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Developing 3D printable waste paper based biocomposites is a potentially greener alternative to traditional waste paper recycling methods. In this paper, waste office paper (WOP) filled polylactide acid (PLA) biocomposites were prepared as filaments for Fused Filament Fabrication (FFF). The morphology, rheology, thermal properties, and physical properties of PLA-WOP composites were investigated. Results revealed that the addition of WOP improved the composites' melt flow abilities. The T g and T m of composites remained similar to the neat PLA. However, tensile strengths of the prints decreased with the increase of WOP content, which could be attributed to the heterogeneous dispersion and aggregation caused by the abundance of WOP in the system. When 5% WOP was used, the elongation at break increased in comparison with pure PLA specimens. Nonetheless, when the WOP content was increased to 15%, the elongation at break decreased. To improve the mechanical properties of the prints, a silane coupling agent (γ-methacryloxypropyltrimethoxylsilane, KH570) was used to modify WOP granules. The mechanical properties were clearly enhanced post KH570 treatment. Furthermore, FTIR analyses demonstrated that the hydrogen bonding improved interfacial adhesion between WOP fillers and the PLA matrix. Thermal decomposition showed that the PLA-WOP composites had virtually no degradation below 260 °C, indicating that the composite filaments are safe for indoor 3D printing. [ABSTRACT FROM AUTHOR]

Abstract We developed a paper-type electrode for the next-generation wearable devices by complementary hybridization of methyl cellulose and carbon nanotubes (CNTs). The large-scale hybrid paper was fabricated using an incomparably simple and low-cost solution process. Structural features, surface hydrophobicity, and chemical interaction between CNTs and cellulose of the hybrid papers were systematically explored by adjusting the concentration of CNTs. The hybrid papers demonstrated superb mechanical durability even under highly strained conditions such as folding, crumpling and re-flattening regardless of the concentration of CNTs. The electrical properties of the CNTs/methyl cellulose were well-preserved even when folded as origami or submerged in water. [ABSTRACT FROM AUTHOR]

The aim of this work is to introduce recycled paper in HDPE matrix composites, an interesting alternative to traditional recycling process for paper. This strategy allows both re-using paper and reducing the amount of virgin polymer used in the same volume. For this application, the recycled paper goes through a micronization process, which uses simultaneously the action of impact and friction. The production of the composite is realized either by traditional injection moulding or by turbomixing. The best fibres' dispersion was obtained by turbomixing and the composites produced in this way have been additivated with maleated polyethylene (MAPE) in the amounts of 1, 3 and 5 wt%. The resulting composites with 10 wt% fibres were characterized from the morphological and mechanical point of view. Tensile tests revealed a rather constant stiffness and some improvement of strength with respect to the neat matrix, also indicating that the best results were obtained by the addition of 1 wt% MAPE. SEM micrographs evidenced that, in the absence of additive, fibre-matrix interface was rather weak. In addition, the samples with added MAPE appear to experience a reduction in microporosity, which was confirmed also by water absorption test. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) paper with outstanding integrated multiple functionalities (good mechanical performance, thermal stability and flame resistance, etc.) is strongly needed for numerous potential applications in cutting-edge fields. In this work, we report a facile and green process to fabricate GO-based nanocomposite papers via introducing functionalized silica (f-SiO 2) nanoparticles. The results reveal that addition of f-SiO 2 produces simultaneous improvements in mechanical strength, stiffness and flame resistance for GO paper. With incorporation of 10 wt% f-SiO 2 , the tensile strength, elastic modulus and toughness of the GO/f-SiO 2 nanocomposite papers can be increased by about 51%, 317%, and 69%, respectively. Various characterizations disclose that hydrogen bonds and covalent interactions between GO sheets and f-SiO 2 mainly contribute to the effective load transfer and energy dissipation between them, and thus leading to the improvements of mechanical properties. Based on the structural observation and analysis, the improved flame resistance of the GO/f-SiO 2 papers should be attributed to the formation of rGO/SiO 2 protective char, which are derived from the decomposition and redeposition of the grafted silane molecules and inorganic SiO 2 and thermal reduction of GO into rGO. Our results suggest that the mechanical and thermal properties of GO papers can be tuned by introducing inorganic/organic f-SiO 2 , providing a new route for the rational designing and development of mechanically flexible and flame-retardant GO-based nanocomposite paper materials. • Graphene oxide/APTS modified silica nanocomposite papers were designed and synthesized. • The obtained nanocomposite papers show simultaneous improved mechanical properties and flame resistance. • The enhanced hydrogen bonds and covalent interactions between graphene oxide sheets and nanoparticles contribute to the improved mechanical properties. • The formation of SiO 2 protective layer derived from the decomposition of grafted silane molecules endows GO/f-SiO 2 papers an attractive flame retardant property. [ABSTRACT FROM AUTHOR]

This paper represents a critical review on alkali-activated materials (AAM) containing organics with high homogeneity at nano-scale (<1 μm). Organics including organosilicons, surfactants, water-soluble polymers and epoxy resins can contribute to performance enhancement and tailorability of AAM based on their molecular characteristics. Hence, AAM with organics can generally possess improved characteristics between organic and inorganic components and may even exhibit emerging functional properties. According to the hybridisation modes between AAM and organics such as chemical bonding, physical adsorption, electrostatic attraction or phase crosslinking, these AAM with organics are categorised into four distinct types: organic-grafted, organic-adsorbed, phase-crosslinked and phase-separated AAM. In this paper, the hybridisation modes and reaction mechanisms of AAM with organics are summarised, for the first time, followed by a comprehensive discussion on the phase assemblage, microstructure, mechanical properties, durability and potential applications. Afterwards, the fundamental insights are gained and the remaining challenges for future research are identified and discussed. [ABSTRACT FROM AUTHOR]

This paper examined the impact of graphene's different scales on carbon fibre-reinforced thermoplastic composites' thermal and mechanical properties (CFRTPs). Experiments using a mixing design method with graphene content of large, medium, and small scales as variables, thermal conductivity (λ) and mechanical properties (flexural (F), compression (C), and tensile strength (T)) as response values. The thermal-mechanical properties of multi-component composites were analyzed and modelled to improve them. Graphene with different scales could effectively bridge and enhance heat flow transfer along the graphene thermal conductivity network, significantly improving the composite's thermal conductivity. It was verified that the optimized composites exhibited excellent thermal conductivity (λ = 1.329 W/m·K), 140.3 % higher than that pure composite. Furthermore, the mechanical properties of the optimized composites saw significant enhancements, with flexural strength, compressive strength, and tensile strength increasing by 18.9 %, 22.8 %, and 13.2 %, respectively. Moreover, the optimized composite's thermal properties and energy storage modulus were also notably improved. [Display omitted] • Synergistic modification of CF/PPBESK composites using graphene at different scales. • Modelling of thermal conductivity and mechanical properties of composites was established. • Theoretical model fits well and predicts accurately. • Thermal conductivity and mechanical properties of composites improved significantly. [ABSTRACT FROM AUTHOR]

