GFRP Composite Materials Research Articles

The Development of New Type GFRP Hollow Panels

Under the background of global energy transformation, pumped storage power stations are becoming more and more important. Most of their water retaining structures adopt face rockfill dams, but their concrete panels will have many problems such as durability. In this study, a new type of GFRP hollow panel was developed for face rockfill dam. The nonlinear behavior and damage process of the material were simulated by finite element analysis and UMAT subroutine. Through analysis and comparison, it is found that the triangular section form is superior to other forms in terms of stress distribution and bearing capacity. After optimization design, the optimal section takes into account the stability, safety and economic benefits of the structure. The research results provide a high-performance panel solution with high construction efficiency and low maintenance cost for the face rockfill dam, and provide an important design reference for the application of GFRP composite materials in water conservancy projects in the future.

Retracted: Effect of Grey and White Portland Cement Fillers on Flexural and Shear Strength of GFRP Composite Material

Retracted: Effect of Grey and White Portland Cement Fillers on Flexural and Shear Strength of GFRP Composite Material

Toward tailoring the mechanical and dielectric properties of short glass fiber‐reinforced epoxy composites

AbstractGlass fiber‐reinforced polymer‐matrix (GFRP) composites are used to manufacture devices such as radomes, electrical insulators, and radar‐absorbing structures, many of which are used in applications with strict mechanical and dielectric property requirements. As such, designs and properties of GFRP composite materials should be regularly improved to guarantee their safe operation and meet their constantly evolving application requirements. In this study, glass fiber (GF) particles and epoxy resin 128 (EP‐128) were used to manufacture high‐performance EP/GF‐X composites with GF particle contents ranging from 5% to 40%. An investigation into their mechanical and dielectric properties revealed that EP/GF‐20 composite specimens presented the best mechanical performance with their bending strength and modulus reaching 159.68 MPa and 6521.92 MPa, respectively, and an average dielectric constant of 4.862 within the 10–105 Hz frequency range. A theoretical analysis of the EP/GF‐X composite specimens' dielectric constants using classic dielectric models based on the Lichtenecker, Bruggeman, Jaysundere‐Smith, and Maxwell‐Garnett rule‐of‐mixture equations indicated that the dielectric model based on the Bruggeman rule‐of‐mixture equation provided the dielectric constants closest to the measured values with a maximum deviation of less than −0.321% for EP/GF‐40 composites. This study provides a feasible strategy to control the mechanical and dielectric properties of GFRP composites.Highlights Glass fiber (GF) particles and epoxy 128 (EP‐128) resin were used to manufacture high‐performance glass fiber‐reinforced epoxy (EP/GF‐X) composites. The composite manufacturing process was carefully controlled to ensure uniform distribution and orientation of GF particles in the EP‐128 resin. The mechanical and dielectric properties of the manufactured EP/GF‐X composites were effectively tailored by controlling the content and distribution of GF particles in the EP‐128 resin matrix. The dielectric constants of the EP/GF‐X composites were measured experimentally and predicted using various theoretical dielectric models. The Bruggeman model provided the dielectric constants of the EP/GF‐X composites closest to the measured values.

Tribo-Mechanical Investigation of Glass Fiber Reinforced Polymer Composites under Dry Conditions.

Tribo-mechanical experiments were performed on Glass Fiber Reinforced Polymer (GRFP) composites against different engineering materials, and the tribological behavior of these materials under dry conditions was investigated. The novelty of this study consists of the investigation of the tribomechanical properties of a customized GFRP/epoxy composite, different from those identified in the literature. The investigated material in the work is composed of 270 g/m2 fiberglass twill fabric/epoxy matrix. It was manufactured by the vacuum bag method and autoclave curing procedure. The goal was to define the tribo-mechanical characteristics of a 68.5% weight fraction ratio (wf) of GFRP composites in relation to the different categories of plastic materials, alloyed steel, and technical ceramics. The properties of the material, including ultimate tensile strength, Young's modulus of elasticity, elastic strain, and impact strength of the GFPR, were determined through standard tests. The friction coefficients were obtained using a modified pin-on-disc tribometer using sliding speeds ranging from 0.1 to 0.36 m s-1, load 20 N, and different counter face balls from Polytetrafluoroethylene (PTFE), Polyamide (Torlon), 52,100 Chrome Alloy Steel, 440 Stainless Steel, and Ceramic Al2O3, with 12.7 mm in diameter, in dry conditions. These are commonly used as ball and roller bearings in industry and for a variety of automotive applications. To evaluate the wear mechanisms, the worm surfaces were examined and investigated by a Nano Focus-Optical 3D Microscopy, which uses cutting-edge μsurf technology to provide highly accurate 3D measurements of surfaces. The obtained results constitute an important database for the tribo-mechanical behavior of this engineering GFRP composite material.

