Low Modulus Fibers Research Articles

Modeling and experimental investigations of mechanical properties of hybrid composite rods with gradient composition

The concept of creating a functionally gradient material characterized by a smooth change in composition was used in the fabrication of hybrid composite rods. A hybrid core structure with a glass fiber core and a carbon fiber shell was adopted as the basis. To reduce the risk of delamination at the core-shell interface, a gradual transition was implemented from the core of the rod, made based on high-modulus fiber, to the outer shell composed of low-modulus fiber. The strength and modulus of elasticity in bending for hybrid composite rods were modeled. Using the proposed model, an optimal scheme for distributing glass and carbon fibers across the cross-section of a composite rod was selected. Hybrid composite rods with a diameter of 25 mm, with the same matrix (31±0,1%) and fiber (69±0,1%) content, but with different distribution patterns of glass and carbon fibers along the cross-section, were manufactured via pultrusion technique. The bending strength and stiffness characteristics of composite rods were experimentally determined. Mechanical properties of rods with different reinforcement schemes were compared: homogeneous, core-shell, single, and double gradient. The results indicate that a hybrid rod with a gradient reinforcement scheme exhibits higher values of strength and modulus of elasticity during bending. The modulus of elasticity of the rod with the "double gradient" structure was 103 GPa, for comparison, the modulus of elasticity of the rod made by the "core-shell" scheme was 82 GPa. The simulation aligns well with the experimental data.

Comparative ultimate tensile strength of concrete and fibre concrete

The study is aimed at comparing the ultimate tensile stresses with respect to the crack resistance criteria of concrete and fibre concrete based on theoretical and experimental data. The resistance of concrete to cracking is determined by the ability to resist the formation and growth of cracks. According to the cracking resistance criterion, concrete deformations are limited by the ultimate tensile strength of the concrete matrix, insignificant for heavy concrete, and the introduction of dispersed reinforcement can significantly increase its tensile strength and crack resistance. Recommended methods for calculating the crack resistance of fibre concrete structures are based on the procedures, used to calculate the crack resistance of structures, reinforced with bars, and incompletely account the features of a fibre concrete as a structural material. In addition, although even a significant crack opening cause no effect on the bearing capacity of fibre concrete structures, generally accepted methods for calculating fibre concrete structures exclude cracking. The article discusses various options for calculating the ultimate tensile stresses of concrete and fibre concrete for ensuring crack resistance based on reference normative and experimental data. Dispersed reinforcement with metal fibres was established at least doubling the ultimate tensile strength according to the crack resistance criterion with even lowmodulus fibres effectively improving the crack resistance, which ensures a more reliable operation of structures, including during winter concreting.

A comparative study of polylactic acid (PLA)-Based unidirectional green hybrid composites reinforced with natural fibers such as kenaf, bamboo and coir

Plant-based composites are considered as new generation materials that offer sustainability, eco-friendly and green chemistry, utilized by numerous sectors. Composites of green hybrid made from polylactic acid (PLA) and three different plant fibers were prepared using two symmetrical fibers stacking sequences; namely high modulus and brittle (HMB) fibers (kenaf-bamboo-coir/PLA) and low modulus and ductile (LMD) fibers (coir-bamboo-kenaf/PLA) in the outmost layers. The stacking sequence was prepared using a simple slot tool to properly align the fibers and it was dried at 50 °C before being compressed using hot press. It was found that the tensile strength and tensile modulus of both hybrid composites increased linearly up to 158 MPa and 7 GPa respectively. It shows that the stacking sequences had no significant effect on tensile strength, but fracture strain increased by 58% produced by LMD fibres. However, the use of HMB fibres in the outmost layers significantly improved flexural strength up to 49% higher than that of LMD fibres. In contrast, the impact strength of the green hybrid composites using LMD fibres in the outmost layers was 21% higher than that of its counterpart. Like other plant fiber composites, both composites had an increased water absorption capacity of up to 39% due to increased fibre content. These stacking sequence properties are essential to fabricate a specific application to ensure properties suitable for the job's features. High modulus and brittle composites require a high load to deform permanently, as well as low modulus and ductile composites. Both exhibit versatile mechanical characteristic, providing a balance of sealant toughness and the ability to retain overall shape, such as in sound absorption and vibration in transportation.

