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The serious damage caused to 3D braided carbon fiber (CF)/epoxy (EP) composites in high-energy irradiation environments is a pressing research topic that has not yet been reported. This study analyzed the γ-irradiation multi-scale damage of the matrix, interfaces, and near-interface regions in 3D braided CF/EP composites with three different braiding angles (18°, 28°, 38°) at atomic, microscopic, and macroscopic scales. The molecular structure and atomic charge information alterations of epoxy matrix were characterized using soft X-ray absorption spectroscopy (sXAS). When the irradiation dose reached 1000 KGy, the compressive strength of composites decreased by 20.88 %, 18.07 %, and 16.60 %, respectively, with an increase in the braiding angle. Micro-CT observation, along with statistical computing, confirmed that irradiation causes interface damage and increases the defect volume of 3D braided composites. Nanoindentation was used to compare the modulus of carbon fiber, interface, near-interface regions and matrix in irradiated composites and the function of CF/resin interface as an irradiation defect capture site in the irradiation resistance of resin-matrix composites has been newly established. In addition, the mechanism behind the effect of braiding angle on macroscopic properties was also analyzed. [Display omitted] • The braided structures exhibited varying responses to irradiation, with 3D-38° showing the highest performance retention. • Soft X-ray absorption spectrometry was developed to characterize the valence changes of oxygen and carbon in irradiated resin. • Interface as an irradiation defect capture site consumes most of the energy and reduces the damage of resin near the interface. [ABSTRACT FROM AUTHOR]

Abstract The understanding of dynamic damage and failure of thermo-oxidative aged 3D carbon fiber/epoxy braided composite is critical to its durability design. Here we aim at a fine description of damage and failure of aged composites under impact compression by means of experiment and finite element analysis (FEA). The composites and epoxy resins were aged in air at 110 °C, 130 °C and 150 °C for prescribed time, respectively. The failure processes were recorded with high-speed camera. We found that with the increase of ageing temperature, the interface damage becomes more serious and the epoxy resins tend to a rubbery behavior. For the composites aged at lower temperature (110 °C), the impact resistance degradation is mainly attributed to the degradation of epoxy resin. While interface degradation is found to be the dominant degradation mechanism when the composites aged at higher temperature (130 °C, 150 °C). FEA results showed that in the process of impact, the plastic deformation induced temperature and thermal stress of the aged composites decrease compared with the unaged composite. For the unaged composites and the composites aged at lower temperature, the damage of reins is the main factor that affects the energy absorption of fiber tows. The interface damage plays a more important role in the energy absorption of fiber tows when the composites aged at higher temperature. [ABSTRACT FROM AUTHOR]

We proposed a thermo-mechanical coupled model to better understand the coupling effects of thermo-oxidative aging and braiding structure on the high-speed impact responses of 3D braided carbon fiber reinforced epoxy composite. The impact responses of the aged and unaged braided composites with different braiding structures were experimentally and numerically investigated. We found that both thermo-oxidative aging and braiding structure have a significant influence on the impact responses of braided composites, and they also affect each other. Stress, adiabatic temperature rise, thermal strain and thermal stress of composites will decrease after aging, while increase with the increase of braiding angle. Increasing the braiding angle of the braided composite can effectively reduce the effect of thermo-oxidative aging on the impact responses. When the braiding angle is 42, the mechanical properties and damage of the composites are almost unaffected by thermo-oxidative aging, but the thermal stress in the impact process decreases significantly after aging. • The coupling effects of braiding structure and thermo-oxidative aging on the high-speed impact responses were experimentally and numerically investigated. • Stress, adiabatic temperature rise, thermal strain and thermal stress of composites will decrease after aging, while increase with the increase of braiding angle. • Increasing the braiding angle of the braided composite can effectively reduce the effect of thermo-oxidative aging on the impact responses. [ABSTRACT FROM AUTHOR]

