scholarly journals Evaluate the Fatigue Life of CFRC Subjected to Coupled Thermo–Mechanical Loading

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2886
Author(s):  
Junjie Ye ◽  
Wangpeng He ◽  
Yang Shi ◽  
Yiwei Wang ◽  
Gaigai Cai ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ambient Temperature ◽  
Mechanical Loading ◽  
Fatigue Failure ◽  
Composite Laminates ◽  
Elevated Temperatures ◽  
Temperature Cycling ◽  
External Loading ◽  
Stress Distributions ◽  
Temperature Variations

Mechanical properties of composites manufactured by high-temperature polymer polyether ether ketone (PEEK) with continuous reinforced fibers are closely dependent on ambient temperature variations. In order to effectively study fatigue failure behaviors of composites under the coupled thermo–mechanical loading, a well-established microscopic model based on a representative volume element (RVE) is proposed in this paper. Stiffness degradation behaviors of the composite laminates at room and elevated temperatures are firstly investigated, and their failure strengths are compared with experimental data. To describe the fatigue behaviors of composites with respect to complex external loading and ambient temperature variations, a new fatigue equation is proposed. A good consistency between theoretical results and experimental data was found in the cases. On this basis, the temperature cycling effects on the service life of composites are also discussed. Microscopic stress distributions of the RVE are also discussed to reveal their fatigue failure mechanisms.

Notched Strength Prediction and Verification of APC-2 Composite Laminates at Elevated Temperature

2009 ◽  
Vol 79-82 ◽  
pp. 1563-1566 ◽  
Author(s):  
Ming Hwa R. Jen ◽  
Yi Chun Sung ◽  
Yu Chung Tseng
Keyword(s):  
Experimental Data ◽  
Elevated Temperature ◽  
Composite Laminates ◽  
Elevated Temperatures ◽  
Characteristic Length ◽  
Tensile Tests ◽  
Stress Criterion ◽  
Static Tensile ◽  
Notched Strength ◽  
Good Agreement

The notched strength of AS-4/PEEK (APC-2) composite laminates with a central hole at elevated temperature was systematically studied by both analytical and empirical methods. First, the APC-2 cross-ply [0/90]4s panels were fabricated and cut into samples. Each sample was drilled a hole in the center with five kinds of diameters, such as d=0(unnotched), 1, 2, 3, and 4mm. Then, the samples were subjected to quasi-static tensile tests at elevated temperatures, including 25°C (RT), 75, 100, 125, 150 and 175°C, to measure their mechanical properties. The average values of received notched strength were affected significantly by stress concentration and high temperature. In analysis the prediction of residual strength by point stress criterion (PSC) was adopted first and found unsatisfactory due to at least 15% errors with experimental data. Then, the modified PSC was used with the varied characteristic length dependent on nature of material and specimen geometry. The predicted notched strengths by the modified PSC model were in very good agreement with experimental data. The predictive results were not only precisely validated, but extended to the application at elevated temperature.

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

2019 ◽  
pp. 9-14
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Relative Deformation ◽  
Deformation Characteristics ◽  
Compression Tests ◽  
Strain Behavior ◽  
Different Temperatures ◽  
Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

Dielectric Breakdown in Printed Circuit Boards at Elevated Temperatures

1996 ◽  
Author(s):  
P. Singh ◽  
G.T. Galyon ◽  
J. Obrzut ◽  
W.A. Alpaugh
Keyword(s):  
Experimental Data ◽  
Thermal Degradation ◽  
Printed Circuit Boards ◽  
Printed Circuit Board ◽  
Elevated Temperatures ◽  
Dielectric Breakdown ◽  
Circuit Board ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Data Matching

Abstract A time delayed dielectric breakdown in printed circuit boards, operating at temperatures below the epoxy resin insulation thermo-electrical limits, is reported. The safe temperature-voltage operating regime was estimated and related to the glass-rubber transition (To) of printed circuit board dielectric. The TG was measured using DSC and compared with that determined from electrical conductivity of the laminate in the glassy and rubbery state. A failure model was developed and fitted to the experimental data matching a localized thermal degradation of the dielectric and time dependency. The model is based on localized heating of an insulation resistance defect that under certain voltage bias can exceed the TG, thus, initiating thermal degradation of the resin. The model agrees well with the experimental data and indicates that the failure rate and truncation time beyond which the probability of failure becomes insignificant, decreases with increasing glass-rubber transition temperature.