In the past decade, the additive manufacturing of Fiber-Reinforced Polymer Composites (FRPCs) has become an attractive research area. This can be attributed to the ease and versatility of manufacturing, wherein the design of final products takes less time and labor when compared with conventional composite manufacturing techniques. However, due to the inherited nature of the "layer-by-layer" additive manufacturing process, 3D-printed composites are highly susceptible to delamination failure. Continuous efforts are being made in the research community to develop critical techniques involving the optimization of significant printing parameters to enhance the fracture toughness of 3D-printed composite parts toward their structural reliability for different industrial applications. In this comprehensive review, we have discussed the latest developments in improving the mechanical properties and fracture toughness of 3D-printed FRPCs. A holistic review of the properties of low-melting-temperature polymers such as polylactic acid (PLA) and high-melting-temperature polymers like polyetheretherketone (PEEK) based 3D-printed composites is also presented. This paper further covers the effects of changing processing parameters on the fracture toughness of 3D-printed composite structures. These processing parameters comprise printing temperature, printing speed, layer thickness, nozzle geometries, etc., and other key factors influencing the fracture properties of printed parts, such as surface treatment, annealing, and porosity. This is followed by an insightful representation of current challenges, future perspectives, and potential solutions. [Display omitted] [ABSTRACT FROM AUTHOR]

The paper is concerned with design, analysis and fabrication of the small size Unmanned Aerial Vehicle composite frame structure. The frame has the form of a lattice composite structure manufactured by 3D printing of continuous carbon fibers and two matrix materials – thermoset, which is used to join the elementary fibers in the tow, and thermoplastic, which consolidates the cured tows into a unidirectional composite. The paper consists of contains the description of the 3D printing procedure, finite element analysis of the structure, test results for mechanical properties of the structural elements and the fabricated frame. The result of analysis is in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

The use of Textile-Reinforced-Matrix (TRM) systems is gaining consensus as a possible technical solution for strengthening masonry structures. In this context, the use of natural fabrics (among which those made of flax) instead of synthetic ones can have a positive impact on several sustainability-related aspects, such as renewability, recyclability, biodegradability, low price. However, both mechanical properties and durability performance of natural fibres and fabrics needs to be further investigated with the aim to make it possible their use in composites for construction. Furthermore, this paper reports the results of a fundamental study on a bidirectional flax fabric eventually intended as the reinforcement in cement-based composite systems. Specifically, it aims at determining the tensile strength of flax of fibres, threads and the fabrics, and investigating how they are influenced by various environmental exposures and aging processes. The results in the experimental tests reported herein show that fibres and fabrics suffered no significant reduction in tensile strength due to the considered environmental exposure. Despite the common belief that natural fibres may be affected by durability issues, the results demonstrate that the flax fabric under investigation can be utilised as a reinforcement in TRM systems, which is the main novelty and original contribution of this paper. [ABSTRACT FROM AUTHOR]

In this paper, a novel approach to evaluate the neutron shielding performance of multiphase neutron absorber reinforced aluminum matrix composites was proposed through the establishment of a direct relationship between equivalent B areal density (EBAD) of the composite and its thermal neutron shielding coefficient. It was found when the EBAD of the composite was 0.1105 g/cm2, the thermal neutron shielding coefficient will achieve 99%. Based on this proposed approach, (1% Gd+15% B 4 C)/6061Al composite plates were successfully fabricated using vacuum hot pressing method followed hot rolling. The results showed that when the EBAD of the composite was 0.1871 g/cm2, the thermal neutron shielding coefficient was above 99.9%, which was consistent with the theoretical calculation. The 5 mm-thick composite plate also had a good shielding effect on the Am-Be neutron source. Meanwhile the composite possessed a 380 MPa tensile strength as well as an elongation of 5% after hot rolling. In all, the (Gd + B 4 C)/6061Al composite designed in this paper showed better comprehensive performance compared with the literature's. The work of this paper has a great guiding significance for the design and preparation of neutron absorbing composites with high thermal neutron shielding performance as well as high strength and plasticity. Image 1 • EBAD was proposed to evaluate neutron shielding performance of composites. • The direct relationship between EBAD and thermal neutron shielding performance was established. • The idea of equivalent substitution for the design of composites with good performance is of great significance. • (1%Gd+15%B 4 C)/6061Al composite possessed good mechanical and neutron shielding properties. [ABSTRACT FROM AUTHOR]

Abstract Lignin is a by-product of paper and pulp production resulting from extraction of cellulose, the world's most abundant natural polymer. In this study, we manufactured polypropylene (PP)/PP-grafted maleic anhydride (PP-g-MAH)/glass fiber (GF)/lignin composites via reactive extrusion process for value-addition of lignin, often discarded as wood waste. To enhance adhesion in composites at interphases, diisocyanate was added in-situ during the extrusion process, leading to chemical primary bonding. Structure-property relationship of PP/PP-g-MAH/GF/lignin composites revealed two different reinforcement mechanisms that were supported by FT-IR, TGA, hardness, tensile, flexural, and impact tests, SEM, and density. Up to 7.5 wt% of isocyanate loading, linear urethane bonding was formed; further addition of isocyanate resulted in evolution of chemical crosslinking via allophanate bonding. [ABSTRACT FROM AUTHOR]

Abstract Fiber-Reinforced Polymer (FRP) represents one of the most diffuse and effective strengthening technique for retrofitting columns in existing buildings when presenting insufficient mechanical properties. In fact, the confinement effect provided by wraps with high-tensile strength and stiffness induces significant enhancement of the mechanical behaviour. In this paper experimental results of axial compression tests on both un-confined and FRP-confined prismatic yellow tuff masonry columns are presented. In particular, two types of masonry arrangements, regular and irregular, were reproduced in order to investigate the effectiveness of the confinement on column typologies widely used in the past in Southern Italy and Mediterranean basin. The performed experimental tests allowed to obtain the constitutive axial and transversal stress-strain laws and to evaluate the improvement of the mechanical behaviour, in terms of strength and ductility, due to FRP confinement. The results have highlighted a significant difference in the shape of the constitutive law for confined masonry with respect to the one of confined concrete. Contrary to FRP confined concrete members, in the case of confined masonry members specific theoretical constitutive model has been not yet developed. To this aim, in this paper the various stress-strain laws developed for FRP-confined concrete elements has been applied to masonry elements too and a comparative analyses between experimental and theoretical results has been carried out. [ABSTRACT FROM AUTHOR]

Although TiB reinforced titanium matrix (TiB-Ti) composites exhibit superior wear resistance and strength, they still demonstrate severe problems resulted from lowered toughness and ductility, as compared with titanium and its alloys. To reduce these problems, this paper tailors a three-dimensional quasi-continuous network (3DQCN) microstructure within TiB-Ti composites by in-situ laser deposition-additive manufacturing process. Results show that the laser power has great impacts on the formation of 3DQCN microstructure and the 3DQCN microstructure is beneficial to both strengthening and toughening effects on TiB-Ti composites. To have a quantitative understanding of strengthening effects, this paper, for the first time, has modeled the yield strength of TiB-Ti composites with 3DQCN microstructure. [ABSTRACT FROM AUTHOR]

