Reinforced Polymer Materials Research Articles

Numerical analysis of reinforced concrete beams strengthened in shear using carbon fiber reinforced polymer materials

Purpose This paper aims to analyze the performance of reinforced concrete (RC) beams strengthened in shear with carbon fiber-reinforced polymer (CFRP) sheets subjected to four-point bending. Design/methodology/approach ANSYS software is used to build six models. In addition, SOILD65, LINK180, SHELL181 and SOLID185 elements are used, respectively, to model concrete, steel reinforcement, polymer and steel plate support. A comparative study between the nonlinear finite element and analytical models, including the ACI 440.2 R-08 and FIB14 models as well as experimental data, is also carried out. Findings The comparative study of the nonlinear finite element results with analytical models shows that the difference between the predicted load capacity ranges from 4.44%–24.49% in the case of the ACI 440.2 R-08 model, while the difference for FIB14 code ranges from 2.69%–26.03%. It is clear that there is a good agreement between the nonlinear finite element analysis (NLFEA) results and the different expected CFRP codes. Practical implications This model can be used to explore the behavior and predict the RC beams strengthened in shear with different CFRP properties. They could be used as a numerical platform in contrast to expensive and time-consuming experimental tests. Originality/value On the basis of the results, a good match is found between the model results and the experimental data at all stages of loading the tested samples. Load capacities as well as load deflection curves are also presented. It is concluded that the differences between the loads at failure ranged from 0.09%–6.16% and 0.56%–4.98%, comparing with experimental study. In addition, the increase in compressive strength produces an increase in the ultimate load capacity of the beam. The difference in the ultimate load capacity was less than 30% when compared with the American Concrete Institute and FIB14 codes.

Efficiency of flexural strengthening RC beams using fiber reinforced polymer materials

The purpose of this study is to evaluate the efficiency of the flexural strengthening of reinforced concrete (RC) beams using the fiber reinforced polymer (FRP). The calculation procedures according to design standards including ACI 440.2R-17 and FIB-2019 are employed to assess the flexural capacity of strengthened RC beams. Three types of FRP materials, which are glass FRP (GFRP), aramid FRP (AFRP), and carbon FRP (CFRP), are used. For CFRP, three kinds of tensile strengths consisting of low (CFRP-L), medium (CFRP-M), and high (CFRP-H) levels are also utilized in calculations and assessments. A numerical model of FRP strengthening beam is developed in ANSYS and then verified with the results of design standards. Comparative studies on the efficiency of flexural capacity and cost benefit between the use of FRP sheets and a conventional retrofitting method are conducted considering a specific area of FRP sheets and 50% flexural strengthening target. The results reveal that flexural strength after strengthening based on ACI and FIB is very similar. The optimal options considering the strength and cost effects are CFRP-L and CFRP-M when using a constant area of FRP. Additionally, we suggest using CFRP-H or CFRP-M for strengthening the RC beams with satisfying a target strength improvement of 50%. Comparing with the conventional method such as section increment, using FRP is more beneficial for both required strength and costs as well.

Analytical, experimental and finite element analysis of the width/diameter hole ratio effect in vinylester/carbon hybrid twill weave composites

This study analyzes the influence of hybridization type and the presence of open holes in two bidirectional hybrid twill fabric-reinforced (glass/carbon fibers and carbon/aramid fibers) polymer composite laminates. Stress concentration based on the variation of the w/D ratio (specimen width/hole diameter) is studied. Analytical and numerical studies were based on the Point Stress Criterion (PSC) and Average Stress Criterion (ASC), in addition to the Finite Element Method (FEM). An experimental study based in tensile testing was conducted and the results showed that analytical and numerical modeling associated with experimental data generally exhibit good agreement with those reported in the literature for polymer composite laminates.

