Fiber-reinforced Hybrid Research Articles

Multi-objective robust optimization of multi-directional carbon/glass fibre-reinforced hybrid composites with manufacture related uncertainties under flexural loading

Multi-objective robust optimization of multi-directional carbon/glass fibre-reinforced epoxy hybrid composites has been presented in this study. Two conflicting objectives, namely minimizing the density and minimizing the cost under the constraint of a specified minimum flexural strength, were considered with the design variables being the fibre type, fibre orientation angle and fibre volume fraction of each lamina. A modified version of the non-dominated sorting genetic algorithm (NSGA-II) was used in order to find the Pareto optimal solutions. Furthermore, robust optimization problems were defined by including manufacturing related uncertainties in the thickness and orientation of each lamina. These uncertain variables were considered as uncertain-but-bounded with the worst case for the minimum flexural strength being determined through an internal anti-optimization solver. The optimization and anti-optimization problems were solved with Pareto optimal and robust solutions being presented for carbon/glass fibre hybrid composites with different levels of minimum flexural strength. The results showed that, in general, consideration of uncertainties in thickness and fibre orientation angle increased the material cost and/or density with this effect being more important for high strength composites.

Validation of fatigue damage model for composites made of various fiber types and configurations

Empirical model for predicting fatigue damage behavior of composite materials developed recently has been applied to composite materials made of different fibers in various configurations: carbon and glass fiber noncrimp fabric reinforced epoxy composites, chopped strand mat glass fiber-reinforced polyester composites, randomly oriented nonwoven hemp fiber-reinforced polyester composites, and glass/hemp fiber-reinforced polyester hybrid composites. The fatigue properties were evaluated in tension–tension mode at stress ratio R = 0.1 and frequency of 1 Hz. The experimental fatigue data were used to determine the material parameters required for the model. It has been found that the model accurately predicts the degradation of fatigue life of composites with an increase in number of fatigue cycles. The scope of applicability of this model has thus been broadened by using the fatigue data of natural fiber and noncrimp fabric composites.

Steel and PVA Fibres Reinforced UHPC Exposed to High Temperatures - Analysis of Residual Properties

Residual parameters of Ultra High Performance Concrete (UHPC) exposed to high temperatures were experimentally accessed. The UHPC was provided by hybrid fibre reinforcement based on polyvinyl alcohol (PVA) and steel fibres. Among the studied material properties, bulk density, matrix density, total open porosity, pore size distribution, water vapour transmission and liquid water transport properties were examined. The UHPC samples were exposed to the temperatures 400 °C, 600 °C, 800 °C, and 1000 °C respectively. For comparative purposes, the reference UHPC samples cured at laboratory temperature were tested as well. Based on the obtained results, correlation between concrete structural changes and tested parameters was found out. The applied temperature load highly affected the concrete porosity, pore size, and thus both liquid and gaseous moisture transport parameters. Disintegration of concrete structure, colour change, cracking, damage of steel fibres (melting), and failure of their cohesion was apparent from optical microscopy analysis.

Effect of matrix voids, fibre misalignment and thickness variation on multi-objective robust optimization of carbon/glass fibre-reinforced hybrid composites under flexural loading

Abstract The robust and optimal design of carbon/glass fibre-reinforced epoxy hybrid composite laminates under the constraint of a specified minimum flexural strength was investigated in this study. Two conflicting objectives, minimizing material cost and weight, were considered with the design variables being fibre type, fibre orientation angle and fibre volume fraction of the laminas. Three sources of uncertainties, namely, fibre misalignment, lamina thickness variation and the presence of matrix voids were incorporated into the model. This multi-objective robust optimization problem was solved by combining a modified version of the non-dominated sorting genetic algorithm (NSGA-II) with a simple genetic algorithm (GA) as an anti-optimizer. Pareto optimal and robust solutions were found for different levels of minimum flexural strength and the significance of each uncertainty source on the optimal cost and weight of the optimal designs were investigated by conducting analysis of variance (ANOVA) tests. The results indicated that, in general, all three uncertainties affected the cost and weight of the optimal designs with the effect of voids being more critical for void contents of greater than 2%.

