scholarly journals An Experimental Investigation of Thermal Properties of Fabric Reinforced Epoxy Composites

2019 ◽  
Vol 57 (2) ◽  
pp. 159-168
Author(s):  
Iulian Gabriel Birsan ◽  
Vasile Bria ◽  
Marina Bunea ◽  
Adrian Circiumaru
Keyword(s):  
Experimental Investigation ◽  
Specific Heat ◽  
Fiber Orientation ◽  
Linear Expansion ◽  
Epoxy Composites ◽  
Linear Expansion Coefficient ◽  
Thermal Coefficient ◽  
Thermal Measurements ◽  
Thermal Linear Expansion Coefficient ◽  
Coefficient Of Linear Expansion

Specific heat and thermal linear expansion coefficient of epoxy composites reinforced with carbon, aramid, glass and hybrid fabrics with unfilled and filled stratified matrices were studied. The thermal measurements of specific heat were performed with Differential Scanning Calorimeter (DSC instrument) and those of thermal coefficient of linear expansion were realized with Thermomechanical Analyzer (TMA instrument). It was analyzed the influence of fiber orientation at various angles (�15�, �30� and �45�) and the effects of two types of filler mixtures added into polymeric matrix on the thermal behavior of composite materials. It was found that in case of epoxy matrix the added filler mixtures reduced its thermal coefficient of linear expansion and had an insignificant influence on specific heat. In case of epoxy composites reinforced with fabrics, the fiber orientation and fillers addition showed different effects on the investigated thermal parameters in dependence of the used reinforcement types.

scholarly journals Specific Heat and Thermal Expansion Coefficient of Hybrid Epoxy Composites

2020 ◽  
Vol 57 (3) ◽  
pp. 61-69
Author(s):  
Georgel Mihu ◽  
Vasile Bria ◽  
Adrian Circiumaru ◽  
Iulian Gabriel Birsan ◽  
Marina Bunea
Keyword(s):  
Thermal Expansion ◽  
Carbon Black ◽  
Specific Heat ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Hybrid Composites ◽  
Epoxy Composites ◽  
Linear Expansion Coefficient ◽  
Thermal Linear Expansion Coefficient ◽  
Ply Orientation

Thermal behavior of hybrid epoxy composites reinforced with different types of plain weave fabrics and ply orientation at various angles was investigated in this research. It was analyzed their thermal linear expansion coefficient and specific heat measured with Thermomechanical Analyzer (TMA) and Differential Scanning Calorimeter (DSC) respectively. Also, in this paper was studied the influence of carbon black - aramid powder and carbon black - barium ferrite mixtures added into epoxy matrix between certain plies of the hybrid composites. The experimental results showed that the addition of filler mixtures led to a significant decreasing of thermal expansion coefficient and specific heat of the hybrid epoxy composite with carbon outer plies. It was recorded a good structural stability in case of hybrid carbon-glass composite in the temperature range of 40-60�C.

The ‘instantaneous’ elasticity of active muscle

1953 ◽  
Vol 141 (903) ◽  
pp. 161-178 ◽  
Keyword(s):  
Elastic Properties ◽  
Long Range ◽  
Linear Expansion ◽  
Thermal Coefficient ◽  
Active Muscle ◽  
Absolute Size ◽  
Rapid Fall ◽  
Experimental Relation ◽  
Coefficient Of Linear Expansion ◽  
Resting Muscle

When the tension of a muscle contracting isometrically is rapidly lowered, there is an immediate and proportional rise of temperature. This is not due to physiological shortening, which is a relatively slow process, but is directly connected with the fall of tension. A similar effect occurs in any material possessing a normal (positive) thermal coefficient of linear expansion. It is the opposite of what is observed in bodies with long-range rubber-like elasticity. The experimental relation, in active muscle, between the heat (∆ Q ) immediately produced and the rapid fall of tension (-∆ P ) is ∆ Q = 0∙018 l o (-∆ P ), where l o is the standard length of the muscle. The constant 0∙018 is considerably greater than for metals but about the same as for ebonite and wood. In resting muscle, in the range of moderate tensions, the constant is of the opposite sign, and its absolute size is five to ten times as great. Resting muscle, in this range, has rubber-like elastic properties. During active contraction, therefore, the contractile filaments possess normal and not long-range elasticity. The force exerted by active muscle is not of thermokinetic origin. Unlike resting muscle its entropy and its internal energy both decrease when its tension is rapidly lowered. The power of physiological shortening, at a rate depending on the tension, is not directly derived from elastic properties. In normal relaxation after an isometric contraction there is known to be a substantial production of heat. This is derived partly from elastic energy developed earlier during contraction, in the series elastic component: the balance is fully accounted for by the thermo­elastic heat resulting from the fall of tension.

scholarly journals Fiber Orientation and Fillers Effects on Specific Heat of Fabric Reinforced Hybrid Epoxy Composites

2019 ◽  
Vol 42 (2) ◽  
pp. 32-38
Author(s):  
Marina BUNEA ◽  
◽  
Mihaela Claudia GOROVEI ◽  
Claudia Veronica UNGUREANU ◽  
Vasile BRIA ◽  
...  
Keyword(s):  
Specific Heat ◽  
Fiber Orientation ◽  
Epoxy Composites

scholarly journals CALCULATION OF THE THERMODYNAMIC CHARACTERISTICS OF Fe – P SYSTEM BY METHOD OF MOLECULAR DYNAMICS

2019 ◽  
Vol 62 (9) ◽  
pp. 725-731
Author(s):  
A. V. Markidonov ◽  
D. A. Lubyanoi ◽  
V. V. Kovalenko ◽  
M. D. Starostenkov
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Latent Heat ◽  
Linear Expansion ◽  
Computer Experiments ◽  
Theoretical Research ◽  
P System ◽  
Thermal Coefficient ◽  
Method Of Molecular Dynamics ◽  
Coefficient Of Linear Expansion

