scholarly journals Static and Flexural Fatigue Behavior of GFRP Pultruded Rebars

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 297
Author(s):  
Michał Barcikowski ◽  
Grzegorz Lesiuk ◽  
Karol Czechowski ◽  
Szymon Duda
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Fatigue Behavior ◽  
Constant Load ◽  
Fatigue Tests ◽  
Bending Test ◽  
Radial Compression ◽  
Sinusoidal Waveform ◽  
Constant Load Amplitude ◽  
Steel Rebars

This paper presents the experimental results of composite rebars based on GFRP manufactured by a pultrusion system. The bending and radial compression strength of rods was determined. The elastic modulus of GFRP rebars is significantly lower than for steel rebars, while the static flexural properties are higher. The microstructure of the selected rebars was studied and discussed in light of the obtained results—failure processes such as the delamination and fibers fracture can be observed. The bending fatigue test was performed under a constant load amplitude sinusoidal waveform. All rebars were subjected to fatigue tests under the R = 0.1 condition. As a result, the S-N curve was obtained, and basic fatigue characteristics were determined. The fatigue mechanism of bar failure under bending was further analyzed using SEM microscopy. It is worth noting that the failure and fracture mechanism plays a crucial role as a material quality indicator in the manufacturing process. The main mechanism of failure under static and cyclic loading during the bending test is widely discussed in this paper. The results obtained from fatigue tests encourage further analysis. The diametral compression test reflects the weakest nature of the composite materials based on the interlaminar compressive strength. The proposed methodology allows us to invariantly describe the experimental transversal strength of the composite materials. Considering the expected durability of the structure, the failure mechanism is likely to significantly improve their fatigue behavior under the influence of cyclic bending. The reasonable direction of searching for reinforcements of composite structures should be the improvement of the bearing capacity of the outer layers. In comparison with steel rebars (fatigue tensile test), the obtained results for GFRP are comparable in the HCF regime. It is worth noting that in the near fatigue endurance regime (2–5 × 106 cycles) both rebars exhibit similar behavior.

scholarly journals Development of a Vibration Technique Based on Geometric Optimization for Fatigue Life Evaluation of Sandwich Composite Structures

2021 ◽  
Vol 12 (1) ◽  
pp. 16
Author(s):  
Marco Menegozzo ◽  
Frederick A. Just-Agosto ◽  
David Serrano Acevedo ◽  
Basir Shafiq ◽  
Andrés Cecchini ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Composite Structures ◽  
Sandwich Panels ◽  
Cost Effective ◽  
Fatigue Tests ◽  
Geometric Optimization ◽  
Bending Test ◽  
Sandwich Composite ◽  
Vibration Technique ◽  
Stress Ratios

A major obstacle to obtaining cost-effective experimental data on the fatigue life of sandwich panels is the prohibitive amount of time and cost required to carry out millions of cycles. On the other hand, vibration techniques applied to sandwich geometries fail to match the stress patterns that are obtained from standard flexural fatigue tests. To overcome such limitations, a vibration-based fatigue technique is proposed, which entails the use of sandwich specimens whose geometries are optimized to reproduce the stress distribution observed during three point bend loading while vibrating at the first resonant frequency. The proposed vibration technique was experimentally validated. The results, compared with the average number of cycles to failure at different stress ratios obtained via the Three-Point Bending test, showed high levels of accuracy. The proposed method is robust and time effective and indicates the possibility of attaining fatigue lifetime prediction of a wide class of composite elements, such as sandwich panels.

scholarly journals Fatigue Behavior of Smart Composites with Distributed Fiber Optic Sensors for Offshore Applications

2021 ◽  
Vol 6 (1) ◽  
pp. 2
Author(s):  
Monssef Drissi-Habti ◽  
Venkadesh Raman
Keyword(s):  
Composite Structures ◽  
Large Scale ◽  
Fiber Optic ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Mechanical Tests ◽  
Fiber Optic Sensors ◽  
Fatigue Tests ◽  
Offshore Wind ◽  
Smart Composites