Fatigue Failure Model for Composite Laminates under Multi-Axial Cyclic Loading

2000 ◽  
Vol 183-187 ◽  
pp. 945-950 ◽  
Author(s):  
Chong Soo Lee ◽  
W. Hwang ◽  
Hyun Chul Park ◽  
Kyung Seop Han
Keyword(s):  
Cyclic Loading ◽  
Fatigue Failure ◽  
Composite Laminates ◽  
Failure Model ◽  
Axial Cyclic Loading

Evaluation of energy generation in Iraqi territory by solar photovoltaic power plants with a capacity of 20 MW

2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Qusay Hassan ◽  
Saadoon Abdul Hafedh ◽  
Ali Hasan ◽  
Marek Jaszczur
Keyword(s):  
Experimental Data ◽  
Wind Speed ◽  
Power Plant ◽  
Ambient Temperature ◽  
Solar Irradiance ◽  
Electricity Generation ◽  
Power Plants ◽  
Solar Photovoltaic ◽  
Photovoltaic Power ◽  
Plant Capacity

Abstract The study evaluates the visibility of solar photovoltaic power plant construction for electricity generation based on a 20 MW capacity. The assessment was performed for four main cities in Iraq by using hourly experimental weather data (solar irradiance, wind speed, and ambient temperature). The experimental data was measured for the period from 1st January to 31st December of the year 2019, where the simulation process was performed at a 1 h time step resolution at the same resolution as the experimental data. There are two positionings considered for solar photovoltaic modules: (i) annual optimum tilt angle and (ii) two-axis tracking system. The effect of the ambient temperature and wind on the overall system energy generated was taken into consideration. The study is targeted at evaluating the potential solar energy in Iraq and the viability of electricity generation using a 20 MW solar photovoltaic power plant. The results showed that the overall performance of the suggested power plant capacity is highly dependent on the solar irradiance intensity and the ambient temperature with wind speed. The current 20 MW solar photovoltaic power plant capacity shows the highest energy that can be generated in the mid-western region and the lowest in the northeast regions. The greatest influence of the ambient temperature on the energy genrated by power plants is observed in the southern regions.

Determination of the Residual Stresses in Composite Laminate Using the Compliance Method

2005 ◽  
Vol 490-491 ◽  
pp. 533-538 ◽  
Author(s):  
Guillaume Montay ◽  
Olivier Sicot ◽  
X.L. Gong ◽  
Abel Cherouat ◽  
Jian Lu
Keyword(s):  
Experimental Data ◽  
Residual Stresses ◽  
Composite Laminates ◽  
Composite Laminate ◽  
Constant Width ◽  
Strain Gages ◽  
New Methods ◽  
Structure Surface ◽  
Finite Elements Simulation

Residual stresses play an important role on the mechanical behavior of composite laminate. The development of new methods to determine the residual stresses gradient within the laminates is necessary. This article presents the adaptation of the compliance method in the case of composite laminates carbon/epoxy [02/902]s. The incremental drilling of a constant width groove allows for each increment to measure the strains (using strain gages) and displacements (using an optical device) of particularly points of the structure surface. These experimental data are compared with results given by a finite elements simulation. This comparison allows to raise the residual stresses in the composite laminate.

Kinetic equations of creep and damage for description of materials with non-monotonic dependence of fracture strain on stress

2021 ◽  
Vol 23 (3) ◽  
pp. 139-154
Author(s):  
Inna Banshchikova ◽  
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Damage Accumulation ◽  
Elevated Temperatures ◽  
Fracture Strain ◽  
Least Squares Method ◽  
Kinetic Equations ◽  
Steel 12Kh18n10t ◽  
Static Mode ◽  
Creep Curves

Introduction. Reducing the level of damage accumulation during pressure treatment of materials at elevated temperatures in creep and close to superplasticity modes in the manufacture of parts can significantly increase its service life in the cold state. Finding temperature and power conditions leading to a reduction in damage of material during the production process and operation is an important task. The purposes of the work: 1) to show the possibility of using the Sosnin-Gorev creep and damage model for alloys with a non-monotonic dependence of strain at fracture on diagrams with creep curves; 2) to carry out comparative analysis of damage accumulation under conditions of uniaxial tension at constant stress and at constant strain rates for alloy with such a dependence. Research methods. Used scalar damage parameter is equated to the normalized deformation, i.e. to the ratio of the current strain to the fracture strain. To find the coefficients of relations creep and damage, the similarity of the creep curves in the normalized values “normalized strain – normalized time”, i.e. the presence of single normalized curve of damage accumulation is checked. The least squares method is used to approximate the experimental data. Numerical integration methods are used for comparative analysis of deformation modes. Results and discussion. Determination of the parameters of the creep and damage equations by the method of a single normalized curve is carried out on the example of experimental data for steel 12Kh18N10T (12Cr18Ni10Ti) at 850 °C, which has a minimum of fracture strain in diagrams with creep curves. Analysis of the static and kinematic modes of deformation for studied material showed that damage accumulation in both cases is practically the same for stresses close to the stress at which this minimum is reached. If the stresses are lower, then the lower level of damage accumulation will be in the kinematic mode; if the stresses above the minimum value, then the static mode will lead to a lower level of damage accumulation. Application. The obtained results can be useful when choosing rational modes of forming structural elements from alloys with a non-monotonic dependence of the fracture strain on stress, as well as in evaluating it for long-term strength during operation.

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