Experimental investigation and phenomenological modeling of hygrothermal effect on tensile fatigue behavior of carbon/epoxy plain weave laminates

2018 ◽  
Vol 52 (27) ◽  
pp. 3803-3818 ◽  
Author(s):  
M Khay ◽  
AD Ngo ◽  
R Ganesan
Keyword(s):  
Fatigue Life ◽  
Composite Laminates ◽  
Fatigue Behavior ◽  
Tensile Load ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Plain Weave ◽  
Hygrothermal Effect ◽  
Tensile Fatigue ◽  
Delamination Propagation

The purpose of this paper is to study the hygrothermal effect on fatigue behavior of quasi-isotropic carbon/epoxy plain weave aerospace laminates containing artificial flaw under axial tension–tension loading. Dry and wet specimens were tested at tensile load-controlled cyclic loading with a stress ratio R = 0.1 and a load frequency of 7 Hz at room temperature (RT) and at 82℃ under different stress levels. Allowable stiffness change as a failure criterion was used to determine the delamination propagation onset threshold under cyclic tensile loading at each environmental condition. The delamination propagation onset was verified using the ultrasonic imaging (C-Scan) technique. The experimental results show that (1) fatigue life of CFRP specimens was more individually affected by moisture than by temperature and (2) combined moisture and temperature cause a drastic decrease in fatigue life. Finally, an investigation of the effect of hygrothermal conditions on stiffness degradation and damage of composite laminates subjected to tensile fatigue loading has been also carried. On the basis of the residual stiffness degradation, a damage variable was presented and phenomenological damage models were proposed by employing fatigue modulus and secant modulus concepts as measure of material damage.

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.

Effects of environmental conditions on the axial tension–compression fatigue behavior of carbon/epoxy plain-weave laminates containing flaws

2020 ◽  
Vol 54 (27) ◽  
pp. 4215-4230
Author(s):  
Marc-Claudel Deluy ◽  
Mohamed Khay ◽  
Anh Dung Ngo ◽  
Martine Dubé ◽  
Rajamohan Ganesan
Keyword(s):  
Fatigue Life ◽  
Environmental Conditions ◽  
Cyclic Load ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Real Life ◽  
Compressive Load ◽  
Fatigue Loading ◽  
Plain Weave ◽  
Strain Increase

The objective of this work is to investigate the effects of environmental conditions on the axial fatigue behavior of a carbon/epoxy plain-weave laminate with an embedded flaw subjected to a partially reversed cyclic load (stress ratio R = −0.1) in tension–compression. This specific material is more commonly used in aerospace engineering for the manufacturing of aircraft structural parts, which are directly exposed to various environmental conditions during service. Specific environmental and loading conditions that are appropriate to simulate real-life conditions are considered to observe and collect information about the material's behavior. For the investigation, dry and wet coupons were submitted to room temperature, 82 and 121 ℃ under loading frequencies of 7 and 15 Hz. A maximum allowable strain increase criterion is used to monitor the flaw growth threshold or delamination onset, during fatigue testing. The ultrasonic imaging (C-scan) technique is used to verify and confirm the delamination onset. Results show that the delamination onset strain increase criterion, along with fatigue life, generally decreased as the operating temperature and humidity were increased and that frequency had little effect on the delamination onset fatigue life. The S– N curves obtained from the tension–compression fatigue data were then compared to those of a previous work carried out in tension–tension fatigue loading. Results show a clear degradation in the delamination onset fatigue life of the coupons tested under tension–tension cyclic loading when the minimum tensile component of the cyclic load was replaced with a compressive load of the same magnitude.

Life Prediction and Stiffness Degradation Modeling of Glass/Epoxy Composites Subjected to Flexural Fatigue Loading

2016 ◽  
Author(s):  
Vinod B. Suryawanshi ◽  
Evan T. Kimbro ◽  
Ajit D. Kelkar
Keyword(s):  
Fatigue Life ◽  
Prediction Model ◽  
Life Prediction ◽  
Epoxy Composite ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Degradation Model ◽  
Flexural Fatigue ◽  
Plain Weave ◽  
Life Prediction Model

Textile composite are extensively used as structural materials for automotive, aerospace, energy, transportation and construction applications. During their service life these structures are subjected to different types of static and cyclic loading. For structural health monitoring of these structures, it is important to know the fatigue life and damage occurred at any stage of the life of the structure. Fatigue life is generally estimated using suitable life prediction model, while fatigue damage can be predicted by monitoring measurable damage parameters such as stiffness and strength. Two mathematical models namely fatigue life prediction model and stiffness degradation model are proposed for plain weave glass/epoxy composite subjected to flexural fatigue loading. Three different functions namely linear, exponential and sigmoid are evaluated to represent S-N diagram for plain weave glass/epoxy composite. Using predicted fatigue life along with initial modulus as inputs, the stiffness degradation model can predict residual stiffness at any stage of the fatigue loading life cycle. Logarithmic function used to represent stiffness degradation in the model is derived by inverting Boltzmann sigmoid function. The results of both, fatigue life model and stiffness degradation model were found to be in good agreement with those of the experimental results.

