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.

OMPARATIVE ASSESSMENT OF PHYSICO-CHEMICAL AND MECHANICAL PROPERTIES OF ALKALI AND FUNGAL TREATED MUSA PARADISIACA L. FIBER

The current study deals with the investigation on the properties of lignocellulose fibre from the stem of Musa paradisiaca L. The Musa paradisiaca L. fibres were extracted from its pseudo stem by mechanical process. The extracted fibres were treated with five different concentrations of NaOH and two different fungal cultures (Aspergillus niger and Aspergillus cereus). The treated fibres were analysed for physical, chemical and mechanical properties as per standard procedure with raw banana fibre. From the chemical investigation, lignin content of the Raw Banana fibre (15.98%) was decreased in the fibre treated with 25% of NaOH (13.56%), Aspergillus niger (11.40%) and Aspergillus cereus (12.54%). Mechanical properties of treated fibre were shows progressive results in comparison with raw banana fibre. In conclusion, the investigation proved that banana fibre treatment with the NaOH and Aspergillus spp has a significant effect on the physiochemical properties

Effect of rice husk (treated/untreated) and rice husk ash on fracture toughness of epoxy bio-composite

Present work studies the effect of particle reinforcement on fracture toughness of bio-composites. The filler used has been taken as rice husk. Epoxy resin has been taken as matrix material. Composites with varying filler loading of 10, 20, 30 and 40 wt.% were fabricated. The fracture toughness was seen to be increasing with increase in filler loading. However beyond 20% there was a decrease in fracture toughness with increase in filler loading. The effect of fibre treatment on toughness was also observed. Rice husk fibres pre-treated with NaOH were used. It was observed that fracture toughness further improved due to treatment. The increase in fracture toughness was significant. Fracture toughness increased from 1.072 to 2.7465 MPa√mm for 20% reinforcement and after treatment it increased to 2.876 MPa√mm. It was observed that concentration of treatment media also affects the fracture toughness. Further the effect of hybridization was observed by addition of rice husk ash as a secondary reinforcement. The fracture toughness of the resulting composites was remarkably higher than that of pure epoxy.

The effect of fibre treatment on water absorption and mechanical properties of buri palm (Corypha utan) fibre reinforced epoxy composites

Over the past century, there has been a dramatic increase in natural fibre composites in which natural fibre has served as reinforcement in polymer. However, the existence of moisture and defects in natural fibres has impacted the mechanical and physical properties of natural fibre polymer composites. The main objective of this study is to fabricate the buri palm fibre reinforced epoxy composite and evaluate the effects of fibre treatment on water absorption and tensile properties. The buri palm fibre were treated by using 5 wt.% NaOH for 24 h and the laminated composite of untreated and treated four-layer and five layer fibres were fabricated via hand lay-up process. The tensile specimens are prepared according to the ASTM D638 standard and the water absorption experiment was conducted by immersing the specimen in distilled water at room temperature until it reached the saturated moisture absorption. The results revealed that the percentage of moisture uptake was reduced to 69% and 95% in treated four-layer and five-layer sequences. It is observed that the thickness swelling of the composite increased with the increase of sequence layering, while the thickness swelling decreased with treated fibre. Alkali treatment affected the properties of buri palm fibre which improved the interfacial bonding between the fibre and epoxy matrix for better tensile properties and reduced water absorption. Finally, morphology examinations were carried out to analyse the fracture behaviour and fibre failure on the tensile test specimen by using microscope analysis.

Abrasion and Physical Properties of Rattan Cane (Calamus deeratus) Fibre Based Epoxy Composites

The effects of fibre content (5–30 wt%) and fibre treatment on abrasion, water absorption, specific gravity, and density properties of epoxy/rattan cane fibre composites were studied. Epoxy resin reinforced with the alkaline treated rattan cane fibre fibres was produced by compression technique in predetermined proportions. Abrasion and physical properties tests were carried out on the developed composites. The results showed that the reinforced composite samples have better enhancement in all the properties tested than the unreinforced control sample. Least Water Absorption (WA) value of 1.4 % were obtained within the 1 week and 2 week for the reinforced samples. Samples reinforced with 10 wt. % rattan fibres had the highest abrasion resistance, while the sample with 5 wt.% rattan fibre addition had the best water absorption resistance. The products of this research could find applications in automotive fields where exposure to moisture and wear are encountered.