A new methodology to predict the sequence of GFRP layers using machine learning and JAYA algorithm

In this paper, the best stacking sequence using experimental tests of GFRP composites is investigated. The main objective of this work is to determine the main specification of GFRP composite material, which is represented by its physics-mechanical properties, weight, and cost, before performing a series of experimental tests based on various stacking sequences. Our methodology is divided into three stages. The first stage is characterized by extracting the bending data from mechanical tests of some GFRP composites. In the second stage, the validated numerical model is used to simulate numerous cases of stacking sequences. In the last stage, the extracted data is used to determine the parameters for different stacking sequences using an inverse technique based on ANN and JAYA algorithm. The results provide a good prediction of parameters as well as a good orientation to make decisions on the best GFRP stacking sequence to be used, according to the required specifications of the manufacturer. The experemental data analysis can be found at https://github.com/Samir-Khatir/Sequence-GFRP

Influence of steel yielding and resin toughness on debonding of wrapped composite joints

The concept of an innovative bonded joining technology where welding is not required is presented as an alternative to traditional welded connection for steel circular hollow section (CHS). Wrapped composite joints have potential to greatly improve fatigue endurance when applied in multi-membered truss structures, e.g. offshore jackets for wind turbines. This paper focuses on characterization of influence of chemical bonding resistance, fracture toughness of resins, and steel yielding on debonding of wrapped composite joints. Uniaxial splice joints (A-joints) are made with GFRP composite material wrapped around steel sections, and tested under static tensile loading conditions until failure. Different chemical bonding properties by application of bonding primer, different types of polymer resins and steel grade are used during the wrapping procedure. Debonding on the bonded interface are identified by surface strain measurements through 3D digital image correlation (DIC) technique. Testing results indicate that steel yielding limits full utilization of the resistance of the bonded interface. Wrapped composite A-joints with high-strength steel exhibits 75% larger ultimate load where yielding is prevented. Larger fracture toughness of toughened vinyl-ester resin contributes to 30% larger displacement of the joints at failure compared to regular vinyl-ester and polyester resins.

Terahertz Spectroscopic Characterization and Thickness Evaluation of Internal Delamination Defects in GFRP Composites

The use of terahertz time-domain spectroscopy (THz-TDS) for the nondestructive testing and evaluation (NDT&E) of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials. In this study, the THz-TDS system is used to detect, localize and evaluate hidden multi-delamination defects (i.e., a three-level multi-delamination system) in multilayered GFRP composite laminates. To obtain accurate results, a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight (TOF) signals. The thickness and location of each delamination defect in the z-direction (i.e., through-the-thickness direction) are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates. A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712% relative error, while the relative error of the non-de-noised signals reaches 16.388%. Also, the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches. The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS. Also, the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.

Structural analysis of experimentally fabricated glass fiber reinforced (GFRP) composites

Engineering materials play major role in the production system with wide applications since ancient periods till today. Engineering materials like metals, non-metals, ceramics, plastics and composites are selected based on their properties suitable in the field of applications. GFRP are compared to the fiber glass material, GFRP wide real time applications as in case of research laboratories,MRI units, manufacturing critical impact parts, home build equipments like interior works, high fatigue purposes and high compressive structural equipment designs. Composite materials have wide range of structural applications in engineering fields also. In this work, glass fiber reinforced composite material (GFRP) with different layers of laminates is prepared as per the required dimensions and experiments are conducted for structural analysis of GFRP composite material. The present research work the Mechanical structural analysis conducted. The experimental results also reveal that plays a significant role in the enhancement of mechanical properties such as tensile strength, failure strain, and hardness. Again the experimental properties obtained for GFRP material from statistical tests are compared with its theoretical properties. Also the properties of GFRP are compared with the other composite materials to have real time applications of fiber glass material. The experimental results indicated an outstanding improvement in the tensile, impact, and flexural properties of hybrid composite materials. The results showed Young’s modulus of 25.42 GPa, and maximum bending deflection attained at yield stress of 133 MPa with ultimate tensile stress of 533 MPa.