Continuous inspection of critical zones is essential to monitor the state of strain within offshore wind blades, thus, enabling appropriate actions to be taken when needed to avoid heavy maintenance. Wind-turbine blades contain various substructures made of composites, sandwich panel, and bond-joined parts that need reliable Structural Health Monitoring (SHM) techniques. Embedded, distributed Fiber-Optic Sensors (FOS) are one of the most promising techniques that are commonly used for large-scale smart composite structures. They are chosen as monitoring systems for their small size, being noise-free, and low electrical risk characteristics. In recent works, we have shown that embedded FOSs can be positioned linearly and/or in whatever position with the scope of providing pieces of information about actual strain in specific locations. However, linear positioning of distributed FOS fails to provide all strain parameters, whereas sinusoidal sensor positioning has been shown to overcome this issue. This method can provide multiparameter strains over the whole area when the sensor is embedded. Nevertheless, and beyond what a sensor can offer as valuable information, the fact remains that it is a “flaw” from the perspective of mechanics and materials. In this article and through some mechanical tests on smart composites, evidence was given that the presence of embedded FOS influences the mechanical behavior of smart composites, whether for quasi-static or fatigue tests, under 3-point bending. Some issues directly related to the fiber-architecture have to be solved.

scholarly journals Development of a Delamination Fatigue Testing Machine for Composite Materials

Machines ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 27 ◽  
Author(s):  
Pereira ◽  
Fernandes ◽  
de Morais ◽  
Carvalhoso
Keyword(s):  
Composite Materials ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Testing Machine ◽  
Experimental Studies ◽  
Strain Energy Release ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Hydraulic Testing ◽  
Fatigue Tests

Experimental studies on fatigue behavior are usually conducted on servo-hydraulic testing machines that are expensive and have high maintenance costs. In this work, a much simpler testing machine was developed, intended mainly for delamination fatigue tests on composite materials. After a literature review on the methods and parameters of such tests, the machine was designed, and its parts manufactured and assembled into a fully operational testing machine. Additionally, the electrical components and the control and data acquisition software were also developed and implemented. Finally, several mode II delamination fatigue tests were conducted using the end-notched flexure test. The results were consistent with the well-known Paris law, which for composite materials relates the crack propagation rate to the strain-energy release rate range. Therefore, the developed machine seems to be an excellent alternative to the highly costly testing machines.

scholarly journals Effect of Elevated Temperature on Bending Fatigue Behavior for Neat and Reinforced Polyamide 6,6

2020 ◽  
Vol 23 (3) ◽  
pp. 232-237
Author(s):  
Orhan Sabah Abdullah ◽  
Shaker S. Hassan ◽  
Ahmed N. Al-khazraji
Keyword(s):  
Fatigue Life ◽  
Elevated Temperatures ◽  
Fiber Composite ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Bending Test ◽  
Test Machine ◽  
Carbon Fiber Composite ◽  
Bending Fatigue ◽  
Different Temperatures

Recently, considering polymer composite in manufacturing of mechanical parts can be caused a fatigue failure due to the very long time of exposure to cyclic loading and may at environmental temperatures higher than their glass transition temperature; therefore, in this paper, a comprehensive investigation for bending fatigue behavior at room and elevated temperatures equal to 60 °C, 70°C, and 80 °C will be done. Rotating bending test machine was manufactured for this purpose supplied with a connected furnace to perform fatigue tests at elevated temperatures. The obtained results appeared that the increase in applied stress and temperature caused a clear reduction in fatigue life; also the addition of carbon nanotubes enhanced the fatigue life at different temperatures by 183%, 205%, 218%, and 240%, respectively while the addition of short carbon fibers improved fatigue life by 324%, 351%, 387%, and 415%, respectively. As well as, Polyamide 6,6/carbon fiber composite appeared fatigue limit at temperatures equal to 20°C and 60°C and stresses approximately equal to 55 MPa and 38 MPa respectively.

scholarly journals Fatigue Life for Type 316L Stainless Steel under Cyclic Loading

