkable robustness in the face of complex usage environments as a result of the outstanding thermal, acid, and alkali resistance properties of aramid fibers. Such a thin, efficient, and environmentally resistant EMI shielding film provided new ideas for the broad EMI shielding market. [ABSTRACT FROM AUTHOR]

To develop and implement reinforcing fibers of small diameter (less than 15 μm) and an elastic modulus exceeding 50 GPa, it is necessary to determine their mechanical properties. However, most of the conventional methods are challenging to apply to such objects due to the scale effect of the gauge length (distance between grips) on the static modulus when measuring fiber deformation by moving the grips (crosshead movement). This paper examines several advanced high-modulus fibers, including Twaron and Armos, along with introducing a model for calculating real modulus from measured values. To validate the model, experimental tests were carried out for several aramid fibers. [ABSTRACT FROM AUTHOR]

We proposed a feasible and straightforward approach for fabricating a superhydrophobic polytetrafluoroethylene coated polyphenylene sulfide/aramid composite film (PTFE@PPS/ACFs porous membrane) for oil-water separation. This process involves utilizing a wet paper making process combined with a spray coating technique. The PPS/ACFs composite membrane displays a three-dimensional network structure by the application of wet papermaking approach. The uniformly spray coating of PTFE on its surface results in a superhydrophobic PTFE@PPS/ACFs porous membrane (PPAM). The membrane obtained through this method can effectively separate oil and water. It is remarkable in separating oil-water lotion stabilized by surfactant, achieving a separation efficiency of up to 99.9 % with a high flux of 8000 L/m2·h−1. Additionally, owing to the inherent thermal stability of the membrane, the PPAM is recyclable. In summary, the PTFE@PPS/ACFs porous membrane is a promising for separating various oil-water emulsions. Its outstanding performance, including high separation efficiency, flux, and recyclability, underscores its potential for practical applications for oil-water separation. [Display omitted] • The PPAM porous membrane has high separation efficiency and a high flux. • Significant repetitive recyclability of the membrane suggest its applications in environmental protection. • After 20 cycles of oil-water separation, the membrane maintained high separation efficiency and flux. [ABSTRACT FROM AUTHOR]

• The tool-workpiece contact rate of the straight blade is systematically analyzed. • The theoretical model of fracture force at the blade edge is established. • The theoretical model of friction force on blade surfaces is established. • Reduction mechanism of cutting forces in ultrasonic cutting is revealed. Aramid honeycomb has extensive applications in the aerospace and rail transportation industries. Ultrasonic cutting (UC) with the straight blade (SB) is an advanced technology used for the profile machining of honeycomb materials. Cutting force is an important factor affecting machining quality, and its accurate modelling is particularly important. However, SB is a flake tool, and chips of honeycomb are removed in block or strip forms during cutting, and its structure and material removal method are obviously different from conventional machining. Existing simplified cutting force models based on kinematic analyses and experiments are incapable of describing the cutting process. In this paper, a geometrical kinematics analysis of SB is conducted. Further, the modelling of tool-workpiece contact rate (TWCR) for UC with SB is established, which is utilized to analyze the tool-material contact state. Based on the principle of conservation of energy, the fracture force at the blade edge is analyzed. Based on the analysis of instantaneous friction force, the friction force model on blade surfaces is established. Multiple-cutting experiments are conducted to separate fracture force and friction force. The influence of machining parameters (ultrasonic amplitude, lead angle, cutting speed) on TWCR, cutting force, fracture force, and friction force have been theoretically and experimentally studied, and the reduction mechanism of the cutting force is revealed. Furthermore, the machining quality under different machining parameters is observed and the relationship with cutting force is analyzed. The paper not only provides theoretical guidance for the study of the UC mechanism but also helps to guide the UC process of aramid honeycomb. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, short Kevlar fiber was added to epoxy resin adhesive to form a short fiber toughened adhesive, and its effect on the static strength and elongation at break of Carbon fiber laminate adhesively bonded single lap joints was investigated. 1 wt%, 2 wt%, 3 wt% and 4 wt% short Kevlar fibers were added to make short fiber toughened adhesive joints to investigate the effects of different contents of short Kevlar fibers on the connecting properties of the test pieces of Carbon fiber laminate single lap adhesively bonded joints; In addition, microscopic toughening mechanism of short Kevlar fiber in adhesives revealed by combining DIC technique and SEM technique. The test results showed that the addition of appropriate amount of short Kevlar fiber could slow down the crack extension compared with the without toughening specimens, but the toughening effect was weakened by excessive content. 2 wt% short Kevlar fiber toughened specimens achieved the best toughening effect, with 30.52 % increase in peak load and 25.78 % increase in elongation in tensile test. The combination of DIC and SEM further showed that short Kevlar fiber toughened joints absorb crack strain energy through fiber-bridging thus increasing adhesive properties. [ABSTRACT FROM AUTHOR]