Structural changes of GFRP composite material after immersion in liquid nitrogen and normal water

Composite materials are specially created today, with the best micro and macrostructural compositions. This type of material provides certain characteristics of composition, manufacture and design and provides some important advantages over traditional materials such as rigidity, mechanical strength, low weight, resistance to fatigue, impact and wear and a low manufacturing cost. In recent years, such materials have been produced and used in various fields such as the automotive industry, naval, railway, medical, sports, etc. The paper presents the results of the variations in the tensile curves of the GFRP composite material reinforced with fiberglass, used wind turbine blades construction. Tensile tests were carried out for determination of mechanical properties on four samples with aim of increasing the service life and to investigate the flaws during operation. One sample was immersed for 4 days in liquid nitrogen at an initial temperature of -70°C, the second sample was immersed in regular water for 7 days and the two other samples were dry. All sample having reinforcement at [0 ° / 90 °]. To establish the elastic properties of the material on the specimen immersed in liquid nitrogen and on the dry specimen a T-type rosette was mounted.

Investigation of the effect of AWJ drilling parameters for delamination factor and surface roughness on GFRP composite material

PurposeThe purpose of this study is to optimize processing parameters to get the smallest average surface roughness (Ra) and delamination damage (Fd) values during drilling via abrasive water jet (AWJ) of the glass fiber-reinforced polymer composite material produced at [0°/90°]s fiber orientation angles.Design/methodology/approachDrilling experiments were done via AWJ with three-axis computer numerical control (CNC) control system. Machine processing parameters such as water pressure of 3,600, 4,300, 4,800 and 5,300 bar; stand-off distance of 1, 2, 3 and 4 mm; traverse rate of 750, 1,500, 2,000 and 3,000 mm/min; and hole diameters of 8, 10, 12 and 14 mm have been selected. The effects of processing parameters in drilling experiments were investigated in conformity with the Taguchi L16 orthogonal array and the data obtained were analyzed using Minitab 17 software. The signal/noise (S/N) ratio was taken as a basis for evaluating the test results. Optimum processing conditions were determined by calculating the S/N ratio for both Ra and Fd in conformity with the “smaller is better” approximation. The effects of processing parameters on Ra and Fd were statistically investigated using analysis of variance, S/N ratio and Taguchi-based gray relational analysis. Ra and Fd were predicted by evaluating with the ANN model and were predicted with the least amount of error.FindingsIt has been determined that the most effective parameter for Ra and Fd is the water pressure and then the stand-off distance.Originality/valueThe novel approach is to reduce cost and the time spent by using Taguchi optimization as a result of AWJ drilling the material in this fiber orientation [0°/90°]s.

Characterization of out-of-plane tensile stress–strain behavior for GFRP composite materials at elevated temperatures

Three-dimensional stress–strain constitutive parameters in various environments are essential for understanding the mechanical behavior of thick cross-section composite load-bearing structures. This work aims to expand a short-beam bending test combined with a digital image correlation method to obtain the out-of-plane (interlaminar) stress–strain behavior for polymer–matrix composites at elevated temperatures. A simple and repeatable digital speckle pattern fabrication method was used based on the water transfer printing (WTP) technique to reduce deformation measurement uncertainty induced by the quality of the speckle pattern. The effects of DIC parameters and misalignment of the DIC stereo camera system on the uncertainty of deformation measurement have been studied. The out-of-plane properties, including elastic modulus and tensile strength for a 50-ply thick S6C10/AC318 glass/epoxy unidirectional panel, have been obtained at elevated temperatures for the first time. The experimental results showed that the out-of-plane modulus and tensile strength were 15.95 GPa and 76 MPa at room temperature. The modulus was nearly unchanged at 50 °C and decreased 18% at 80 °C. The out-of-plane tensile strength decreased 9% at 50 °C and 22% at 80 °C, respectively, indicating that the tensile strength degradation is more sensitive to temperature rising than the modulus. The study suggests that the improved short-beam bending test combined with the DIC method can guarantee reproducible results and usability at elevated temperatures.