Development of rectangular hybrid-stiffened-plate structural system with fibre-reinforced polymer fabric composite in tension zone

Reinforced concrete plates stiffened by the beams in the orthogonal directions are widely used in bridges and buildings. Local failure occurs due to stiff beams whereas shallow beams cause global collapse failure in the plate. A theoretical model using inelastic analysis (yield line analysis) has been formulated to predict the behaviour of the rectangular hybrid-reinforced concrete-stiffened-plate system which recognized the benefits of different types of fibre-reinforced polymer fabric and ferrocement in tension side. Parametric study was also conducted to capture the influence of different parameters such as number of panels, plate aspect ratio and beam strength parameter on the flexural capacity of plate system. Designer can select the proportionate hybrid-stiffened-plate system which fails globally to avoid negative yield lines through design chart. In the experimental study, four rectangular hybrid-stiffened-plate structural systems were developed with two internal beams in each perpendicular direction incorporating ferrocement and unidirectional carbon fibre–reinforced polymer fabric, unidirectional basalt fibre–reinforced polymer fabric and bidirectional glass fibre–reinforced polymer fabric sheet on the bottom side. The experimental ultimate load was recorded maximum in unidirectional carbon hybrid–stiffened-plate system, however, unidirectional basalt hybrid–stiffened-plate system gave the best performance with respect to the cost analysis. The numerical analysis had a reasonable consistency with experimental and analytical results.

Study of Early Stages in the Growth of Boron‐Doped Diamond on Carbon Fibers

With the aim to improve the properties of aeronautical carbon fiber (CF)‐reinforced polymer materials, boron‐doped diamond (BDD) has been grown on commercial CFs by microwave plasma‐enhanced chemical vapor deposition. The growth of a BDD layer on CF is expected to increase the mechanical, electrical, and thermal conductivities of the composite. The present contribution reports the different growth stages and their associated nanostructures of the BDD/CF resulting system using transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. The revealed carbon nanostructure shows four steps of growth with the following characteristics: 1) transitional interlayer, 2) graphite nanowall, 3) cauliflower‐like nanocrystalline diamond, and 4) microcrystalline diamond.

Physico Chemical Characterization of Fiber from Melia Azedarach Barks as an Effective Reinforcement in Polymer Matrices

ABSTRACT The present study aimed to investigate the physico-chemical properties of new cellulosic fiber obtained from the bark of Melia Azedarach tree. The investigation outcomes revealed that, the cellulose content, crystallinity index and density of Melia Azedarach Fiber (MAF) were determined as 66.5 wt.%, 45.45% and 950 Kg/m3, respectively. The MAF had thermal stability up to 220θC which is evidenced from the thermo gravimetric analysis. The Fourier Transform Infra Red test clearly specified the existence of cellulosic and non-cellulosic substance in MAF. The morphological analysis showed that MAF contains smooth surfaces and its diameter is measured as 48.2 ± 2 µm. The results of this investigation on MAF were evident that it can be used as future reinforcement material to develop the green composite for potential applications.

Effect of Silane Coupling Treatment on the Adhesion between Polyamide and Epoxy Based Composites Reinforced with Carbon Fibers

The increasing efforts aimed to design structures with reduced weight and better mechanical performances has led in recent years to a growing use of fiber reinforced polymer materials in several fields such as marine. However, these materials can be composed of chemically very different elements and, hence, may be difficult to joint. This research aims to improve the adhesion between a thermoplastic matrix of polyamide reinforced with short carbon fibers (PA12-CR) and a carbon fiber reinforced epoxy matrix (CFRP). Two different silane coupling agents, (3-Aminopropyl)trimethoxysilane (AM) and (3-Glycidyloxypropyl)trimethoxysilane (EP), were applied, through the spray deposition method, on the PA12-CR substrate to create a reactive layer between the adherents. Different deposition methods and coupling agents curing conditions were also investigated. The wettability of the PA12-CR surface as well as the chemical modifications induced by silane treatments were investigated through contact angle and Fourier Transform Infrared spectroscopy (FTIR) analyses. Furthermore, the interfacial adhesion between PA12-CR and CFRP substrates was evaluated through Mode I delamination tests (DCB). The effectiveness of the most promising treatment was finally verified on sandwich structures, having PA12-CR printed as internal core and CFRP laminates as external skins, through quasi-static three-point bending mechanical tests. Overall, the epoxy-based silane (EP) allowed significantly better resistance to the delamination up until the tensile failure of the CFRP substrate.

