CFRP Composite Materials Research Articles

Experimental investigation into lock-in characteristics of the composite hydrofoils

Abstract This study experimentally investigates the lock-in characteristics of structural vibration of hydrofoils made of CFRP composite material. The synchronous experimental measurement system constituted of high-speed framing camera, LDV, velocity and pressure regulation systems are set up. It can be found that the Com+45° hydrofoil accelerates the cavitation inception, and the Com-45° hydrofoil defers it. The evolution of the dominant vibration frequency and cloud cavity shedding frequency are semblable. As the cavitation evolution gradually develops, the larger dominant frequency reduces, while the lower frequency remains unchanged. The scope of frequency lock-in meets the magnitude relationship Com+45° hydrofoil> Com-45° hydrofoil> Com0° hydrofoil. The wavelet transformation of structural vibration displacement and non-dimensional cavity area shows that both f shed and f shed,lock-in exist in the lock-in condition.

Numerical simulation of the effect of projectile shape and size on the high-velocity impact of carbon fiber reinforced composite laminates

To investigate the impact response and damage mechanism of CFRP composite materials for high-speed trains under high-speed impact from foreign objects of different shapes and sizes, high-speed impact experiments and simulations were conducted on CFRP composite laminate at a velocity of 163 m/s. A finite element simulation model was established in Abaqus/Explicit. This model adopts the 3D-Hashin failure criterion considering strain rate effects to simulate the failure of fibers and matrix. Bonded elements with zero thickness were inserted along the fiber direction in the laminate to replicate the damage phenomena of fiber bundle debonding and pull-out. The effectiveness of the finite element model was validated by high-speed photography of the impact process and ultrasonic C-scan damage images recorded during the experiments. Based on this simulation model, the influence of projectiles of different shapes and sizes on the impact response of CFRP composite materials was studied. Projectiles of different shapes exhibit their own characteristics in terms of the time of peak force occurrence, manifestation, and characteristics of laminar damage. The peak force of the cylindrical projectile is 245.01% greater than that of the spherical one, while the conical projectile is 52.26% smaller than the spherical one. When the projectile size increases from 10 mm to 20 mm, the peak force of the spherical projectile, conical projectile, and cylindrical projectile increases by 79.67%, 120.12%, and 283.13% respectively. The total area of delamination in laminated plates is positively correlated with the size of the impacting body.

Experimental investigation of micro EDM drilling in the CFRP using response surface methodology

Recently, most of the conventional (industrial) materials such as steel, aluminum, and copper are being replaced by composite materials. Among the various composite materials, CFRP material is one of the most popular materials in many industries due to its excellent mechanical properties like-high strength, high modulus, compressive strength, etc. However, the micro hole in micro EDM drilling in the CFRP composite material is challenging due to fiber orientation, uneven distribution of conducting fiber, and delamination affecting the material removal rate (MRR) and micro hole quality performance. The objective of the article is to optimize the process parameters for optimum hole quality in the micro EDM drilling of CFRP composites. For this purpose, response surface methodology is applied to investigate the effect of the input process parameters which are voltage, capacitance, and tool rotation speed on material removal rate, roundness error, and tapper of the micro-hole. The experiments have been conducted according to the box behnken design of experiments. Regression equations, and response surfaces are developed. Optimum responses are determined by the desirability function approach. The experimental investigation shows that capacitance is the highly significant factor among the input process parameters affecting hole quality output responses such as material removal rate, roundness error, and tapper. The MRR increases with increasing the capacitance and tool rotation speed initially but its value decreases on further increasing the capacitance at a particular voltage. Roundness error and the tapper initially decrease on increasing capacitance and tool rotation speed then increases. The optimum material removal rate and hole quality are obtained in a range of 150–250 nF capacitance, and 1400–1600 rpm tool rotation speed, at 100 voltage.

Dynamic Analysis of Flexible two Link Robotic Arm Considering Joint Stiffness

The robotic manipulator is a machine that can perform a variety of tasks according to specifications without the need of human interference. In order to model and control such devices, vibration analysis of flexible manipulators has become a critical field of study. The finite element approach has been used to analyze single and double connection flexible manipulators made of advanced composite material in the current study. For the modelling and study of the versatile composite manipulators, a three-noded beam feature is used. The effects of the taper angles of tapered flexible composite manipulators on the final product effector movement and vibration has been considered. In present work CATIA V5 is used to model the flexible single link robotic arm and static structural analysis to find stress and total deformation, dynamic analysis is carried out to find different modes, corresponding frequency, and life estimation of flexible single and double link robotic arm and also material optimization is done using different material composition for structural steel, aluminium and CFRP composite material using ANSYS WORKBENCH 18.2 (Finite Element Approach) for life estimation and evaluation using analytical approach.

