Multi-axial Fatigue Behavior of Notched Composite Structures

Low-Cycle Axial Fatigue Behavior of Mild Steel

Symposium on Fatigue Tests of Aircraft Structures: Low-Cycle, Full-Scale, and Helicopters ◽

10.1520/stp44457s ◽

2009 ◽

pp. 5-5-20 ◽

Cited By ~ 2

Author(s):

J. T.P. Yao ◽

W. H. Munse

Keyword(s):

Mild Steel ◽

Fatigue Behavior ◽

Axial Fatigue

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Modeling Delamination Growth in Composite Panels Subjected to Fatigue Load

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.627.21 ◽

2014 ◽

Vol 627 ◽

pp. 21-24 ◽

Cited By ~ 4

Author(s):

Aniello Riccio ◽

F. Ronza ◽

Andrea Sellitto ◽

Francesco Scaramuzzino

Keyword(s):

Composite Structures ◽

Fatigue Behavior ◽

Fatigue Loading ◽

Numerical Approach ◽

Delamination Growth ◽

Paris Law ◽

Load Carrying ◽

Number Of Cycles ◽

Delamination Front ◽

Critical Aspects

One of the most critical aspects of composite structures is indeed associated to delamination phenomenon, especially with reference to their fatigue behavior. As a matter of facts, delaminations are strongly influenced by the fatigue induced degradation phenomena which can lead to a significant increase of delaminated area with the number of cycles, reducing the structural load carrying capability. In the present paper, an advanced numerical approach, very similar to the Paris Law formulation and based on the Energy Release Rate, is presented. The proposed formulation, in the frame of a geometrical non-linear analysis, is able to take into account the local damage accumulation along the delamination front in order to evaluate the delamination growth under fatigue loading conditions. In order to test the effectiveness of the proposed numerical approach, the fatigue behavior of a delaminated panel with a central hole has been simulated and the obtained numerical results have been compared with literature experimental results.

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Tensile and Fatigue Behaviour of Glass Fibre Reinforced Polyester Composites

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i3.17.16615 ◽

2018 ◽

Vol 7 (3.17) ◽

pp. 25

Author(s):

Roy Hanson Jimit ◽

Kamarul Ariffin Zakaria ◽

Omar Bapokutty ◽

Sivakumar Dhar Malingam

Keyword(s):

Fatigue Strength ◽

Glass Fibre ◽

Composite Structures ◽

Fatigue Behavior ◽

Fatigue Behaviour ◽

International Conference ◽

Glass Fibre Reinforced ◽

Chopped Strand Mat ◽

Glass Fibre Reinforced Composites ◽

Materials Used

This document contains the formatting information for the papers presented at the International conference on “4th International Conference on Recent Advances in Automotive Engineering & Mobility Research (ReCAR IV)”. The conference would be held at Hotel Bangi-Putrajaya during August 8-10, 2017. Fibreglass composites are one of the materials that can be used in manufacturing of the vehicles part due to their excellent lightweight properties. Composite structures may undergone the fatigue failure when subjected to a certain numbers of cyclic loading, which is normally occurs below the ultimate strength of material. However, there still lack of studies on the effect of fibre orientations on the fatigue strength of glass fibre reinforced composites (GFRC). Therefore, the purpose of this study is to determine which orientation would have the highest fatigue strength. The fibre materials used in this study is unidirectional glass fibre with [0/90]°, [ ±45]° orientation and chopped strand mat (CSM). The composite is fabricated from glass fibre and polyester resin using a hand lay-up technique according to ASTM D3039 for tensile test and ASTM D3479 for fatigue test. The results were presented in the form of S-N curve. The results show that the mechanical properties and fatigue behavior were significantly affected by the fibre orientation of the GFRC

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

Journal of Composites Science ◽

10.3390/jcs6010002 ◽

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.

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Static and Flexural Fatigue Behavior of GFRP Pultruded Rebars

Materials ◽

10.3390/ma14020297 ◽

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.

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Effect of multiwalled carbon nanotube alignment on the tensile fatigue behavior of nanocomposites

Journal of Composite Materials ◽

10.1177/0021998317745585 ◽

2017 ◽

Vol 52 (17) ◽

pp. 2365-2374 ◽

Cited By ~ 4

Author(s):

Sasidhar Jangam ◽

S Raja ◽

K Hemachandra Reddy

Keyword(s):