Static and dynamic compressive properties of ultra-high performance concrete (UHPC) with hybrid steel fiber reinforcements

Ultra-high performance concrete (UHPC) is promising in construction of concrete structures that suffer impact and explosive loads. In order to make UHPC structures more ductile and cost-effective, hybrid fiber reinforcements are often incorporated. In this study, a reference UHPC mixture with no fiber reinforcement and five mixtures with a single type of fiber reinforcement or hybrid fiber reinforcements of 6 and 13 mm in length at a total dosage of 2%, by the volume of concrete, were prepared. Quasi-static compressive and flexural properties of those mixtures were investigated. Split Hopkinson press bar (SHPB) testing was adopted to evaluate their dynamic compressive properties under three impact velocities. Test results indicated that UHPC with 1.5% long fiber reinforcements and 0.5% short fiber reinforcements demonstrated the best static and dynamic mechanical properties. The static compressive and flexural strengths of UHPC with 2% long fiber reinforcements were greater than those with 2% short fiber reinforcements, whereas comparable dynamic compressive properties were observed. Strain rate effect was observed for the dynamic compressive properties, including peak stress, dynamic increase factor, and absorbed energy. The reinforcing mechanisms of hybrid fiber reinforcements in UHPC were eventually discussed.

Sulfate and Calcium Chloride Resistance of Steel/Glass Fiber-Reinforced Polymer Hybrid Panel for Improved Movable Weir Application

This study evaluated the performance of a hybrid panel that can overcome the current problem of corrosion of the steel panels of improved movable weirs when they are exposed to a sulfate and calcium chloride environment such as sea water. A hybrid panel with glass fiber-reinforced polymer (GFRP) layers on both sides of a steel panel means that the central panel is not exposed to the external elements, which can avoid corrosion problems. In this study, to maximize the hybrid panel’s strength and durability, the moisture absorption characteristics and the durability in an accelerated environment were evaluated. The test results were considered to indicate no durability issues as the final absorption ratio was approximately 2.0% or less in all environments. Also, from the accelerated deterioration test results when the steel panel processed by sand blasting was applied in all accelerated deterioration environments, it satisfied the residual strength level of 65% or more. However, in the case without surface processing, upon exposure to MgSO4 solution, it did not satisfy the standard residual strength level of 65%. These results show that sand blasting on the surface of a steel panel is adequate for hybrid panels for improved movable weirs.

Karakterisasi Kekuatan Tarik Komposit Hybrid Lamina Serat Anyam Sisal dan Gelas Diperkuat Polyester

Hybrid fiber composite is a combination of two or more types of fiber that can be based on the architecture or type of the reinforcement. In this study, smoothly spun agave sisalana and cotton yarn were woven to produce sisal-cotton hybrid fabric . The sisal-cotton hybrid fabric (S) was combined with woven glass fabric (FG) to produce hybrid fiber reinforcing system. Four variations of hybrid fiber reinforcement, i.e. three layers of woven glass fabric (FG-FG-FG), glass-sisal-glass fabrics (FG-S-FG), sisal-glass-sisal fabrics (S-FG-S), and three layers of woven sisal-cotton fabric (S-S-S), each embedded in polyester resin were fabricated using cold press mold method. It was expected that the hybrid fiber composite exhibited new properties derived from both types of fiber so that the advantages of each fiber type would appear on the mechanical properties of the hybrid composite systems. The properties being evaluted were tensile properties and density. The results showed that the highest tensile strength of the hybrid systems (FG-S-FG: 117 MPa) is a combination of those of both types of reinforcement, tend to obey the rule of mixtures, i.e. higher than that of natural fiber composite (S-S-S: 48 MPa) but lower than that of glass fiber composite (FG-FG-FG: 133 MPa). Tensile strain-to-failure was noted being sharply increase from 0.33% for GFRP composit up to above 1.07% by replacing the middle layer of FG reinforcement with S reinforcement. Whilst the density of the S-FG-S hybrid system seems to obey the rule of mixtures, that of the FG-S-FG hybrid system was observed lower than expected. This may due to the resin requires longer time to wetthe fibers so that the air between fibers did not posses enought time to evacuate at the jell time being reached such that producing void leading to lowering the density.

Bond performance of GFRP and deformed steel hybrid bar with sand coating to concrete

In this study, we experimentally investigated the bond performance of a glass fiber-reinforced polymer hybrid bar with a core section comprising a deformed steel bar and a sand coating. The glass fiber-reinforced polymer and deformed steel hybrid bar (glass fiber-reinforced polymer hybrid bar) can contribute to longer durability and better serviceability of reinforced concrete members because of the increased modulus of elasticity provided by the deformed steel bar. Uniaxial tensile tests in compliance with ASTM D 3916 showed that the modulus of elasticity of the glass fiber-reinforced polymer hybrid bar was enhanced up to three times. For the bond test, a total of 30 specimens with various sand-coating and surface design parameters such as the size of the sand particles (0.6 mm and 0.3 mm), sand-coating type (partially or completely), number of strands of fiber ribs (6 and 10), and pitch space (11.4 mm to 29.1 mm) of the fiber ribs were tested. The completely sand-coated glass fiber-reinforced polymer hybrid bar exhibited a higher bond strength (90.5%) than the deformed steel bar and a reasonable mode of failure in concrete splitting. A modification parameter to the Eligehausen, Popov, and Bertero (BPE) model is suggested based on the representative experimental tests. The bond stress–slip behavior suggested by the modified BPE model in this study was in reasonable agreement with the experimental results.