Modifying the Sand Concrete with Recycled Tyre Polymer Fiber to Increase the Crack Resistance of Building Structures

Recently, the use of recycled tyre polymer fiber derived from waste tires as a concrete reinforcement has received a great deal of attention. The recycled tyre polymer fiber is a promising additive to concrete for building materials which require resistance against cracking. In this work, the effect of treated and untreated fiber on the properties of sand concrete was studied. It was shown that recycled tyre polymer fiber consists mainly of different fractions of crumb rubber, fiber, and metal fiber. The main polymer components in the fiber are polyamide and polyester threads of 6.5 mm length (l) and 0.05 mm diameter (d); the ratio l/d = 150; and the average fiber density is 0.923 g/cm3. It was established that the addition of untreated recycled tyre polymer fiber in the amounts of 11 and 19 kg/m3 into sand concrete leads to a decrease in compressive and flexural strengths by 15% and 21%, respectively. The reinforcement of concrete with the treated fiber in the amounts of 5 and 10 kg/m3 increases the flexural strength by 14% and 23.4%, respectively. The prismatic strength of the concrete which contents 5 and 10 kg/m3 of the treated polymer fiber was lower than that of ordinary concrete by 10.8% and 4.6%, respectively. The obtained results showed that the use of recycled tyre polymer fiber increases the crack resistance of concrete. The recycled tyre polymer fiber can be used as a cost-effective alternative to other types of low-modulus fibers to produce durable building materials.

Mechanical properties of hybrid fiber reinforced ternary-blended alkali-activated materials

This study employed fly ash, blast furnace slag and steel slag to synthesize ternary-blended alkali-activated materials (AAMs) in order to make full use of the industrial solid wastes and improve the mechanical performance by synergistic effects of the precursors. However, peudo-brittle nature is still the main problem of ternary-blended AAMs. To solve this problem, the effect of hybrid fibers consisting of high-modulus steel (ST) fiber and low-modulus Polyvinyl Alcohol (PVA) fiber on the mechanical properties of the ternary-blended AAMs was evaluated by testing their setting time, flowability, uniaxial compressive strength (UCS), indirect tensile strength (IDT), uniaxial tensile strength (UTS), and three-point bending strength (3PBS). Also, the microstructure of the matrix and fibers were analyzed using a scanning electron microscope. The results show that the flowability and setting time increased with the increasing replacement of PVA fiber by ST fiber. At the PVA/ST fiber volume ratio of 1:1, the AAMs cured for 28 days achieved the highest UCS, IDT, UTS, and 3PBS, which were 32 %, 91 %, 80 % and 114.7 % higher than the AAMs without fiber reinforcement, respectively. The fracture pattern and microstructure illustrated that the best synergistic effect of hybrid fibers was achieved at the PVA:ST fiber ratio of 1:1, at which the small-sized PVA fibers and large-sized ST fibers can inhibit the propagation of micro- and macro-cracks at early and late deformation processes. Furthermore, the ultimate elongation of the composite was improved from 2.62 % to 4.21 % and 5.3 % by modifying the PVA fiber with acrylic polyurethane copolymer and replacing the PVA fiber with polyethylene fiber, respectively, implying the significance of surface hydrophilicity of low-modulus fiber on the ductility of AAMs. This study provided a guide for synthesizing and tailoring the mix design of hybrid-fiber-reinforced ternary AAMs with better strength and ductility.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ РАСЧЕТА КОЭФФИЦИЕНТА ИНТЕНСИВНОСТИ НАПРЯЖЕНИЙ ПО РЕЗУЛЬТАТАМ РАВНОВЕСНЫХ И НЕРАВНОВЕСНЫХ ИСПЫТАНИЙ

