RU164403U1 - SCHEME OF HEAT PROTECTIVE COATING BASED ON GRADIENT POROUS CARBON-CERAMIC COMPOSITE MATERIAL - Google Patents

Abstract

1. Heat-resistant coating, characterized by a composition of layers of a woven and non-woven carbon skeleton and a matrix containing carbon and silicon carbide components, and related to coatings of substantially anisotropic materials with different physical-mechanical and thermal characteristics of both layers and the thickness of the material, namely, having a scheme consisting of five successive layers: the first outer (frontal) layer of carbon-ceramic composite material (UKKM) based on fabric o carbon skeleton with a residual porosity of less than 5% and a thickness of 3 to 5 mm to provide heat and oxidation resistance, the second layer under the first layer of at least 5 mm thick of a carbon-ceramic composite material based on a non-woven carbon skeleton with a residual porosity of at least 18 %, the third layer under the second layer with a thickness of at least 5 mm from a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 22%, the fourth layer under the third layer with a thickness of not less than 5 mm from a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 38%, the fifth layer under the fourth layer of a thickness of at least 5 mm from a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 48% At the same time, the heat-shielding coating is multiple, namely at least 10 cycles with a duration of each cycle of at least 5 minutes, is operable under thermal loads up to temperatures of 2000 K in an oxidizing environment. 2. Thermal insulation coating according to claim 1, characterized

Description

Technical field

The utility model relates to heat-shielding composite coatings that can be used in aviation and rocket and space technology.

State of the art

A number of patents are known for thermal protection coatings for the protection of aerospace aircraft, namely: RU 2497783, RU 2482146.

However, all these coatings are weakly correlated with the proposed utility model.

The author’s article “Prediction of the thermophysical and thermomechanical characteristics of porous carbon-ceramic composite materials for the thermal protection of aerospace aircraft” is published, published by the Engineering Physics Journal, 2015, Volume 88, No. 3 (MAY-JUN), under the agreement on the provision of subsidy No. 14.577. 21.0099 between the Ministry of Education and Science of the Russian Federation and MSTU. N.E. Bauman, where the results of studies of the thermophysical and thermomechanical characteristics of porous carbon-ceramic composite materials (UKKM) of thermal protection of aerospace aircraft are presented.

However, this article does not present specific results in the form of a description of a multilayer heat-protective coating scheme based on a gradient porous UKKM.

Utility Model Disclosure

A non-ablative (insufferable) heat-resistant heat-resistant coating with a maximum working temperature in an oxidizing environment up to 2000 K consists of layers of a woven and non-woven carbon skeleton and a matrix containing carbon and silicon carbide components, and refers to coatings of substantially anisotropic materials with physico-mechanical and thermophysical characteristics of both layers and the thickness of the material. A coating is proposed consisting of five layers arranged in series: the first outer (frontal) layer of carbon-ceramic composite material (UKKM) based on a woven carbon frame with a residual porosity of less than 5% and a thickness of 3 to 5 mm to provide heat and oxidation resistance, the second layer under the first layer of at least 5 mm thick of a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 18%, the third layer under the second layer is at least 5 mm from a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 22%, the fourth layer under the third layer of at least 5 mm thick from a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 38 %, the fifth layer under the fourth layer is at least 5 mm thick of a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 48%. The heat-shielding coating maintains its operability with at least 10 loading cycles with a duration of each cycle of not more than 5 minutes in an oxidizing medium at a temperature of 2000 K.

As a filler for a heat-protective material based on a gradient porous UKKM, carbon fibers from artificial cellulose fiber, carbon fibers from PAN fiber and carbon fibers from pitch can be used.

List of figures

FIG. 1 - Photograph of the microstructure of the UKKM layer.

FIG. 2 - A geometric model of a representative microstructure element of UKKM based on carbon fabric of plain weaving with a residual porosity of 20%.

FIG. 3 - Geometric models of a representative element of the microstructure of UKKM based on a non-woven frame with a residual porosity of 20 (a), 25 (b), 40 (c) and 50% (g)

FIG. 4 - Change in thermal conductivity coefficients of UKKM on the basis of a non-woven frame depending on its residual porosity along the X and Y axes in the reinforcement plane and along the Z axis in the direction perpendicular to the reinforcement plane

FIG. 5 - Change in linear thermal expansion coefficients (CTE) of a UKKM based on a nonwoven carcass depending on its residual porosity along the X and Y axes in the reinforcement plane and along the Z axis in the direction perpendicular to the reinforcement plane.

FIG. 6 - Temperature difference across the thickness of the experimental samples from UKKM under the action of operational loads, K.

Utility Model Implementation

In accordance with the terms of reference for applied research (PNI) under the agreement on the provision of subsidies No. 14.577.21.0099 between the Ministry of Education and Science of the Russian Federation and MSTU. N.E. Bauman as experimental samples of heat-protective coatings from layers of porous and gradient heat-resistant UKKM were considered:

- flat samples measuring 50 × 50 mm and a thickness of 5 mm;

- cylindrical samples with a diameter of 70 mm and a height of 70 mm.

As samples of structural elements of coatings made of porous and gradient heat-resistant UKKM were considered:

- structural elements of conical shape with a diameter of 100 mm and a height of 200 mm;

- structural elements of cylindrical shape with a diameter of up to 100 mm and a height of up to 200 mm.

In FIG. 1, 2, 3 are presented respectively: photograph of the microstructure of the UKKM layer; a geometric model of a representative microstructure element of UKKM based on carbon fabric of plain weaving with a residual porosity of 20%; as well as geometric models of a representative element of the UKKM microstructure based on a non-woven frame with a residual porosity of 20 (a), 25 (b), 40 (c) and 50% (d). Geometric models were used in the computer simulation of thermomechanical processes in coating samples in order to evaluate the thermophysical and thermomechanical characteristics of UKKM. As a filler for a heat-protective material based on a gradient porous UKKM, carbon fibers from artificial cellulose fiber, carbon fibers from PAN fiber and carbon fibers from pitch can be used.