Bond and cracking behavior of lap-spliced reinforcing bars embedded in hybrid fiber reinforced strain-hardening cementitious composite (SHCC)

Abstract An experimental study was conducted to examine the effect of hybrid fiber, polyethylene (PE) and steel fiber, reinforcement on the bond and cracking characteristics of lap-spliced reinforcing bars embedded in strain-hardening cementitious composite (SHCC) in the tension zone and subjected to monotonic and cyclic tension loads. This study focused on the confinement effects with respect to the compressive strength of SHCC mixtures with hybrid fiber reinforcement. The SHCC mixtures contained two types of reinforcing fibers: polyethylene and steel fiber with aspect ratios of 1000 and 79, respectively. The test parameters include normal compressive strength (30 MPa) and high strength (100 MPa) and spliced lengths in tension (40% and 60% of the splice length recommended by ACI 318) for the SHCC mixtures. The results indicate that SHCC mixtures can be used effectively to reduce the development length of rebar up to 60% of the splice length required by the American Concrete Institute 318 equation according to splitting failure control by multiple cracking behavior of SHCC mixtures.

Mechanical Behavior of Nettle/Wool Fabric Reinforced Polyethylene Composites

ABSTRACTNatural fibers have lately been used to reinforce plastics that are employed in the production of different engineering products. These stand to be the preferable reinforcement material for polymer matrix composites on account of their biodegradability, low cost, and good mechanical properties. As a result, synthetic fiber (glass, Kevlar) reinforced composites in many engineering applications are now being replaced by natural fiber reinforced composites. An increasing interest is now apparent in hybridizing different natural fibers to come up with high performance composite materials. Designing hybrid biocomposites could involve combining a synthetic and a natural fiber (biofiber) or blending two natural fibers in a matrix. In the present experimental endeavor, new hybrid fiber reinforced composites based on low-density polyethylene matrix with both protein (wool) and lignocellulose (nettle) natural fiber were prepared using compression moulding process. Weight percentages of 15, 20, and 25 of the hybrid fiber reinforcement were used and its effect on the mechanical properties of the developed composites was experimentally examined. Scanning electron microscope has also been used to develop a good understanding of the failure mechanism of the developed composites.

Thermo-physical properties of short banana–jute fiber-reinforced epoxy-based hybrid composites

The utilization of natural fiber-reinforced polymer composites is rapidly increasing in many industrial applications and fundamental research. In this work, short banana-jute fiber-reinforced epoxy-based hybrid composite was prepared by varying the fiber loading (0–40 wt.%) and different weight ratios of banana and jute fiber (1:1, 1:3, and 3:1). The physical and thermal properties such as density, water absorption, thermal conductivity, specific heat and thermal diffusivity were evaluated as per ASTM standards. A new micromechanical model was developed for evaluating the effective thermal conductivity of short fiber-reinforced hybrid composites by using the law of minimal thermal resistance and equal law of specific equivalent thermal conductivity. The thermal conductivity was calculated numerically by using the steady state heat transfer simulations. The proposed model and numerical results were validated with the experimental results and analytical methods existing in the literature. The effective thermal conductivity was predicted with the proposed model, and the finite element method is in good agreement with the experimental values and observed an acceptable range of 0–6.5% and 0–11% error, respectively. The results reveal that the composite made with banana and jute in the weight ratio of 1:3 shows minimum void content, water absorption, thermal conductivity, and thermal diffusivity at all fiber loadings. The fabricated hybrid composites were suitable for building components and automobiles in order to reduce the energy consumption.