Implementation of carbon fibre treatment couches in the XiO® and Monaco® Treatment Planning Systems

Purpose: Carbon fibre treatment couches on linear accelerators provide a strong, rigid framework for patient support. Patient safety is a priority, therefore the dosimetric properties of treatment couches need to be accurately incorporated in treatment plans, to minimize differences between planned and delivered dose. This study aims to determine the attenuation effect of treatment couches for 3-D Conformal Radiotherapy (3-D CRT) and to validate the implementation thereof in the XiO and Monaco treatment planning systems (TPS).Material and methods: Attenuation measurements were performed on the ELEKTA Connexion couches of the ELEKTA Precise and Synergy-Agility linear accelerators. Measurements were made at 10° intervals in RMI-457 Solid water (30 cm x 30 cm x 30 cm) using a PTW Farmer-type ionization chamber (TW30013) positioned at the accelerator’s isocentre. The percentage attenuation was calculated as the ratio of the electrometer readings for parallel-opposed fields. The Computed Tomography (CT) data sets of the set-ups were obtained on a Philips Big Bore 16-slice CT scanner and exported to the TPS. The individual couch structures were delineated and electron density (ED) values were assigned using the commissioned CT-to-ED curve. Test treatment plans were generated with 100MU per field at 10° gantry intervals.Results: The percentage attenuation was determined to be within 2% and 3% for beams perpendicular to the couch surface for XiO and Monaco, respectively. The maximum attenuation was observed for oblique fields which was significantly higher than the manufacturer specified values. TPS validation showed an agreement to 1% for XiO and Monaco. At extreme oblique angles, both planning systems overestimated this effect up to a maximum of 4%.Conclusions: Couch attenuation differs significantly with gantry angle and beam energy. As a result, the treatment couch models should be included in all treatment planning calculations.

Effects of Processing Variables of Extrusion–Pultrusion Method on the Impregnation Quality of Thermoplastic Composite Filaments

Carbon fibre-reinforced polypropylene composite filaments were fabricated via the extrusion–pultrusion method. One of the important factors influencing composites’ filament processability and structural properties is the impregnation quality, which can be represented by interfacial adhesion between the matrix and fibre. To improve the interfacial shear strength (IFSS) of the filament, four processing variables—melt temperature, pulling speed, number of pins in the impregnation die and fibre treatment—have been optimised using the Box–Behnken response surface methodology (RSM). Analysis of variance (ANOVA) was conducted to evaluate the linearity of the response surface models. Three levels were set for each independent variable. The melt temperature was varied at levels 190, 210 and 230 °C, while the pulling speed was set at three levels, namely, 40, 47 and 50 cm/min. The number of spreader pins was varied at 1, 2 and 3 pins, and there were three variations of the fibre treatment, namely, vinyltrimethoxysilane (VTMS), γ-aminopropyltriethoxy silane (APTS) and liquid nitrogen. Twenty-seven experimental runs were conducted, and a significant regression for the coefficient between the variables was obtained. The filament IFSS was measured by a customised pull-out test, and its surface morphology was characterised using a scanning electron microscope. ANOVA showed that fibre treatment significantly affected the IFSS due to their surface roughness, followed by pulling speed and melt temperature in quadratic order. Liquid nitrogen is recommended for carbon fibre treatment because of the high surface roughness, thereby providing a better matrix–fibre bonding effect. The results demonstrated that a melt temperature of 190 °C, pulling speed of 40 cm/min, three spreader pins and treatment of the fibre with liquid nitrogen afforded the optimum impregnation quality. It is important to keep a reasonable low processing temperature to obtain the geometrical stability of the product.

Kenaf fibre treatment and its impact on the static, dynamic, hydrophobicity and barrier properties of sustainable polystyrene biocomposites

Natural fibre-polymer adhesion can be improved by treating the fibre surface or polymer.