Search

The manufacturing of ballistic impact-resistant (BIR) body armours has evolved over the years with the aim of reducing their weight and enhancing their energy-absorbing capacity upon ballistic impacts. The incorporation of nanoparticles into advanced BIR body armour systems is considered one of the promising techniques. The methods employed in incorporating various nanoparticles in the manufacturing of textile-based body armour systems face a research gap in the optimisation of the associated parameters. This article discusses the mechanism involved in the energy absorption of composites and nanocomposites upon ballistic impact. The current review article highlights the chemical, physical, and mechanical properties of various nanoparticles incorporated into BIR body armour systems. BIR nanocomposites consisting of carbon nanotubes, graphene nanoplatelets, nano-silica, nanoclays, nano-alumina, etc., have been discussed herein. In addition, the significance of various techniques for the dispersion of these nanoparticles was also highlighted. Various methods, such as sol–gel, PVD, CVD, thermal spray, and electroless methods for coating the nanoparticles on the surface of the fibre/fabric were also discussed.

Wood and bamboo are the greenest renewable materials used for construction, furniture, and decor from the ancient ages. However, wood and bamboo have intrinsic faults like durability, ductility, physical and mechanical strength, and stability, limiting their applications in the industry. On the other hand, nanotechnology is a popular technology having numerous applications in different fields, resulting in a significant increase in expectations among academics, investors, the government, and industries. In contrast, nanotechnology can protect wood and bamboo from extreme conditions (bacteria, climate, etc.) by improving physicochemical characteristics because of its unique features. Nowadays, the trend of merging nanotechnology and forest industries to overcome the limitations mentioned above and get economically sustainable materials for construction, furniture manufacturing, flexible sensors developments, energy storage, battery manufacturing, and many more is increasing. Presently, several reviews on wood and bamboo modification by nanoparticles and nanomaterials have already been published. But, at this time, this study is essential because it aims to provide a brief guide about the recently developed eco-friendly sustainable materials from wood and bamboo, their uses, and how they can affect people’s daily life and helps to point out the gap of the current knowledge. In addition, we briefly describe the conventional and modern modification methods, including the influence of nanomaterials on wood and bamboo structures. This article is outlined as follows: The first phase of the review deals with wood and bamboo modification methods. The second phase explains how the modification method improves the properties of wood and bamboo materials, and the last step will describe the recent innovation of wood and bamboo materials.

The aim of this research is to measure the dielectric properties and electromagnetic interference (EMI) shielding effectiveness (SE) of silicone rubber reinforced with graphene nanoplates. In a two-roll mill, different amounts of graphene are mixed together. This is followed by compression moulding at 170°C and post-curing for 4 h at 200°C. Between 1 MHz and 1 GHz, the waveguide transmission line method and a vector network analyser are used to measure the dielectric and EMI SE parameters. As the amount of graphene is increased from 0 to 7 wt%, AC conductivity goes up, reaching 1.19 × 10−3 S/cm at 7 wt%. The same composition gives the highest EMI SE of 43.22 dB at 1 GHz. The high-frequency structural simulation of different compositions shows how shielding works, and the results agree with what has been seen in experiments.

Impact loads lead to the failure of structures and significantly diminish their operational lifespan. The necessity to enhance impact performance has shown gradual progress, resulting in utilising nano-fillers as an additional reinforcement within the matrix. Despite the significant number of studies that have been done on this unique hybrid material, there have only been a few reviews published that discuss the effect of production processes on mechanical properties and performance in these hybrid composites under projectile impact. There have been conflicting results obtained in experimental results from the literature. The disparity is related to the variation in dispersion, bonding states, and inconsistent fabrication processes. This work defines the pros and cons of carbon nanotube (CNT)-based composites along with a systematic representation of the development of CNT-reinforced composites under projectile impact using experimental, analytical, and numerical techniques. The potential of CNT reinforcement on fibre-reinforced polymers (FRPs) and its effect on mechanical properties have been discussed. Furthermore, different impact test setups are explored to determine the effective method to determine the impact performance of CNT-reinforced laminates. Moreover, the impact of surface treatment is discussed using different non-destructive methods, and the influence of CNT reinforcement is determined. In addition, mechanical and impact response with varying configurations of fibres is gathered from the available literature, and optimal design based on the required application is suggested. Also, analytical methods developed to determine the impact response of laminates are discussed to determine the parameters dominating the impact response of the laminate. This review will help researchers find the right combination of FRP materials for a given application.

