Enhanced Thermal Stability, Mechanical Properties and Structural Integrity of MWCNT Filled Bamboo/Kenaf Hybrid Polymer Nanocomposites

Recently, there has been an inclination towards natural fibre reinforced polymer composites owing to their merits such as environmental friendliness, light weight and excellent strength. In the present study, six laminates were fabricated consisting of natural fibres such as Kenaf fibre (Hibiscus cannabinus L.) and Bamboo fibre, together with multi-walled carbon nanotubes (MWCNTs) as reinforcing fillers in the epoxy matrix. Mechanical testing revealed that hybridization of natural fibres was capable of yielding composites with enhanced tensile properties. Additionally, impact testing showed a maximum improvement of ≈80.6% with the inclusion of MWCNTs as nanofiller in the composites with very high energy absorption characteristics, which were attributed to the high specific energy absorption of carbon nanotubes. The viscoelastic behaviour of hybridised composites reinforced with MWCNTs also showed promising results with a significant improvement in the glass transition temperature (Tg) and 41% improvement in storage modulus. It is worth noting that treatment of the fibres in NaOH solution prior to composite fabrication was effective in improving the interfacial bonding with the epoxy matrix, which, in turn, resulted in improved mechanical properties.

Use of Hemp Fibres in 3D Printed Concrete

The use of fibres as reinforcement of 3D printed concrete is widely known and applicable in many situations. However, most of the applied fibres are not produced from renewable resources. Natural fibres are commonly considered as an ecological alternative for these fibres. In order to contribute to improvement of the sustainability of 3D printed concrete, natural fibres such as hemp can replace these synthetic fibres. The objective of this study is therefore to study the possibilities of adding hemp fibres for 3D printing purposes. Due to the comparable properties of hemp and synthetic fibres, natural fibres tend to be suitable for printing purposes. Mixes are made at laboratory scale using batches of 1 – 3 kg. The study examines the effect of adding hemp fibres for the mechanical and fresh state properties of hemp-based concrete. Mechanical properties from bending tests and direct tensile tests show comparable properties of mortars containing hemp fibres and mortars containing synthetic fibres. The fresh state behaviour of the designed concrete mix showed promising and comparable results for a mix based on 0.5wt% of hemp fibres. One of the major issues regarding the use of natural fibres is the irregularity and high water uptake of the fibres. Due to its high hydrophilicity natural hemp fibres take up much water and can therefore degrade. For this study the effect of water uptake did not have much influence on the mixing and printing purposes. By printing a wall element on laboratory scale the use of hemp fibre-reinforced 3D concrete is validated.

Composite materials based on natural fibres applied for structural reinforcement

Environmental problems and environmental protection triggered a rapid development of natural fibres as sustainable materials for the reinforcement of reinforced concrete structures. Synthetic fibre polymer composite materials have been widely accepted by the construction industries as an effective external reinforcement material to rehabilitate deficiencies in existing structures. These materials have exceptional performance such as high strength to weight ratio, corrosion resistance and lightness. However, the disadvantages include high costs during manufacturing and end-of-life services, less environmentally friendly and causing adverse effects on human health. This article presents an experimental program on the use of natural fibres as reinforcement in composite materials for structural strengthening. Different types of natural fibre fabrics (hemp, flax, mixed hemp and cotton) in terms of their mechanical properties were studied. The fibre and fibre fabric sheets were tested in tension test and compared with carbon and glass fibre fabric sheet as reference. So, this study carries out the effect of natural hemp and flax fibre fabric thickness on ultimate loads of specimens. In addition, the ultimate load and stiffness of strengthened beams were investigated. In fact, the results show that the reinforcement technique allows to increase the load-bearing of strengthened structure by 8% to 35% in bending tests.