Poly(l -lactide) (PLLA) is regarded as a polymer with excellent biocompatibility, but its inherent brittleness property greatly restricts its application in the biomedical engineering field. Blending PLLA with other polymers is one of the sufficiently viable methods of property improvement. In this paper, the Poly(l -lactide) (PLLA)/Polyvinylidene fluoride (PVDF) blend was first prepared by melt-compounding, and then microinjection molded into the blend micro bone screw with high strength and toughness. The experimental results show that the PVDF dispersed phases could in situ form the highly oriented fibers with shish-kebab structures under the effect of strong shear stress field of microinjection molding along flow direction. These parallelly aligning PVDF fibers could simultaneously realize the significant enhancement in both toughness and strength of the micro bone screw. Specifically, in the bending test the blend micro bone screw with oriented PVDF fibers can withstand the compression displacement of nearly 2 mm, while the neat PLLA one would break within only 0.5 mm displacement. In addition, a bending recovery phenomenon was observed in the load-displacement curve of the blend, demonstrating the mechanical transition from brittle fracture to ductile fracture. Moreover, with addition of 30 % PVDF, the elongation at break increases from 7.8 % to 57.8 %, while the tensile strength increases from 60.9 MPa to 74.3 MPa. The PLLA/PVDF micro screws possess better toughness and excellent biocompatibility compared to pure PLLA products. They also exhibit great potential for stimulating the proliferation of cells through piezoelectric output, opening up new possibilities for the development of next-generation fracture fixation materials. Combing melt-compounding and microinjection molding strategy achieves the in situ formation of highly oriented PVDF dispersed phase fibers with shish-kebab structure in PLLA/PVDF blend, resulting in high performance of the fabricated biomedical micro bone screw for bone repair. [Display omitted] • Highly oriented PVDF fibers with shish-kebab structures were in situ formed in the PLLA matrix during microinjection molding. • The PLLA/PVDF microparts exhibit the synchronously improved strength and toughness, as well as piezoelectric output property. • Microinjection molding is used to manufacture the PLLA/PVDF blend micro bone screws with exceptionally high toughness. • The biological experiments have demonstrated the excellent biocompatibility and osteogenesis ability of the micro bone screws. [ABSTRACT FROM AUTHOR]

Ceramic matrix composites have garnered significant attention in aerospace and other fields due to their outstanding properties. However, as a common and critical defect, density defect often results in non-uniform matrix distribution and internal pore formation, posing a substantial risk to component safety. This paper presents a novel method aimed at deliberately inducing varying degrees of density defects in SiC f /SiC. The feasibility of this method is validated using infrared thermography and computed tomography. As density defects aggravate, the porosity of the sample's defective region gradually increases, with both the number of micropores and the dimensions of larger pores expanding. This trend underscores the decreased compactness of the SiC matrix. Additionally, there is an initial decline in tensile strength followed by stabilization, while the tensile elastic modulus exhibits a continued decrease. The retention rates of the minimum tensile strength and tensile elastic modulus are 83.89 % and 64.77 %, respectively, compared to those of the defect-free samples. In terms of compressive properties, both compressive strength and compressive elastic modulus exhibit progressive decreases, culminating in final retention rates of 76.54 % and 72.02 %, respectively. Density defects reduce the matrix cracking stress and introduce new defects such as delamination, thereby altering the material's damage mechanism. This study provides innovative perspectives for risk assessment and lifespan prediction of density defects, especially concerning more complex components like turbine blades. • Artificial defects containing locally varying density values are controlled in SiC f /SiC for the first time. • Tensile strength demonstrates higher tolerance to more severe density defects than compressive strength. • Evaluating density defects by correlating pore geometry with material mechanical properties offers a novel approach. [ABSTRACT FROM AUTHOR]

Combining tomographic imaging with digital volume correlation allows in-situ 3D strain mapping, leading to a quantitative assessment of damage mechanisms and associated material properties in structural materials. Being based on pattern recognition, digital volume correlation is well-suited for materials with intrinsic and stable microstructural heterogeneity, such as certain biological tissues. Unfortunately, conventional polymers and fibre-reinforced polymer composites lack the required heterogeneity. Recently, solutions like doping the polymers with particles have been explored to overcome this limitation. The particles embedded in the polymer matrix provide a random, volumetric speckle pattern, acting as displacement trackers for the digital volume correlation algorithm. However, the particles might influence the mechanical and rheological behaviour of the polymer, which is detrimental in investigations of the composite material properties. This paper investigates the mechanical, mechanistic, and rheological representativeness of an epoxy doped with two types of sub-micrometre particles optimised for digital volume correlation. Since particle dispersion is considered a key driver for representativeness, we simultaneously quantitatively assess the dispersion by combining scanning electron microscopy and X-ray computed tomography. [Display omitted] • A methodology for assessment of 3D random speckle pattern is proposed. • Virtual DVC indicates particles are needed for microscale DVC of polymer composites. • Particle dispersion assessment depends heavily on the image spatial resolution. • A certain level of agglomeration can offer a multiscale speckle pattern. • Agglomerates influence the mechanical and mechanistic representativeness of polymer. [ABSTRACT FROM AUTHOR]

Plastic solid waste (PSW) of polymers (like: high density polyethylene (HDPE), low density polyethylene (LDPE), Nylon etc.) is creating new challenges, which in today's scenario are major research concerns. A sharp rise has been observed in production of different products based on different plastic material. This huge increase in plastic commodities also increases the waste generation thus creating new challenges. Some researchers have reported work in the field of PSW management with different recycling methods. This paper compiles the different research work done by researchers in this field of recycling and progress in recovery and management of PSW by different methods (i.e. Primary, secondary, tertiary and quaternary) along with the various identification/separation techniques. Further, this paper reviews the effect on properties of virgin and recycled HDPE/LDPE/Nylon PSW with different reinforcements like sand, natural fibre, hemp fibre, metal powder etc. [ABSTRACT FROM AUTHOR]

This paper will show that a simple membrane (e.g. balloon) is not always the minimal mass pressure vessel. Of course one could always add cables to support the membrane, or plate, to reduce the thickness and hence mass required of the membrane. By minimizing the sum of the mass of the membrane plus the mass of the cable network, a minimal mass solution for the pressure vessel can be found. We will show the necessary and sufficient conditions (involving material choices and cable network topology) for which a composite system, composed of a membrane and cable network, has less mass than a membrane alone. The main motivator for this study is a spin-stabilized pressurized space structure useful for artificial gravity habitats. To contain and support the membrane, we will optimize the topology of the class of prestressable structures called tensegrity. These structures are usually composed of a network of axially-loaded compressive and tensile members. In the pressurized examples of this paper, inflation provides the compressive forces, and hence the optimized tensegrity topology eliminates the compressive structures when they are not needed. The minimal mass designs herein produce easily-tunable prestressed networks, and control systems that allow deployment and stiffness tuning features. The minimal mass design of those structures, for different load combinations (pressure loads and centrifugal loads), produces a composite structure composed of membranes and cable network. Two different composite systems are analyzed and compared with simple uniform membranes: the first system is composed of a cylindrical membrane supported by circular ring cables, the second system is composed by a membrane surrounded by ring cables and longitudinal cables. The comparison of the minimal mass designs with the single continuous membrane clearly highlights the advantage of the composite systems made of high-performance materials. When the material of the membrane and cables are the same, there is no advantage to the composite system, but various requirements usually demand different properties of the membrane and cable material. [ABSTRACT FROM AUTHOR]