Based on parametric modeling, calculated data were obtained on the thermophysical and thermomechanical characteristics of UKKM based on a woven and non-woven reinforcing frame depending on the residual porosity, which are presented in Table 1, 2 and in FIG. 4, 5.

In FIG. Figure 4 shows the calculated data on the change in the thermal conductivity coefficients of a UKKM based on a nonwoven carcass depending on the residual porosity (the X, Y axes are in the reinforcement plane, the Z axis is perpendicular to the reinforcement plane), and in FIG. 5 - calculated data on the change in the CTE of the UKKM based on the non-woven frame depending on the residual porosity (X, Y axis in the reinforcement plane, Z axis perpendicular to the reinforcement plane), K ^-1

The results obtained made it possible to evaluate the relationship between thermophysical and thermomechanical characteristics, the UKKM density and the residual porosity. Based on the calculated data on the parametric analysis, the temperature distribution in the experimental samples and prototypes of structural elements was estimated to ensure the minimum temperature on the back surface and the mass of the gradient thermal protection.

To calculate the temperature distribution in the samples and samples of structural elements, to calculate the stress-strain state with a different type of UKKM structure, we used the method of mathematical modeling - the finite element method. On the basis of geometric models finite element models were constructed, and, to obtain mesh-independent solutions, calculations were performed on grids with varying degrees of element discreteness.

Figure 6 presents graphs of temperature gradients along the thickness of the experimental samples from UKKM under the action of operational loads, K.

To assess the mass efficiency, together with the heat-insulating ability, we compared the mass of experimental samples from different types of CCM. The following values were obtained by weight of the experimental samples:

- UKKM on the basis of a woven frame without residual porosity: 0.0227 kg;

- UKKM based on a woven frame with residual porosity: 0.0205 kg;

- UKKM based on a non-woven frame with a residual porosity of 20%: 0.0192 kg;

- UKKM on the basis of a nonwoven frame with a residual porosity of 25%: 0.0173 kg;

- UKKM on the basis of a non-woven frame with a residual porosity of 40%: 0.0151 kg;

- UKKM on the basis of a nonwoven frame with a residual porosity of 50%: 0.0142 kg.

The results made it possible to identify patterns of influence of the UKKM type on the heat-insulating properties and mass efficiency of experimental samples. It was determined that the smallest mass and the highest thermal insulation ability is provided by UKKM based on a non-woven frame with a residual porosity of 50%, however, this material has low strength characteristics in comparison with UKKM based on a woven frame that has the highest density. In this connection, for the rational and effective design of multilevel protection systems for uncooled heat-stressed structural elements of rocket and space technology from UKKM, it is necessary to alternate layers of material with different densities to create gradient structures. To solve this problem, it was necessary to simulate the temperature and stress-strain state of the gradient structure, which will allow us to evaluate the contribution of each layer, as well as the influence of various thermal and thermophysical characteristics on the overall performance.

The use of an outer layer based on a woven carbon skeleton with a residual porosity of less than 5% (i.e., practically without residual porosity) and a thickness of 3 to 5 mm is due to the need to ensure thermal stability and operability of the gradient material when exposed to significant temperature, power and oxidative loads on the front surface. The choice of the sequence of layers from highly porous to as dense is due to the technological features of the process of compaction with a silicon carbide matrix, where in the process of obtaining coating layers, you can control the deposition zone of the layers.

Taking into account the numerous experimental results obtained, computer simulation of the distribution of temperature fields, temperature displacements, thermal stresses in different directions and planes, and mass data in experimental samples of porous and gradient UKCMs, and a mass data, an option for combining UKKM layers with a woven and non-woven reinforcing frame was selected to create effective thermal protection of rocket and space technology, which is presented in the formula and The proposed utility model. The proposed coating must withstand at least 10 cycles of thermal loading in an oxidizing environment lasting up to 5 minutes each at a temperature level of 2000 K.

At the subsequent stages of the PNI, by agreement No. 14.577.21.0099, the production of prototypes of this coating scheme and their full-scale testing are to be carried out.

Claims (2)

1. Heat-resistant coating, characterized by a composition of layers of a woven and non-woven carbon skeleton and a matrix containing carbon and silicon carbide components, and related to coatings of substantially anisotropic materials with different physical-mechanical and thermal characteristics of both layers and the thickness of the material, namely, having a scheme consisting of five successive layers: the first outer (frontal) layer of carbon-ceramic composite material (UKKM) based on fabric o carbon skeleton with a residual porosity of less than 5% and a thickness of 3 to 5 mm to provide heat and oxidation resistance, the second layer under the first layer of at least 5 mm thick of a carbon-ceramic composite material based on a non-woven carbon skeleton with a residual porosity of at least 18 %, the third layer under the second layer with a thickness of at least 5 mm from a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 22%, the fourth layer under the third layer with a thickness of not less than 5 mm from a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 38%, the fifth layer under the fourth layer of a thickness of at least 5 mm from a carbon-ceramic composite material based on a non-woven carbon frame with a residual porosity of at least 48% At the same time, the heat-shielding coating is repeatedly, namely at least 10 cycles with a duration of each cycle of at least 5 minutes, operable under thermal loads up to temperatures of 2000 K in an oxidizing environment. 2. The heat-shielding coating according to claim 1, characterized in that carbon fibers from artificial cellulose fiber, carbon fibers from PAN fiber and carbon fibers from pitch can be used as filler for heat-protective material based on gradient porous UKKM.

Images