2013 ◽  
Vol 701 ◽  
pp. 77-81
Author(s):  
Khairul Azhar Mohammad ◽  
Edi Syam Zainudin ◽  
S.M. Sapuan ◽  
Nur Ismarrubie Zahari ◽  
Ali Aidy
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
316L Stainless Steel ◽  
Load Ratio ◽  
Constant Load ◽  
Fatigue Tests ◽  
Constant Frequency ◽  
Technology Market ◽  
Constant Load Amplitude

The paper presents the determination of fatigue life of 316L stainless steel at room temperature. Plenty of steel in the world has been investigated for a lot of application in the science and technology market. The mechanisms of fatigue of 316L stainless steels were studied and investigated. Fatigue tests of specimens were performed in accordance with ASTM E466-96. The fatigue tests were performed in constant load amplitude, constant frequency of 5 Hz with load ratio R=0.1. Fracture surface of specimens were examined by using Scanning Electron Microscope (SEM). The results showed that the endurance fatigue limit of 316L stainless steel was 146.45 MPa.

An Investigation on Flexural Fatigue Behavior of CFRP Quasi-Isotropic Laminates

2020 ◽  
Author(s):  
K. Panbarasu ◽  
V. R. Ranganath ◽  
Raghu V. Prakash
Keyword(s):  
Fatigue Life ◽  
Failure Modes ◽  
Fatigue Behavior ◽  
High Amplitude ◽  
Constant Load ◽  
Cfrp Laminates ◽  
Lower Load ◽  
Carbon Fibre Reinforced Plastic ◽  
Constant Load Amplitude ◽  
Low Amplitude

Abstract In this study, AS4/914 grade carbon fibre reinforced plastic (CFRP) laminates with two different quasi-isotropic (QI) layup sequences are compared for their performance under four point bend flexure fatigue loads. The QI laminates were designated and fabricated as Laminate-1 (L1) [0/45/-45/90]2S and Laminate-2 (L2) [0/90/45/-45]2S, respectively. These laminates were designed, such that the 0° layers are placed at a similar position in both the laminate systems by changing the other layers. During the test, load and displacement data was monitored online along with instantaneous number of constant load amplitude (CLA) fatigue cycles to calculate the stiffness degradation. Three load levels of 90%, 80%, and 70% of the ultimate flexure strength (UFS) were chosen for assessing the flexure fatigue behavior of the laminates. A few tests were also attempted under variable amplitude loads: (i) high amplitude cycles followed by low amplitude and (ii) low amplitude cycles followed by high amplitude to examine load sequence effect on fatigue life, if any, as compared to the fatigue life under CLA. It has been observed that the laminate L1 performs better under higher amplitudes, while the laminate L2 shows increased life under lower load and variable amplitudes. The results obtained in the form of data plots and failure modes, supported by microscopic images, are discussed in the paper.

Fatigue of Unidirectional Cord-Rubber Composites

1999 ◽  
Vol 27 (1) ◽  
pp. 48-57 ◽  
Author(s):  
Y. Liu ◽  
Z. Wan ◽  
Z. Tian ◽  
X. Du ◽  
J. Jiang ◽  
...  
Keyword(s):  
Damage Accumulation ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Constant Load ◽  
Testing System ◽  
Rubber Composites ◽  
Cycle Frequency ◽  
Periodic Loading ◽  
Fatigue Damage Accumulation ◽  
Rubber Composite

Abstract A fatigue testing system is established with which the real-time recording of stress, strain, temperature, and hysteresis loss of rubbers or cord-rubber composite specimens subjected to periodic loading or extension can be successfully carried out. Several problems are connected with the experimental study of the fatigue of rubber composites. In constant extension cycling, the specimen becomes relaxed because of the viscoelasticity of rubber composites, and the imposed tension-tension deformation becomes complex. In this method, the specimen is unlikely to fail unless the imposed extensions are very large. Constant load cycling can avoid the shortcomings of constant extension cycling. The specially designed clamps ensure that the specimen does not slip when the load retains a constant value. The Deformation and fatigue damage accumulation processes of rubber composites under periodic loading are also examined. Obviously, the effect of cycle frequency on the fatigue life of rubber composites can not be ignored because of the viscoelasticity of constituent materials. The increase of specimen surface temperature is relatively small in the case of 1 Hz, but the temperature can easily reach 100°C at the 8 Hz frequency. A method for evaluating the fatigue behavior of tires is proposed.

