Stiffness Degradation in Fatigue Life of Composites using Dielectric State Variables

2021 ◽  
pp. 114272
Author(s):  
Muthu Ram Prabhu Elenchezhian ◽  
Partha Pratim Das ◽  
Minhazur Rahman ◽  
Vamsee Vadlamudi ◽  
Md Rassel Raihan ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Stiffness Degradation ◽  
State Variables ◽  
Dielectric State

Study on the stiffness degradation in concrete continuous beam with externally prestressed CFRP tendons under fatigue loading

2021 ◽  
pp. 136943322199249
Author(s):  
Xing Li ◽  
Jiwen Zhang ◽  
Jun Cheng
Keyword(s):  
Fatigue Life ◽  
Fatigue Loading ◽  
Load Level ◽  
Fiber Reinforced Polymer ◽  
Stiffness Degradation ◽  
Test Results ◽  
Reinforced Polymer ◽  
Continuous Beams ◽  
Practical Engineering ◽  
Good Agreement

This paper presents fatigue behaviors and the stiffness degradation law of concrete continuous beams with external prestressed carbon fiber-reinforced polymer (CFRP) tendons. Three specimens were tested under fatigue loading, and the influence of different load levels on the stiffness degradation and fatigue life were studied, and it was found that the stiffness degradation of three test specimens exhibited a three-stage change rule, namely rapid decrease, stable degradation, and sharp decline, but there are obvious differences in the rate and amplitude of stiffness degradation. The load level has a significant influence on the fatigue life of the test specimens. An analytical model with load level considered was proposed to calculate the residual stiffness and predict the stiffness degradation, which is in good agreement with the test results. The model of stiffness degradation presents a possible solution for practical engineering applications of concrete continuous beams with externally prestressed CFRP tendons subjected to different fatigue loadings.

Stiffness Degradation of Digital Polypropylene Under Fatigue Loading: Investigations via 3-Dimensional Polyjet Printed Coupons

2020 ◽  
Author(s):  
Ravi Pratap Singh Tomar ◽  
Furkan I. Ulu ◽  
Ajit Kelkar ◽  
Ram V. Mohan
Keyword(s):  
Experimental Data ◽  
Regression Analysis ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Damage State ◽  
3 Dimensional ◽  
Accumulated Damage ◽  
Polyjet Printing

Abstract The utilization of additively manufactured parts is gaining popularity in functional applications. Polymer-based additive manufacturing (AM) parts are utilized in a variety of engineering applications for automotive, aerospace, and energy. AM printed parts are however newer class of materials, and structural performance of these materials is not fully understood completely, and very limited exists currently on precisely performance of Polyjet printed parts and associated digital materials under fatigue loading. This paper investigates the stiffness degradation under tension-tension fatigue loading of digital polypropylene using homogenous 3-Dimensional test coupons formed using PolyJet printing. Homogeneous 3-Dimensional test configuration employed in the present study eliminates the process-induced limitations of traditional ASTM D638 2D fatigue test coupons for AM processed materials. Fatigue data is analyzed to present an empirical model of effective elastic modulus and an analytical model of the accumulated damage state, as defined on the basis of stiffness degradation during cyclic loading. Further, the actual damage accumulation due to cyclic loading with the predicted model is compared. Modeling of the S-N diagram provides a better estimation of fatigue life and fatigue life modeling of AM printed test coupons and is obtained via linear regression analysis of experimental data with high correlation coefficient R2 (0.9971). The analytical model of the accumulated damage state is based on the stiffness degradation and is derived from the regression analysis of experimental data of stiffness degradation at different loading percentages assuming a polynomial of degree 4. Present study provides insight into the fatigue damage state and cyclic performance of digital polypropylene from Polyjet printing.

In-situ fatigue life prognosis for composite laminates based on stiffness degradation

2015 ◽  
Vol 132 ◽  
pp. 155-165 ◽  
Author(s):  
Tishun Peng ◽  
Yongming Liu ◽  
Abhinav Saxena ◽  
Kai Goebel
Keyword(s):  
Fatigue Life ◽  
Composite Laminates ◽  
Stiffness Degradation ◽  
Life Prognosis

Multi-Scale Modeling and Experimental Validation for Component Fatigue Life Prediction

2007 ◽  
Author(s):  
Sunilkumar Soni ◽  
Jun Wei ◽  
Aditi Chattopadhyay ◽  
Pedro Peralta
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Internal State ◽  
Fatigue Life Prediction ◽  
Scale Model ◽  
Stress Effect ◽  
State Variables ◽  
Finite Element Software ◽  
Joint Specimen ◽  
Meso Scale

A fatigue failure prediction procedure is discussed based on a two scale micro meso mechanical model for metallic structures. This model predicts the fatigue life and accounts for physical quantities like the mean stress effect in high cycle fatigue. Another model developed at meso-scale level with BCJ (Bammann, Chiesa and Johnson, 1996, Theoretical and Applied Mechanics, Tatsumi, Watanabe and Kambe (Editors), 359–376) internal state variables, is used to predict progressive damage in ductile materials. This meso-scale model is incorporated within the general purpose finite element software ABAQUS through a user subroutine VUMAT. A lug joint specimen is simulated using the BCJ model modified for fatigue and the location of the crack initiation sites is found. Experiments are conducted with the lug joint specimen under fatigue loading and the models are validated for the fatigue life prediction and location of the damage sites.

Prediction of the Fatigue Life Based on Stiffness Degradation Concept

2008 ◽  
Vol 33-37 ◽  
pp. 199-204
Author(s):  
Y.H. Wang ◽  
Zheng Dao Wang ◽  
X.X. Zhao
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Fatigue Life ◽  
Polymer Composites ◽  
Stress Level ◽  
Stiffness Degradation ◽  
New Model ◽  
Fatigue Stress ◽  
Model Based ◽  
Hybrid Thin Films

In order to predict the fatigue life of matrix-dominated polymer composites, a new model based on stiffness degradation concept was proposed. The effect of off-axis was considered by defining a non-dimensional modified stress level, and the expression of fatigue stress limit could be provided in the new model. Based on the fatigue tension-tension experiment of PI/SiO2 hybrid thin films under different stress levels, the simulated results was confirmed to be well agreeable with the experimental data.

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