The paper investigated the experimental study of composite spherical-roof contoured-core (SRCC) sandwich panels under a V-shaped quasi-static indentation (QSI) test. The carbon fiber, glass fiber, aramid fiber, hybrid carbon/aramid, and glass fiber chopped strand mat sheets were used to manufacture the composite cores, which used the hand layup and hot compression techniques. The polylactide (PLA) core was fabricated using fused deposition modelling (FDM). The V-shaped indenter had a 65° angle and was set at 1 mm/min as indentation speed in the experimental test. It was found that the maximum indentation deflection was 35.49 mm on the SRCC sandwich panel with a hybrid carbon/aramid core compared to other composite cores. Furthermore, it was localized fiber fracture, matrix damage, delamination, inwards fronds, and debonding damage mode on composite SRCC sandwich panels, which was visually shown at the central SRCC core unit cell. It is highlighted that aramid fiber and hybrid carbon/aramid materials can provide outstanding impact characteristics, which have great potential to be used as impact-resistant sandwich structures. [Display omitted] • Composite spherical-roof contoured core (SRCC) sandwich panels are manufactured. • The impact damage of composite sandwich panels is determined under the V-shaped quasi-static indentation loading. • The hybrid carbon/aramid SRCC core sandwich panel exhibits the maximum indentation deflection of 35.49 ± 2.63 mm. • Carbon fiber-reinforced plastic SRCC core sandwich panel had the highest peak load mass ratio value of 17.92 ± 0.32 N/g. [ABSTRACT FROM AUTHOR]

• 16-DOF 1D nonlinear element for Fiber Reinforced Cementitious Matrix FRCM composites. • Separate modelling of matrix layers, fiber net and interfaces (fiber–matrix and matrix substrate) • Possibility to investigate accurately the global and local behavior of strengthened specimens. • Treatment of non-linearity and softening with progressive reduction of the elastic moduli. • Comparison with experimental tests carried out on FRCM reinforced curved masonry pillars. The paper presents a novel non-linear one-dimensional finite element with 16 degrees of freedom aimed at modelling Fiber Reinforced Cementitious Matrix strengthening systems. Such composite is typically constituted by three superimposed layers −namely an outer matrix, a central fiber textile and an inner matrix- subjected to a prevailing longitudinal monoaxial stress state. They interact by means of interfaces exchanging both tangential and −when the reinforcing system is applied to curved substrates- traction/compression stresses. Matrix is made by mortar −possibly reinforced- exhibiting medium to high strength, whereas the fiber net can be aramid, carbon, glass, steel, basalt, etc. The reinforcing system is then connected to a substrate by means of a further interface. The finite element is a two-noded assemblage of three trusses representing matrix and fiber layers. Shear and normal springs are lumped at the nodes, mutually connecting contiguous trusses and the inner matrix to the substrate. They represent the interfaces and exchange normal and shear actions between contiguous layers or transfer them from the reinforcing system to the substrate. The degrees of freedom, 8 per node, are the longitudinal and transversal displacements of the three layers and of the substrate, evaluated at the nodes. Material non-linearity can be considered both for trusses and springs, giving the possibility to account for all the experimentally documented damaging cases that can be encountered in practice. Both softening and inelastic behavior are numerically tackled with a fully explicit algorithm where the elastic modulus of the layers and the stiffness of the interfaces are reduced at the new iteration if in the previous one the elastic limit is exceeded. The stiffness matrix is provided straightforwardly also in the inelastic case, showing the promising simplicity of the element when coupled with the non-linear solver. The performance of the novel finite element is validated against a comprehensive experimental dataset referring to curved masonry pillars reinforced with Fiber Reinforced Cementitious Matrix and tested in single lap shear. [ABSTRACT FROM AUTHOR]

