GB/T 3139-2026 Test methods for thermal conductivity of fiber reinforced plastics English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS
CCS
National Standard of the People's Republic of China
GB/T 3139-2026
Test methods for thermal conductivity of fiber reinforced plastics
纤维增强塑料导热系数试验方法
Issue date: 2026-01-28 Implementation date: 2027-02-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Guarded Hot Plate Method (Method A)
5 Guarded Heat Flow Meter Method (Method B)
6 Flash Method (Method C)
7 Test Report
Test method for thermal conductivity of fiber reinforced plastics
1 Scope
This document describes the principles, test specimens, testing instruments, test conditions, test procedures, calculation of results and test reports for the determination of thermal conductivity of fiber reinforced plastics by the guarded hot plate method (Method A), the guarded heat flow meter method (Method B) and the flash method (Method C).
This document is applicable to the determination of thermal conductivity of fiber reinforced plastics. Composite materials with other structural forms may use this document as a reference. The guarded hot plate method (Method A) and the guarded heat flow meter method (Method B) are steady-state heat transfer test methods, while the flash method (Method C) is a transient heat transfer test method.
2 Normative References
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 1446, General principles for test methods for properties of fiber reinforced plastics
GB/T 3961, Terms for fiber reinforced plastics
GB/T 22588, Determination of thermal diffusivity or thermal conductivity by the flash method
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 3961 and the following apply.
3.1
heat flow rate
amount of heat passing through a given area per unit time
3.2
density of heat flow rate
heat flow rate (3.1) per unit area
3.3
thermal conductivity
density of heat flow rate (3.2) per unit temperature gradient
3.4
mean temperature
arithmetic mean of the high-temperature surface temperature and the low-temperature surface temperature of the test specimen under steady-state heat transfer conditions (i.e., where the temperature distribution within the material does not change with time)
3.5
thermal resistance
temperature difference between two surfaces perpendicular to the direction of heat flow divided by the density of heat flow rate (3.2) under steady-state heat transfer conditions
4 Guarded Hot Plate Method (Method A)
4.1 Principle
In the guarded hot plate method (Method A), under steady-state heat transfer conditions, unidirectional heat flow passes perpendicularly through a plate-shaped test specimen. The thermal conductivity of the test specimen can be calculated by measuring the one-dimensional constant heat flow rate over a given heat transfer area and the temperature difference between the hot and cold surfaces of the test specimen.
4.2 Test Specimen
4.2.1 The test specimen shall be prepared in accordance with the provisions of GB/T 1446.
4.2.2 The dimensions of the test specimen are specified as follows:
a) The test specimen may be square or circular. The side length or diameter of the test specimen shall be equal to that of the heating plate (see a or D0 in Figure 2). For a single-specimen apparatus, the side length or diameter of the test specimen should be 100 mm; for a double-specimen apparatus, the side length or diameter of the test specimen should be 300 mm. The dimensional error should not exceed ±0.6 mm.
b) The thickness of the test specimen shall be at least 5 mm and should preferably not exceed 1/10 of its side length or diameter.
4.2.3 The upper and lower surfaces of the test specimen shall be parallel and flat. The flatness error shall not exceed 0.50 mm/m, and the parallelism error shall be within 1.0% of the test specimen thickness.
4.2.4 Each group of test specimens shall consist of no fewer than 3 specimens.
4.3 Test Instruments
4.3.1 Testing apparatus
The guarded hot plate method (Method A) thermal conductivity test instruments are generally divided into two types: single-specimen apparatus and double-specimen apparatus.
In a single-specimen apparatus, the test specimen is placed on the upper surface of the heating plate, while the lower surface of the heating plate is provided with insulating material and a bottom heating plate, as shown in Figure 1a). The temperature difference between the upper and lower surfaces of the insulating material shall be controlled to not exceed 0.5 °C.
In a double-specimen apparatus, two identical test specimens are placed on both the upper and lower surfaces of the heating plate, as shown in Figure 1b).
4.3.2 Heating plate
4.3.2.1 The heating plate consists of a main heating plate and a guard heating plate that surrounds the main heating plate with a certain gap. Each heating plate has independent heaters and surface plates.