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.

Assessment and propagation of mechanical property uncertainties in fatigue life prediction of composite laminates

2018 ◽  
Vol 52 (24) ◽  
pp. 3381-3398 ◽  
Author(s):  
Oscar Castro ◽  
Kim Branner ◽  
Nikolay Dimitrov
Keyword(s):  
Fatigue Life ◽  
Composite Laminates ◽  
Fatigue Behavior ◽  
Limit State ◽  
Turbine Blades ◽  
Laminated Composite ◽  
Load Level ◽  
Wind Turbine Blades ◽  
Laminated Composite Materials ◽  
Fatigue Limit State

A probabilistic model for estimating the fatigue life of laminated composite materials considering the uncertainty in their mechanical properties is developed. The uncertainty in the material properties is determined from fatigue coupon tests. Based on this uncertainty, probabilistic constant life diagrams are developed which can efficiently estimate probabilistic ɛ-N curves at any load level and stress ratio. The probabilistic ɛ-N curve information is used in a reliability analysis for fatigue limit state proposed for estimating the probability of failure of composite laminates under variable amplitude loading cycles. Fatigue life predictions of unidirectional and multi-directional glass/epoxy laminates are carried out to validate the proposed model against experimental data. The probabilistic fatigue behavior of laminates is analyzed under constant amplitude loading conditions as well as under both repeated block tests and spectral fatigue using the WISPER, WISPERX, and NEW WISPER load sequences for wind turbine blades.

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.

NUMERICAL PREDICTION OF STIFFNESS DEGRADATION OF THIN-PLY CFRP LAMINATES UNDER FATIGUE LOADING

2021 ◽  
Author(s):  
RYOMA AOKI ◽  
RYO HIGUCHI ◽  
TOMOHIRO YOKOZEKI
Keyword(s):  
Composite Laminates ◽  
Damage Mechanics ◽  
Crack Density ◽  
Continuum Damage Mechanics ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Cfrp Laminates ◽  
Mechanics Model ◽  
Element Simulation ◽  
Proposed Model

This study aims to conduct a fatigue simulation for predicting the stiffness degradation of thin-ply composite laminates with several ply thicknesses. For the simulation, a fatigue evolution model of intra-laminar damage in thin-ply composite laminates considering the effect of ply thickness was proposed. The intra-laminar damage evolution was modeled using the continuum damage mechanics model and the static and fatigue evolution law were formulated by relating the transverse crack density to the damage variable. The finite element simulation using the proposed model was conducted to predict the stiffness degradation of the laminates as a function of the number of loading cycles. The simulation results show that the experimental data can be reproduced by using the proposed fatigue model.

Accounting for Inclusions and Voids Allows the Prediction of Tensile Fatigue Life of Bone Cement

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Oliver J. Coultrup ◽  
Martin Browne ◽  
Christopher Hunt ◽  
Mark Taylor
Keyword(s):  
Fatigue Life ◽  
Bone Cement ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Acoustic Emissions ◽  
Gauge Length ◽  
Uniaxial Tensile ◽  
Micro Computed Tomography ◽  
Dog Bone ◽  
Tensile Fatigue

Previous attempts by researchers to predict the fatigue behavior of bone cement have been capable of predicting the location of final failure in complex geometries but incapable of predicting cement fatigue life to the right order of magnitude of loading cycles. This has been attributed to a failure to model the internal defects present in bone cement and their associated stress singularities. In this study, dog-bone-shaped specimens of bone cement were micro-computed-tomography (μCT) scanned to generate computational finite element (FE) models before uniaxial tensile fatigue testing. Acoustic emission (AE) monitoring was used to locate damage events in real time during tensile fatigue tests and to facilitate a comparison with the damage predicted in FE simulations of the same tests. By tracking both acoustic emissions and predicted damage back to μCT scans, barium sulfate (BaSO4) agglomerates were found not to be significant in determining fatigue life (p=0.0604) of specimens. Both the experimental and numerical studies showed that diffuse damage occurred throughout the gauge length. A good linear correlation (R2=0.70, p=0.0252) was found between the experimental and the predicted tensile fatigue life. Although the FE models were not always able to predict the correct failure location, damage was predicted in simulations at areas identified as experiencing damage using AE monitoring.

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