Carbon Nanotubes ◽

Fatigue Life ◽

Carbon Nanotube ◽

Composite Structures ◽

Fatigue Behavior ◽

Crack Propagation Rate ◽

Dimensional Structure ◽

Multiwalled Carbon ◽

Weight Percentage ◽

Tensile Fatigue

The one-dimensional structure of carbon nanotubes makes them highly anisotropic, making them to possess unusual mechanical properties, and hence employed as promising nanofiller for the composite structures. However, various carbon nanotube properties are not completely utilized when they are used as reinforcement in composites due to inadequate and immature processing techniques. In the present work, an attempt has been made to utilize the strong anisotropic nature of multi-walled carbon nanotubes (MWCNTs) for improving the fatigue life of nanocomposites only by considering a very low weight percentage (<0.5 wt%). The anisotropy of MWCNTs was imparted into the nanocomposites by aligning them in the epoxy matrix with DC electric field during composite curing. Nanocomposites were made for three MWCNT loadings (0.1, 0.2, and 0.3 wt%). The tensile fatigue behavior was investigated under stress control by applying cyclic sinusoidal load with the frequency range of 1–3 Hz and stress ratio, R = 0.1. The specimens were tested for the fatigue load until the failure or 1E+05 cycles. The fractured surfaces were examined through scanning electron microscope to analyze the fatigue fracture behavior. A small weight percentage of MWCNT loading (0.2 wt%) into the polymer composite has enhanced on an average 13% to 15% fatigue life, which is encouraging to develop the low cost, improved fatigue life composite structures. Also, the energy dissipation mechanism in MWCNT dispersed nanocomposites has shown a reduced crack propagation rate.

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Multiple Axial Fatigue of Pressure Armors in Flexible Risers

Volume 4: Pipeline and Riser Technology ◽

10.1115/omae2011-50210 ◽

2011 ◽

Author(s):

Naiquan Ye ◽

Svein Sævik

Keyword(s):

Oil And Gas ◽

Fatigue Behavior ◽

Equivalent Stress ◽

Local Stress ◽

External Pressure ◽

Mean Stress ◽

Stress Range ◽

Stress Components ◽

Flexible Risers ◽

Axial Fatigue

The design of flexible risers has been challenged by the exploration of oil and gas goes into ever-deep regions as in Mexico Gulf and West Africa. Comparing to the fatigue analysis of the tensile armors which have been extensively investigated in recent years, much less effort has been devoted in the fatigue of pressure armor. The fatigue of the pressure armor is much more complicated than the tensile armors. For the tensile armor, the longitudinal stress along the helix path dominates the fatigue behavior, while for the pressure armor, more stress components will play together to affect its fatigue. If the fatigue of the tensile armor can be characterized as a uni-axial fatigue phenomenon, the fatigue of the pressure armor will be a typical multi-axial problem. The stress components in the pressure armor consist of contribution from the following sources: stress in the hoop direction due to internal/external pressure, stress in the radial direction due to the pressure and contact pressure from the tensile armor layer, stresses caused by the ovalization when the riser is bent, and local stresses due to local bending (nub/valley contact). The friction between the nub and valley interface is reflected in the local stress components as well. A Finite Element (FE) based computer program BFLEX developed by MARINTEK for the stress analysis of flexible risers are capable of calculating the complicate stress components of the pressure armors. In order to perform fatigue damage calculation for the pressure armor, mean stress and stress range must be computed based on these stress components. Mean stress correction becomes very important due to large mean stress experienced by the pressure armor. There are several ways to make use of these stress components to derive the mean stress and stress range. Equivalent stress models and critical plane models are the main models to address the general feature of the multi-axial fatigue. The application of these models on the fatigue of the pressure armor of the flexible risers will be discussed in this paper. The best suited model will be suggested based on the specific stress components in the pressure armor.

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Degradation mechanisms of balsa wood and PVC foam sandwich core composites due to freeze/thaw exposure in saline solution

Journal of Sandwich Structures & Materials ◽

10.1177/1099636217706895 ◽

2017 ◽

Vol 21 (3) ◽

pp. 990-1008 ◽

Cited By ~ 2

Author(s):

Elias A Toubia ◽

Sadra Emami ◽

Donald Klosterman

Keyword(s):

Composite Structures ◽

Saline Solution ◽

Sea Water ◽

Fatigue Behavior ◽

Compression Modulus ◽

Sandwich Composite ◽

Foam Core ◽

Balsa Wood ◽

Freeze Thaw ◽

Core Materials

Structural engineers commonly use balsa wood and PVC foam as core materials for sandwich composite structures. These structures are frequently exposed to thermal cycling in sea water. The long-term performance and damage mechanism of these composite sandwich structures under such environmental conditions are still unclear. To simulate these effects, sandwich panels using balsa wood (SB100) and foam core (Airex C70.55) with fiber glass/vinyl ester face sheets were exposed to 100 days of freeze/thaw exposure (−20℃ to 20℃). The freezing and thawing occurred in presence of a saline solution. A total of 150 samples were tested for core shear, core compression, and peel tests. Results confirmed that exposure reduced the balsa wood core shear strength by 14%, compression strength by 36%, and compression modulus by 33%. Interestingly, the PVC foam core shear modulus increased by 25% after exposure, whereas the compression modulus reduced by 12%. Simulated lifetime core shear fatigue curves were developed and evaluated. Additional testing techniques such as scanning electron microscopy, optical microscopy, dynamical mechanical analysis, and X-ray computed tomography were used to rationalize the static and fatigue behavior of the core materials.

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