Temperature In Composite Materials Research Articles

Establishing the influence of the type of micro- and nanofillers on the thermophysical properties of highly heat conductive polymer composites based on polyamide 6

The object of this study is the thermophysical properties of polymer micro- and nanocomposites, as well as the dependence of their heat conductivity with structural characteristics when using different types of fillers. A set of experimental studies of heat conductivity and specific heat capacity of polymer micro- and nanocomposite materials for polyamide 6 and carbon nanotubes, copper and aluminum as matrix and fillers was carried out. When obtaining composites, a method was used that is based on the mixing of components in the polymer melt. The content of fillers varied from 0.3 to 10 %, and the temperature of composite materials – from 305 to 500 K. Experimental dependences of heat conductivity coefficients of the studied composites on the content of the filler were derived. It was established that according to the value of these coefficients in order of their reduction, these composite materials are ranked as follows: composites with fillers with carbon nanotubes, copper, and aluminum. It was found that only one percolation threshold is observed, when using a polyamide 6 matrix. The regularities of changes in the specific heat capacity of the composites under consideration on their temperature when varying within the above limits of the filler content were investigated. The analysis of the influence of the content of fillers on the degree of crystallinity of the polymer matrix of the investigated composite materials was carried out. It is shown that with an increase in the content of fillers, the degree of crystallinity decreases. The relationship between the thermally conductive properties of the composites under consideration and the specified degree of crystallinity has been established. Higher values of heat conductivity of composites correspond to lower values of the degree of crystallinity. The reported results can be widely used in the development of highly heat conductive composites for various engineering applications.

Modelling the Heating Process in the Transient and Steady State of an In Situ Tape-Laying Machine Head

As the use of composite materials increases, the search for suitable automated processes gains relevance for guaranteeing production quality by ensuring the uniformity of the process, minimizing the amount of scrap generated, and reducing the time and energy consumption. Limitations on production by traditional means such as hand lay-up, vacuum bagging, and in-autoclave methods tend not to be as efficient when the size and shape complexity of the part being produced increases, motivating the search for alternative processes such as automated tape laying (ATL). This work aims to describe the process of modelling and simulating a composite ATL with in situ consolidation by characterizing the machine elements and using the finite differences method in conjunction with energy balances in order to create a digital twin of the process for further control design. The modelling approach implemented is able to follow the process dynamics when changes are made to the heating element and to predict the composite material temperature response, making it suitable for use as a digital twin of a production process using an ATL machine.

Application of a Pyrometer and Standard Sample to Determine The Surface Temperature of Materials Under Study

The methodology of determining the surface temperature of composite materials with unknown emissivity is studied. The methodology is implemented by using a standard sample of spectral normal emissivity over the range of wavelengths 1.65–1.80 μm and the industrially produced Metis M322 pyrometer functioning in the same range. The surface temperatures of the composite material under study and platinum, with significantly different values of spectral normal emissivity is determined by the temperature of the standard sample mounted on the materials under study, as measured by the pyrometer. The relative methodological error of determination of the surface temperature of materials under study did not exceed 1.7 and 0.5%, respectively, for the composite material and platinum for surface temperatures approximately 973 K. In the calculation of the error, the results of measuring the surface temperatures of the materials under study were used, obtained taking into account the temperature of the standard sample and in the absence of a standard sample. The imprecision of a priori data regarding emissivity of a standard sample in the interval (–0.01; 0.01) relative to the mean emissivity, equal to 0.19, increases the relative error of determination of the temperature of the composite material by 0.68%. Installation of a standard sample on the materials under study results in temperature modifications on the periphery of the surface, not exceeding 0.47 and 0.05%, respectively, for the composite material and platinum.

Crystallization Kinetics of Composite Materials Based on Polyethylene Mixture with High and Low Density

The influence of the ratio of high-density polyethylene and low-density polyethylene on the regular changes in breaking stress, tensile yield stress, elongation, and chilling temperature of composite materials are considered. In accordance with the Avrami equation, the formation and development of crystallization centers in a zone of the first-order phase transition are investigated.