The efficiency of CFRP strengthening and repair system on the flexural behavior of RC beams constructed with different concrete compressive strength

This paper presents experimental investigation on the effectiveness of CFRP strengthening and repair system on the load carrying capacity, stiffness, flexural behavior, and failure mode mechanism of RC beams constructed with different concrete compressive strength (fc′). Eight RC simply supported beams were strengthened and repaired with one layer of CFRP composite and tested experimentally under flexural load. The beams were built with varying the concrete compressive strength (fc′) value of (21.1, 36.1, 48.2, and 68.5) MPa, to demonstrate low, normal, and high strength. The results obtained in this work revealed that the performance of the CFRP composite material was inversely correlated to the concrete compressive strength in repaired beams while a proportion relation was observed in strengthened beams only with low to normal concrete strength. Finally, reasonable agreement between the estimated bending moment capacities for strengthened beams (based on the ACI 440.2R-17 provision) and the experimental results within ±16% were obtained.

Modelling and Analysis of CNC Milling Machine Bed with UHM CFRP composite Material

Abstract: Structural materials are used in a machine tool have a key role in defining the productivity, accuracy and Size proportions of the part manufactured by machine tool. The conventional structural materials like cast iron and Stainless or carbon steel at high operating speeds but used in precision machine tools grow positional errors due to the vibrations transferred into the Machine tool structure. Faster cutting speeds can be achieve only by structure which has good damping characteristics and high stiffness. Clearly the life of a machine tool is proportional to the levels of vibration Produce by machine. The further Work is carried out to Study the deformation and natural frequency using Static analysis and Modal analysis respectively. The bed in machine tool Took Major role in the precision in components. It is one of the greatest vital tool structures which is absorb the vibrations resultant from the cutting operation. To analyse the bed for possible material changes and Structure changes that could increase stiffness, decrease weight, expand damping characteristics and segregate natural frequency at the operating range. So main enthusiasm behind the impression to go for a composite Material in model involving ultra-High Modulus Carbon Fibre Reinforced Polymer Composite Material (UHM CFRP). In a carbon has good stiffness and strength properties but its absences in damping requirements. On the other hand, polymers, though its deficiencies in strength but, good damping in characteristics and it is easily holding the carbon fibres. So, this is makes greatest combination of materials in an appropriate manner. In this work, a machine tool’s bed is selected for the analysis static loads. Then study is carried out to decrease the weight of the machine tool’s bed without affecting its structural rigidity. The 3D CAD model of the bed has been created by using commercial 3D modelling software and analyses were carried out using ANSYS 2021 R2. Keywords: Composite material, hybrid structures, Milling machine bed, UHM CFRP.

Strength Analysis of Dissimilar Adhesive-Bonded Joints

The article discusses aspects related to material surface engineering and the strength of adhesive-bonded joints as well as presents results concerning the surface wetting angle and the free surface energy of steel S335, aluminium alloy AW7075 (T6) and the CFRP composite material in relation to three surface treatment conditions. The authors emphasize that surface preparation is of key importance as regards the obtainment of potentially high-strength joints. The article also discusses results concerning the roughness of the surface of the steel and the aluminium alloy in relation to various grades of abrasive paper granularity. The final part of the article presents test results concerning the shear strength of dissimilar adhesive-bonded joints (i.e. steel S335 – CFRP composite and aluminium alloy AW 7075 (T6) – CFRP composite) and discusses related images of ruptured joints.

Impact of Adhesive Layer Thickness on the Behavior of Reinforcing Thin-Walled Sigma-Type Steel Beams with CFRP Tapes.

This paper presents selected issues related to the reinforcement of steel element cold-formed with CFRP tapes. The first section of the paper is a review of source literature and a presentation of the basic information on cold-formed thin-walled steel elements and CFRP composite materials, stressing the advantages and disadvantages of using them to reinforce steel structures. Next, the authors present original research on reinforcing bent thin-walled sigma-type steel beams using adhesive CFRP tapes. Reference beams with a cross-section of Σ200 × 70 × 2 and a length of 3 m, reinforced with CFRP tape, were tested in the four-point bending scheme. Then, the paper discusses a developed numerical model that is consistent with the subject matter of the laboratory tests. The developed numerical model was prepared to represent the failure of the connection between the beam and the composite tape. This was followed by a number of numerical analyses in order to determine the optimum adhesive layer that would allow us to achieve the maximum reduction of the displacements and strains in bent thin-walled sigma-type beams. Three thicknesses of the SikaDur adhesive layer were analyzed in the study. Based on the analyzes, it was found that the increase in the thickness of the adhesive layer slightly reduced the strain and displacement in the beams, but caused a significant decrease in the load value, at which damage appeared in the glued joint.