4.3.2.2 The width of the guard heating plate shall be 1/4 of the side length or diameter of the heating plate, as shown in Figure 2, and appropriate thermal insulation measures shall be provided. Other dimensions shall ensure that the error in the measured thermal conductivity value is within 8%.
4.3.2.3 The temperature difference at points on the surface of the main heating plate shall not exceed 2% of the temperature difference between the two surfaces of the test specimen under steady-state heat transfer conditions. The temperature difference at points on the surface of the guard heating plate shall not exceed 5% of the temperature difference between the two surfaces of the test specimen under steady-state heat transfer conditions.
4.3.2.4 The two surfaces of the heating plate shall be parallel and flat, with a flatness error not exceeding 0.25 mm/m.
4.3.2.5 The area occupied by the gap between the main heating plate and the guard heating plate within the surface of the heating plate should not exceed 5% of the area of the main heating plate.
4.3.3 Cooling plate
The dimensions and surface condition of the cooling plate in contact with the test specimen shall be the same as those of the heating plate, but the cooling plate is not provided with a gap.
4.3.4 Temperature and power measurement accuracy
4.3.4.1 Temperature measurement shall be accurate to 1% of the temperature difference between the two surfaces of the test specimen under steady-state heat transfer conditions, but not more than 0.5 °C.
4.3.4.2 The power supplied to the main heating plate shall be measured with an accuracy of 1%.
4.4 Test Conditions
4.4.1 Test environment
The test environmental conditions shall comply with the provisions of GB/T 1446.
4.4.2 Temperature difference across the test specimen
The temperature difference between the hot and cold surfaces of the test specimen should preferably be not less than 10 °C.
4.5 Test Procedure
4.5.1 The test specimen shall be visually inspected in accordance with the provisions of GB/T 1446. The flatness error of the specimen surface shall be checked using a straightedge.
4.5.2 The test specimen shall be conditioned in accordance with the provisions of GB/T 1446 or treated according to the product technical requirements.
4.5.3 Measure the thickness of the test specimen at no fewer than 5 positions, including the centre, edges and other locations. Calculate the arithmetic mean value, accurate to 0.01 mm.
4.5.4 Open the test chamber. For a single-specimen apparatus, install the single test specimen on the upper surface of the heating plate. For a double-specimen apparatus, install the two test specimens on both the upper and lower surfaces of the heating plate. When installing the test specimens, move them laterally to eliminate trapped air, apply a certain pressure, and ensure that the specimens are properly aligned with the surface of the heating plate.
4.5.5 Start the testing apparatus and adjust the temperatures of the main heating plate, guard heating plate and bottom heating plate. When the temperature difference between the main heating plate and the guard heating plate, as well as between the main heating plate and the bottom heating plate, does not exceed 0.5 °C, and the temperature fluctuations of the main heating plate, guard heating plate and bottom heating plate do not exceed 0.5 °C for a duration of no less than 10 min, equilibrium is reached. Record the temperatures of the main heating plate, guard heating plate and bottom heating plate at this time, and maintain the test specimen at this temperature.
4.5.6 With the power of the main heating plate unchanged, when the surface temperature fluctuation of the test specimen is not more than 1% of the temperature difference between the two surfaces of the test specimen, and does not exceed 0.5 °C, for a duration of no less than 30 min, steady-state heat transfer conditions are reached. Record the power of the main heating plate and the temperatures of the two surfaces of the test specimen at this time. The current test ends.
4.6 Calculation of Results
4.6.1 Calculation of thermal conductivity for a single-specimen apparatus
The thermal conductivity for a single-specimen apparatus shall be calculated using Formula (1), retaining 3 significant figures.
Calculate the thermal conductivity of each test specimen and take the arithmetic mean value.
4.6.2 Calculation of thermal conductivity for a double-specimen apparatus
Standard
GB/T 3139-2026 Test methods for thermal conductivity of fiber reinforced plastics (English Version)
Standard No.