Response of glass fiber-reinforced hybrid shear thickening fluid (STF) under low-velocity impact

This paper addresses the response of glass fiber-reinforced shear thickening fluid (STF) under low-velocity impact. Experimental tests were performed according to ASTM: D5628 for initial impact energy 6.89 J and for samples with STF+ nanoclay (30% silica and 3% clay nanoparticles), STF+ nanoclay (30% silica and 1% clay nanoparticles), STF (30% silica nanoparticles), and STF (20% silica nanoparticles).The effect of impregnating glass fabrics with STFs on their quasi-static puncture resistance performance has been investigated. A STF was prepared successfully, and rheological behavior was investigated. The results of rheological tests indicate that the increase in the fraction weight of nanosilica and nanoclay leads to the increase in suspension viscosity and reduction in the critical shear rate. One of the disadvantages of STF is high concentration. Glass fabrics were soaked in STF/ethanol solution to prepare STF–glass fabric composite and STF–nanoclay–glass composite. For better immersion of fibers, at first STF is diluted in ethanol, and then, the fibers are left therein for a specified period in order to impregnate all fibers with the fluid. After this stage, to eliminate the ethanol in the sample, it is heated at a temperature range of 60–70 °C. The composite’s sensitivity to the impact will be reduced through ethanol combining with the fluid and its elimination. Quasi-static resistant tests were carried out on both the neat glass fabrics and STF–glass fabric and STF–nanoclay–glass fabrics composites using a hemispherical penetrator based on the areal density. This study clearly displays a significant enhancement in penetration resistance of glass fabric impregnated with different combination of STF and STF–nanoclay. In sample with higher weight fraction of nanosilica and nanoclay, displacement to yield point is higher and resistance to penetration does not have much difference.

Effects of Hybrid Fibre Reinforcement on Fire Resistance Performance and Char Morphology of Intumescent Coating

Recent researches of fire retardant intumescent coatings reinforced by single Rockwool and single glass wool fibre at various weight percentages and lengths showed some improvements to the mechanical properties of the coatings and the char produced. Therefore, in this research the fibres were combined together in intumescent coating formulation at several weight percentages and fibre lengths to study their effects towards fire resistance performance and char morphology. The hybrid fibre reinforced intumescent coatings were subjected to two types of fire tests; Bunsen burner at 1000°C and the electric furnace at 800°C for 1 hour, respectively. Steel temperature of the coated samples during Bunsen burner test was recorded to determine the fire resistance performance. Thermal stability of the intumescent coatings and chars was determined by Thermogravimetric Analysis (TGA). The morphology of the coatings and char was then examined by using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS) was conducted to obtain elemental composition of the samples. This research concluded that long-hybrid fibre at 12-mm length and 0.6% fibre-weight produced the top performing hybrid fibre intumescent formulation. The hybrid fibres form survived at elevated temperature, hence helped to provide structure and strengthen the char with the highest fire resistance was recorded at steel temperature of 197°C.

Aluminium-carbon fibre-reinforced polymer hybrid crash management system incorporating braided tubes

Aluminium-carbon fibre-reinforced polymer hybrid crash management system incorporating braided tubes

Aluminium-carbon fibre-reinforced polymer hybrid crash management system incorporating braided tubes

Based on axial crushing tests on generic braided carbon fibre-reinforced polymer (CFRP) tubes, a finite element (FE) simulation approach for these structures is developed. In a first step, an approach with individual material cards for different types of braiding structures is pursued and thus generalised to an approach, which can be conveniently adapted for different braiding parameters. Using this simulation approach, the braiding structure with the best specific energy absorption is determined and is consequently applied in the development of an aluminium-CFRP hybrid crash management system. This system incorporates a braided tube in a metallic crash box and is designed as a suitable substitute for the crash management system of a luxury class vehicle. Using FE approach, the structure is designed to absorb the kinetic energy in a low-speed collision (research council for automobile repair structural crash test) to prevent severe damage to the vehicle body, drive train, and chassis. Thus, the derived hybrid structure is built as physical prototype and tested under the boundary conditions of the reference test using a crash sled.

Design Method and Cost-Benefit Analysis of Hybrid Fiber Used in Asphalt Concrete

Fiber, as an additive, can improve the performance of asphalt concrete and be widely studied, but only a few works have been done for hybrid fiber. This paper presents a new and convenient method to design hybrid fiber and verifies hybrid fiber’s superiority in asphalt pavement engineering. Firstly, this paper expounds the design method used as its applied example with the hybrid fiber composed of lignin, polyester, and polypropylene fibers. In this method, a direct shear device (DSD) is used to measure the shear damage energy density (SDED) of hybrid fiber modified asphalts, and range and variance statistical analysis are applied to determine the composition proportion of hybrid fiber. Then, the engineering property of hybrid fiber reinforced asphalt concrete (AC-13) is investigated. Finally, a cost-benefit model is developed to analyze the advantage of hybrid fiber compared to single fibers. The results show that the design method employed in this paper can offer a beneficial reference. A combination of 1.8% of lignin fiber and 2.4% of polyester fiber plus 3.0% polypropylene fiber presented the best reinforcement of the hybrid fiber. The cost-benefit model verifies that the hybrid fiber can bring about comprehensive pavement performance and good economy.

