scholarly journals The Elephant Problem—Determining Bulk Thermal Diffusivity

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7444
Author(s):  
Robert Beaufait ◽  
Sebastian Ammann ◽  
Ludger Fischer
Keyword(s):  
Numerical Simulation ◽  
Composite Material ◽  
Thermal Diffusivity ◽  
Material Properties ◽  
Measurement Method ◽  
Bulk Material ◽  
Transient Temperature ◽  
Material Structure ◽  
Curve Fit ◽  
Arbitrary Geometries

This study investigates a measurement method of thermal diffusivity for samples with arbitrary geometries and unknown material properties. The aim is to curve fit the thermal diffusivity with the use of a numerical simulation and transient temperature measurement inside the object of interest. This approach is designed to assess bulk material properties of an object that has a composite material structure such as underground soil. The method creates the boundary conditions necessary to apply analytical theory found in the literature. It was found that measurements best correlated with theory and simulation at positions between the center and surface of an object.

scholarly journals Analysis of the possibility of determining the internal structure of composite material by estimating its thermal diffusivity

2014 ◽  
Vol 35 (1) ◽  
pp. 3-15
Author(s):  
Stanisław Kucypera
Keyword(s):  
Composite Material ◽  
Heat Conduction ◽  
Thermal Diffusivity ◽  
Internal Structure ◽  
Fibrous Composite ◽  
Electric Heater ◽  
Transient Temperature ◽  
Inverse Heat Conduction ◽  
Filtration Method ◽  
Fibrous Composite Material

Abstract The aim of this paper is analysis of the possibility of determining the internal structure of the fibrous composite material by estimating its thermal diffusivity. A thermal diffusivity of the composite material was determined by applying inverse heat conduction method and measurement data. The idea of the proposed method depends on measuring the timedependent temperature distribution at selected points of the sample and identification of the thermal diffusivity by solving a transient inverse heat conduction problem. The investigated system which was used for the identification of thermal parameters consists of two cylindrical samples, in which transient temperature field is forced by the electric heater located between them. The temperature response of the system is measured in the chosen point of sample. One dimensional discrete mathematical model of the transient heat conduction within the investigated sample has been formulated based on the control volume method. The optimal dynamic filtration method as solution of the inverse problem has been applied to identify unknown diffusivity of multi-layered fibrous composite material. Next using this thermal diffusivity of the composite material its internal structure was determined. The chosen results have been presented in the paper.

scholarly journals Low-speed impact damage analysis of aviation composite material structure

2021 ◽  
Vol 260 ◽  
pp. 03021
Author(s):  
Jun He ◽  
Meng Cao ◽  
Zhishu Wang ◽  
Fanglin Cong
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Composite Material ◽  
Composite Structures ◽  
Impact Damage ◽  
Low Velocity Impact ◽  
Material Structure ◽  
Damage Analysis ◽  
Low Speed ◽  
The Impact

Although the carbon fiber reinforced composite material has high specific strength and stiffness, design-versatility, anti-corrosion and other excellent features, but the impact resistance of composite structures is poor. Therefore, the composite laminates low-speed damage analysis has important significance. Based on a three-dimensional analysis theory of cumulative damage, using the commercial finite element analysis software ABAQUS to establish laminates subjected to low velocity impact finite element model. according to the numerical results and the consistency of the test results, shows that the used model of the article is reasonable and accurate, and the numerical simulation method is verified to be feasible. Finally, through the numerical simulation of process of laminated plates low speed impact damage, the damage characteristics and damage mechanism of the laminates at different times are analyzed, and the forming reasons and expanding rules of the main damage forms of fiber damage and matrix damage are revealed.

Acoustic waves in finely layered media

Geophysics ◽  
1995 ◽  
Vol 60 (4) ◽  
pp. 1217-1221 ◽  
Author(s):  
Jens M. Hovem
Keyword(s):  
Numerical Simulation ◽  
Composite Material ◽  
Sound Velocity ◽  
Material Properties ◽  
Acoustic Waves ◽  
Close Agreement ◽  
Stratified Medium ◽  
Scattering Loss ◽  
Propagator Method ◽  
The Waves

The propagation of acoustic waves through a periodically stratified medium is examined theoretically and experimentally with the purpose of determining how the velocity of the composite material depends on the periodicity structure, the material properties, and frequency. A numerical simulation of a recently published experiment shows that the propagator method gives results in close agreement with the experimental observations. Using eigenvalue analysis, an expression for the sound velocity and scattering loss is calculated for all frequencies. The results show that, for frequencies lower than a certain critical (or limiting) frequency, the propagation is dispersive and no loss occurs. Above this frequency the waves are evanescent and suffer scattering loss at each interface. An expression for the limiting frequency is derived which takes into account the contrast in impedance between the two media.

scholarly journals Clinching of Thermoplastic Composites and Metals—A Comparison of Three Novel Joining Technologies

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2286
Author(s):  
Benjamin Gröger ◽  
Juliane Troschitz ◽  
Julian Vorderbrüggen ◽  
Christian Vogel ◽  
Robert Kupfer ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Composite Material ◽  
Process Design ◽  
Failure Mechanisms ◽  
Thermoplastic Composites ◽  
Material Structure ◽  
Shear Tests ◽  
Load Bearing ◽  
Lap Shear ◽  
Resultant Material

