Notch Sensitivity on Fatigue Behavior of Carbon-Carbon Composites

2020 ◽  
Vol 858 ◽  
pp. 89-94
Author(s):  
Sobahan Mia ◽  
Md. Shafiul Ferdous
Keyword(s):  
Fatigue Limit ◽  
Critical Stress ◽  
Fatigue Behavior ◽  
Notch Sensitivity ◽  
Experimental Result ◽  
Shear Mode ◽  
Carbon Composites ◽  
Notched Specimens ◽  
Damage Condition ◽  
The Impact

The fatigue strengths in notched specimens of carbon-carbon composites were investigated. Slits of different length were cut on both sides of a test section to investigate the impact of notch sensitivity on fatigue life. Specimens with blunt-notches on the both side of the specimen, and center hole were also used to compare the critical stress, sw. The fatigue limit was measured using S-N curves. From the experimental result, it was found that specimens with blunt-notches have lowest fatigue limit. The relationships between critical stress, sw and specimen geometry were investigated by stress concentration factor, Kt and stress intensity factor, KI which was done two dimensional body forced methods. Consequently, it was discussed that the damage condition in the vicinity of the notch or slit, and the crack initiation behavior affects the fatigue strength. Also, the S-N curve and fatigue limit was related to the crack growth in shear mode.

scholarly journals Environmental Effect on Fatigue Behavior of Epoxy Coating Used for Water Tanks

2020 ◽  
Vol 3 (3) ◽  
pp. 64-72
Author(s):  
Haider Hadi
Keyword(s):  
Fatigue Limit ◽  
Potable Water ◽  
Fatigue Behavior ◽  
Water Storage ◽  
Storage Tanks ◽  
Test Apparatus ◽  
Water Media ◽  
Microscopic Inspection ◽  
Water Tanks ◽  
The Impact

The fatigue limit and lifetime of epoxy-based coatings may be affected by various factors, especially the environmental effects. This paper evaluates the impact of air, potable water media, and pollution gases (CO2, H2S, and SO2) on the fatigue performance of two types of epoxy-based coatings (polyamine and polyamide epoxy-based coatings) used as lining for potable water storage tanks. The fatigue test apparatus is assembled in the laboratory and utilized for testing. Different factors are discussed, including absorption, adsorption, and the reaction of environmental gasses with polyamine and polyamide coating surfaces. The influence of porosity on the epoxy-based coatings is experimentally determined, and its effects on fatigue limit and fatigue life are discussed in detail. As a result, the coatings were applied to improve the fatigue resistance of stainless steel. The fatigue limits of both types of coatings tested in potable water are lower than the value obtained when tested in air or gas environments. The fatigue limit of polyamine coating is greater than the polyamide coating. The microscopic inspection indicated a different mechanism for initiating fatigue crack, and the test environments are affected by the nature of the fracture surface.

Effect of Specimen Thickness on Fatigue Limit in Carbon Composites

2015 ◽  
Vol 1110 ◽  
pp. 13-18 ◽  
Author(s):  
Chobin Makabe ◽  
Takuya Nakayama ◽  
Masaki Fujikawa ◽  
Kazuo Arakawa ◽  
Ding Ding Chen
Keyword(s):  
Carbon Fiber ◽  
Fatigue Limit ◽  
Fracture Behavior ◽  
Crack Growth Behavior ◽  
Carbon Composites ◽  
Fiber Direction ◽  
Specimen Thickness ◽  
Shear Damage ◽  
Notched Specimens ◽  
Specimen Axis

The fracture behavior and fatigue limit in notched specimens of C/C composites were investigated. Also, the effect of specimen thickness on fatigue limit was discussed. Two plates of different thicknesses of plates of C/C composites using fine-woven carbon fiber laminates with α=0°/90° direction were used for testing. α is the angle between the carbon fiber direction and specimen axis. The crack growth behavior and failure mechanism of specimens are derived from the shear damage in the fiber bundle and matrix. Slits of several sizes were cut on both sides of a test section and different geometries of the specimens were prepared. Specimens with slits and blunt-notches were used to compare the fatigue strength. The fatigue limit is related to the method of making the plate of carbon composites. Large sizes of voids are observed in the case of specimens of thinner thickness. The fatigue limit was related to the void fraction, and thinner specimens showed a lower fatigue limit.