In the typical structures of carbon-fibre-reinforced plastics (CFRP), multiple layers are stacked together with a particular sequence in order to give specific mechanical characteristics. Layers are organized with different angles, different sequences and different technological processes to obtain innovative materials. This paper introduces a new parameter, able to improve mechanical properties of composites. It analyses an unconventional fibres orientation combined with the through-the-thickness stitching on the in-plane mechanical properties of CFRP. Conventional carbon fibres orientation is generally referred to a Cartesian coordinate system, in which fibres are arranging in bundles along different angle orientations respect to the zero lamina. In this paper a polar coordinate system of continue carbon tow is introduced to create specimens as well as complex geometry components in an easy way. Five different configurations are studied: two are classified as traditional composites (unstitched and Cartesian orientation of woven carbon cloth), three are defined as innovative composites (stitched laminates and continue carbon tow organized in polar or Cartesian system). The application of this technique aims to introduce some advantages in the material's manufacturing process and if compared with the conventional strategy seems to be very promising since it appears to be very efficient in stopping delamination phenomenon. [ABSTRACT FROM AUTHOR]

In the industrial sector, ultra-high molecular weight polyethylene (UHMWPE) fibers are often recognized as superlative reinforcement owing to their unmatchable characteristics like impressive toughness, exceptional weight-to-strength ratio, low density, excellent wear, and chemical resistance. The remarkable features of UHMWPE fiber/polymer composites have gained substantial attention, rendering them ideal for advanced engineering materials. Despite this, advancements in developing high-performance UHMWPE fiber polymer composites have been constrained by the fiber's smooth and chemically inert surface, resulting in a weak interface between UHMWPE and the polymer matrix. Numerous techniques have emerged to enhance the surface of UHMWPE fibers, aiming to bolster the fiber-polymer matrix interface. These modifications amplify surface chemical activity and roughness, thus achieving robust mechanical interlocking and chemical bonding. This review paper aims to elucidate how the physical and chemical surface modifications of UHMWPE fibers fortify the interface with polymer matrices. Researchers can leverage the presented techniques to design advanced composites with improved performance and durability. This article provides a concise overview of current developments in various surface modification techniques for UHMWPE fibers and their role as polymer reinforcements. Last, ongoing challenges and potential research directions in UHMWPE reinforced FRPCs are also discussed. [ABSTRACT FROM AUTHOR]

The wave absorbers with dual functions of structural load-bearing and radar absorption have become the solution strategy to cope with the increasingly complex electromagnetic environment. In this paper, a conical structure absorber based on natural flake graphite (NFG)/Fe 3 Si/SiCnw ternary composites was successfully prepared by selective laser sintering (SLS) 3D printing technique starting from multi-scale design. From the material level, the in-situ grown one-dimensional SiC nanowires effectively improve the dielectric properties of the material, which increases the magnetic/dielectric loss synergy together with the magnetic material Fe 3 Si. The minimum reflection loss is −54.21 dB and the effective absorption bandwidth (EAB) is 4.6 GHz when the thickness is 1.5 mm. The unit structure of the conical structure absorber was structurally designed and experimentally verified at the structural level, and broadband electromagnetic absorption at 14.45 GHz was achieved and the compressive yield stress was 5.21 MPa. In addition, the EAB of both transverse electric-polarization (TE) and transverse magnetic-polarization (TM) under the variation of incidence angle from 0 to 50° exceeded 12 GHz, indicating that the conical structure absorber has excellent wide-angle absorption properties. The broadband microwave absorption performance of conical structure absorbers is attributed to the synergistic enhancement effect of improved impedance matching on the macroscopic scale and multiple electromagnetic loss mechanisms on the microscopic scale. The conical structure absorber prepared by SLS achieves material-structure-function integration of electromagnetic microwave absorption, and the multifunctional integrated design contributes to the practical application of stealth technology in the field of industrialized electromagnetic microwave absorption. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced polymer (CFRP) is prone to produce significant thermal damage such as heat-affected zone (HAZ) during laser cutting, which seriously affects the processing quality. In this paper, a new method of dimethicone-assisted interlaced scanning mode (DISM) compound cutting is proposed to regulate the surface damage of CFRP nanosecond UV laser hole cutting. Based on the simulation and experimental testing analysis, the coupling effect of heat conduction and heat accumulation during the laser cutting process, as well as the suppression mechanism of heat effects by compound cutting methods have been described. Compared to the default cutting method, DISM can effectively reduce the damage of CFRP laser hole cutting. The average matrix recession (MR) width of the hole entrance edge is reduced by 47.54% for DISM, while eliminating the heat-damaged matrix (HDM) zone, resulting in a comprehensive reduction of HAZ by 85.2%. The most obvious parameter combination for the reduction of MR width is 50 kHz, 1000 mm/s, and 0.06 mm, where the MR is reduced by 61.31% (37.61 μm→14.55 μm). Interlaced scanning mainly reduces MR width, while dimethicone-assisted processing exhibits suppression of HDM. The compound cutting method significantly reduces thermal damage and improves CFRP mechanical properties. [ABSTRACT FROM AUTHOR]

Fibers are essential in reinforcing the mechanical properties of ultra-high performance concrete (UHPC), particularly the tensile and flexural strength. This paper conducts a systematic review on the effect of fibers with different textures and geometry on the properties of UHPC from the following aspects: (1) the bond mechanism of steel fibers with the UHPC matrix; (2) the effect of fiber shape, fiber orientation and hybridization of steel fibers on the microstructure, failure mode, mechanical properties, autogenous shrinkage and durability of UHPC; (3) the reinforcing mechanism of synthetic fibers (polyvinyl alcohol fibers (PVA), polypropylene fiber (PP), polyethylene fibers (PE)), mineral fibers (basalt fibers, wollastonite fibers) and carbon fibers in UHPC and their effect on the performance of UHPC; (4) the use of hybrid fibers and their synergetic effect on the mechanical performance and shrinkage of UHPC. Finally, this paper discussed the further research trends of fibers in UHPC. [ABSTRACT FROM AUTHOR]

A kind of epoxidized natural rubber (ENR)/CNCs composites without using conventional crosslinking agents was successfully fabricated in this paper, in which a supramolecular network based on hydrogen bonds is formed. FTIR confirmed that parts of hydroxyl groups of CNCs reacted with the epoxy group of ENR and hydrogen bonds were developed between CNCs and ENR. This made CNCs involve in the formation of supramolecular network, effectively improving the mechanical properties and endowing the ENR/CNCs composites with superior self-healing capacity simultaneously. The tensile strength of ENR/CNCs composites with 20 wt% CNCs rises to 1.19 MPa, almost 2 times than that of the neat ENR. Importantly, the ENR/CNCs composite with a filler loading of 20 wt% exhibits impressive self-healing efficiency of 83% of the its original strength and 95% of the original extensibility without any external stimulus at room temperature. Healing behavior is strongly influenced by CNCs contents, healing temperature, healing time and its times. [ABSTRACT FROM AUTHOR]

Polyvinyl butyral (PVB) is the polymeric interlayer material most used in laminated glass elements. As other used interlayers, the PVB mechanical behavior is viscoelastic. Therefore, its mechanical characterization can be carried out by static (creep and relaxation) or dynamic tests in a dynamic mechanical analyser (DMA). However, the PVB layers constrained in laminated glass elements are subject to high temperature and pressure conditions in an autoclave during the manufacturing process, which can affect to the mechanical properties of the interlayer. In this paper, the mechanical properties of PVB constrained in laminated glass beams have been determined by static and dynamic tests on laminated glass beams with different boundary conditions and at different temperatures. The estimated curves are compared with those obtained by testing free PVB specimens in a DMA. [ABSTRACT FROM AUTHOR]