Failure modes of bonded wrapped composite joints for steel circular hollow sections in ultimate load experiments

The concept of an innovative bonded joining technology where welding is not required is presented as an alternative to traditional welded connection for steel circular hollow section (CHS). Wrapped composite joints have potential to greatly improve fatigue endurance when applied in multi-membered truss structures, e.g. offshore jackets for wind turbines. This paper focuses on characterization of resistance and understanding of failure modes of wrapped composite joints in static experiments, as the prerequisite for harvesting its potential for high fatigue endurance. Wrapped composite joints at two scales and with two different angles of X-joint geometry are made with GFRP composite material wrapped around steel sections without welding, and tested in 3 monotonic loading cases, tensile, compression and in-plane bending, until failure. Counterpart welded joints are tested at the smaller scale for stiffness, elastic limit and ultimate load comparisons. Two general failure modes of wrapped composite joints, debonding and fracture of the composite material are identified and quantified by surface strain measurements through 3D digital image correlation (DIC) technique. Testing results indicate that wrapped composite joints have 30% to 56% larger stiffness and 3% to 68% larger ultimate load compared to welded counterparts. Debonding and final pull-out of steel brace member from the composite wrap is predominant failure mode in tensile experiments at both scales while cracking of the composite material is the governing failure mode in the bending experiment. In tensile, compressive and bending experiments failure load of wrapped composite joints exceeds the yield resistance of the steel CHS indicating opportunity to optimize the composite wrapping thickness and length.

Free Vibration Analysis of Hybrid And Non-Hybrid GFRP Composite Wind Turbine Blade

Wind energy is one prominent solution to mitigate the increasing energy demand. Composite materials are exhibiting enormous advantages with their tailor-made properties. With the development of renewable energy power generation, the issue of blade vibration reduction has gotten a lot of technical attention. It has become an essential technique for blade analysis and design. Various attempts were recorded to reduce the vibration of the blade and enhance its natural frequencies. The present work aimed to characterize the mechanical properties of the GFRP composite material and the GFRP composite with 4wt% of the MWCNT filler. Both hybrid and non-hybrid GFRP are subjected to characterization, with the same free vibration analysis of NACA 63-415 wind turbine blades being analyzed. The study results revealed that the hybrid GFRP has more stiffness, which causes it to enhance the free vibrations in all mode shapes.

A Comparative Fatigue Analysis of GFRP, CFRP and Structural Steel for Connecting Rod Using ANSYS

Abstract The connecting rod, as an important part in internal combustion engines, has been most widely used in automotive industry, and its main function is to transfer the reciprocating motion of the piston into the rotatory motion of the crankshaft. In this study, fatigue analysis of the connecting rod is performed numerically for different engine speeds. With this aim, it is attempted to reduce the weight of the connecting rod by choosing the low density and high strength of GFRP and CFRP composite materials instead of structural steel. In this way, it is possible to improve the engine efficiency with saving unnecessary balancing weights as well as reducing the cost of the connecting rod. In the current study, the connecting rod was modeled using Solidworks software, and its CAD model was transferred to the ANSYS/Workbench software for Finite Element Analyses (FEA). In FEA, fatigue analyses were performed to determine fatigue parameters such as alternating stress, deformation, fatigue life and safety factor according to Soderberg’s fatigue model. Results from this study showed that alternating stress and safety factor reached a critical value between piston pin end and crank end near to the piston pin end. Alternating stress values of the GFRP and CFRP connecting rods were much lower than those of structural steel rod. In contrast to reduction of the weight by 1/5, fatigue life of the connecting rod with structural steel material was much greater than those of GFRP and CFRP providing a higher safety factor compared with composite materials.

Effectiveness of Hybrid and Partially Confined Concrete Subjected to Axial Compressive Loading Using CFRP and GFRP Composite Materials

Abstract This paper presents the results of an experimental study that investigates the compression behavior of concrete and evaluates the effect of hybrid reinforcement by multiple geometries, and total and partial confinement, using CFRP and GFRP composite materials. A total of nine (09) variants of concrete cylindrical specimens, including one (01) variant of unconfined concrete and eight (08) variants of confined concrete with different geometries were subjected to axial load compression. The objectives of this study were to verify the applicability and effectiveness of partial and total confinement to improve the behavior of concrete, evaluate the effect of the hybrid confinement used, and obtain a typical reinforced model. The results obtained clearly show the effectiveness of the hybrid confinement and partially confined concrete in improving the compressive strength and deformation of the concrete, so it is possible to replace CFRP total confinement by partially confined concrete with two CFRP layers or by a hybrid confinement with a CFRP layer in the central zone and GFRP layers on the top and bottom of the specimen.