Clinching continuous fibre reinforced thermoplastic composites and metals is challenging due to the low ductility of the composite material. Therefore, a number of novel clinching technologies has been developed specifically for these material combinations. A systematic overview of these advanced clinching methods is given in the present paper. With a focus on process design, three selected clinching methods suitable for different joining tasks are described in detail. The clinching processes including equipment and tools, observed process phenomena and the resultant material structure are compared. Process phenomena during joining are explained in general and compared using computed tomography and micrograph images for each process. In addition the load bearing behaviour and the corresponding failure mechanisms are investigated by means of single-lap shear tests. Finally, the new joining technologies are discussed regarding application relevant criteria.

scholarly journals A methodology for hygrothermal modelling of imperfect masonry interfaces

2021 ◽  
pp. 174425912198938
Author(s):  
Michael Gutland ◽  
Scott Bucking ◽  
Mario Santana Quintero
Keyword(s):  
Boundary Conditions ◽  
Material Properties ◽  
Structural Integrity ◽  
Bulk Material ◽  
Weather Conditions ◽  
Masonry Wall ◽  
Two Dimensional ◽  
Liquid Transport ◽  
Imperfect Contact ◽  
Moisture Contents

Hygrothermal models are important tools for assessing the risk of moisture-related decay mechanisms which can compromise structural integrity, loss of architectural features and material. There are several sources of uncertainty when modelling masonry, related to material properties, boundary conditions, quality of construction and two-dimensional interactions between mortar and unit. This paper examines the uncertainty at the mortar-unit interface with imperfections such as hairline cracks or imperfect contact conditions. These imperfections will alter the rate of liquid transport into and out of the wall and impede the liquid transport between mortar and masonry unit. This means that the effective liquid transport of the wall system will be different then if only properties of the bulk material were modelled. A detailed methodology for modelling this interface as a fracture is presented including definition of material properties for the fracture. The modelling methodology considers the combined effect of both the interface resistance across the mortar-unit interface and increase liquid transport in parallel to the interface, and is generalisable to various combinations of materials, geometries and fracture apertures. Two-dimensional DELPHIN models of a clay brick/cement-mortar masonry wall were created to simulate this interaction. The models were exposed to different boundary conditions to simulate wetting, drying and natural cyclic weather conditions. The results of these simulations were compared to a baseline model where the fracture model was not included. The presence of fractures increased the rate of absorption in the wetting phase and an increased rate of desorption in the drying phase. Under cyclic conditions, the result was higher peak moisture contents after rain events compared to baseline and lower moisture contents after long periods of drying. This demonstrated that detailed modelling of imperfections at the mortar-unit interface can have a definitive influence on results and conclusions from hygrothermal simulations.

Numerical Simulation of Thermoplastic Composite Material by ANSYS

2011 ◽  
Vol 279 ◽  
pp. 181-185 ◽  
Author(s):  
Guo Hua Zhao ◽  
Qing Lian Shu ◽  
Bo Sheng Huang
Keyword(s):  
Numerical Simulation ◽  
Composite Material ◽  
Composite Structures ◽  
Material Model ◽  
General Purpose ◽  
Thermoplastic Composite ◽  
Finite Element Code ◽  
Peek Composite ◽  
Test Result ◽  
Good Agreement

This paper proposes a material model of AS4/PEEK, a typical thermoplastic composite material, for the general purpose finite element code—ANSYS, which can be used to predict the mechanical behavior of AS4/PEEK composite structures. The computational result using this model has a good agreement with the test result. This investigation can lay the foundation for the numerical simulation of thermoplastic composite structures.

Thermo-mechanical analysis of a FGM plate subjected to thermal shock – A new numerical approach considering real time temperature dependent material properties

2021 ◽  
Vol 63 (4) ◽  
pp. 341-349
Author(s):  
Mete Onur Kaman ◽  
Nevin Celik ◽  
Resul Das
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Shock ◽  
Temperature Variation ◽  
Material Properties ◽  
Ambient Air ◽  
Transient Temperature ◽  
Heated Plate ◽  
The Heat Transfer Coefficient

Abstract In present the study, sudden cooling, in other words thermal shock, is applied to a plate that is originally a functionally graded material (FGM). The flat plate is assumed to have an edge crack on it. Hence a numerical couple-field analysis is performed on the plate. The FGM is a combination of Ni and Al2O3. The thermal and mechanical properties of the FGM are assumed to depend on temperature variation. The mixing percentages of the Ni and Al2O3 throughout the plate are considered to vary (i) linearly, (ii) quadratically and (iii) in half-order. In order to solve the problem, a new subroutine depending on temperature is written using APDL (ANSYS Parametric Design Language) codes. Three values of the heat transfer coefficient are applied to the initially heated plate. As a result, the transient temperature variation and stress intensity factor are presented to show the thermo-mechanical relation of the plate. The material properties changing with temperature results in more reliable temperature values. Increasing the heat transfer coefficient results in better cooling and in a lesser amount of time to reach ambient air temperature.

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