Highlights • Multiscale geometrical model of 3D braided composite was established. • Thermal behavior and surface crack of epoxy resin after ageing were characterized. • Impact fracture behaviors were compared after different ageing time. • Ageing mechanisms were analyzed at multiscale geometrical levels. Abstract Fracture behaviors of thermo-oxidative aged 3D braided composites are significantly affected by interfacial weakening and matrix degradation. Here we report the impact fracture behaviors of three-dimensional four direction (3D4d) and five directional (3D5d) braided composites under thermo-oxidative conditions. Specimens were exposed at hot air (180°C) for 2, 4, 8 and 16 days, respectively. The oxidation-induced crack widths in aged specimen surface were observed and analyzed. The impact fracture behaviors and damage evolutions of braided specimens were recorded with high-speed camera. Based on the test results, we established a multi-scale finite element analyses (FEA) model to reveal interface failure, stress distribution and energy absorption of virgin and aged specimens at microstructure level. The impact fracture behaviors of both different braided composites continuously decreased with increasing ageing time. The matrix degradation and interfacial weakening are main degradation mechanisms. In addition, the FEA results show that the impact fracture properties significantly depend on the braided structures. The braided preform is the main energy absorption component and the axial yarns contribute the highest energy absorption capacity. With the insertion of axial yarns, the 3D5d braided composites exhibit a better fracture resistance after thermo-oxidative ageing. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract When serving as a lightweight structural member in many areas, the dynamic mechanical behavior of fiber-reinforced polymeric matrix composites, especially under different strain rates, means a lot to the optimization of structure design as to high-speed impact. Under different loading rates and directions, we experimentally and numerically investigated the strain rate effect on the impact compressive behavior of 3-D angle-interlock woven composites (3-D AWCs) composed of carbon fiber and epoxy resin. Based on the factual geometrical architecture of 3-D AWC, the meso-scale model, which considers the interfacial damage between the reinforcements and matrix, was established to visually characterize the deformation history and damage morphologies of 3-D AWCs during impact compression process. Further, we performed high strain rate compressive tests on the split Hopkinson pressure bar (SHPB) apparatus integrated with a high-speed photography system for capturing images of progressive damage process to validate the proposed mesoscopic model. The stress-strain curves of various strain rates show strain rate effect varies depending on loading direction. The rate sensitivity on the compressive failure strength exists at weft direction and through-thickness direction except for warp direction. Moreover, both from images and finite element model results, the localized adiabatic shear band induced by intense plastic strain, initiates mainly from epoxy resin matrix and propagates along the interface at all three loading directions. [ABSTRACT FROM AUTHOR]

• Modified metal-organic framwork are applied to improve the radiation resistance of epoxy resins and investigate the anti irradiation mechanism of metal-organic framework. • UIO-66-OH nanoparticles can effectively improve the tensile modulus and thermal stability of epoxy resin. • 88.7% reduction in free radical concentration of UIO-66-OH / EP composite compared to epoxy resin. Understanding the degradation mechanism of epoxy resin under irradiation and enhancing the radiation resistance of epoxy resin are of great significance for its application in aerospace and nuclear industries. In this study, we investigated the radiation resistance of epoxy reinforced by UIO-66-OH metal-organic framework. Outstanding radiation resistance was achieved by using UIO-66-OH nanoparticles as radical scavengers to retard epoxy degradation. The introduction of UIO-66-OH reduces the content of free radicals generated after irradiation by 88.17%. UIO-66-OH also improves the mechanical and thermal properties of epoxy before and after irradiation. The scavenging radicals mechanism of hydrogen atom transfer of UIO-66-OH is more dominant than that of graphene oxide and carbon nanotubes. The radiation resistance of UIO-66-OH nanoparticles is related to hydroxyl functionalization and porous structure. This work provides a new idea and method for improving the stability of epoxy resin under gamma ray radiation. [ABSTRACT FROM AUTHOR]

The cross-section of carbon fibers (CFs) possessed radial heterostructure, which restricted its mechanical properties. In this paper, heating and γ-irradiation were integrated during PAN fibers stabilization process to improve the radial structure of CFs. The synergy between irradiation and heating during stabilization caused the decrease of I D /I G , increase of crystal size, and reduction of pore fractal dimension in whole CFs. Through Raman spectra along fibers cross-section, a radial heterogeneity was found during the whole carbonization process. The combination of γ-irradiation and heating reduced the I D /I G of core part more significantly compared to the skin part of CFs, which weakened radial heterogeneity of CFs. At the same time, it significantly enhanced the tensile strength of CFs. Subsequently, a hierarchy model with three zones containing outer-surface, sub-surface and core parts was presented to explain the evolution of tensile strength for CFs. The γ-irradiation during stabilization enhanced the structure of each part in CFs by generating more cross-linked structures. [Display omitted] • γ-irradiation in stabilization enhance tensile strength of carbon fibers (CFs). • Three-zone radial heterogeneity model for CFs. • γ-irradiation in stabilization reduce I D /I G and radial heterogeneity of CFs. • Study on micromechanics of CFs by nanoindentation. [ABSTRACT FROM AUTHOR]