Polymer as well as polymer composites are inclined to premature due to effect on mechanical and physical properties during service time. In this paper, the effect of thermal cycling (−30 to 80 °C) on the physical and tensile properties of Polypropylene (PP), Kenaf/PP, Kenaf/PP/CNTs and Kenaf/CNTs/MAPP/PP hybrid composites for the injection moulded car battery tray was investigated. Although this study had found no physical changes on the samples in terms of colour or cracking, the samples, however, had experienced warpage and dimensional changes. The dimension of samples containing CNT had increased by 20%, while the PP and PP/Kenaf samples had decreased by 3.5% and 87%, respectively. Although the process of thermal cycling was found to have rapidly decreased the hardness of Pure PP and Kenaf/PP composites, it had, however, gradually increased the hardness of composites with CNT fillers. The tensile strength, Young's modulus and elongation of the composites had also been examined in this research. Furthermore, according to the fractographic investigations using scanning electron microscope, it is perceived that the fracture morphology of the samples is strongly influensed by thermal cycling. [ABSTRACT FROM AUTHOR]

Abstract In this paper, experimental studies on the ballistic impact behaviour of nanomodified glass fibre-reinforced polymer (GFRP) are reported. The epoxy matrix of the GFRP was modified by the addition of graphene platelets (GNPs), carbon nanotubes (CNTs), combined hybrid hexagonal boron nitride nanosheets (BNNS)/CNT, and combined boron nitride nanotubes (BNNTs)/GNPs nanoparticles. Ballistic impact tests were carried out on GFRP laminates at two projectile velocities of 76 ± 1 m s−1 for full-field deformation measurements and 134.3 ± 1.7 m s−1 for perforation tests. The behaviour of the plates during impact was recorded using digital image correlation (DIC), in order to monitor strain and out-of-plane deformation in panels with nanoreinforced matrices. Following penetrative impact tests, pulse thermography was used to characterise the delamination of impacted plates. The results of full-field deformation, exit velocity and energy absorption measurements from the ballistic tests show significant improvements in impact resistance for the panels made from nanomodified epoxies relative to laminates with the unmodified epoxy matrix. The highest absolute absorbed energy was observed for the GFRP panels fabricated using the epoxy matrix loaded with BNNT/GNP at 255.7 J, 16.8% higher than the unmodified epoxy matrix. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the effect of temperature on the microstructure, failure mechanism and compressive mechanical properties of newly developed ZA27 syntactic foams. Two different types of filler particles are considered, i.e. expanded perlite (P) and expanded glass (G). Metallic syntactic foam (MSF) has been produced via a counter-gravity infiltration process of packed particle beds, followed by controlled thermal exposure. Quasi-static compressive tests were carried out on cylindrical samples at five different in-situ testing temperatures between 25 °C and 350 °C. At all considered temperatures, P-MSF exhibits superior mechanical properties compared to G-MSF. The mechanical properties of both foam types decrease significantly with increasing testing temperature. For comparison, solid ZA27 samples were compressed at the same testing temperatures. Due to microstructural changes, a significant strength degradation of solid ZA27 was observed starting at 100 °C. Comparison of results indicates that the temperature-dependent mechanical properties of P-MSF and G-MSF are strongly controlled by the matrix material. However, the addition of particles decreased the relative reduction of plateau stress and volumetric energy absorption of ZA27 MSF at elevated temperatures. [ABSTRACT FROM AUTHOR]

Abstract This paper demonstrates a three-dimensional electromagnetic interference shielding nanocomposite flexible sheet which is consisted of NiFe 2 O 4 spinel ferrite nanoparticles, and carbon source materials such as graphite, graphene oxide and reduced graphene oxide in the elastomer matrix. The prepared nanocomposite exhibited ferromagnetic behavior. The total shielding effectiveness was up to 28.5 dB for the elastomer nanocomposite sheet having filler NiFe 2 O 4 nanoparticles with reduced graphene oxide. The coexistence of electric and magnetic dipoles in the prepared shielding nanocomposite sheet can response highly to electromagnetic waves and consequently high electromagnetic loss. The high value of shielding efficiency is also related to dual interfaces of NiFe 2 O 4 and reduced graphene oxide in the ternary NiFe 2 O 4 -Reduced Graphene Oxide-Elastomer nanocomposite. The investigated results indicate that the absorption attenuation is a dominant mechanism for electromagnetic interference shielding. The current study demonstrates a facile strategy to develop advanced lightweight electromagnetic interference shielding nanocomposite flexible sheet. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Engineering structures are often subjected to the conditions of cyclic-loading, which onsets material fatigue, detrimentally affecting the service-life and damage tolerance of components and joints. Carbon fibre reinforced plastics (CFRP) are high-strength, low-weight composites that are gaining ubiquity in place of metals and glass fibre reinforced plastics (GFRP) not only due to their outstanding strength-to-weight properties, but also because carbon fibres are relatively inert to environmental degradation and thus show potential as corrosion resistant materials. The effects of cyclic loading on the fatigue of CFRP are detailed in several papers. As such, collating research on CFRP fatigue into a single document is a worthwhile exercise, as it will benefit the engineering-readership interested in designing fatigue resistant structures and components using CFRP. This review article aims to provide the most relevant and up-to-date information on the fatigue of CFRP. The review focuses in particular on defining fatigue and the mechanics of cyclically-loaded composites, elucidating the fatigue response and fatigue properties of CFRP in different forms, discussing the importance of environmental factors on the fatigue performance and service-life, and summarising the different approaches taken to modelling fatigue in CFRP. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a progressive fatigue damage modeling technique is proposed based on Reifsnider's critical element concept. The static and fatigue behavior of the unidirectional E-glass/epoxy composite plies in the fiber and matrix direction is obtained experimentally. Considering suitable material property degradation models, a computer code is developed which integrating with the Abaqus software it is capable of predicting the fatigue life of a notched composite ring with different layup configuration under arbitrary states of stress. To evaluate the applicability of the model, a number of fatigue tests under different states of stress are conducted on the notched composite rings. It is proved that by having unidirectional properties of a composite, this model is capable of estimating the static strength of the notched rings with less than five percent deviation and putting forward a reliable prediction for fatigue life with less than twenty percent underestimation. Graphical abstract Image 1 Highlights • The static strength of a notched ring can be estimated by 5% deviation. • The fatigue life of a notched ring can be predicted by 20% underestimation. • The hoop stress at the notch region is two times more than the average stress. • The bending at the gap between split-disks causes 30% more stress in the inner layers. [ABSTRACT FROM AUTHOR]