This article deals with volatile organic substances (VOCs) and odours that can be released into the indoor environment from synthetic leathers that are part of upholstered furniture. The primary task of this study was to provide a detailed analysis of selected synthetic leathers and assess their emission characteristics, including odour substances. VOC emissions were determined using the test chamber method (ČSN EN ISO 16000-9) at a temperature of 23°C and a relative humidity of 50%. The emitted compounds were adsorbed by standard stainless steel tubes with Tenax TA sorbent. VOCs were analysed by thermal desorption and gas chromatography with mass spectrometry The properties of odours were tested using a Sniffer 9000 device, which was directly connected to a gas chromatograph with a flame ionization detector. The dominant substances (with the highest concentration) that were emitted by samples of tested synthetic leathers include toluene (118.2 µg·m−3), 1,2-propanediol (46.2 µg·m−3), and limonene (153.0 µg·m−3). Ohio synthetic leather produced the most unpleasantness hedonic tone (-4) from all evaluated materials.

Due to environmental and financial concerns, there is a growing demand for composite materials in a wide range of industries, including construction and automotive industries. In 2020, the market for wood plastic composites was estimated to be worth $5.4 billion. By 2030, it is expected to have grown to $12.6 billion, with a compound annual growth rate of 8.9% between 2021 and 2030. The fundamental disadvantage of reinforced composites by natural fibers is the different nature of the hydrophilic lignocellulosic and the hydrophobic thermoplastic polymers, although natural fibers would lower total costs. These composites typically fail mechanically as a result of fiber debonding, breaking, and pull-out. In a fiber-reinforced composite, the matrix’s function could be described as distributing the force to the added fibers using interfacial shear stresses. A strong connection between the polymeric matrix and the fibers is necessary for this procedure. Weak adhesion at the interface prevents the composite from being used to its maximum potential and leaves it open to attacks from the environment that could damage it and shorten its lifespan. Poor mechanical performance is caused by insufficient adhesion between hydrophobic polymers and hydrophilic fibers in natural fiber-reinforced polymer composites. Consequently, during the past 20 years, a variety of chemical, thermal, and physical methods have been employed to address these issues. These methods largely concentrated on the grafting of chemical groups that could enhance the interfacial contacts between the matrix and natural fibers. This review article aimed to give information on several types of fiber treatments and natural fiber-treated composites with a specific focus on their physical and mechanical properties.

Builders, designers, and the research community are becoming interested in incorporating timber and concrete based composite structures because they effectively integrate the structural qualities of timber and concrete. The structure’s stiffness, ductility, and load capacity are all affected by the quality of the timber connections used in construction. However, timber-concrete-based structures are limited due to a lack of design knowledge and the brittle failure behaviour of timber under shear or tensile loading. Experimental, numerical, and analytical methods have been proposed in the literature, and the key parameters influencing the performance of timber-concrete structures have been discussed. This study addresses the current challenges in designing timber-concrete connections and their failure modes and suggests simple performance-based analytical models that determine the failure mode. It looks at some of the best numerical design methods used in the past and tries to determine the best way to use timber as a possible way to use safe design principles for timber–concrete composite structures in the future.