• A virtual fiber model for multilayer biaxial weft knitted (MBWK) fabric is built for simulating the in-plane shear performance. • The shear angle distribution due to unique MBWK structure is revealed. • The interaction between the deformation of stitch and the rearrangement of axial yarn is evaluated in depth. The multilayer biaxial weft knitted (MBWK) fabrics and their composites have been widely applied in fields of complex structural products due to their flexible curved deformability. The existence of stitch in MBWK complicates the deformation behavior under the in-plane shear loading. However, it has not been well explored and understood. In this study, a numerical micro-scale virtual fiber modeling was built to investigate the in-plane shear performance of MBWK by considering the micro geometric features and fiber property that are difficult to be characterized solely by experiment. The strain conditions of the stitch that determine the fabric shear behavior are discussed. The deformation behavior leads to local deformation and morphological locking of the stitch. In the early stage of the shearing, the deformability of stitch provides enough space to accommodate the rearrangement of axial yarns. In the shear locking stage, the restriction of stitch and compression within axial yarns at high shear angles restricts the axial yarns from movement in the loading direction. When the theoretical shear angle is 20°, the shear angle located in different shear regions varies. The maximum shear angle near the loading area is 19.1°, while the minimum shear angle near the fixed area is approximately 17°. The results illustrate the deformation mechanism of MBWK under in-plane shearing and provide an excellent guidance for the design of large deformation fabrics, especially for curved surfaces, thus realize the effective utilization of fabrics in engineering applications. [ABSTRACT FROM AUTHOR]

Water pollution has caused serious water shortage, and this trend becomes increasingly serious in the world. Therefore, how to efficiently access water resources is crucial for human beings. Considering the easy blockage problem of traditional fog-harvesting mesh, we used the fog catcher brushes structure to avoid the problem effectively. Besides, most of the modified coatings on fog-harvesting materials contain fluorosilane, which is expensive, harmful and unstable for a long time using. In addition to the general properties of dimethyl silicone oil, hydrogen methyl silicone oil can participate in a variety of chemical reactions and have a good film-forming performance due to its molecular structure containing active Si–H keys compared to the similar studies about the oil-infused coating. Besides, the low contact angle hysteresis of the droplet can benefit for the droplet sliding off the surface, which further improve the fog-harvesting efficiency. In this paper, mechanical cutting method, water bath method, and spray coating method were successfully combined to construct slippery "fog catcher brushes" with alumina micro-needle structured surfaces from micro control to macro design. Furthermore, the effect of wettability, pattern shape and pattern size on fog-harvesting performance were investigated. Experiment results indicated that slippery surface benefited for the fog deposition and transportation compared with the superhydrophilic and plain surface. When the fog droplets passed through the sample with 10-teeth arc-shaped pattern, it would fully contact the surface, and only a small amount of fog droplets escaped from the surface. With the adjacent droplets coalescing, the droplets slided off along both sides of the pattern, then the contact surface decreased gradually from the top to the bottom, so droplets could transport rapidly. Analysis demonstrated that the slippery arc-shaped fog catcher brushes with 10-teeth had a good effect on the capturing and transporting of fog droplets, which offered a way to rationally construct materials with enhanced fog-harvesting performance from micro control to macro design. In this study, bioinspired from the cactus-inspired special geometry structure and nephenthes-inspired slippery surface, the fog catcher brushes have been prepared by the cut method and water bath method. Integrating the macro pattern design with the micro structure control, the fog-harvesting materials with different parameters were fabricated. Results of the fog harvesting performance indicated that the arc shape sample with 10-teeth showed the best fog-harvesting performance after wettability modification. [Display omitted] • Bio-inspired from the cactus special geometry and nephenthes slippery surface. • The fabrication is a simple method combined with the cutting and water bathing process. • PMHS coating has a stable contact angle hysteresis and environment friendly property. • The slippery arc shape sample with small size shows the best fog-harvesting efficiency. [ABSTRACT FROM AUTHOR]