Abstract Even if the knowledge on the fatigue behaviour of plant fibre composites has increased steadily in the last few years, some issues still remain open at the present time. Such is the case, for instance, of the high-cycle fatigue strength. Actually, most of the fatigue studies available in the open literature to date are limited to a maximum of 1–2 million cycles. All available stress-life plots exhibit linear trends with constant slope and does not reveal any fatigue limit for these given cycle numbers. So, this paper proposes to investigate the High-Cycle Fatigue behaviour of a flax-epoxy laminated composite. The effect of loading frequency is firstly evaluated on the Low-Cycle Fatigue behaviour using a multi-instrumented analysis including infrared thermography and acoustic emission. Results show that high frequency could be a suitable method to shorten the fatigue tests and study the High Cycle Fatigue behaviour of this type of composite material. Based on this result, high-frequency (30 Hz) is used to investigate the behaviour of the flax-epoxy composite on a range of 106- 108 cycles. Results show that fatigue damage continues to evolve and the maximum stress continues to decrease as a function of increasing number of cycles, following a power-law trend. This result suggests that, if a fatigue limit does exist for unidirectional flax-epoxy composite laminates, it is so low that it cannot observed in tests up to 108 cycles. It is also recommended to take it into consideration when designing plant fibre composite structures. [ABSTRACT FROM AUTHOR]

Abstract We prepared poly(lactic acid) (PLA)/bamboo cellulose nanowhiskers (BCNW) bionanocomposite with a high toughness but a low modulus in the previous work. In this paper, a new reinforcement, silane surface-modified ultrafine bamboo-char (UFBC), was employed to strengthen the binary PLA/BCNW bionanocomposite. The ternary bionanocomposite films were fabricated by a solution casting with different contents of surface-treated UFBC in the range of 0.25 wt% to 4.0 wt%. The functionalization of UFBC with (3-mercaptopropyl)trimethoxysilane (A-189) favored its dispersion in the PLA matrix; sea-island and nuclear-shell characteristics were observed by the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). When the UFBC content was 0.25 wt%, the tensile strength and elongation at break increased by 99.26% and 104.93%, respectively, comparing to the neat PLA. Differential scanning calorimetry (DSC) results showed that glass transition temperature, crystallization temperature, crystallization enthalpy and crystallinity increased with the increase of UFBC contents. Thermogravimetric analysis demonstrated that the thermal degradation stability decreased with the UFBC addition. BCNW and UFBC produced a synergistic effect on composites' toughening and strengthening. These results provided a basic understanding of PLA enhancement mechanism and a simple approach for PLA composite manufacture with sound mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract Expanded perlite is worldwide used material. Due to its low bulk density is used mainly in building materials technology as a filler in lightweight composites, thermal, acoustic, fire insulation as well as in horticulture and agriculture. Due to its extremely low bulk density waste expanded perlite is difficult to handle, utilize and causes dust formation. Paper presents method of utilization of volcanic rock as perlite in two structures (raw or expanded) as a valuable, high performance filler to produce a polymer composites material. The composites were prepared by twin-screw extrusion combined with compression molding at a concentration between 0 and 20 wt %. The effect of reinforcement content and ratio of each particle was studied via morphological (SEM), mechanical (tension), rheological (shear) and thermal (DSC) properties The properties were evaluated in both solid and melt state to determine the mechanical performance of these materials. The results show that better dispersion, distribution and interfacial adhesion of the raw perlite in the PP matrix was achieved compared to the expanded perlite. In general, the mechanical properties and thermal stability of PP were improved with perlite addition. For example, the Young's modulus of raw perlite reinforced composites increased by up to 41% (at 15 wt %) compared to the neat PP. Highlights • Polymer bio-composites with Argan nut shell Fillers (ANS) are produced and tested. • The effect of filler content and coupling agent on the properties is evaluated. • Dynamic mechanical characterization are carried out. • ANS may be considered as possible reinforcements of thermoplastics bio-composites. [ABSTRACT FROM AUTHOR]

Abstract This paper intends to contribute to a better understanding of the failure mechanisms on short fibers composites with high fiber volume fractions, for which relatively low values of stiffness and resistance efficiency are reached. For the aforementioned purpose, the current work used composite plates that were manufactured by compression molding and incorporating short carbon fibers reinforcements (0.5 mm in length with 5–20% volume fiber fraction) into an epoxy resin. For low volume fractions, the composites exhibit static mechanical properties nearly proportional with fiber content. However, for high volume fraction lower efficiency was observed for both tensile stiffness and strength. As expected, the strain at failure decreases with the increasing of the fiber content. Fatigue strength follows a similar behavior of static strength, increasing until the fiber content is of 17.5% in volume, but afterwards remains nearly constant. Fatigue life is mainly influenced by fiber dispersion and porosity. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the results of a study about the mechanical behaviour, before and after aging, of two cement-based composites reinforced with long sisal fibres cured at early age in a CO 2 environment. After curing, samples of both composite systems were submitted to wetting and drying cycles to accelerate the aging of the materials allowing the evaluating of the efficiency of the CO 2 treatment. Besides promoting CO 2 capture, the used cure also allowed the increase in the durability of the sisal fibre-cement based composites by the Calcium Hydroxide (CH) consumption and pH decrease promoted by the carbonation reactions. The lime-pozzolanic material composite was also treated with CO 2 at early stages of formation, with the carbonation and pozzolanic reactions acting simultaneously to deplete the Ca(OH) 2 thus improving its durability. Four-point bending test, thermogravimetry analysis of the matrix and SEM analysis of the fibres were done before and after aging to study the durability mechanisms of the composites. The obtained results showed that the CH free cement-based composite containing metakaolin and fly ash presented the best mechanical behaviour before and after accelerated aging. The early age carbonation of the lime-pozolan composites improved its mechanical response, before and after accelerated aging, when compared with the non-carbonated samples. The thermogravimetry test showed that the increase of the carbonation time of the reference Portland cement-based composite consumed the C S H, compromising the ductility and strain capacity of this composite family after aging. The SEM pictures showed petrified fibre effect by the migration of hydrated products after 10 and 20 cycles of ageing for this composite system. [ABSTRACT FROM AUTHOR]

Abstract To evaluate the effective mechanical properties of the composites with complicated micro-structures, the RVE based FE homogenization method with the periodic boundary condition is introduced and implemented in this paper, and the emphasis is on the periodic boundary condition and its numerical implementation algorithm. The pre-processing (such as the generation of geometry model and application of periodic boundary condition), FE analysis and post-processing (such as the average of stress and strain and stress contouring of the surface nodes) concerning the evaluation of the effective mechanical properties of the composites with complicated micro-structures are conducted in the FE package ABAQUS through the Python Interface. Numerical results show that the proposed numerical implementation algorithm of the periodic boundary condition guarantees the stress and strain continuities and uniaxial deformation constraint of the RVEs for the composites with complicated micro-structures. Compared with the Halpin-Tsai model and two-step M-T/Voigt mean-field homogenization method, the RVE based FE homogenization method with the periodic boundary condition is verified to accurately predict the effective elastic properties and elasto-plastic responses of the composites with the complicated micro-structures. [ABSTRACT FROM AUTHOR]