GB/T 3139-2026
Status
to be valid
Language
English
File Format
PDF
Word Count
10000 words
Price(USD)
300.0
Implemented on
2026-12-1
Delivery
via email in 1~5 business day
Detail of GB/T 3139-2026
Standard No.
GB/T 3139-2026
English Name
Test methods for thermal conductivity of fiber reinforced plastics
GB/T 3139-2026 Test methods for thermal conductivity of fiber reinforced plastics English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS
CCS
National Standard of the People's Republic of China
GB/T 3139-2026
Test methods for thermal conductivity of fiber reinforced plastics
纤维增强塑料导热系数试验方法
Issue date: 2026-01-28 Implementation date: 2027-02-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Guarded Hot Plate Method (Method A)
5 Guarded Heat Flow Meter Method (Method B)
6 Flash Method (Method C)
7 Test Report
Test method for thermal conductivity of fiber reinforced plastics
1 Scope
This document describes the principles, test specimens, testing instruments, test conditions, test procedures, calculation of results and test reports for the determination of thermal conductivity of fiber reinforced plastics by the guarded hot plate method (Method A), the guarded heat flow meter method (Method B) and the flash method (Method C).
This document is applicable to the determination of thermal conductivity of fiber reinforced plastics. Composite materials with other structural forms may use this document as a reference. The guarded hot plate method (Method A) and the guarded heat flow meter method (Method B) are steady-state heat transfer test methods, while the flash method (Method C) is a transient heat transfer test method.
2 Normative References
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 1446, General principles for test methods for properties of fiber reinforced plastics
GB/T 3961, Terms for fiber reinforced plastics
GB/T 22588, Determination of thermal diffusivity or thermal conductivity by the flash method
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 3961 and the following apply.
3.1
heat flow rate
amount of heat passing through a given area per unit time
3.2
density of heat flow rate
heat flow rate (3.1) per unit area
3.3
thermal conductivity
density of heat flow rate (3.2) per unit temperature gradient
3.4
mean temperature
arithmetic mean of the high-temperature surface temperature and the low-temperature surface temperature of the test specimen under steady-state heat transfer conditions (i.e., where the temperature distribution within the material does not change with time)
3.5
thermal resistance
temperature difference between two surfaces perpendicular to the direction of heat flow divided by the density of heat flow rate (3.2) under steady-state heat transfer conditions
4 Guarded Hot Plate Method (Method A)
4.1 Principle
In the guarded hot plate method (Method A), under steady-state heat transfer conditions, unidirectional heat flow passes perpendicularly through a plate-shaped test specimen. The thermal conductivity of the test specimen can be calculated by measuring the one-dimensional constant heat flow rate over a given heat transfer area and the temperature difference between the hot and cold surfaces of the test specimen.
4.2 Test Specimen
4.2.1 The test specimen shall be prepared in accordance with the provisions of GB/T 1446.
4.2.2 The dimensions of the test specimen are specified as follows:
a) The test specimen may be square or circular. The side length or diameter of the test specimen shall be equal to that of the heating plate (see a or D0 in Figure 2). For a single-specimen apparatus, the side length or diameter of the test specimen should be 100 mm; for a double-specimen apparatus, the side length or diameter of the test specimen should be 300 mm. The dimensional error should not exceed ±0.6 mm.
b) The thickness of the test specimen shall be at least 5 mm and should preferably not exceed 1/10 of its side length or diameter.
4.2.3 The upper and lower surfaces of the test specimen shall be parallel and flat. The flatness error shall not exceed 0.50 mm/m, and the parallelism error shall be within 1.0% of the test specimen thickness.
4.2.4 Each group of test specimens shall consist of no fewer than 3 specimens.
4.3 Test Instruments
4.3.1 Testing apparatus
The guarded hot plate method (Method A) thermal conductivity test instruments are generally divided into two types: single-specimen apparatus and double-specimen apparatus.
In a single-specimen apparatus, the test specimen is placed on the upper surface of the heating plate, while the lower surface of the heating plate is provided with insulating material and a bottom heating plate, as shown in Figure 1a). The temperature difference between the upper and lower surfaces of the insulating material shall be controlled to not exceed 0.5 °C.
