GB/T 3139-2005Fiber-reinforced plastics composites-Determination of thermal conductivity (English PDF)

3.1 Heat flow rate

The heat passing through a surface per unit time. [GB/T 3102.4-1993, definition 4-7]

3.2 Density of heat flow rate

The heat flow rate per unit area perpendicular to the direction of heat flow. [GB/T 4132-1996, definition 6.2.3]

3.3 Thermal conductivity

A physical indicator of the thermal conductivity of a material. The value is equal to the density of heat flow rate divided by the negative temperature gradient. [GB/T 4132-1996, definition 6.2.5]

3.4 Mean temperature

In the steady state, the arithmetic average of the high-temperature surface's temperature and low-temperature surface's temperature of the specimen; it can also be referred to as the average temperature for short.

3.5 Temperature difference

In the steady state, the difference between the high-temperature surface's temperature and the low-temperature surface's temperature of the specimen.

6.1 Heating plate

The heating plate is composed of a main heating plate, a guard heating plate with a certain gap surrounding the main heating plate, a bottom heating plate.

Each heating plate has an independent heater and a surface plate.

6.1.1 The side length or diameter of the heating plate is generally 100 mm; the width of the guard heating plate is 1/4 of the side length or diameter of the heating plate, with proper insulation measures. If there are special measures to ensure that the measurement error of the thermal conductivity coefficient is within 8%, this value can also be changed appropriately.

6.1.2 The temperature difference at each point on the surface of the heating plate is not more than 2% of the temperature difference between the two sides of the specimen under the steady state, meanwhile the maximum shall not be Water inlet Water outlet more than 0.5 °C. The temperature difference at each point on the surface of the guard heating plate shall not be more than 5% of the temperature difference between the two sides of the specimen in the steady state; meanwhile the maximum shall not be more than 1 °C.

6.1.3 The unevenness of the heating plate surface shall not be greater than 0.25 mm/m.

6.2 Cooling plate

The cooling plate shall have an internal threaded two-way liquid loop; the size of the cooling plate and the surface state of the contact specimen are the same as the heating plate, but the cooling plate is not spaced.

6.3 Temperature and power measurement accuracy

The temperature measurement shall be accurate to 1% of the temperature difference between the two sides of the specimen in the steady state; but the maximum shall not be greater than 0.5 °C.

Measure the power of the main heating plate, which shall be accurate to 1%.

7.1 Test environment

The test environmental conditions shall comply with the provisions of Chapter 3 of GB/T 1446-2005.

7.2 Specimen temperature and temperature difference

The temperature of the heating plate generally does not exceed 260 °C; the temperature of the cold plate rises from room temperature to the required temperature. The temperature difference between the two sides of the specimen is not less than 10 °C.

8.1 Visual inspection of specimen

The appearance inspection of the specimen is in accordance with the provisions of 4.2 in GB/T 1446-2005; the unevenness of the specimen surface is inspected with a knife-shaped flat ruler.

8.2 Conditioning of specimen state

The state of the specimen is conditioned according to the provisions of 4.4 in GB/T 1446-2005, or according to the technical requirements of the product.

8.3 Measurement of specimen thickness

Measure the thickness of the specimen at least 4 times, accurate to 0.01 mm; take the arithmetic average.

8.4 Specimen installation

When installing the specimen, pay attention to eliminate the air interlayer and apply a certain pressure to the specimen.

8.5 Conditioning balance

Adjust the temperature difference between the main heating plate and the guard heating plate and between the main heating plate and the bottom heating plate to achieve a balance. The test error of thermal conductivity coefficient as caused by the imbalance shall not exceed 1%.

8.6 Measurement

After reaching a steady state, measure the power of the main heating plate and the temperature difference between the two sides of the specimen, then the test can be ended. The so-called steady state means that the fluctuation of surface temperature of the specimen within 30 min is not more than 1% of the temperature difference between the two sides of the specimen under the condition that the power of the main heating plate remains unchanged; meanwhile the maximum shall not be greater than 1 °C.