ASTM E471-22
(Test Method)Standard Test Method for Obtaining Char Density Profile of Ablative Materials by Machining and Weighing
Standard Test Method for Obtaining Char Density Profile of Ablative Materials by Machining and Weighing
ABSTRACT
This test method covers the determination of the char density profile of a charred ablator. The total thickness of the char and degradation zone must be larger than the machining thicknesses required. Density variation throughout a charred ablator material is determined by successively measuring, machining, and weighing a sample of known size to obtain the density of the material removed by machining. The apparatus required for this method includes a laboratory balance capable of measuring to the nearest ten thousandth gram, and a machining technique capable of removing material in increments as small as a thousandth mm.
SCOPE
1.1 This test method covers the determination of the char density profile of a charred ablator that can be used with the following limitations:
1.1.1 The local surface imperfections must be removed, and the char must be able to be machined off in a plane parallel to the char-virgin material interface before the density profiles can be determined.
1.1.2 The char must be strong enough to withstand the machining and handling techniques employed.
1.1.3 The material should have orderly density variations. The total thickness of the char and degradation zone must be larger than the machining thicknesses required.
1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.2.1 Exception—Certain inch-pound equivalent units are included in parentheses for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:E471 −22
Standard Test Method for
Obtaining Char Density Profile of Ablative Materials by
1
Machining and Weighing
This standard is issued under the fixed designation E471; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Theablationcharacteristicsofcharringmaterialsmustbewellknowninordertodesignthematerial
for a specific set of environmental conditions. The char density profile and the environmental
conditions under which it was formed can provide useful information about the ablation performance.
Amethod of obtaining the char density profile from a charred sample of material is described in the
following sections. Some chars are very friable and are easily broken before they can be measured.
Other chars are relatively strong and can be handled with ease. The type of char density profile
measurement described in this method is applicable if the char is strong enough to be machined
without breaking.
1. Scope ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This test method covers the determination of the char
mendations issued by the World Trade Organization Technical
density profile of a charred ablator that can be used with the
Barriers to Trade (TBT) Committee.
following limitations:
1.1.1 The local surface imperfections must be removed, and
2. Summary of Test Method
the char must be able to be machined off in a plane parallel to
the char-virgin material interface before the density profiles 2.1 Density variation throughout a charred ablator material
can be determined. is determined by successively measuring, machining, and
1.1.2 The char must be strong enough to withstand the weighing a sample of known size to obtain the density of the
machining and handling techniques employed. material removed by machining.
1.1.3 The material should have orderly density variations.
3. Apparatus
The total thickness of the char and degradation zone must be
larger than the machining thicknesses required.
3.1 The apparatus required for this method includes a
laboratory balance capable of measuring to the nearest 0.0001
1.2 Units—The values stated in SI units are to be regarded
as standard. No other units of measurement are included in this g, and a machining technique capable of removing material in
increments as small as 0.025 mm (0.001 in.). For example, flat
standard.
1.2.1 Exception—Certain inch-pound equivalent units are specimens can be machined with a surface grinder using a
medium fine grit ceramic grinding wheel of a soft grade
included in parentheses for information only.
dressed to the proper contour. Cylindrical specimens can be
1.3 This standard does not purport to address all of the
mounted in a lathe and the char can be removed with a sharp
safety concerns, if any, associated with its use. It is the
carbide or diamond tip tool.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Sampling
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor-
4.1 The charred sample selected for machining and weigh-
dance with internationally recognized principles on standard- ing should be taken from a representative section of the ablated
specimen where the environmental conditions are well known,
1
and where the surface is parallel to the char-virgin material
This test method is under the jurisdiction of ASTM Committee E21 on Space
Simulation andApplications of Space Technology and is the direct responsibility of
interface. Where large sections are available, this condition is
Subcommittee E21.08 on Thermal Protection.
usually met. For small samples which have been exposed to
Current edition approved Aug. 1, 2022. Published August 2022. Originally
varying environmental conditions along the length of the
approvedin1973.Lastpreviouseditionapprovedin2016asE471 – 96(2016).DOI:
10.1520/E0471-22. sample, the sample size will be smaller.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
E471−22
FIG. 1Typical Specimen for Measuring Char Density Profile
5. Test Specimens the machining process has resulted in a continuous surface all
over the specimen) allow the specimen to stabilize at the
5.1 A typical specimen size obtain
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E471 − 96 (Reapproved 2016) E471 − 22
Standard Test Method for
Obtaining Char Density Profile of Ablative Materials by
1
Machining and Weighing
This standard is issued under the fixed designation E471; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The ablation characteristics of charring materials must be well known in order to design the material
for a specific set of environmental conditions. The char density profile and the environmental
conditions under which it was formed can provide useful information about the ablation performance.
A method of obtaining the char density profile from a charred sample of material is described in the
following sections. Some chars are very friable and are easily broken before they can be measured.
Other chars are relatively strong and can be handled with ease. The type of char density profile
measurement described in this method is applicable if the char is strong enough to be machined
without breaking.
1. Scope
1.1 This test method covers the determination of the char density profile of a charred ablator that can be used with the following
limitations:
1.1.1 The local surface imperfections must be removed, and the char must be able to be machined off in a plane parallel to the
char-virgin material interface before the density profiles can be determined.
1.1.2 The char must be strong enough to withstand the machining and handling techniques employed.
1.1.3 The material should have orderly density variations. The total thickness of the char and degradation zone must be larger than
the machining thicknesses required.
1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard.
1.2.1 Exception—Certain inch-pound equivalent units are included in parentheses for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
1
This test method is under the jurisdiction of ASTM Committee E21 on Space Simulation and Applications of Space Technology and is the direct responsibility of
Subcommittee E21.08 on Thermal Protection.
Current edition approved April 1, 2016Aug. 1, 2022. Published April 2016August 2022. Originally approved in 1973. Last previous edition approved in 20112016 as
E471 – 96 (2011).(2016). DOI: 10.1520/E0471-96R16.10.1520/E0471-22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
E471 − 22
FIG. 1 Typical Specimen for Measuring Char Density Profile
2. Summary of Test Method
2.1 Density variation throughout a charred ablator material is determined by successively measuring, machining, and weighing a
sample of known size to obtain the density of the material removed by machining.
3. Apparatus
3.1 The apparatus required for this method includes a laboratory balance capable of measuring to the nearest 0.0001 g, and a
machining technique capable of removing material in increments as small as 0.025 mm (0.001 in.). For example, flat specimens
can be machined with a surface grinder using a medium fine grit ceramic grinding wheel of a soft grade dressed to the proper
contour. Cylindrical specimens can be mounted in a lathe and the char can be removed with a sharp carbide or diamond tip tool.
4. Sampling
4.1 The charred sample selected for machining and weighing should be taken from a representative section of the ablated specimen
where the environmental conditions are well known, and where the surface is parallel to the char-virgin material interface. Where
large sections are available, this condition is usually met. For small samples which have been exposed to varying environmental
conditions
...
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