Effect of Hemp Fibre Surface Treatment on the Fibre-Matrix Interface and the Influence of Cellulose, Hemicellulose, and Lignin Contents on Composite Strength Properties

Natural fibres have recently become an attractive alternative to synthetic fibres in the implementation of polymer composite structures. Inherent flaws within natural fibres in terms of their constituent contents (hemicellulose, cellulose, and lignin) reduce the compatibility of these fibres with polymer matrices. In this study, the effects of chemical treatments on hemp fibres and the resulted polyester matrix composite are investigated. The fibres were treated with alkali (0–10% NaOH), acetyl, and silane chemicals. Long unidirectional fibre composites were prepared by vacuum-assisted resin transfer moulding (VARTM) process. Thermal properties of the fibres were tested using differential scanning calorimetry (DSC) analyses. The mechanical properties of the composite samples were tested using compression and bending tests. Failure analysis of tested composites was undertaken through Optical Microscope (OM) and Scanning Electron Microscope (SEM). The results showed that the treatments of the 4% NaOH reduced interfacial bonding strength and decreased composite properties compared to untreated samples. At higher concentrations (6–10% NaOH), the mechanical properties of the composites increased as a result of greater interfacial bonding. Different trends were observed in the case of alkalised fibres that were further treated with acetyl and silane treatments. It was observed that the treated fibres effectively improved the bonding properties of composites and was in agreement with the micrographs.

Gold and silver nanoparticles as high-value colourants and multi-functional entities for natural fibres and minerals

<p>Significant opportunities exist in both the scientific and industrial sectors for the development of novel multi-functional materials that combine the inherent properties of all precursor components in a synergistic manner, thereby providing new products and opportunities. Processes that add value to natural materials in a facile and refined manner are particularly sought after. Thus this research combines useable substrates, notably natural protein fibres and minerals with gold or silver nanoparticles, producing high value, multi-functional materials that display the strength, softness and shine (of the protein fibres), or high surface area and dispersibility (of the minerals) with the high value and wealth associated with the noble metal nanoparticles, their broad spectrum of intense colours, anti-microbial, insecticide and anti-static properties. This adds significant worth to the substrates, transforming them from commodities to valuable materials. Silk, merino wool and crossbred wool were the natural fibres employed kaolinite and halloysite clays the minerals. They were combined with gold and silver nanoparticles of various sizes and shapes (and hence colours) producing the following composite materials: • Gold nanoparticle-merino wool composites • Gold nanoparticle-crossbred wool composites • Gold nanoparticle-silk composites • Silver nanoparticle-kaolinite composites • Silver nanoparticle-halloysite composites The most successful method for producing silver nanoparticle-clay composites involved the external preparation of silver nanoparticles and their subsequent attachment to the clay substrates by means of a layer-by-layer deposition approach, which capitalised on electrostatic interactions between oppositely charged polyelectrolytes capping the nanoparticles and bound to the clay surfaces. Three general approaches were employed in the production of the gold nanoparticle-natural fibre composite materials. The nanoparticles were either synthesised ex-situ and subsequently attached to the fibres, or the natural fibres were utilised as redox active biotemplates in which the wool or silk absorbed and subsequently reduced Au³⁺ to nanoparticulate Au⁰ on and within the fibres. Thirdly, a seed mediated growth approach was employed in which additional Au³⁺ was reduced to nanoparticulate Au⁰ on the surface of gold nanoparticles already bound to the fibres. This was facilitated by an external reductant.</p>

Gold and silver nanoparticles as high-value colourants and multi-functional entities for natural fibres and minerals