• The composite has a good energy dissipation characteristic. • The von Mises stresses on the skull are not enough to induce injury. • The Back Face Signature obtained are in line with standards. The research involved analyzing a material solution for a 9 mm Full Metal Jacket (FMJ) Parabellum loaded with ballistic impact on a resin laminate strengthened with extra aramid layers. The goal of this research is to determine the impact of material (aramid/DCPD) layer thickness on the energy absorption performance of the laminate for blunt trauma as blunt criterion (BC). For this purpose, aramid fiber laminate with dicyclopentadiene (DCPD) resin matrix was prepared. Laminate samples were tested on the drop test and were subjected to ballistic loads. The ABAQUS/Explicit program and finite element method were used to conduct the study. Individual material systems' optimal solutions were created using numerical analysis, and they were then classified using the mass-efficiency criterion. The numerical results were compared with the experimental using samples prepared according to the modeling methods. Selected results were shown and discussed in the later part of the paper. [ABSTRACT FROM AUTHOR]

In this work, the probability of water channel formation was calculated for several polymeric materials, and with that information, the desalination capacity of each material was assessed. Using a 3D lattice model for a flat sheet, the Gibbs free energy change (Δ G) that results from the formation of the first water channel from the top to the bottom surface of the sheet was calculated as a function of the hydrophilicity/-phobicity of the polymeric material (w), the total fraction of water in the 3D lattice (x), and the thickness of the lattice (n). With this result, an equation was further derived to evaluate (x b) the fraction of water which is related to the channel formation, and (x b / x), the ratio of x b to x. It was found that the values of x b are closely related to the fractional free volume (FFV) measured by positron annihilation lifetime spectroscopy (PALS) and the percent free volume of percolated open spaces where water could pass through obtained by molecular dynamics simulation (MDS). These equations were then used to assess the usefulness of each material for making reverse osmosis membranes. When x b is too large, too many channels form, and those channels join to form large pores through which salt can pass, rendering reverse osmosis unsuccessful. On the other hand, when x b is too small, not enough water channels are formed, so reverse osmosis cannot occur then either. It was found that x b was too small for polyvinylidene fluoride (PVDF) and polyethersulfone (PES); suitable for cellulose acetate (CA), aromatic polyamide (APA) and aromatic polyamidehydrazide (APAH); and too large for cellophane (CE). This paper determines which circumstances allow water to form channels in a membrane, and it provides a novel method to assess a material's suitability for reverse osmosis. [Display omitted] • The probability of water channel formation in a polymeric membrane was evaluated by statistical thermodynamics. • Using a 3D lattice model for a flat sheet, the Gibbs free energy change for water channel formation was calculated. • The Gibbs free energy change was used to assess the usefulness of polymeric materials for reverse osmosis membranes. • The computational results were compared with the FFV obtained by PALS and water content of the channel obtained by MDS. [ABSTRACT FROM AUTHOR]

Semi-aromatic polypiperazine-amide (PPA) nanofiltration (NF) membranes are widely used in water treatment applications, but the resistance to free chlorine and other biocidal agents need to be improved. Understanding the chlorination mechanisms of PPA NF membranes is of great significance for avoiding membrane degradation and developing new chlorine-resistant membranes. In this paper, the effects of chlorination on the rejection selectivity as well as the surface charge, hydrophilicity and roughness, and pore size distribution of PPA NF membranes are presented. In addition, the chlorination mechanisms of the membranes are proposed through functional groups characterization of the stripped PPA active layer, element composition analysis, quantum mechanical calculations based on density-functional theory, and use of model compound ((3,5-dimethylphenyl)(4-methylpiperazin-1-yl)methanone) for PPA material. The molecular active chlorine species, HOCl, predominantly induces the cleavage of C–N bonds, whereas the primary reaction pathway caused by the ionic active chlorine species, ClO−, involves the ring-opening of benzene. Under the same chlorination conditions, HClO has a more severe impact on membrane properties and performance than ClO−. NF membranes with a looser polyamide layer are more susceptible to the attack by active chlorine species. [Display omitted] • Chlorination's impacts on PPA NF membranes performance and properties were studied. • DFT calculations with model compounds supported functional group characterization. • HOCl was more destructive than ClO− in degrading the PPA, via different pathways. • Active layer of lower cross-linking degree was more susceptible to chlorine attacks. [ABSTRACT FROM AUTHOR]