scholarly journals Defects and uncertainties of adhesively bonded composite joints

2021 ◽  
Vol 3 (9) ◽  
Author(s):  
Sadik Omairey ◽  
Nithin Jayasree ◽  
Mihalis Kazilas
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Production Efficiency ◽  
Adhesive Bonding ◽  
Detection Methods ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Wide Range ◽  
Bonded Composite

AbstractThe increasing use of fibre reinforced polymer composite materials in a wide range of applications increases the use of similar and dissimilar joints. Traditional joining methods such as welding, mechanical fastening and riveting are challenging in composites due to their material properties, heterogeneous nature, and layup configuration. Adhesive bonding allows flexibility in materials selection and offers improved production efficiency from product design and manufacture to final assembly, enabling cost reduction. However, the performance of adhesively bonded composite structures cannot be fully verified by inspection and testing due to the unforeseen nature of defects and manufacturing uncertainties presented in this joining method. These uncertainties can manifest as kissing bonds, porosity and voids in the adhesive. As a result, the use of adhesively bonded joints is often constrained by conservative certification requirements, limiting the potential of composite materials in weight reduction, cost-saving, and performance. There is a need to identify these uncertainties and understand their effect when designing these adhesively bonded joints. This article aims to report and categorise these uncertainties, offering the reader a reliable and inclusive source to conduct further research, such as the development of probabilistic reliability-based design optimisation, sensitivity analysis, defect detection methods and process development.

scholarly journals Introduction to Macroscopic Optimal Design in the Mechanics of Composite Materials and Structures

2021 ◽  
Vol 5 (2) ◽  
pp. 36
Author(s):  
Aleksander Muc
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Constitutive Relations ◽  
A Priori ◽  
Chemical Properties ◽  
Composite Plates ◽  
Failure Criteria ◽  
Lagrange Equations ◽  
Homogenization Methods ◽  
Mechanics Of Composite Materials

The main goal of building composite materials and structures is to provide appropriate a priori controlled physico-chemical properties. For this purpose, a strengthening is introduced that can bear loads higher than those borne by isotropic materials, improve creep resistance, etc. Composite materials can be designed in a different fashion to meet specific properties requirements.Nevertheless, it is necessary to be careful about the orientation, placement and sizes of different types of reinforcement. These issues should be solved by optimization, which, however, requires the construction of appropriate models. In the present paper we intend to discuss formulations of kinematic and constitutive relations and the possible application of homogenization methods. Then, 2D relations for multilayered composite plates and cylindrical shells are derived with the use of the Euler–Lagrange equations, through the application of the symbolic package Mathematica. The introduced form of the First-Ply-Failure criteria demonstrates the non-uniqueness in solutions and complications in searching for the global macroscopic optimal solutions. The information presented to readers is enriched by adding selected review papers, surveys and monographs in the area of composite structures.

The effect of nanoparticle additive on surface milling in glass fiber reinforced composite structures

2021 ◽  
pp. 096739112110141
Author(s):  
Ferhat Ceritbinmez ◽  
Ahmet Yapici ◽  
Erdoğan Kanca
Keyword(s):  
Composite Materials ◽  
Glass Fiber ◽  
Composite Structures ◽  
Fiber Composite ◽  
Cutting Speed ◽  
Fiber Reinforced ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite ◽  
Glass Fiber Reinforced ◽  
Composite Layers

In this study, the effect of adding nanosize additive to glass fiber reinforced composite plates on mechanical properties and surface milling was investigated. In the light of the investigations, with the addition of MWCNTs additive in the composite production, the strength of the material has been changed and the more durable composite materials have been obtained. Slots were opened with different cutting speed and feed rate parameters to the composite layers. Surface roughness of the composite layers and slot size were examined and also abrasions of cutting tools used in cutting process were determined. It was observed that the addition of nanoparticles to the laminated glass fiber composite materials played an effective role in the strength of the material and caused cutting tool wear.

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