In the face of fierce competition in the automotive market, severe environmental problems, and the consistent enhancement of consumer demands for vehicle performance, research and development for new automotive materials have increased. Fiber metal laminate (FML) is a representative hybrid composite in recent years but the application of FMLs in the automotive industry is still rare. In order to boost the strengths and applications of FMLs, a lot of effort has been put into enhancing their mechanical properties. In this review article, up-to-date information on the mechanical performance of FMLs for automotive components is presented. The mechanical testing methods, materials selection, structure design, fabrication methods, and the application of hybrid FMLs were explored. The objective of this review article is to study different factors that influence the mechanical properties of FMLs and provide some optimization directions from various aspects. From recent research, there will be great opportunities for hybrid FMLs utilizing natural fibers and bio-polymers in the automotive field in the future.

Bamboo is one of the renewable materials which can be applied in the engineering field widely. Previous research has shown that bamboo’s inherent poor durability can limit the application of bamboo materials. And nanotechnology has been receiving more and more attention on improving the properties of natural materials, simultaneously. This article aims to promote the application of nanotechnology on bamboo by presenting some guides. And this article has been organized as follows: first, the characteristics and nanomechanical behavior of bamboo in mesoscopic and nanoscopic scale have been introduced. Then, nanomaterials for modifying bamboo have been presented. Next, some analyses on the improvement of some properties of nano-modified bamboo materials have been made. Finally, future perspectives have been discussed.

The moisture content of wood influences its machinability and the resulting quality of the machined surface. This study aims to explore the impact of varied moisture content on the final quality of beech wood cut by a CO2 laser (Fagus sylvatica L.). Laser cutting was performed on beech lumbers conditioned at moisture levels of 0%, 8%, 12%, and 18%. The laser-cut specimens were evaluated for surface roughness and waviness by using a stylus surface profilometer at three measuring locations: top, middle, and bottom. The total color difference ΔE was also assessed using a spectrophotometer at the same three locations. The most intriguing findings revealed that surface specimens with higher moisture content are lighter than those with lower moisture content. Specifically, the top areas of specimens with different moisture content exhibited lighter shades than those in the middle and bottom areas. Notably, the surface profile of the specimens remained unaffected by variations in moisture content levels. [ABSTRACT FROM AUTHOR]

Thermal modification is an environment-friendly technology for improving various wood properties, especially the dimensional stability, decay resistance, and color homogeneity. In this work, four tropical wood species (African padauk, merbau, mahogany, and iroko) were thermally modified by the ThermoWood process. The influence of heat treatment on the color and chemical changes of wood was studied by spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, and wet chemistry methods. As the temperature increased, a decrease in lightness (L*) and a simultaneous decrease in chromatic values (a*, b*) were observed, indicating darkening and browning of the wood surface. As a result of the heat treatment, the relative content of hemicelluloses decreased the most in merbau and mahogany, while the thermal stability of iroko and African padauk was higher. All examined wood species showed a strong correlation between the lightness difference value (ΔL*) and the content of hemicelluloses (r = 0.88–0.96). The FTIR spectroscopy showed that the breakdown of C═O and C═C bonds in hemicelluloses and lignin plays an important role in the formation of chromophoric structures responsible for the color changes in the wood.

The development of hybrid composite materials using honeycomb structure, typically a lightweight material, is commonly used in aircraft structures. However, the use of honeycomb with natural or synthetic composite remains unexplored in the literature. Therefore, this study aims to partially replace synthetic fiber, woven glass with a natural fiber of woven kenaf and honeycomb core. An experimental analysis investigated the mechanical strength of three different compositions using glass, kenaf, and honeycomb materials for structural application purposes. The properties of the sample were evaluated through the tensile, flexural, and impact strength, and the morphological damage was observed using scanning electron microscopy. The results showed that the composition of GKGKG laminate composite is the highest in tensile strength (147.64 MPa) and modulus (3.9 GPa), while the GKHKG composite was good in flexural strength (219.03 MPa) and modulus (11.47 GPa). In terms of impact properties, there was a slight difference in energy level (20–30 J) by GKGKG and GKHKG, showing the optimal hybrid configuration of composite for the newly developed material. In conclusion, the application of the new hybrid of GKHKG composite is promising in semi-structural and structural light-weight applications.