Enhancement of electrocaloric response through quantum effects

A semiclassical approach that incorporates quantum mechanical behavior of heat capacity in direct caloric effect simulations is proposed. Application of this methodology to study electrocaloric effect in prototypical ferroelectrics ${ \rm PbTiO_3 }$, and ${ \rm BaTiO_3 }$, reveals severe underestimation of electrocaloric response at lowest temperatures by classical simulations. The discrepancy between semiclassical and classical results are found to be largest in ferroics with Debye temperature exceeding the Curie point. A route to enhance electrocaloric effect by tuning the Debye temperature in composite materials is proposed.

A multi-pattern compensation method to ensure even temperature in composite materials during microwave curing process

Microwave curing technologies have many advantages in manufacturing fiber reinforced polymer composite materials used in aerospace products, compared with traditional autoclave curing technologies. However, the uneven electromagnetic field of microwave in the cavity of the curing chamber results in uneven temperature on the surface of composite laminates during curing, which has been a major obstacle in industrial applications worldwide. Existing methods attempted to solve the problem by the random superposition of uneven electromagnetic fields, but the results were still not satisfactory to meet the high quality requirements of aerospace parts. This paper reveals the one-to-one correspondence between heating patterns of composite parts and microwave curing system settings, and reports a new concept to solve this problem by continuously monitoring and compensating the uneven temperature distribution in real-time. Experimental results from both fiber optical fluorescencesensors and infrared thermal imagers showed significant improvement in temperature uniformity compared with existing methods.

A multi-pattern compensation method to ensure even temperaturein composite materials during microwave curing process

Microwave curing technologies have many advantages in manufacturing fiber reinforced polymer composite materials used in aerospace products, compared with traditional autoclave curing technologies. However, the uneven electromagnetic field of microwave in the cavity of the curing chamber results in uneven temperature on the surface of composite laminates during curing, which has been a major obstacle in industrial applications worldwide. Existing methods attempted to solve the problem by the random superposition of uneven electromagnetic fields, but the results were still not satisfactory to meet the high quality requirements of aerospace parts. This paper reveals the one-to-one correspondence between heating patterns of composite parts and microwave curing system settings, and reports a new concept to solve this problem by continuously monitoring and compensating the uneven temperature distribution in real-time. Experimental results from both fiber optical fluorescence sensors and infrared thermal imagers showed significant improvement in temperature uniformity compared with existing methods.

Simple method of calculating the transient thermal performance of composite material and its applicable condition

Degree of mixing of composite material is defined and the condition of using the effective thermal diffusivity for calculating the transient thermal performance of composite material is studied. The analytical result shows that for a prescribed precision of temperature, there is a condition under which the transient temperature distribution in composite material can be calculated by using the effective thermal diffusivity. As illustration, for the composite material whose temperatures of both ends are constant, the condition is presented and the factors affecting the relative error of calculated temperature of composite materials by using effective thermal diffusivity are discussed.

Mechanical evaluation of SiC particle reinforced oxynitride glass and glass-ceramic composites

In silicon oxynitride glasses, the nitrogen occupies anion sites and is bonded to three silicons. Hence, replacement of divalent oxygen ions by trivalent nitrogen ones results in a considerable improvement of the mechanical resistance. In this exploratory work, the authors investigate some basic mechanical properties at room temperature of composite materials prepared by adding some SiC particles to a highly refractory Y-Mg-Si-Al-O-N oxynitride glass. Taking advantage of both constituents, the brittle particulate composites exhibit much better fracture strength and toughness and higher elastic moduli than the glassy matrix. Due to the easy crystallization of the selected glass, a further improvement is attainable through a crystallization treatment of the matrix. Fracture toughness and Young's modulus as high as 5.4 MPa.m[sup 0.5] and 215 GPa respectively have been measured on the glass-ceramic composite containing 50 vol.% SiC.

Shock Parameters in a Two Component Mixture

A thermodynamically consistent procedure, based on the Gibbs free energy, is described for computing the thermodynamic properties of a mixture in equilibrium at constant pressure and temperature. This is used to compute temperatures, pressures, Gruneisen parameters and sound velocities on the Hugoniot for mixtures of polyethylene and quartz. The results show that a simple mass-weighted average for the Gruneisen parameter is inaccurate and that the mixture of two mate rials for which Γ/V = constant does not itself have a constant value of r/V. Some comments are made on problems of equilibrium of stress and temperature in composite materials.