Modelling of micro-damage and intrinsic self-healing in unidirectional CFRP composite structures

This work presents a micromechanical constitutive model of an intrinsically self-healing unidirectional CFRP composite material. The model is implemented into Abaqus/Standard user material subroutine UMAT and validated using experimental results of three-point bending tests available in the literature. Tested specimens consist of thermally mendable bis-maleimide tetrafuran (2MEP4F), and GA045 unidirectional carbon fibres. The matrix material is modelled using the elastic-plastic micro-damage-healing constitutive model. On the other hand, the reinforcing fibres are modelled as linear elastic. A three-dimensional micromechanical model, based on principles of the Rule Of Mixtures, is employed to model the homogenised composite. Finally, a parametric analysis is conducted to evaluate the effect of various parameters on the damage evolution and the healing performance, and afterwards, the results are discussed. The validation results have shown that the developed constitutive model is able to accurately simulate the micro-damage and healing processes in the intrinsically self-healing unidirectional composite structures.

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.

Experimental and numerical analysis of stability and failure of compressed composite plates

This paper investigates the stability, load-carrying capacity and failure analysis of thin-walled plate elements weakened by cut-out and subjected to axial compression. Tested plates were made in asymmetric configuration from CFRP composite material with used autoclave technique. The scope of the research included experimental tests on real samples and numerical calculations with using the finite element method in the ABAQUS® program. The influence of the compressive load on the buckling and postbuckling behavior and loss of load capacity of thin-walled composite plates were investigated. Both, the experimental tests and the numerical analysis were carried out in the full load range, up to the structure failure. In the experimental tests, acoustic emissions were used to analyze the damage state of the composite material. Numerical calculations were carried out with the use of progressive failure analysis, based on the initiation of the failure from the Hashin's theory and the further evolution of the failure based on the energy criterion. Numerical results of critical and post-critical state were compare with experimental research showing areas prone to failure of the material. A measurable effect of the conducted research was obtaining a high compatibility of the results of numerical and experimental calculations.

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.

Experimental-numerical study into the stability and failure of compressed thin-walled composite profiles using progressive failure analysis and cohesive zone model

This study investigates the stability and failure of thin-walled composite structures with a top-hat cross section under axial compressive loading. The tested profiles were made of CFRP composite material by autoclaving. The scope of the research included experimental tests of real samples and numerical analysis by the finite element method using the ABAQUS® program. Both experimental tests and numerical analysis were performed over the full range of loading until structural failure. In experiments, postbuckling equilibrium paths and acoustic emission signals were measured, which allowed a comprehensive analysis of failure for the composite material. Numerical calculations were performed by progressive failure analysis, considering the failure initiation criteria under Hashin’s theory and failure evolution based on the energy criterion. Additionally, the cohesive zone model (CZM) was used to simulate delamination. Numerical results and experimental findings show high agreement. Moreover, the results reveal an interesting relationship between the compressive load and the buckling, postbuckling and failure of the analyzed structures.

Abrasive water jet machining of CFRPs: single response optimization using taguchi method optimization

Taguchi method was applied to assess and optimize machining parameters and their effect on kerf characteristics during abrasive water jet machining (AWJM) of carbon fiber reinforced polymeric composites (CFRPCs). The main responses selected for these analyses are kerf width, kerf taper, metal removal rate, and surface roughness, the consistent machining parameters focussed for this study are abrasive flow rate, pressure, traverse rate, thickness of the workpiece and standoff distance, each parameter has three levels. Twenty-seven experiments were conducted on a typical CFRP composite workpiece materials based on Taguchi L27 design. The response curves and response tables were used to assess the data obtained to control the major significant process factors statistically affecting the kerf characteristics. The optimal settings of process parameters for each response are set up. From the analysis, it was detected that the percentage contribution of the control factors affecting the kerf width is standoff distance, workpiece thickness, abrasive flow rate, traverse rate, and pressure correspondingly. The results exposed that the thickness, feed rate, and standoff distance were the most significant factors affecting the kerf taper, metal removal rate, and surface roughness respectively.