In a double-specimen apparatus, two identical test specimens are placed on both the upper and lower surfaces of the heating plate, as shown in Figure 1b).
4.3.2 Heating plate
4.3.2.1 The heating plate consists of a main heating plate and a guard heating plate that surrounds the main heating plate with a certain gap. Each heating plate has independent heaters and surface plates.
4.3.2.2 The width of the guard heating plate shall be 1/4 of the side length or diameter of the heating plate, as shown in Figure 2, and appropriate thermal insulation measures shall be provided. Other dimensions shall ensure that the error in the measured thermal conductivity value is within 8%.
4.3.2.3 The temperature difference at points on the surface of the main heating plate shall not exceed 2% of the temperature difference between the two surfaces of the test specimen under steady-state heat transfer conditions. The temperature difference at points on the surface of the guard heating plate shall not exceed 5% of the temperature difference between the two surfaces of the test specimen under steady-state heat transfer conditions.
4.3.2.4 The two surfaces of the heating plate shall be parallel and flat, with a flatness error not exceeding 0.25 mm/m.
4.3.2.5 The area occupied by the gap between the main heating plate and the guard heating plate within the surface of the heating plate should not exceed 5% of the area of the main heating plate.
4.3.3 Cooling plate
The dimensions and surface condition of the cooling plate in contact with the test specimen shall be the same as those of the heating plate, but the cooling plate is not provided with a gap.
4.3.4 Temperature and power measurement accuracy
4.3.4.1 Temperature measurement shall be accurate to 1% of the temperature difference between the two surfaces of the test specimen under steady-state heat transfer conditions, but not more than 0.5 °C.
4.3.4.2 The power supplied to the main heating plate shall be measured with an accuracy of 1%.
4.4 Test Conditions
4.4.1 Test environment
The test environmental conditions shall comply with the provisions of GB/T 1446.
4.4.2 Temperature difference across the test specimen
The temperature difference between the hot and cold surfaces of the test specimen should preferably be not less than 10 °C.
4.5 Test Procedure
4.5.1 The test specimen shall be visually inspected in accordance with the provisions of GB/T 1446. The flatness error of the specimen surface shall be checked using a straightedge.
4.5.2 The test specimen shall be conditioned in accordance with the provisions of GB/T 1446 or treated according to the product technical requirements.
4.5.3 Measure the thickness of the test specimen at no fewer than 5 positions, including the centre, edges and other locations. Calculate the arithmetic mean value, accurate to 0.01 mm.
4.5.4 Open the test chamber. For a single-specimen apparatus, install the single test specimen on the upper surface of the heating plate. For a double-specimen apparatus, install the two test specimens on both the upper and lower surfaces of the heating plate. When installing the test specimens, move them laterally to eliminate trapped air, apply a certain pressure, and ensure that the specimens are properly aligned with the surface of the heating plate.
4.5.5 Start the testing apparatus and adjust the temperatures of the main heating plate, guard heating plate and bottom heating plate. When the temperature difference between the main heating plate and the guard heating plate, as well as between the main heating plate and the bottom heating plate, does not exceed 0.5 °C, and the temperature fluctuations of the main heating plate, guard heating plate and bottom heating plate do not exceed 0.5 °C for a duration of no less than 10 min, equilibrium is reached. Record the temperatures of the main heating plate, guard heating plate and bottom heating plate at this time, and maintain the test specimen at this temperature.
4.5.6 With the power of the main heating plate unchanged, when the surface temperature fluctuation of the test specimen is not more than 1% of the temperature difference between the two surfaces of the test specimen, and does not exceed 0.5 °C, for a duration of no less than 30 min, steady-state heat transfer conditions are reached. Record the power of the main heating plate and the temperatures of the two surfaces of the test specimen at this time. The current test ends.
4.6 Calculation of Results
4.6.1 Calculation of thermal conductivity for a single-specimen apparatus
The thermal conductivity for a single-specimen apparatus shall be calculated using Formula (1), retaining 3 significant figures.
Calculate the thermal conductivity of each test specimen and take the arithmetic mean value.
4.6.2 Calculation of thermal conductivity for a double-specimen apparatus