Abstract The present paper is dealing with the reinforcement of epoxy and high density polyethylene (HDPE) matrices using stainless steel flakes (SSFs). Particulate composite specimens of different wt SSFs contents up to 10% were produced for each case of polymer matrix. The so-obtained SSFs/epoxy and SSFs/HDPE composites underwent tensile, three-point bending and compression tests. The tensile and flexural performance of the composites of both matrices seemed to be negatively affected by the SSF loading. However, the response on plastic deformation under tensile loading for the SSFs/HDPE composites was considerably enhanced for low SSFs contents. The compression response was enhanced in the case of SSFs/HDPE composites as well. The tensile, flexural and compression performance is being explained on the basis of the microstructural observations for each case of reinforced matrix. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the experimental study on the mechanical and thermal properties of nano-biocomposite made of polypropylene/kenaf fiber/polypropylene-grafted maleic anhydride (PP/kenaf/PP-g-MA) biocomposite and multiwall carbon nanotubes (MWCNTs). To meet this objective, the specimens were produced with different contents of MWCNTs (0, 0.5, 1, 1.5 and 2 wt%) by melt blending process in an internal mixer and in the following the standard form of specimens were made by compression molding. The amounts of chopped kenaf fiber loading and PP-g-MA compatibilizer were fixed at 30 wt% and 5 wt% for all formulations based on the preliminary studies. Tensile strength and modulus, flexural strength and modulus and notched Izod impact strength of the nano-biocomposites were evaluated, which obviously found that the mechanical properties of PP/kenaf/PP-g-MA biocomposites were enhanced by the addition of MWCNTs. The optimum in mechanical strengths was detected at 1 wt% MWCNTs. Thermogravimetric analysis (TGA) was carried out to investigate the thermal stability of nano-biocomposites. The results illustrated that the values of the different weight loss temperatures and second decomposition peak temperatures increased after incorporation of MWCNTs due to barrier effect of the MWCNTs. Morphological study which characterized using scanning electron microscopy (SEM) technique verified that a good and homogeneous distribution of MWCNTs through the biocomposites. However, some aggregates were revealed at higher MWCNT content. Fourier transform infrared (FTIR) spectroscopy analysis did not show any chemical interaction between MWCNTs and the PP/kenaf/PP-g-MA biocomposites. [ABSTRACT FROM AUTHOR]

Abstract Composite materials are becoming the most useful material for aircraft structures. Their main advantage is connected to the possibility of deeply reducing weight and costs by maintaining high performances in terms of strength and security. The second major advantage in using this them depends on the possibility they could be proper designed to guarantee services they are made to. Many ways to combine them lead to the necessity of planning experimental tests in order to evaluate the real both elastic and plastic mechanical properties and to compare their variability as function of the fiber type, matrix type and manufacturing technology involved for realizing them. In this paper, a comparison between two innovative Carbon Fiber Reinforced Plastic materials was done. They differ, one from each other, for the matrix type (PEEK and BENZOXAZINE) and for the manufacturing process used to assemble the matrix with the reinforcement (Compression Molding and Resin Transfer Molding). On the other hand, the resin percentage weight content of both materials is maintained constant for all the tests: it is 42% for PEEK matrix and 64% for BENZOXAZINE matrix. The aim of the work is to critically analyze the results in order to get useful information for choosing the best one intended for designing and making the back section of fuselage of a regional aircraft. The component will consist of a front portion with structural aims (zoom phase) and a back part able to withstand to elevated temperatures. [ABSTRACT FROM AUTHOR]

Abstract This paper reviews the application of molecular dynamics simulations on mechanical and tribological properties of polymer composites reinforced by carbon nanotubes and graphene sheet as reinforcements. A variety of simulation studies on modelling, calculation and analysis on enhanced elastic, tensile, fracture properties of carbon nanotubes and graphene sheet/polymer composites are introduced and reviewed. The capabilities of molecular dynamics simulations on exploring inherent mechanisms on improved tribological properties of carbon nanotubes and graphene sheet/polymer composites from atomic views are particularly discussed. Different methods of surface modifications of the two nano reinforcements on further enhancing the strength of polymer composites are summarized. Summary and recommendations for potential researches are also provided. This review is intended to provide a state-of-the-art and better understanding on applications of carbon nanotubes and graphene sheet for enhancing mechanical and tribological properties of polymer composites by molecular dynamics simulations, and inspire future efforts in this area. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract In recent years, the use of industrial by-products and waste-based materials in the construction industry has received significant attention to develop eco-friendly and greener construction materials with the aim of reducing the impact of construction industry on the environment. The development of new concretes where cement is replaced with industrial by-products, such as ground granulated blast furnace slag (GGBS) and fly ash (FA), and natural sand (NS) is replaced with waste-based sands, such as lead smelter slag (LSS) and glass sand (GS), would lead to enormous environmental and health benefits by enabling the use of abundant wastes, reducing the extraction of non-renewable natural resources, and reducing the CO 2 emissions associated with concrete production. This paper presents an experimental study on the properties of geopolymer mortars prepared with FA/GGBS, LSS, and GS under ambient curing condition. A total of 12 batches of geopolymer mortars were manufactured and experimental tests were conducted to determine the flowability, hardened density, compressive strength, direct tensile strength, water absorption, and drying shrinkage of each batch together with the alkali-silica reaction (ASR) expansion of batches containing GS. Microstructural analysis was undertaken to describe the reasons for the obtained experimental results. The results show that the compressive and tensile strength of geopolymer mortars increase with an increase in the amount of GGBS. The results also show that an increase in the GGBS amount leads to a decrease in the water absorption of geopolymer mortars. Owing to the lower void amount at the binder-sand interaction zones, LSS- and GS-based geopolymer mortars containing up to 50% GGBS exhibit superior mechanical properties compared to those of their NS-based counterparts. These highly promising findings suggest that the full replacement of NS by LSS and GS can provide an attractive avenue to reduce the environmental impact of abundant waste products and conserve non-renewable natural resources. [ABSTRACT FROM AUTHOR]

Abstract Thermoplastic elastomer (TPE) incorporates the large deformation capability of rubber with the formability and recyclability of thermoplastics. When mixed with conductive carbon allotropes, it has potential application for sensors. Herein, various weight ratios of one-dimensional carbon nanotubes (CNTs) to zero-dimensional carbon black (CB) are introduced to the biocompatible TPE poly(styrene-ethylene-butylene-styrene) (SEBS) system to modulate its sensing behaviors, including electrical, mechanical hysteresis and piezoresistive sensitivity properties. The lowest percolation threshold is achieved experimentally when this ratio is 1:3. Energy loss due to the mechanical hysteresis decreases when CNTs are replaced with CB, which indicates a good recoverability for sensors under repeated stretching and releasing loads. Respecting to piezoresistive sensibility, theoretical models are proposed to explain the sensing mechanism. Especially, the highest gauge factor (GF = 9.872) meaning the highest sensitivity is obtained for this formula. SEM is used to illustrate the correlated mechanisms. This paper presents a promising tunable technology for large deformation sensors. Highlights • SEBS nanocomposites filled by CNTs and CB are prepared and their electrical conductivities are investigated experimentally. • The mechanisms of the decrease of mechanical hysteresis energy losses due to the replacement of CNTs with CB are explained. • The replacement of CNTs with CB brings a higher and more stable piezoresistive sensitivity and the mechanisms are explained. • Mathematical models of sensing mechanisms are proposed and all parameters are identified to explore the sensing mechanisms. • This study provides a guideline for tailoring the sensing behaviors using hybrid nanofillers for large deformation sensors. [ABSTRACT FROM AUTHOR]