Depth resolved pulse compression favourable frequency modulated thermal wave imaging for quantitative characterization of glass fibre reinforced polymer

InfraRed Thermography is an expeditiously growing non-destructive testing and evaluation technique widely used to estimate the subsurface defect details in fibre reinforced polymer materials due to its remote, fast, easy, safe and wide area monitoring abilities. In order to explore the details of subsurface anomalies in active infrared thermography, a modulated heat flux with a predefined intensity and bandwidth is employed to excite the test sample. Among various widely used active infrared thermographic techniques for non-destructive testing and evaluation applications, pulse based and modulated lock-in thermography are predominantly in use. However, these conventional techniques limits their applicability due to high peak power heat source requirements (pulse based techniques) and poor resolution (modulated lock-in thermography) for detecting the defects located at various depths of different lateral dimensions. The present paper highlights a pulse compression favourable frequency modulated thermal wave imaging which can be carried out with moderate peak power heat sources in a limited span of time with improved test resolution and sensitivity. Further the proposed experimentation is validated with the analytical as well as numerical simulations on glass fibre reinforced polymer samples having flat bottom hole defects.

Manufacture of a bio-tissue based on nanocrystalline cellulose from chilean bamboo Chusquea quila and a polymer matrix using electrospinning

Polymers of renewable origin have aroused great interest among researchers due to their sustainable, environmentally friendly nature. This work presents a biopolymer called bio-tissue, as it is created by electrospinning. This bio-tissue was formed with a polymer matrix of cellulose acetate (CA) reinforced with crystalline cellulose (NCC) derived from an autochthonous Chilean bamboo species of no commercial value which is considered a pest, Chusquea quila or quila. Bio-tissues were produced with three concentrations of NCC (1, 5 and 10% as a dry weight proportion of cellulose acetate) and their technological potential as an interior coating in small constructions was assessed. The morphology of the bio-tissues showed that the CA nanofibers containing NCC were of better quality and more uniform diameter than pure CA. The thermal profile showed that the highest concentration of NCC (10% as a dry weight proportion of cellulose acetate) induced earlier degradation; it was less thermally stable and decomposed at lower temperatures. The bio-tissue with 5% as a dry weight proportion of cellulose acetate showed the greatest resistance to traction with a break-point of 30 MPa and an elasticity module of 1.597 MPa. Finally, it was shown that the permeability to water vapour, oxygen and carbon dioxide was low, allowing regulated passage of these molecules. These results show the feasibility of using cellulose nanofibers as a reinforcement in polymer matrices; this could have various applications in fields ranging from the construction industry to food packaging.

Investigation of Wooden Beam Behaviors Reinforced with Fiber Reinforced Polymers

Wood material can be demolished over time due to different environmental factors. Structural elements may need to be strengthened over time as a result of possible natural disasters or during use. Beams are elements under load in the direction perpendicular to their axes. Therefore, they are basically under the effect of bending. When the studies on the behavior of beams against bending test are examined, it is known that the bottom surface of the material generally breaks. For this reason, fiber reinforced polymers (FRP) materials have been used in recent years to reinforce beam members. It is a scientific fact that it is necessary to prefer FRPs for the solution of this problem, as well as their properties such as lightness, corrosion and flexibility, their application without disrupting the appearance of wood.In this study, it was aimed to investigate the effect of reinforcing wooden beams with fiber reinforced polymer materials with different properties on different bending behaviors such as load bearing capacity, ductility, modulus of elasticity. It was observed that the ductility and bearing capacity of wooden beams reinforced with fiber reinforced polymer materials increased significantly compared to non-reinforced beams.

Torsional fatigue in bamboo fibers reinforced epoxy resin composites

Natural fibers are low-priced, abundant and renewable. The application of natural fiber to reinforced polymers materials can reduce cost, decrease weight and increase the mechanical properties of the composites. Many studies were carried out in natural fibers reinforced polymer composites using different natural fibers, one of those is bamboo fibers. Nevertheless, torsional fatigue tests have not been applied to predict the mechanical behavior of the bamboo fibers reinforced polymer composites. In this study, bamboo fiber reinforced epoxy resin composites were molded by compression in a rectangular mold. These specimens were machined according to the schematic of thin-walled tubular specimen suggested by ASTM-2207–15 and tested in torsional fatigue loading with R = −1. A mechanical torsion fatigue testing machine was constructed to perform torsion test with constant amplitude of the twist angle. An angle measuring device was constructed to measure the angular displacement in the useful region of the specimens (gage length). Torsional fatigue life curves were plotted for pure epoxy resin, unidirectional and discontinuous bamboo fibers reinforced epoxy resin composites. Pure epoxy resin specimens presented the longest torsional fatigue life and the poorest results were found in discontinuous bamboo fibers composites. The experimental results suggest that the epoxy resin is strongly related to the torsional fatigue behavior of the composite materials. The fracture surface of test specimens often showed that cracks occurred in the interfacial region of the composites.