Mechanical Properties of High Volume Fly Ash Concrete Reinforced with Hybrid Fibers

Fly ash substitution to cement is a well-recognized approach to reduce CO2emissions. Although fly ash concrete is prone to brittle behavior, researchers have shown that addition of fibers could reduce brittle behavior. Previous research efforts seem to have utlised a single type of fiber or two types of fibers. In this research, three types of fibers, steel, polypropylene, and basalt as 0%, 0.50%, 0.75%, and 1% by volume of concrete, were mixed in varying proportions with concrete specimens substituted with 50% fly ash (class F). All specimens were tested for compressive strength, indirect tensile strength, and flexural strength over a period of 3 to 56 days of curing. Test results showed that significant improvement in mechanical properties could be obtained by a particular hybrid fiber reinforcement combination (1% steel fiber, 0.75% polypropylene fiber, and 0.75% basalt fiber). The strength values were observed to exceed previous research results. Workability of concrete was affected when the fiber combination exceeded 3%. Thus a limiting value for adding fibers and the combination to achieve maximum strengths have been identified in this research.

Experimental observations of self-consolidated hybrid fiber reinforced concrete (SC-HyFRC) on corrosion damage reduction

Correlations between the rate of corrosion damage in reinforced concrete and observable cracking have been established by a multitude of design codes. Based on this relationship, it is inferred that cracking prevention may provide a suitable corrosion protection scheme capable of enhancing the durability/life expectancy of reinforced concrete exposed to potentially corrosive environmental conditions. A self-consolidated hybrid fiber reinforced concrete mixture is tested under a chloride-induced corrosive environment to determine the role of crack suppression in both the initiation and the propagation phases of corrosion damage. It is observed that in the presence of the hybrid fiber reinforcement, chloride migration rates are not significantly altered by the introduction of moderate cyclical mechanical loading in contrast to conventional concrete samples. Furthermore, the accumulation of damage in the propagation phase of reinforcement corrosion is significantly altered by the suppression of splitting cracks emanating radially outward from the reinforcing bar surface. While not a corrosion elimination scheme, the incorporation of hybrid fiber reinforcement is nonetheless capable of prolonging the life expectancy of a given reinforced concrete element and providing an increased measure of durability.

Self-consolidating hybrid fiber reinforced concrete: Development, properties and composite behavior

The workability of an existing Hybrid Fiber-Reinforced Concrete (HyFRC) composite is improved though the incorporation of concepts from the field of Self-Consolidating Concrete (SCC). The resulting composite, achieved through a described parametric study, allows for easier placement within areas of high reinforcement congestion while maintaining the desired mechanical performance benefits inherent to high performance hybrid fiber-reinforced concrete composites. Retention of the strengthening and ductility enhancement, characteristic of the original HyFRC, is gauged by material response to direct tension and four point bending tests. The designated goal of the SC-HyFRC mix is to provide an optimal structural material for construction in which concrete might be expected to face tension, compression and bending as part of a common service load and must be designed to withstand high levels of deformation under maximum credible earthquake or similar design scenarios. The ductility response of Self Consolidating Hybrid Fiber Reinforced Concrete (SC-HyFRC) to severe loading is then investigated through a comparison with conventional concrete by conducting reinforced compression and tensile tests. In both scenarios the presence of hybrid fiber reinforcement is shown to provide an improvement to the phenomena of internal confinement and tension stiffening, for compression and tension loading respectively, which allow for a significantly improved post cracking response.

Multi-objective robust optimisation of unidirectional carbon/glass fibre reinforced hybrid composites under flexural loading

A multi-objective robust optimisation (MORO) of carbon and glass fibre-reinforced hybrid composites under flexural loading based on an a posteriori approach has been presented in this paper. The hybrid composite comprised of T700S carbon/epoxy laminate at the tensile side and E glass/epoxy laminate at the compressive side. The conflicting objectives for optimisation were to minimise the cost and weight of the composite subject to the constraint of a minimum specified flexural strength. Fibre angles and thicknesses of each lamina were considered as uncertain but bounded variables with the worst-case analyses being performed as a non-probabilistic method and the effect of uncertainties being determined. A hybrid multi-objective optimisation evolutionary algorithm (MOEA) was introduced through modification of an elitist non-dominated sorting genetic algorithm (NSGA-II) and combining it with the fractional factorial design method. The performance of the hybrid algorithm was found to be superior to that of the original version of NSGA-II. The multi-objective robust optimisation of the hybrid composite was solved by utilising the proposed algorithm for several levels of strength with the robust Pareto optimal sets being generated and compared. Three scenarios have been considered to illustrate the applicability of the obtained solutions in an a posteriori decision making process.