Reverse localization on composite laminates using attenuated strain wave

Abstract Carbon Fiber Reinforced Polymer (CFRP) composite materials have been widely used in high-tech fields because of their outstanding physical properties. However, barely visible impact damage can be introduced by low velocity impact, which might bring tremendous risk. Monitoring impact forces is essential for the integrity and reliability of CFRP structures. In this paper, a reverse localization scheme on CFRP composite materials is developed. The scheme is based on a predictive mode of attenuated strain wave. The signals induced by low velocity impact are obtained by strain gauges. The proposed localization scheme has been verified by experimental tests of the CFRP plates with symmetrical stacking [0/45/90/−45]2s The errors occurring in the test can be accepted for engineering application. The calculated impact locations are generally in consistent with the testing impact locations.

Enhanced out of Plane Electrical Conductivity in Polymer Composites Induced by CO2 Laser Irradiation of Carbon Fibers

The creation of a hierarchical interface between the carbon fiber (CF) and the epoxy resin matrix of fiber-reinforced polymer (CFRP) composites has become an effective strategy for introducing multifunctional properties. Although the efficacy of many hierarchical interfaces has been established in lab-scale, their production is not amenable to high-volume, continuous, cost effective fiber production, which is required for the large-scale commercialization of composites. This work investigates the use of commercially available CO2 laser as a means of nano-structuring the surface of carbon fiber (CF) tows in an incessant throughput procedure. Even though the single carbon fiber tensile strength measurements showed a decrease up to 68% for the exposed CFs, the electrical conductivity exhibited an increment up to 18.4%. Furthermore, results on laminates comprised of irradiated unidirectional CF cloth, demonstrated an enhancement in out of plane electrical conductivity up to 43%, while preserved the Mode-I interlaminar fracture toughness of the composite, showing the potential for multifunctionality. This work indicates that the laser-induced graphitization of the CF surface can act as an interface for fast and cost-effective manufacturing of multifunctional CFRP composite materials.

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.

Effect of eccentric loading on the stability and load-carrying capacity of thin-walled composite profiles with top-hat section

The paper investigates the influence of eccentric compressive load on the buckling, post-buckling and load-carrying capacity of thin-walled top-hat section composite columns. The columns were made of a CFRP composite material with a symmetrical arrangement of the layers by the autoclave technique. The scope of the presented study involved performing experimental tests on actual profiles as well as numerical calculations using the FEM analysis in ABAQUS® software. The experimental tests were carried out in the full range of loading, until the structure’s failure (post-buckling equilibrium paths and acoustic emission signals were measured). Regarding to FEM analysis, a nonlinear calculations using Newton-Raphson method were made. The damage initiation of the composite material was estimated based on Hashin’s theory, whereas damage evolution was described by the energy criterion (progressive failure analysis were used). The numerical results of eccentric compressive load on buckling and load-carrying capacity of composite columns were in good agreement with the experimental results.

Milling Examination on CFRP Composites for Automobile Structures.

The CFRP is widely used in automobiles to reduce vehicle weight and give higher fuel efficiency due to greater strength to weight ratio. It should be needed to machine with accurate structure and integrity. The post curing process is necessary after machining the CFRP composite material to remove burr and delamination. The dual helix mill tool is used to perform slotting to eliminate burr formation and delamination. From the study there is no delamination is occurred when CFRP is machined at the cutting speed of 2500 rpm, feed rate of 600 mm/min and 1 mm depth of cut and also burr formation is highly reduced at this condition.

An investigation of the effect of tool approaching angle in turning of CFRP composite materials

Abstract Carbon Fibers Reinforced Plastics (CFRP) composite material bars were machined on the lathe. In experiments −15°, 0°, 15°, 30°, and 45° approach angles, 0.1 mm × rev-1, 0.15 mm × rev-1, and 0.2 mm × rev-1 feed rates and 560 rpm, 800 rpm, and 1120 rpm spindle speeds were selected. At −15° and 0° approach angles, the deformation influence was dominant on surface roughness and chip morphology, while the cutting effect taking place at the cutting edge was dominant at 30° and 45° approach angles. Primarily at 45°, the most significant roughness values and the shortest cut fibers were achieved due to the occurrence of maximum shear stress according to Tresca. However, fibers were removed from samples on the whole form as bundles, without any cutting, at −15° and 0° approach angles, by the effect of deformation. According to ANOVA, regression and variance analysis results were obtained with p-values and probability results of surface roughness smaller than 0.05 and 5 %, respectively. These results showed that the feed rate was the most influential parameter for turning of CFRP material, followed by the approach angle and spindle speed, respectively. However, the least influential parameter in the processes was spindle speed.