This article explores the practical use of methods for determining the stress intensity factor at normal separation: eccentric compression of notched cubes and four-point bending of a notched beam. During non-equilibrium tests, the stress intensity factor value was calculated from the value of the breaking load. During equilibrium tests, the stress intensity factor value was determined from the complete equilibrium deformation diagram, taking into account the energy indicators of destruction. The test used nanofiber-reinforced concrete, in which carbon nanotubes are used as crack propagation inhibitors at the level of the cementing agent, and various macro-sized fibers are used at the level of fine-grained concrete. As a result of the tests, it was found that the methods for determining the recovery factor from cubes with a notch and from deformation diagrams showed a good degree of convergence. Fiber reinforcement affects the fracture toughness of a nanocement composite, and high-modulus fiber has a greater effect on fracture toughness than low-modulus fiber. The stress intensity factor is a good indicator for comparing different types of fiber reinforcement in terms of their effect on fracture toughness.

Experimental investigation of the tensile and modal properties of epoxy based symmetric interlayer glass/carbon hybrid composites

:Interlayer hybrid composites can be tailored for enhanced strength and stiffness. Research on enhancing the mechanical properties of Interlayer hybrid composites is being explored by varying fiber orientations, layup sequence, different type of fiber materials. The objective of this work is to investigate the effect of stacking sequence of the high modulus carbon fibers on the tensile and modal properties of symmetric glass/carbon fiber interlayer composite. The interlayer hybrid composites were fabricated for different stacking sequence of carbon fibers using hand layup technique. Tensile strength and modulus were evaluated as per ASTM 3039 standard. Experimental modal analysis was carried out for two boundary conditions (Free-Free and Cantilever). The modal properties such as natural frequency, mode shapes and damping were studied. The results show that interlayer hybridizations by using low & high modulus fibers along with their stacking sequence about the neutral axis of the laminate have significant influence on the tensile and modal properties. Interlayer hybridization technique offers the potential to provide better mechanical and modal properties in design of high-performance composites.

Effect of low-modulus polypropylene fiber on physical and mechanical properties of self-compacting concrete

The article presents the results of laboratory experiments investigating the necessity and expediency of disperse reinforcement of self-compacting concrete (SCC) to increase its physical and technical parameters and the study of deformative properties of SCC with the use of fibers. For collaboration with manufacturers to improve physical and mechanical properties and durability, to deduce basic laws, researchers on the basis of previously published results, offered disperse reinforcement of SСС by polypropylene fibers of 6, 9, 12, 15 mm in size and quantity from 0.5 to 2 kg per 1 m3 of concrete mixture. From the work done it can be concluded that the addition of 1–2 kg per 1 m3 of fiber with 9÷15 mm in size improves the physical and technical properties of SCC, such as flexural strength by 10%, and shrinkage deformations reduced to 75% compared to the concrete without fiber. In the course of this study, it was found that the disperse reinforcement with low-modulus fiber increases the characteristics of SCC in production. Based on the results obtained, practical recommendations for the optimal size and amount of fiber in SCC were presented in order to derive the optimal price-quality ratio, as well as to improve the quality of concrete works at high temperatures > 20 °C.

Workability and Flexural Properties of Fibre-Reinforced Geopolymer Using Different Mono and Hybrid Fibres.

The effects of mono (single type) and hybrid (mixed types) fibres on the workability, compressive strength, flexural strength, and toughness parameters of fly ash geopolymer mortar were studied. The ratio of sand to geopolymer paste of the mortar was 2.75. It was found that workability of mortar decreased more with the use of PP fibres due to its higher dispersion into individual filaments in geopolymer mortar compared to the bundled ARG and PVA fibres. Compressive strength increased by 14% for using 1% steel with 0.5% PP fibres compared to that of the control mixture, which was 48 MPa. However, 25 to 30% decrease of compressive strength was observed in the mortars using the low-modulus fibres. Generally, flexural strength followed the trend of compressive strength. Deflection hardening behaviours in terms of the ASTM C1609 toughness indices, namely I5, I10 and I20 were exhibited by the mortars using 1% steel mono fibres, 0.5% ARG with 0.5% steel and 1% PVA with 0.5% steel hybrid fibres. The toughness indices and residual strength factors of the mortars using the other mono or hybrid fibres at 1 or 1.5% dosage were relatively low. Therefore, multiple cracking and deflection hardening behaviours could be achieved in fly ash geopolymer mortars of high sand to binder ratio by using steel fibres in mono or hybrid forms with ARG and PVA fibres.