A comparative analysis of adhesive bonding and interference fitting as joining technologies for hybrid metal-composite gear manufacturing

The aim of this work is to compare two different joining technologies for steel and carbon fibre reinforced polymer materials in a hybrid gear in order to improve the dynamic behaviour in terms of natural frequencies and damping properties. A comprehensive approach for the design and prototyping of hybrid metal-composite gears with interference fitting and adhesive bonding is provided. In a following phase, an accurate description of the experimental impact tests is shown in order to investigate modal performances. Successively, in a finite element environment, modal analyses are conducted and frequency response functions of the gear model are analysed by means of complex stiffness matrix that accounts for structural damping. Impact tests and simulations indicate that the solution with interference fitting is stiffer than the one with adhesive, even if the damping capacity is lower. The results for both technologies show that it is possible to enhance noise and vibrations behaviour of gears through the application of composite materials in place of conventional full-metal solutions.

Comparative study of mechanical technologies over laser technology for drilling carbon fiber reinforced polymer materials

More researchers have been worked to increase the quality of the machined composite materials. In this paper, acomparative experimental study of mechanical techniques over the laser techniques has been performed in the drillingprocess by using the carbon fiber reinforced polymer (CFRP). In order to identify the best process among the mechanicaldrilling (MD) and laser drilling (LD) technology various analysis methods like normality analysis, control chart analysis,and process capability analysis have been performed. Process capability index analysis for case study 1 and interval plotanalysis for case study 2 have been employed to evaluate the best process comparatively. Experiments have been performedin a vertical machining center (VMC) and CO2 laser. The final results revealed that the MD process is the best technologyfor drilling CFRP. Therefore, this work has been important for small-scale industries.

Evaluation and analysis of delamination during drilling on Sisal-Glass Fibres Reinforced Polymer

Now-a-days, composite materials with reinforcement have a wide range of industrial applications such as automobile, aerospace and marine because of its high strength-to-weight ratio and high stiffness to weight ratio. In composite parts assembly, delamination is being a critical issue during drilling operation due to its anisotropy property. The present work aims to study the effect of delamination during drilling on Sisal-Glass Fibres Reinforced Polymer (S-GFRP) material. The experiments were planned with Taguchi’s approach to determine the delamination. The damaged zone around the drilled holes was measured using a profile projector and subsequently analyzed through ImageJ software. Signal-to-noise (S/N) ratio was used to analyze and optimize the working parameters for minimum delamination. The delamination determined by the two different approaches, namely profile projector and image processing has consistent results and has good agreement with each other.

Examination of Tensile Strength and End Notch Flexure Properties of Unidirectional Basalt Fabric Reinforced Polymer Composites With and Without Addition of Biochar Filler

The effect of biochar filler (carbon particle) on the mechanical properties over the inter-laminar surfaces of basalt unidirectional fabric/polyester resin is going to be scrutinized using Mode II delamination method. The ENF (end notch flexure) specimen is fabricated using hand layup method. Here basalt fabric is synthesized using unsaturated polymer resin with the help of methyl ethyl ketone peroxide and cobalt naphthenate as a catalyst. Both specimens are manufactured with and without biochar conditions. The laminate length and width will be customized as per the required dimensions of the ASTM standard. The ENF specimens are tested using the universal testing machine and the strain energy released rate and displacement of each specimen are been measured. The biochar based laminated composite has a resistant towards the fracture developed on laminated composite during testing due to the addition of carbon particles.

Dimensionally and environmentally ultra-stable polymer composites reinforced with carbon fibres.

The quest to develop materials that enable the manufacture of dimensionally ultra-stable structures for critical-dimension components in spacecraft has led to much research over many decades and the evolution of carbon fibre reinforced polymer materials. This has resulted in structural designs that feature a near-zero coefficient of thermal expansion. However, the dimensional instabilities that result from moisture ingression and release remain the fundamental vulnerability of the matrix, which restricts many applications. Here, we address this challenge by developing a space-qualifiable physical surface barrier that blends within the mechanical properties of the composite, thus becoming part of the composite itself. The resulting enhanced composite features mechanical integrity and a strength that is superior to the underlying composite, while remaining impervious to moisture and outgassing. We demonstrate production capability for a model-sized component for the Sentinel-5 mission and demonstrate such capability for future European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) programmes such as Copernicus Extension, Earth Explorer and Science Cosmic Visions.