<p>Significant opportunities exist in both the scientific and industrial sectors for the development of novel multi-functional materials that combine the inherent properties of all precursor components in a synergistic manner, thereby providing new products and opportunities. Processes that add value to natural materials in a facile and refined manner are particularly sought after. Thus this research combines useable substrates, notably natural protein fibres and minerals with gold or silver nanoparticles, producing high value, multi-functional materials that display the strength, softness and shine (of the protein fibres), or high surface area and dispersibility (of the minerals) with the high value and wealth associated with the noble metal nanoparticles, their broad spectrum of intense colours, anti-microbial, insecticide and anti-static properties. This adds significant worth to the substrates, transforming them from commodities to valuable materials. Silk, merino wool and crossbred wool were the natural fibres employed kaolinite and halloysite clays the minerals. They were combined with gold and silver nanoparticles of various sizes and shapes (and hence colours) producing the following composite materials: • Gold nanoparticle-merino wool composites • Gold nanoparticle-crossbred wool composites • Gold nanoparticle-silk composites • Silver nanoparticle-kaolinite composites • Silver nanoparticle-halloysite composites The most successful method for producing silver nanoparticle-clay composites involved the external preparation of silver nanoparticles and their subsequent attachment to the clay substrates by means of a layer-by-layer deposition approach, which capitalised on electrostatic interactions between oppositely charged polyelectrolytes capping the nanoparticles and bound to the clay surfaces. Three general approaches were employed in the production of the gold nanoparticle-natural fibre composite materials. The nanoparticles were either synthesised ex-situ and subsequently attached to the fibres, or the natural fibres were utilised as redox active biotemplates in which the wool or silk absorbed and subsequently reduced Au³⁺ to nanoparticulate Au⁰ on and within the fibres. Thirdly, a seed mediated growth approach was employed in which additional Au³⁺ was reduced to nanoparticulate Au⁰ on the surface of gold nanoparticles already bound to the fibres. This was facilitated by an external reductant.</p>

A Further Milestone to the Use of Natural Fibres in Concrete – Past Findings, Barriers and Novel Research Avenues

Concrete as a building material is much appraised for its good compressive strength; however, its low tensile strength makes it a quasi-brittle material. Experiments have proven that fibres such as steel and some polymeric fibres can reinforce and enhance the mechanical strength of concrete. The relatively high production cost of these fibres coupled with environmental issues for their end of life disposal and decline in mechanical strength beyond a certain fibre fraction have encouraged the use of natural fibres; particularly due to their renewability, low cost and good tensile strength. This paper reviews published literature in the field of natural fibres, their extraction methods as well as their effect on the mechanical properties of concrete. Alkaline fibre treatment to improve strength, wettability and subsequently, fibre-concrete matrix interfacial adhesion has also been discussed. As part of the research, the current authors have found that by just using untreated (raw) fibres as reinforcement in fact leads to a decline between 75 % and 90% in compressive strength tested at 8 days for 2 different fibre lengths and volume fractions, respectively. This decline in strength could be co-related with the phenomenon of fibre agglomeration as seen from microscopic analysis. As such, fibre treatment, to remove different impurities from its surface, constitutes an important step towards the manufacture of natural fibre-reinforced concrete. Furthermore, water adjustment in relation to the total water requirement of the cement, aggregates and water needed to saturate the plant fibres is an important property that requires proper control since water content has a direct impact on the workability of the concrete and can turn into a major constraint. The main challenge of the use of natural fibres in concrete is its degradation with time within the highly alkaline concrete environment. Accelerated ageing experiments for natural fibres in concrete as described in literature have confirmed this deleterious occurrence. Thus, as per findings from the current experimental works and literature, the following recommendations are proposed: natural fibre pre-processing to inhibit agglomeration, adequate water addition to cater for all the constituents of the reinforced concrete and the potential implementation of biomimicry to solve the fibre degradation problem.

Mechanical Characterization and Structural Attributes of Biohybrid Composites Derived Using Hemp, Bamboo, and Jute Fibres: an Alternative Approach in the Application of Natural Fibres in Automobile Parts

In the present work, three natural fibres, namely jute, hemp and bamboo have been hybridized with seashell powder and polypropylene resin as biohybrid composites. Nine samples are considered for this study with various weight propositions of bamboo, hemp, and jute. The mechanical characteristics, such as the flexural, impact, and tensile strength of nine samples, are compared, and the Sample 9 shows very good results; the obtained flexural, tensile strength and impact energy of Sample 9 are 239.36 MPa, 47.84 MPa, and 18.33 J, respectively. The main reason for this is the presence of jute material and layering pattern; Sample 9 contains 60 % Jute, 20 % hemp, and 20 % bamboo; the percentage of jute is high compared to the other eight samples. Furthermore, morphological analysis and thermogravimetric analysis (TGA) have been carried out with Sample 9. While comparing the properties of with the existing dashboard material properties, they show more desirable values and thus, the compositions of Sample 9 material can be used for various vehicle parts. When the experimental results are compared with the finite element analysis (FEA) results, the experimental results match with the FEA results, and few variations are noticed.