The problem of dephosphorization of iron-carbon alloys is relevant for the metallurgical industry, since a high concentration of phosphorus contributes to the appearance of a number of extremely undesirable phenomena. A lot of experimental work has been devoted to solving this problem, but it has still not been completely possible to cope with it. Any field experiments aimed at studying the process of phosphorus removal, require considerable material and time costs, but at the same time do not guarantee getting the desired result. Therefore, to search for new approaches to solving this problem, it is much more rational to use numerical simulation methods involving the computational capabilities of modern computers. At present, computer experiments are the same recognized research method as theoretical research and real experiment. To study the behavior of phosphorus atoms in iron using a numerical experiment, it is necessary to build a computational model and test it by calculating various characteristics whose values are known in advance. In this paper, the method of molecular dynamics was chosen as the method of computer simulation. Using this method, one can conduct experiments with given atomic velocities and describe dynamics of the studied processes. To describe the interparticle interaction, we used the potential calculated in the framework of the immersed atom method. The study was conducted on a computational cell simulating α-iron crystal with phosphorus substitution atoms. The constructed model demonstrated satisfactory results when calculating the known characteristics of the simulated system. Dependences of changes in such characteristics as temperature coefficient of linear expansion, melting point, latent heat of melting and heat capacity on the concentration of phosphorus atoms, as well as in some cases on magnitude of the applied external pressure were established. Calculations showed that, for example, the phosphorus concentration of 0.5 % leads to an increase in the average thermal coefficient of linear expansion by 9 %, a decrease in temperature and latent heat of fusion by 5 % and a heat capacity by 7 %.

scholarly journals GENERATION OF NANO-FILLED EPOXY-POLYESTER COMPOSITE MATERIALS FOR PROTECTION OF ELEMENTS OF VESSEL TECHNICAL MEANS

2020 ◽  
Vol 1 (22) ◽  
pp. 154-162
Author(s):  
M. Brailo ◽  
◽  
S. Yakushchenko ◽  
O. Kobelnik ◽  
N. Buketova ◽  
...  
Keyword(s):  
Composite Material ◽  
Silicon Dioxide ◽  
Heat Resistance ◽  
Temperature Coefficient ◽  
Thermophysical Properties ◽  
Linear Expansion ◽  
Technical Equipment ◽  
Thermal Coefficient ◽  
Coefficient Of Linear Expansion ◽  
Pyrogenic Silicon Dioxide

The influence of nanofillers on thermophysical properties of epoxy-polyester composites has been investigated in the work. The filler content (oxidized nanodisperse additive and pyrogenic silicon dioxide) has been varied within q = 0.02…1.0 pts.wt. per 100 pts.wt. of epoxy oligomer ED-20. It has been discovered that the introduction of the oxidized nanodisperse additive in the amount of q = 0.05…0.08 pts.wt. into the epoxy-polyester binder leads to an improvement in the thermophysical properties of the composite. Value of heat resistance (according to Martens) increased from Т = 335 К (for the epoxy-polyester matrix) to T = 346 K at the content of oxidized nanodisperse additive of q = 0.075 pts.wt. Introduction of q = 0.05 pts.wt. of oxidized nanodisperse additive allows to obtain improved values of the temperature coefficient of linear expansion in different temperature ranges: in the region ΔT = 303…323 K – α = 1.0 × 10-5 K-1, in the region ΔT = 303… 373 K - α = 1.9 × 10-5 K-1, in the region ΔT = 303… 423 K – α = 3.4 × 10-5 K-1. It has been determined that the composite material has also improved its heat resistance (according to Martens), which is T = 347 K and the minimum thermal coefficient of linear expansion at the content of q = 0.05 pts.wt. of pyrogenic silicon dioxide nanofiller. Values of the temperature coefficient of linear expansion were: α = 1.0 × 10-5 K-1 in the region (ΔT = 303… 323 K), α = 1.9 × 10-5 K-1 (in the region ΔT = 303… 373 K), Δα = 3.4 ×× 10-5 K-1 (in the region ΔT = 303… 423 K), α = 8.4 × 10-5 K-1 (in the region ΔT = 303… 473 K). It is recommended that in order to form a composite material with improved thermophysical properties to protect the elements of ship technical equipment, it is advisable to introduce the pyrogenic silicon dioxide nanofiller in the amount of q = 0.05 pts.wt. into the epoxy-polyester binder.

Aluminum-Clad Invar Super Heat-Resistant Aluminium Alloy Stranded Wire Sag Calculation

2013 ◽  
Vol 441 ◽  
pp. 58-61 ◽  
Author(s):  
Guo Ju Han
Keyword(s):  
Aluminum Alloy ◽  
Linear Expansion ◽  
Flow Characteristics ◽  
Load Flow ◽  
Linear Expansion Coefficient ◽  
Point Temperature ◽  
Practical Algorithm ◽  
The Wire ◽  
Coefficient Of Linear Expansion ◽  
Current Reality

Comparison with conventional ACSR aluminum clad ultra-resistant aluminum alloy invar wire with low sag, load flow characteristics, linear expansion coefficient of the wire there is migration point, the migration point temperature coefficient of linear expansion around the wire is different, therefore can not be directly calculated using the equation of state migration point directly after the aluminum clad super-resistant aluminum alloy invar wire sag. This combined with engineering examples, the wire sag derived formulas, combined with the current reality of the design units, presents a practical algorithm for reference.

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