Limitation in practical applications of biopolymer–fiber composite is mainly at higher temperatures. Thus, this study highlights the effects of fiber orientation on the durability of polylactic acid (PLA) reinforced with unidirectional (UD) continuous kenaf fibers at elevated temperatures. PLA and long kenaf fiber were fabricated using the hot-pressing method and stacked at fiber orientations of 0°, 45°, or 90°, relative to the tensile force. Dynamic mechanical analysis of the composites shows excellent anti-shock and temperature-resistant properties of the composite. UD PLA–kenaf composites with a 0° fiber orientation showed an ultimate tensile of ∼190 MPa and a flexural strength of ∼235 MPa, and the strength of the composite was able to retain up to 120°C temperature. The debonding behavior of the fiber from the matrix (fiber pull-out) supported by microscopy proved that interfacial failure occurs from the local strains, which initiate cracking. Interfacial failure and stress transfer have caused a remarkable reduction in composite strength when fibers were oriented at 90°. Hence, this current improvement in the performance of the UD PLA–kenaf fiber composite may potentially replace conventional synthetic fibers, especially for structural automotive applications.

It is still little or no knowledge about the properties of layered wood-based composites and nonwood components in the viscoelastic and plastic region of the force-deflection diagram (FDD). The properties of composites in this area are influenced by several factors such as the composition of the layered composite, the method of modification of the individual layers, the type of adhesive used, etc. This paper focuses on the analysis of the effect of the thickness of individual layers (5 and 9 mm) of beech wood (Fagus sylvatica L.), modification of these layers with different degrees of densification (10, 20, 30, and 40%) and the type of the nonwood component (carbon and high-strength glass fibers) used to reinforce the layered composite on the properties of materials in the plastic region of the FDD. The paper describes the impact of selected factors and those interactions behavior of the tangent modulus in the whole FDD. This is the first study that describes the development of layered wood-based composites and nonwood components in the viscoelastic and plastic region and analyzes the impact of most imported types of modifications on the characteristics in the viscoelastic and plastic regions.

As a green material, wood is widely used in building decoration, railway construction, and other fields. However, the wood itself has inherent defects of being easy to absorb water and deform, rot, and decrease in strength. The physical and mechanical strengths and stability of artificial fast-growing forest wood are even worse. As wood modification can improve the dimensional stability, durability, strength, and other properties of wood, it has been widely used. Chemical modification is the main method of wood modification. The development of nanotechnology has brought more possibilities for wood modification. Owing to the extensive literature available, this article summarizes the representative achievements of wood chemical modification and nanotechnology. The principle, production process, advantages, and disadvantages of various wood chemical modification methods were analyzed, compared, and evaluated. Finally, according to the application status of wood-modified materials, the problems existing in the current wood chemical modification methods and the application of nanotechnology, and the development trend in the future are analyzed.

This study aimed to investigate the combined effect of steaming and heating on the equilibrium moisture content (EMC) of Turkey oak (Quercus cerris L.) wood over a nine-year period. The study also aimed to determine the impact of steaming on water absorption and water permeability, crucial for the durability of the species against environmental factors. The specimens underwent thermal modification with and without steaming, then were stored under laboratory conditions for ten years. The mass of the specimens was monitored throughout the ten-year period. To measure the water uptake capacity, the specimens were soaked in water for 120 hours. The water permeability of the specimens was assessed using a pressurised chamber. The results showed that the moisture content of thermally-modified oak was constant under laboratory conditions after nine years, further improved by steam treatment. The research also revealed that the steamed wood absorbed more water during water submersion compared to the unmodified wood. When the steaming treatment was applied, there was a significant increase in permeability in the sapwood compared to the heartwood, due to anatomical variations. Despite this, statistical noise, and material variability, alongside tylosis presence, underline the need for examining more specimens in future studies. [ABSTRACT FROM AUTHOR]