Durability Studies on the Hybrid Fiber reinforced Geopolymer concrete made of M-sand under ambient curing

In the recent decade, there have been a lot of significant developments made in the area of Geopolymer concrete. Geopolymer concrete has been proved for its remarkable durability properties but when alterations are done to the conventional geopolymer concrete through the incorporation of fibers, the durability of the fiber reinforced concrete is uncertain. In this analysis, high elasticity modulus and low elasticity modulus fibers were inserted into geopolymer concrete made of M-sand. As ambient curing is favored in this study, geopolymer concrete is GGBS dependent. As an alkali solution, a mixture of sodium hydroxide solution and sodium silicate solution is used. Durability properties such as water absorption, sorptivity, rapid chloride penetration test, resistance to HCL attack, resistance to H2SO4attack, resistance to sulphate and marine attack are determined in this study. Significant observance has been made with respect to different proportions of glass fiber and polypropylene fiber. Glass fibers yielded fairer results compared to the polypropylene fibers. This study reviews the scope of the use of hybrid fibers made of M-sand in Geopolymer concrete.

Mechanical property analysis on bamboo-glass fiber reinforced hybrid composite structures under different lamina orders

Natural fiber composites are playing the leading role in the recent research fields for their abundance of availability and comparable strength to weight ratio with the synthetic fiber composites. With this motivation, a low modulus fiber (bamboo fibers) hybridized with a high modulus fiber (Glass fibers) epoxy composites are taken for this work to evaluate their desirable mechanical properties. Usually strength of composite specimens is optimized by changing the ply orientation and volumetric ratio of fiber and matrix. But, in this analytics, a novel approach has been followed in which the hybrid composite laminates have been fabricated with five different lamina orders (B/B/B/B, B/G/B/B, G/B/G/B, G/B/G/G and G/G/G/G) using compression moulding machine. Various strength tests such as tensile, flexural and impact strength analyses have been performed. The strength values of the five specimens have been compared under the proposed loading conditions for choosing the better combination of hybrid composite structure exhibiting high strength. To validate the results, numerical analysis has also been made using ANSYS software.

Structural performance of hybrid fiber geopolymer concrete beams

This research work aims at investigating the structural properties of hybrid fiber reinforced geopolymer concrete specimens such as load-deflection behaviour, stiffness, ductility, toughness index. In this research work, effort has been made towards reducing the brittleness of geopolymer concrete by the addition of glass (high modulus) and polypropylene (low modulus) fibers inside GGBS based geopolymer concrete made of M-sand. The glass and polypropylene fibers were added in various proportions such as 1/0, 0.75/0.25, 0.5/0.5, 0.25/0.75,0/1. The research work recorded enhancement of structural properties of geopolymer concrete under ambient curing. This work paved way for the utilization of fibers inside geopolymer concrete and replace cement concrete in all facets.

Modelling the behavior of fiber-reinforced concrete with low-modulus fibers under load

In this work was carried out a study the purpose of which was the development of physical and mechanical modeling of the processes of deformation and destruction of fiber-reinforced concrete. The process of deformation and the mechanism of destruction of fiber-reinforced concrete reinforced with low-modulus polypropylene fibers have been investigated. The method has been improved and the characteristic of adhesion of polypropylene fiber to the matrix has been determined. Theoretical models for forecasting the behavior of fiber-reinforced concrete reinforced with polypropylene fiber under load have been developed.