Size and Temperature Dependent Deposition Model of Micro-Sized Sand Particles

2017 ◽  
Author(s):  
Kuahai Yu ◽  
Danesh Tafti
Keyword(s):  
Contact Force ◽  
Adhesion Force ◽  
Stokes Number ◽  
Experimental Result ◽  
Contact Radius ◽  
Recovery Stage ◽  
Line Force ◽  
Plastic Stage ◽  
Sand Particles ◽  
The Impact

Sand ingestion and deposition in gas turbine engine components can lead to several operational hazards. This paper discusses a physics based model for modeling the impact and deposition of sand particles. The collision model divides the impact process into three stages, the elastic stage, the elastic-plastic stage, and full plastic stage. The recovery stage is assumed to be fully elastic. The contact force, contact radius and work of contact force are conformed to the Hertzian theory, using “Young’s modulus similarity” rule to predict the recovery displacement. The adhesion loss in the recovery stage is considered using Dunn’s model, which describes the adhesion force as an idealized line force with the contact radius. The validation case of steel spherical particle impact on a glass surface with the maximum Stokes number of 10000, shows that the adhesion model with elastoplastic impact model describes the experimental result well. When the Stokes number is less than 12, the particle deposits on the surface. Sand properties are characterized by size and temperature dependencies. Model predictions for particle sizes ranging from 0.5 to 50 micron, impact velocities up to 80 m/s, and temperatures above 1300 K are given and discussed. It is shown that both size and temperature have an effect on the deposition characteristics.

Simulation Analysis of Secondary-Load Rc Square Columns Strengthened with IFRP

2014 ◽  
Vol 501-504 ◽  
pp. 578-582
Author(s):  
Liang Hsu ◽  
Ming Long Hu ◽  
Jun Zhi Zhang
Keyword(s):  
Finite Element ◽  
Simulation Analysis ◽  
Element Model ◽  
Fiber Reinforced Polymer ◽  
Experimental Result ◽  
Compression Process ◽  
Reinforced Polymer ◽  
Secondary Load ◽  
The Impact ◽  
The Finite Element Model

Considering secondary load, simulate the axial compression process of reinforced concrete square columns strengthened with igneous rock fiber reinforced polymer with Abaqus. Make a comparison between the simulation result and experimental result. The finite-element model can simulate the experiment preferably. And the impact of lagged strain is very obvious.

Fatigue Behavior of Impacted Plain-Weave Glass/Epoxy Composites under Tensile Fatigue Loading

2005 ◽  
Vol 297-300 ◽  
pp. 1291-1296 ◽  
Author(s):  
Ki Weon Kang ◽  
Jung Kyu Kim ◽  
Heung Seob Kim
Keyword(s):  
Fatigue Life ◽  
Impact Damage ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Epoxy Composites ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Damage Behavior ◽  
Plain Weave ◽  
The Impact

The goals of this paper are to identify the impact damage behavior of plain-weave E-glass/epoxy composites and predict the fatigue life of the composites with impact-induced damage under constant amplitude loading. To identify these behaviors, the low velocity impact and fatigue after impact tests are performed for glass/epoxy composites having two types of fiber orientations. The impact damage behavior is dependent on the fiber orientation of the composites. The fatigue life of the impacted composites can be identified through the prediction model, which was proposed on the carbon/epoxy laminates by authors regardless of fiber orientations.