Building reinforcement projects are designed to meet the requirements of modern sustainable development. However, the weak bonding performance of continuous glass fiber textiles to mortar presents a challenge in the manufacturing of GTRM composites, hindering their development and application. In this study, the gradient composite design technique was used to modify the interface transition zone between continuous glass fiber textile and mortar by introducing epoxy resin. This successfully resolved the issue of poor bonding between the continuous glass fiber textile and mortar interface, and promoted effective stress transfer between the two materials. The GTRM composites with an interfacial gradient structure exhibit excellent mechanical properties, including a tensile strength of 8 MPa and an interfacial shear force exceeding 27 KN. In addition, digital image correlation (DIC) was utilized to investigate the growth and development of cracks in GTRM composites, and the failure mechanism of tensile and interfacial shear tests was analyzed. Finally, the externally bonded GTRM composites were subjected to a three-point bending test, which demonstrated a significant improvement in the flexural strength and crack resistance of concrete beams. [ABSTRACT FROM AUTHOR]

For decades, single fiber reinforced composites exhibited defects of low damage tolerance resulting from brittle failure mode, which limits their further application. Therefore, hybrid composites are emerging as a new research hotspot. In this work, three-dimensional five-direction hybrid braided composites composed of different configurations of carbon and aramid yarn was manufactured. The short beam shear experiments and full-size mesoscale numerical simulation based on real braided structure computed by computed tomography (CT) image were established to investigate the hybrid effect and progressive damage process of composite. Studies have shown that neat carbon composites display the characteristics of brittle fracture, and hybrid composites demonstrate a remarkably toughening effect. The KaCb (CaKb) sample displays a 102.0% (58.7%) greater failure displacement than neat carbon composite under transverse (longitudinal) loading. Through the increasing bending deformation, the damage mode transforms to a ductile failure. The stress localization in the loaded area is retarded, and the synergistic load-bearing capacity of axial and braiding yarn is improved. This work reveals the synergistic bearing mechanism and progressive damage process of multicomponent composites with complex textile structures, which provides a theoretical basis for designing more types of hybrid composite. [ABSTRACT FROM AUTHOR]

• Stress-strain curves and crack development of TRM composites under tension exhibit four stages. • The fiber bundle configurations of reinforced textiles are the main factors affecting the tensile failure mechanism of TRM composites. • Factors influencing the interfacial bonding response in double-lap shear tests are explored. The purpose of this paper is to study tensile properties and interfacial bonding properties of textile reinforced mortar composites (TRM) widely used for externally strengthening damaged buildings. Based on the digital image correlation (DIC) method and finite element (FE) simulation, the tensile and interfacial shear test results of steel fiber textile and carbon fiber textile reinforced mortar composites were analyzed. First, DIC was used to detect the crack onset and propagation of the specimen during the tensile process. The concept of gradient interface was introduced to improve the bonding performance. The effects of the hydration degree of mortar, and reinforcing textile type on interfacial bonding properties were then evaluated through double-lap shear testing. Last, the stress distribution and load transfer during textile pull-out from the mortar were analyzed based on FE simulation with the bond-slip law extracted from the double-lap shear experiment. [ABSTRACT FROM AUTHOR]

Some special electronic equipment not only need to avoid the interference of external electromagnetic waves (EMWs), but also need to transmit effective signals. Therefore, the development of directional electromagnetic interference (EMI) shielding materials has a great prospect. The asymmetric structure, consisting of the porous magentic rGF (reduced graphene oxide and Fe 3 O 4) layer and the dense electrical conductivity rGM (reduced graphene oxide and MXene) layer, was constructed by dual-needle 3D printing technology. After encapsulation and curing with polydimethylsiloxane (PDMS), the rGF/rGM/PDMS composites were prepared. When the ratio of rGF and rGM layers is 6:4, the SE values of rGF-6/rGM-4/PDMS composites are 38.75 dB and 30.79 dB respectively when EMWs are incident on the rGF layer and rGM layer respectively, and the ΔSE of which is about 8 dB. The results showed that the asymmetric structure composed of porous magnetic layer and dense deeply electric conductive layer could generate a special process of "weak reflection-absorption-strong reflection-reabsorption" for incident EMW. At the same time, the simulation results of the waveguide method validated the experimental results, and further explained the directional EMI shielding mechanism of asymmetric structure. For the first time, this work designs an asymmetric structure based on the double needle 3D printing technology, which provides useful inspiration for the structural design and potential application of directional EMI shielding materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The limitation of plant fiber length can be overcome by using staple spinning to achieve continuity on short fibers. Ramie fiber staple yarn reinforced unsaturated polyester composites (RSYCs) were fabricated with ramie fiber and unsaturated polyester matrix. The unique fiber packing density of staple yarn must be tackled first to reflect the structure of RSYCs. The relationship between fiber packing density of staple yarn and fiber volume fraction of composite was evaluated to investigate the effect of fiber packing density on properties and predict the tensile strength of RSYCs using the rule of mixture. A scanning electron microscope illustrated fiber packing density of staple yarn. When the twist factor was 380 with the optimal yarn count of 80 tex, the fiber packing density was 19.9% higher than that at 260. Compared with the minimum tensile strength of RSYCs at 120 tex, the maximum of RSYCs at 380 was 399.2 MPa, improved by 238.6%. Measured by dynamic mechanical analysis, the viscoelastic rigidity and damping property of RSYCs was the best at 380, with the storage modulus of 31.9 GPa at 40 °C and the tan delta of 0.1226 at 80.59 °C. Compared with the neat resin and ramie fiber, the onset temperature of weight loss of RSYCs tested by thermogravimetric was reduced. The increasing fiber packing density significantly reduced the resin permeability of RSYCs, according to the contact angle and ultrasonic nondestructive testing results. There is no doubt that the obtained fiber packing density possessed great potential for promoting the development of RSYCs. [Display omitted] • Fiber packing density adjusted by yarn count and twist factor. • Fiber packing density influenced the tensile properties of ramie fiber staple yarn reinforced composites. • Fiber packing density overruled fiber volume fraction to improve the rule of mixture. [ABSTRACT FROM AUTHOR]