Effect of Polypropylene fibers over GGBS based Geopolymer Concrete Under Ambient Curing

Geopolymer is being widely used in the construction industry in the recent years. Ground Granulated Blast Furnace Slag (GGBS) based geopolymer concrete is the most suited for ambient curing conditions. It has been perceived that geopolymer concrete is brittle in nature. This brittleness could be reduced by the augmentation of fibers. The objective of this paper is to study the effect of incorporation of polypropylene fibers in Geopolymer Concrete. The various proportions of the ingredients of Geopolymer concrete were calculated from the B.V.Rangan mix design of Geopolymer Concrete. Based on the previous research works conducted by the author, optimum molarity of the sodium hydroxide solution to be used as a part of alkaline activator solution was taken as 13M. Polypropylene fibers were added to the matrix in the ratios from 0.1% to 0.6%. Cubical, Cylindrical and Prism Specimens were casted and subjected to ambient curing. Compaction factor test was performed to measure workability of fresh concrete and tests such as compressive strength test, split tensile strength test and flexural strength test were performed to assess the mechanical properties of hardened Fiber Reinforced Geopolymer Concrete. Tests were carried after curing period of 7days & 28 days and the results were tabulated. Being a low modulus fiber, the fiberposses a good post cracking behaviour and reduce the brittleness of the Geopolymer Concrete. The incorporation of polypropylene fibers increases the compressive strength and flexural strength initially and then decreases.

Development of response surface models for self-compacting hybrid fibre reinforced rubberized cementitious composite

Despite the excellent beneficial mechanical properties and durability behaviour of cementitious composite, the modulus of elasticity is low due to the absence of coarse aggregate and this has hindered in the lone application in structures. The addition of steel fibres in the form of Tirewire along with the PVA (polyvinyl alcohol) as hybrid fibre in cementitious composite, with proper volume of high and low modulus fibers is expected to improve tensile stresses, modulus of elasticity and meanwhile balancing the strain capacity. The partial replacing the fine aggregate with the crumb rubber is to ensure the dispersion of fibres and to limit the fracture toughness of the matrix to improve the performance. The mix designs have been developed using response surface methodology (RSM). The fresh properties for self-compacting were studied and detected that Tirewire diminishes the workability and was conserved through PVA fibre, crumb rubber and superplasticizer. The various hardened properties such as, direct tensile strength, flexural strength and modulus of elasticity was optimized by developing the model equations through analysis of variance (ANOVA). The results revealed that the Tirewire fibre has enhanced the tensile strength, flexural strength and modulus of elasticity. The optimization mixtures were obtained based on the RSM results and are experimentally validated with the less than 5% of error.

Synergetic Effect of Sugarcane Bagasse Ash with Low Modulus of Fiber Reinforced Concrete

This research work has experimentally investigated on the effects of low modulus fibers (PP) used in concrete for the various percentages like 0. 0.5% and 1.0% (by volume fraction) along with different percentage of sugar cane bagasse ash from 0 to 15% replaced in Portland cement (by weight of binding material) for different mixes and tested for the various properties of high-performance concrete (HPC). This experimental test results indicated that the usage of SCBA is restricted up to 10% with 0.5% of PP (Polypropylene) along with 1.5% of superplasticizers produces the higher flexural strength was increased up to 78.30% and compressive strength of concrete was increased up to 25.80% when compared to control (plain) concrete at 28 days. Finally, the usage of low modulus fibre reinforced concrete to act as a corrosion inhibitor agent during the chloride attack than compared to high modulus fibers and reduce the plastic shrinkage due to excellent flexibility in concrete and also increases the life span.

Possibility of Exploring and Applying Wastes from Some Ornamental Plants (Elatior etlingera; Costus comosus; Heliconia bihai) as Sources of Natural Cellulosic Fibers

ABSTRACT The vast market of ornamental plants and flowers generates a large amount of wastes, from where fibers can be extracted. The mechanical properties of these fibers have not yet been reported. Therefore, the possibility of using them as fiber-reinforcement in polymer matrix composites is an open question. In this work the tensile mechanical properties of fibers obtained from the stem of three types of ornamental plants – Etlingera elatior, Costus comosus and Heliconia bihai – are evaluated and compared to the tensile properties of other lignocellulosic fibers. Besides, the tensile strength of the fibers is discussed in terms of the Weibull statistical distribution. E. elatior showed high values for both Young’s modulus and tensile strength, comparable to the properties of fibers with already large use, such as jute. Therefore, fibers extracted from the stem of this ornamental plant are potential candidates to be used as reinforcement in polymer matrix composites. C. comosus and H. bihai on the other hand are low modulus fibers, and their use in composites will be restricted as fillers, reducing cost but not enhancing mechanical properties.