Study on influence of notch triggers on absorption of energy for composite automobile crash box under impact loads

In case of a crash due to collision of vehicles, effective impact energy absorption by the vehicle safety structure is significant as it reduces the damage to the vehicle and its occupants. Components made of composite materials have a more complex mode of deformation, unlike metals, which in general deform with buckling or bending modes. The deformation mode of the component made of a composite is of great importance as the energy absorption level depends on it. Deformation mode can be modified by introducing special geometric features known as triggers in the design of the crash box. A trigger can also be useful in achieving required deformation mode and thereby helpful in attaining target energy and force values. The present study focuses on the effect of geometric shapes along with three novel trigger types on the level of energy absorbed for the GFRP composite material passenger car crash box in a low-velocity impact, named as “RCAR Test” in the automobile industry. All possible combinations of four different types of geometric cross sections, namely, square, cylindrical, hexagonal, and decagonal, and three novel patterns of notch trigger, imparted to a GFRP crash box were considered for study in the present work. The force distribution, energy absorbed, and SEA (specific energy absorption) were estimated. The relative merit of crash boxes with different combinations of cross-sections and trigger types for these parameters was assessed. The best performing combinations made from various notch triggers and different cross sections of crash boxes have been identified.

Tests features of composite materials under complex mechanical loads

The article presents the results of the analysis of existing standardized and scientifically based methods for studying composite materials under quasistatic, low-velocity impacts and cyclic loadings in conditions of normal, high and low temperatures. Based on a review of existing test methods, research methods have been developed and tested to study the changes in the strength and deformation properties of GFRP composite materials under complex mechanical loads. A new type of interpretation of experimental data in the form of diagrams of fatigue and low-velocity impact sensitivity is proposed. Characteristic sections and points are introduced on the diagrams, which make it possible to further use the data from the diagram for the design of products and structures made of composite materials operated under the conditions of unforeseen external mechanical influences. For all developed methods, the results of experimental studies conducted by the authors of the work are presented. As an example, an experimental study of the influence of additional torsional vibrations on the processes of deformation and fracture of unidirectional fiberglass rod samples under quasistatic tension is considered.

Effect of ceramic fillers on flexural strength of the GFRP composite material

The flexural strength of the composite material plays a vital role in the materials. In the present work, an attempt is made to evaluate the flexural resistance of hybrid composite materials. Ceramic fillers with different percentages by weight (5 wt%, 10 wt%, 15 wt%) are introduced into epoxy-based fiber composites, since ceramic materials are rigid in nature and affect property Flexibility in bending. Alumina (Al2O3), Silicon Carbide (SiC) and Titanium Dioxide (TiO2) Particulate Fillers used in producing Composites by Hand Layup technique and tested in accordance with ASTM D 790. Results show that it has a significant effect of loading on the Flexural Strength of the GFRP composite; It varies greatly depending on the filler material and its percentage. The results for titanium dioxide filler based composite are more sensitive to the content of the load in the flexural strength. The silicon carbide filler has lower sensitivity to weight percent to flexural strength of the GFRP composite.

Comparative study of impact response of GFRP and CFRP composite plates against blunt nosed projectile

Three-dimensional finite element simulations were carried out to explore the perforation behavior of the unidirectional GFRP and CFRP plates against the blunt nosed projectile within sub-ordnance velocity regime. The ballistic performance of both the composite plates of 140 mm × 140 mm × 3.3 mm comprising of four layers (each 0.825 mm thick) having unidirectional fibres was evaluated. The mass, diameter and length of projectile was kept constant as 52.5 gm, 19 mm and 50.8 mm respectively. To carry out the numerical simulations, commercial finite element code Ansys/Ls-Dyna was employed. To simulate the high strain rate behavior of GFRP composite material, enhanced composite damage material model was considered whereas for CFRP, Composite failure material model offered better results. The performances of both the plates were evaluated based on residual velocity, ballistic limit and energy absorption. The numerical results were found to be close enough with the experimental results available in the literature. It was found that GFRP plates underperformed than that of CFRP plates.

Micromechanics study on FRP composite cylinder under finite element simulation COMSOL Multiphysics®

Buckling is a major structural instability of composite material that can lead to failure of large component without initial failure. The Finite Element Simulation is performed on CFRP, GFRP and KFRP composite material using COMSOL Multiphysics® and the buckling factor is compared with these composite materials. It is performed with a linear analysis of a composite cylinder under compressive loading and fixed end conditions. The composite materials are made up of eight layer (plies) of a composite. An Equivalent Single Layer (ESL) based approach is used for this analysis. The stacking sequence of composite materials are Layered 1[0/0/45/−45], Layered 2 [90/90/45/−45], Layered 3[90/0/90/0] and Layered 4 [45/45/45/45]. The critical buckling load factor is compared among the three materials with 4 layered sequence. Based on the Finite Element Simulation Result. The Kevlar Fiber Reinforced Polymer has considerable buckling load stability factor compared with other material. It is proposed that the KFRP material is best suitable for larger applications.