On the Decrease of Fatigue Limit Due to Small Prestrain

1992 ◽  
Vol 114 (3) ◽  
pp. 317-322 ◽  
Author(s):  
Y. Nagase ◽  
S. Suzuki
Keyword(s):  
Growth Rate ◽  
Carbon Steel ◽  
Fatigue Limit ◽  
Surface Crack ◽  
Fatigue Behavior ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Small Surface ◽  
Bending Tests ◽  
Rotating Bending

Fatigue behavior of plain specimens of low carbon steel subjected to small tensile prestrain is investigated through rotating bending tests and the mechanism of the decrease of fatigue limit due to the prestrain is discussed. It is found that 3 percent prestraining causes the acceleration of both slip and crack initiations, and increases the growth rate of a small surface crack of less than 0.3 mm. It also decreases the fatigue limit. If prestrained material is aged, the fatigue limit increases. These effects of the small prestrain are explained based on the unpinning of locked dislocations due to the prestrain.

scholarly journals A Particle-Based Cohesive Crack Model for Brittle Fracture Problems

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3573
Author(s):  
Hu Chen ◽  
Y. X. Zhang ◽  
Linpei Zhu ◽  
Fei Xiong ◽  
Jing Liu ◽  
...  
Keyword(s):  
Fracture Process ◽  
Cohesive Crack ◽  
Contact Model ◽  
Experimental Result ◽  
Crack Model ◽  
Mixed Mode Fracture ◽  
Cohesive Crack Model ◽  
Zone Method ◽  
The Impact ◽  
Linear Softening

Numerical simulations of the fracture process are challenging, and the discrete element (DE) method is an effective means to model fracture problems. The DE model comprises the DE connective model and DE contact model, where the former is used for the representation of isotropic solids before cracks initiate, while the latter is employed to represent particulate materials after cracks propagate. In this paper, a DE particle-based cohesive crack model is developed to model the mixed-mode fracture process of brittle materials, aiming to simulate the material transition from a solid phase to a particulate phase. Because of the particle characteristics of the DE connective model, the cohesive crack model is constructed at inter-particle bonds in the connective stage of the model at a microscale. A potential formulation is adopted by the cohesive zone method, and a linear softening relation is employed by the traction–separation law upon fracture initiation. This particle-based cohesive crack model bridges the microscopic gap between the connective model and the contact model and, thus, is suitable to describe the material separation process from solids to particulates. The proposed model is validated by a number of standard fracture tests, and numerical results are found to be in good agreement with the analytical solutions. A notched concrete beam subjected to an impact loading is modeled, and the impact force obtained from the numerical modeling agrees better with the experimental result than that obtained from the finite element method.

Fatigue limit: Crack and notch sensitivity by Finite Fracture Mechanics

2020 ◽  
Vol 105 ◽  
pp. 102407 ◽  
Author(s):  
Alberto Sapora ◽  
Pietro Cornetti ◽  
Alberto Campagnolo ◽  
Giovanni Meneghetti
Keyword(s):  
Fracture Mechanics ◽  
Fatigue Limit ◽  
Notch Sensitivity ◽  
Finite Fracture Mechanics

THE EFFECT OF IMPACT LOADS ON PRESTRESSED CONCRETE SLABS

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Youmn Al Rawi ◽  
Yehya Temsah ◽  
Hassan Ghanem ◽  
Ali Jahami ◽  
Mohamad Elani
Keyword(s):  
Reinforced Concrete ◽  
Prestressed Concrete ◽  
Impact Loading ◽  
Concrete Slab ◽  
Concrete Slabs ◽  
Shear Mode ◽  
Reinforced Concrete Slab ◽  
Finite Element Program ◽  
Reinforced Concrete Slabs ◽  
The Impact

Many research studies have been conducted on the effect of impact loading on structures, and design procedures were proposed for reinforced concrete (RC) slabs; however the availability of these studies and procedures are limited for prestressed slabs. The proposed research will examine, using numerical analysis, the impact of rock fall on prestressed concrete slabs with equivalent moment capacity reinforced concrete slabs. It is expected that prestressed concrete slabs will have different behavior to resist impact loading compared with traditional reinforced concrete slabs. The thickness of the prestressed concrete slab will be 25cm whereas that of the reinforced concrete slab will be 30cm. The impact loading consists of 500Kg drop weight. The drop height will be 10m, 15m and 20m.The structural analysis is performed using a Finite Element program "ABAQUS". A comparison will be done between both slab types in terms of failure mode, damage, and deflection. It has been found that both slabs failed in punching. However, the RC slab performed better than the prestressed concrete slab with respect to the value of the deflection at mid-span, while both showed punching shear mode of failure.

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