Low-Modulus Carbon Fibers for Antifriction Сarbon Plastics

The effect of nanostructures of low-modulus carbon fibers and the properties of the epoxy matrix of antifriction carbon plastics on the processes occurring during frictional interaction with stainless steel in an aqueous medium is considered. The reasons for high tribological characteristics of antifriction carbon plastics based on low-modulus carbon fibers are explained. It is shown that the high antifriction properties and wear resistance of such carbon plastics are due to the structure of low-modulus carbon fibers, high sorption capacity of the carbon plastics, and formation of a graphite-like film in the friction zone.

Optimization of hybrid fibres in engineered cementitious composites

New hybrid fibre reinforced cementitious composite developed using waste materials in the form of tirewires in combination with the PVA (Polyvinyl alcohol) fibers. The two kinds of fibres have been incorporated in the RSM (Response surface methodology) technique from the Design-expert software to evaluate the hybrid proportion of fibers. The Hybrid fibres in ECC (Engineered cementitious composite), with appropriate quantity of high and low modulus fibers is anticipated to enhance both the tensile strength (modulus of elasticity, bulk strength) and strain capacity (mainly for energy absorption). The fresh properties for self-compacting were satisfied according to EFNARC guidelines and observed that tirewire fibre diminished the workability and was preserved through the addition of PVA and superplasticizer. The hardened properties such as flexural strength, direct tensile strength, modulus of elasticity and shrinkage strain were optimized by developing the model equations through ANOVA (analysis of variance) validation with the more than 95% of significance. The appropriate proportions as 0.5% of tirewire and 1.5% of PVA fibers were obtained. The results revealed that the hybrid proportion of fibres adversely effected on workability and it produced a favourable influence on flexural strength, tensile strength and modulus of elasticity. The PVA fibres helped in increasing the strain hardening portion for the hybrid fibre reinforced engineered cementitious composite (HFRECC) and was able to maintain strain capacity up to 5%. The optimized results were validated experimentally with high desirability value of more than 0.97 and the variation between experimental and optimized results from RSM was found to be less than 5%.

Applying the Explicit Time Central Difference Method for Numerical Simulation of the Dynamic Behavior of Elastoplastic Flexible Reinforced Plates

Based on a stepwise algorithm involving central finite differences for the approximation in time, a mathematical model is developed for elastoplastic deformation of cross-reinforced plates with isotropically hardening materials of components of the composition. The model allows obtaining the solution of elastoplastic problems at discrete points in time by an explicit scheme. The initial boundary value problem of the dynamic behavior of flexible plates reinforced in their own plane is formulated in the von Karman approximation with allowance for their weakened resistance to the transverse shear. With a common approach, the resolving equations corresponding to two variants of the Timoshenko theory are obtained. An explicit “cross” scheme for numerical integration of the posed initial boundary value problem has been constructed. The scheme is consistent with the incremental algorithm used for simulating the elastoplastic behavior of a reinforced medium. Calculations of the dynamic behavior have been performed for elastoplastic cylindrical bending of differently reinforced fiberglass rectangular elongated plates. It is shown that the reinforcement structure significantly affects their elastoplastic dynamic behavior. It has been found that the classical theory of plates is as a rule unacceptable for carrying out the required calculations (except for very thin plates), and the first version of the Timoshenko theory yields reasonable results only in cases of relatively thin constructions reinforced by lowmodulus fibers. Proceeding from the results of the work, it is recommended to use the second variant of the Timoshenko theory (as a more accurate one) for calculations of the elastoplastic behavior of reinforced plates.