[Display omitted] • The latest advances of polyurethane/graphene composites including their properties and challenges in the fields of thermal conduction and flame-retardance, antimicrobial, ultraviolet resistance, electromagnetic interference shielding, and oil–water separation are widely presented. • The preparation process, applications and prospects of the PU/graphene composites in high-performance synthetic leather are summarized in this review. • Functionalization of polyurethane and graphene nano-derivatives including covalent and noncovalent modifications of the composites are covered. • We put forward some novel speculations for the composites and their synthetic leather manufacture in advanced areas. In recent years, polyurethane/graphene composites (PUGs) have attracted considerable attention attribute to their wide applications ranging from industrial manufacturing to bioengineering. The addition of graphene-based derivatives to the PU matrix can improve the mechanical, thermal, and electromagnetic properties, etc., to meet the specific demands of quality, functionality, and novelty of polymer composites. There are different modification methods of graphene and structural designs of polyurethane matrix for the applications of PUGs in various areas. Among the major applications, PUGs possess remarkable features in the dipping and coating process of synthetic leather. However, limited comprehensive summaries of functional PUGs have been published in broad fields and synthetic leather. The review aims to provide an overview of the cutting-edge developments of PUGs in the properties of thermal conduction and flame-retardance, antimicrobial, ultraviolet resistance, electromagnetic interference shielding, and oil–water separation respectively, which path a way for researchers to apply these uniquely functional composites for high-performance and advanced applications. And the applications of the PUGs in high-physical synthetic leather and the current challenges and prospects of synthetic leather in advanced fields are briefly presented. [ABSTRACT FROM AUTHOR]

Carbon-based (e.g. carbon fibers or carbon nanotube (CNT)) polymer composite materials, due to the high specific strength, and good chemical stability features, is a promising structural material for energy-efficient applications in aerospace and civil infrastructures. However, the difficulty of viscosity-related infusing and curing of polymer limits composite mechanical performance and manufacturing efficiency. Here we overcome these difficulties and report an electrothermal-triggered flooded thermoset curing to enable rapid and energy-efficient manufacturing of carbon/polymer composite. The underlying concept is based on the two-step localized in- situ infusion and curing in flooded polymer by Joule heating of carbon-based materials to facilitate the flow of polymer into the microstructure in low current, followed by curing of polymer resin in high current. The viscosity adjustment and defoaming process in the infusing process and the curing properties (degree of cure and strength) of the composites were used to prove the effectiveness of this curing strategy in composite fabrication. This electrothermal-triggered curing approach provides a rapid, energy-efficient, scalable, and volumetric composite manufacturing technique. Image 1 • An energy-efficient and scalable electrothermal-triggered thermoset curing approach. • The curing approach exhibits the ability to control the viscosity of the polymer. • Electrothermal preforms can facilitate the flow of polymer into the microstructure. • The preparation process of carbon fibers and CNTs composites was demonstrated. [ABSTRACT FROM AUTHOR]