• A novel carbon/aramid weft-knitted reinforced hybrid composite with good impact resistance was proposed. • The effects of knitted stitches and loop configurations on the low-velocity response of carbon/aramid hybrid composites were investigated. • Multiple damage observation methods were adopted, such as three-dimensional optical microscopy, ultrasonic C-scan, and micro-CT for multi-scale and quantitative damage analysis. Carbon and aramid fiber hybridization is an effective method to improve the impact toughness of composites, thus this paper attempts to develop carbon/aramid hybrid weft-knitted reinforced composites to improve the impact resistance of carbon fiber composites. Three hybrid and two non-hybrid weft-knitted reinforced composites employing carbon and aramid bundles were prepared. Low-velocity impact tests at different impact energies were performed, and the impacted samples were analyzed for visual and internal damages utilizing a three-dimensional optical microscope, ultrasonic C-scan, and micro-CT to explore the damage mechanisms. The results demonstrate that the knitted stitches and loop configuration affect the peak load, deflection, and damage crack initiation and expansion of the composites. The alternating configurations of carbon and aramid fiber in the in-plane and thickness directions incorporate the advantages of the high strength of carbon fibers and the toughness of aramid, exhibiting good impact mechanical properties and damage tolerance. The tight loop laminated structure had excellent impact resistance, with prominent peak loads and tiny damage volumes, but it encountered internal delamination and loop breakages. [ABSTRACT FROM AUTHOR]

With the growing demands in electronics, communications, and energy, conductive composites face a daunting challenge as criteria for conductivity and mechanical properties rise. Extensive search on nanocomposites and amorphous metals has been motivated by the quest for a conductive material that can enhance strength and deformability. However, finding conductive materials that can overcome the drawbacks of their conventional counterparts and exhibit great strength, toughness and quick charge transmission while accomplishing large-scale production remains a significant challenge. This paper describes an approach to high-temperature flexible conductive materials by utilizing composites composed of aramid nanofiber (ANF) and silver nanoparticles (Ag NPs). The ANF is derived from macro-aramid fibers and retains its excellent mechanical properties and heat resistance. Within the composite, Ag NPs effectively enter the special nanofiber matrix to build a tightly connected conductive pathway on the ANF, thus facilitating efficient charge transport. The resulting Ag-ANF composite films exhibit an impressive electrical conductivity of 36,989.68 S m−1 and a tensile strength of 30.3 MPa. Additionally, they provide outstanding EMI shielding with a value of 107.9 dB. This significant achievement opens up the possibility of metallizing the surface of insulated polymer fibers, thereby enabling effective EMI shielding applications even in challenging and extreme conditions. [Display omitted] • Highly shielded Ag-ANF composite films with good mechanical strength and flexibility were fabricated. • Ag-ANF composite films exhibited ultra-high conductivity of 36,989.68 S m−1. • Ag-ANF composite films represented excellent shielding effect exceeding 107.9 dB to electromagnetic waves in the X-band. [ABSTRACT FROM AUTHOR]

Currently, extensive utilization of wireless devices require human being tantamount to tackle electromagnetic wave pollution to avoid serious harm to health body and precision equipment. Herein, asymmetric structure hybrid film were developed from para-aramid nanofiber (PANFs), carboxylated multiwalled carbon nanotubes (c-MWCNT) and silver nanowire (AgNWs) through vacuum-assistant filtration and freeze drying route. The robust and high aspect ratio PANFs established matrix foundation for forming large scale hybrid film, which rendered feasible support for conductive building blocks c-MWCNT and AgNW. Thanks to the unique asymmetric porous structure, the as-prepared c-MWCNT/AgNWs/PANFs hybrid film with 8 wt% of c-MWCNT and 4 wt% of AgNW remained efficient EMI shielding performance, whose shielding effectiveness (SE) and specific effectiveness (SEE/t) reached 40.59 dB and 10678.17 dB cm2 g−1 at thickness of 0.061 mm in X band, respectively. Furthermore, the shielding effectiveness and absorption coefficient could be regulated by c-MWCNT content, AgNW content, and ratio of c-MWCNT and AgNW. With improving the conductive ratio, the c-MWCNT/AgNWs/PANFs hybrid film possessed tunable shielding effectiveness between 9.40～40.59 dB and absorption coefficient between 0.028～0.303. This work provided feasible avenue for controlling electromagnetic feature through tailoring conductive blocks strategy. [Display omitted] • The c-MWCNT/AgNWs/PANFs hybrid film with asymmetric porous structure were constructed via vacuum-assistant filtration and freeze-drying combined route. • The c-MWCNT/AgNWs/PANFs hybrid film exhibited outstanding shielding effectiveness and specific effectiveness, whose value achieved 40.59 dB and 10678.17 dB cm2 g−1, respectively. • The tailoring conductive-building-blocks strategy were proposal to tackle balance between efficient EMI shielding and controllable absorption coefficient. [ABSTRACT FROM AUTHOR]