Plant Extraction and Physicochemical Characterizations of Untreated and Pretreated Diss Fibers (Ampelodesmos mauritanicus)

ABSTRACT The Ampelodesmos mauritanicus plant, Mauritanian grass or also called ‘Diss’, is a perennial abundant plant on the Mediterranean contour, having attractive characteristics for ecofriendly materials. This work aims to highlight the potential of the Diss fibers elements by assessing their use as reinforcement for polymer matrices (bio-composite). So, untreated and treated Diss fibers by chemical (soda, silane and acetic acid) and thermal treatment have been manually extracted and characterized to evaluate their surface condition as well as their chemical composition, their mechanical properties and their thermal stability. The obtained results have shown many advantages look promising for such an application, especially the fact that the Diss fiber bundles has small diameter (89 ± 22 μm), a rough surface with the presence of thorns, a low density of 0.93 g/cm3, and a tensile strength that can reach 270 MPa. Furthermore, all the treatments adopted have shown improvements regarding the fibrillation of fiber bundles (could reach −40% for the diameter), their surface state, their thermal stability and their mechanical behavior (could reach +60% for Young’s modulus and +15% for tensile stress).

A Mechanics Based Surface Image Interpretation Method for Multifunctional Nanocomposites.

Graphene nanosheets and thicker graphite nanoplatelets are being used as reinforcement in polymeric materials to improve the material properties or induce new functional properties. By improving dispersion, de-agglomerating the particles, and ensuring the desired orientation of the nano-structures in the matrix, the microstructure can be tailored to obtain specific material properties. A novel surface image assisted modeling framework is proposed to understand functional properties of the graphene enhanced polymer. The effective thermal and mechanical responses are assessed based on computational homogenization. For the mechanical response, the 2-D nanoplatelets are modeled as internal interfaces that store energy for membrane actions. The effective thermal response is obtained similarly, where 2-D nanoplatelets are represented using regions of high conductivity. Using the homogenization simulation, macroscopic stiffness properties and thermal conductivity properties are modeled and then compared to the experimental data. The proposed surface image assisted modeling yields reasonable effective mechanical and thermal properties, where the Kapitza effect plays an important part in effective thermal properties.

Statistical analysis of notch toughness of epoxy matrix composites reinforced with fique fabric

Reinforcement of polymer matrices with natural lignocellulosic fibers (NLFs) is today presenting great potential for the reduction of both product weight and cost in many industrial sectors as well as the advantage of being renewable and eco-friendly materials. For some industrial applications, especially in ballistic armor, the materials are expected to meet technical and mechanical requirements in terms of impact behavior, which motivate the present work. This work conducted a notch toughness assessment by Izod and Charpy impact tests of epoxy matrix composites reinforced with different volume fractions of fique fabric, up to 50vol%. Statistical analyses indicated significant differences between composites with distinct amount of fique fabric. Failure mechanisms were analyzed by scanning electron microscopy (SEM). The results revealed that composite reinforced with 40vol% of fique fabric presented the best notch toughness performance. Composites with 15 and 30vol% of fique fabric display predominantly brittle fracture associated with lower impact energies. With higher amount, 50vol%, of fique fabric reinforcement both Izod and Charpy impact energy suffered a small decrease according to the Roger and Plumtree model.

Investigation of Green Composite: Preparation and Characterization of Alkali-Treated Jute Fabric-reinforced Polymer Matrix Composites

ABSTRACT Jute, a natural fiber available in India is used as reinforcement in composites because it is cheap, renewable and easy to process. Therefore, jute composites have drawn the attention of various industries and researchers. In this study, a new treating method in which sodium hydroxide solution introduced to treat jute fabric in order to enhance the performance of jute/epoxy composite. Different percentages of alkali-treated jute fabric-reinforced composites have been developed and their mechanical properties, such as tensile strength, flexural strength, and impact strength have been assessed. Physical properties like thickness swelling and water absorption test were studied.