Abstract This paper describes the preparation of polycarbonate/ethylene methyl acrylate (95/5 w/w) nanocomposites using graphene: MWCNT hybrid filler in varying ratios (1:1, 1:3 and 3:1) by melt blending process. The effect of graphene/MWCNT hybrid filler on electrical, mechanical, thermal and electromagnetic interference shielding properties of nanocomposites was investigated. Morphology of these composites was characterized by scanning and transmission electron microscopy. Composites with 10 phr loading of hybrid filler (graphene: MWCNT ratio of 1:3) show the highest tensile strength and tensile modulus as compared to the composites based on graphene or MWCNT at the same loading. The maximum electrical conductivity (1.91 × 10−1 S/cm) was also achieved at a loading of 10 phr of hybrid filler (graphene: MWCNT in the ratio of 1:3), which is higher as compared to the composite prepared using either of the filler alone at the same loading. This significant enhancement in electrical conductivity is responsible to attain up to −34 dB EMI shielding effectiveness in frequency range of 8.2–12.4 GHz (X-band). An increase in mechanical properties, electrical conductivity and EMI shielding for composites having hybrid filler (graphene: MWCNT in ratio 1:3) shows the synergistic effects when such fillers are used in combination. [ABSTRACT FROM AUTHOR]

Abstract The topological optimization of composite structures is widely used while tailoring materials to achieve the required engineering physical properties. In this paper, the problem of topological optimization of the microstructure of a composite aimed at the construction of a material with most effective values of the bulk modulus of elasticity and thermal conductivity taking into account competing mechanical and thermal properties of the materials included in the composite is defined and solved. A two-phase composite consists of two base materials, one of which has a higher Young modulus but lower thermal conductivity, while the other has a lower Young modulus but higher thermal conductivity. A new class of problems for composites containing material pores or technological inclusions of different shapes is considered. Effective thermoelastic properties are obtained using the asymptotic homogenization method. A modified solid isotropic material with penalization (SIMP) model is used to regularize the problem. The problem of the isoperimetric constraints is solved by the method of moving asymptotes (MMA). The influence on optimal topology of the composite in the presence of two competing materials, and optimality criteria using linear weight functions are investigated. Pareto spaces that provide deep understanding of how these goals compete in achieving optimal topology are constructed. [ABSTRACT FROM AUTHOR]

Abstract The paper considers a method for evaluation of reinforced concrete damage due to the bending of concrete beams reinforced with steel and fiberglass reinforcement. The evaluation procedure is based on measuring the electrical response to mechanical impact. Measurements of the electrical response are carried out periodically during a gradual increase in the external load. The analysis of signals in time and frequency is the basis for the algorithm for evaluating the damage processes in reinforced concrete structures subjected to four-point bending. On the basis of numerical simulation and experimental study of the load graphs, the stages of damage process in reinforced concrete beams under bending action were determined. A good correspondence between experimental and theoretical results is shown. As diagnostic parameters characterizing the stages of damage in reinforced concrete beams, it is proposed to use the energy decay coefficient of the electrical responses, the coefficient of cross-correlation of the signal spectrum in the process of loading with the signal spectrum from the same sample before loading, and the frequency shift at which the maximum coefficient of correlation can be observed. Most informative frequency ranges where the proposed diagnostic parameters relation to the degradation processes of reinforced concrete during bending is more reliable were determined. The proposed method can be used to monitor the development of damage in reinforced concrete under bending conditions. [ABSTRACT FROM AUTHOR]

Abstract To overcome the shortness of organic bonding in fiber-reinforced polymer (FRP) retrofitting, textile-reinforced mortar (TRM) has been studied as an alternative composite for retrofitting structural concrete. However, the brittleness of mortar brings the conflict between the efficient using of FRP and durability performance of TRM. To solve this problem, Engineering Cementitious Composite (ECC) can potentially be used to replace mortar in TRM, due to its "ductile" property. The new textile-reinforced composite is named as TR-ECC. In this paper, the tensile failure mechanism and mechanical properties of TR-ECC composite, which was composed of basalt textile grids and one kind of ECC, Ultra High Ductility Cementitious Composite (UHDCC) as the matrix, was investigated. The uniaxial tensile tests on 24 TR-ECC specimens (eight groups) were carried out. The variables include thickness of UHDCC per layer, textile grid geometry configuration and volumetric ratio of textile grids. The influence of variables on the failure pattern, initial elastic and hardening modulus, crack tensile stress, ultimate tensile strain and stress of TR-ECC were analyzed. Finally, the stress-strain behavior and strength of TR-ECC were compared with that of traditional TRM. The test and comparison results show that ECC can largely improve the textile reinforcement effect than the mortar and well control the cracking width. [ABSTRACT FROM AUTHOR]

Abstract Using Carbon Fiber Reinforced Polymers (CFRP) jackets to confine existing concrete masonry columns for capacity and ductility enhancement has been approved in axial compression applications. Considering that the majority of columns in practice are loaded under a combination of axial compression load and bending moment, experimental work for testing reinforced concrete masonry columns confined by CFRP jackets under eccentric loading is needed. This paper presents the results of testing 28 half-scale fully grouted reinforced concrete masonry columns under different concentric, eccentric loading conditions and variations in CFRP jacketing. The ability of CFRP jackets to improve the structural performance is evaluated. Axial force-bending moment interaction diagrams of confined reinforced concrete masonry columns are compared against the unconfined masonry columns to quantify the enhancement in strength and moment. The results indicate that increasing the CFRP jacket thickness enhanced the performance of masonry columns regarding axial strain and strength; however, there was a noticeable reduction in strength gain under strain gradient condition upon increasing the eccentricity level. Also, axial force-bending moment interaction diagrams of confined masonry columns showed an increase in the load and the moment capacity compared to that of unconfined masonry columns. [ABSTRACT FROM AUTHOR]

Abstract During the last two decades, interest in bio-based polymers, especially in bio-based composite materials, has grown as a result of environmental concerns. In this paper new composites obtained from fully bio-based unsaturated polyester resin (UPR) and waste poly(ethylene terephthalate) (PET) were studied for the first time. The composites were prepared by crosslinking the UPR in the presence of functionalized PET particles (3, 6 and 9 wt%), using dimethyl itaconate as reactive diluent. The results showed that the incorporation of the PET particles led to the increase in mechanical properties. However, higher PET loading caused a decrease in the mechanical properties of the composites because of the PET particle agglomeration. [ABSTRACT FROM AUTHOR]

Abstract Geopolymer mortar refers to the mortar manufactured with sand and geopolymer, which is composed by the base materials containing affluent aluminium and silicon that was activated by adopting alkaline solution to serve as a binder. The investigation of the properties and application of the geopolymer mortar has attracted more and more attention of the researchers and cement based industries because of its sustainability advantages. This study reviews the properties of the geopolymer mortars including fresh performance (workability, setting time, and temperature of fresh mortar), physical properties, mechanical properties (compressive strength, tensile strength, elastic properties, flexural performance, bonding behavior, and fracture behavior), durability properties (acid resistance, resistance to elevated temperature, frost resistance, water absorption, and shrinkage properties) and microstructure analysis. This study also reviews the properties of different types of geopolymer mortars prepared using various source materials as base materials. The current study results indicate that the geopolymer mortar has exhibited significant feasibility and application prospect to be used as an environmental friendly building material, which may be an appropriate replacement to the traditional cement mortar in the future. Highlights • 119 papers are reviewed on the properties of geopolymer mortars. • Fresh and physical properties of geopolymer mortars are discussed. • Mechanical properties and durability of geopolymer mortars are also addressed. • Microstructure analysis of geopolymer mortars is reviewed. [ABSTRACT FROM AUTHOR]