GB/T 3855-2026Test method for the resin content of carbon fibre reinforced plastics (English PDF)

5.1 Sample Preparation

5.1.1 The test specimen should be selected from a representative part of the sample or as agreed.

5.1.2 The sample thickness shall not exceed 3 mm, the mass shall be approximately

0.5 g, and the shape shall be unrestricted, as long as it fits comfortably in a container. Each group shall contain no fewer than 3 samples. The shapes of the group of test samples should be consistent.

5.1.3 Remove oil stains from the sample surface.

5.1.4 Method B. In addition to the above requirements, the thickness of the resin-cast specimens should also be the same as that of the carbon fiber reinforced plastic specimens. The sample had a uniform thickness and a mass of approximately 0.5g.

5.2 Sample Conditioning

5.2.1 Before the test, the sample shall be placed in a desiccator for at least 24 hours.

5.2.2 Other state adjustment conditions shall be agreed upon separately.

6.1 Method A. Digestion

6.1.1 Test Instruments The testing instruments shall meet the following requirements.

a) Analytical balance. graduation value

0.1 mg;

b) Heater. Operating temperature not lower than 420°C, with an accuracy of ±10°C;

c) Beaker or flask. 250 mL in volume;

d) Acid-resistant filter. pore size 4.5µm~9.0µm;

e) Suction flask. 500mL;

f) Vacuum pump and pressure gauge. measuring range greater than 20 kPa, accuracy not less than

0.4 grade;

g) Oven. Ambient temperature ~ 300°C, accuracy ±10°C;

h) Dryer. Volume not less than 1L.

6.1.2 Test Reagents The test reagents should meet the following requirements.

a) Sulfuric acid. concentration 95%~98%, analytical grade;

b) Hydrogen peroxide. 30% concentration, analytical grade;

6.1.3.1 Weigh the sample using an analytical balance, accurate to

0.1 mg.

6.1.3.2 Place the sample in a beaker or flask, add at least 30 mL of sulfuric acid, and place it above a heater to raise the temperature to the digestion temperature. Epoxy, Poly The digestion temperature for ester-based carbon fiber reinforced plastics is 220°C±10°C. The digestion temperature for phenolic carbon fiber reinforced plastics is 285°C±5°C. Sulfuric acid... The time required to rise from room temperature to the set temperature should not be less than 15 minutes. After reaching the set temperature, digestion should continue for 60 minutes ± 10 minutes. Other resin digestion... The method for determining the temperature can be based on the selected temperature conditions, such as adding hydrogen peroxide after sulfuric acid digestion to clarify the digestate and ensure complete fiber recovery. The part floats to the surface of the liquid to be determined.

6.1.3.3 Slowly add hydrogen peroxide along the bottle wall until the digestion solution becomes clear and the fibers float to the surface of the solution.

6.1.3.4 Heat the clarified digest solution to the digestion temperature and keep it warm for 10 minutes. If it becomes cloudy again, continue to add hydrogen peroxide dropwise while stirring until it becomes clear. until.

6.1.3.5 Wash and dry the acid-resistant filter until it reaches constant weight. Weigh the acid-resistant filter using an analytical balance, accurate to

0.1 mg.

6.1.3.6 Dilute the clarified and cooled digestate with distilled water, then connect a vacuum pump for filtration. The filtration pressure should be 18 kPa. And use... Filter the solution repeatedly with distilled water until it becomes neutral. Finally, rinse once with acetone (about 30 mL).

6.1.3.7 After filtration, the fibers and filter are placed in an oven preheated to 150°C±5°C and dried for 2 hours, then placed in a desiccator to cool. Bring to room temperature, weigh, accurate to

0.1 mg.

6.1.3.8 Weigh a bundle of fibers identical to the sample and perform a blank test under the same conditions as described above. The mass of the fibers should be approximately equal to the mass of the digested sample. The length of the blank fiber is similar to that of the fiber in the sample, and then the mass loss rate of the blank fiber is calculated.

6.1.4 Calculation

6.1.4.1 The resin content of carbon fiber reinforced plastic is calculated according to formula (1).

6.1.4.2 The density of carbon fiber reinforced plastics shall be determined according to GB/T 1463, and the density of carbon fiber shall be determined according to GB/T 30019.Carbon fiber reinforced plastics The fiber volume content is calculated according to formula (2) or formula (3).

6.2 Method B. Calcination method

6.2.1 Test Instruments The testing instruments shall meet the following requirements.

a) Analytical balance. graduation value

0.1 mg;

b) Tubular furnace. operating temperature not lower than 700°C, accuracy ±10°C;

c) Purging system. Equipped with a flow meter, the purging rate is not less than 300 mL/min, and the accuracy is ±5 mL/min;

d) Crucible. Temperature resistance not lower than 700°C.

6.2.2 Purge Gas The purging gas should meet the following requirements. nitrogen, with a purity of not less than 99.9%.

6.2.3 Test Procedure

6.2.3.1 Place the crucible in a tube furnace, heat it to 500°C~600°C, calcine for at least 1 hour, then remove it and place it in a desiccator to cool before use.

6.2.3.2 Weigh the sample and the corresponding resin casting using an analytical balance, accurate to

0.1 mg.

6.2.3.3 Weigh the crucible using an analytical balance, accurate to

0.1 mg.

6.2.3.4 Place the sample and casting into the crucible and tube furnace respectively, turn on the purging system, and calcine under nitrogen purging. Purging rate The calcination rate is 300 mL/min, the calcination temperature is 560°C±40°C, and the calcination time is not less than 1 hour.

6.2.3.5 After calcination, cool the sample and crucible to room temperature while maintaining nitrogen purging. Weigh the total weight of the residual sample and crucible. Total weight of residual casting and crucible.

6.2.4 Calculation

6.2.4.1 The resin content of carbon fiber reinforced plastic is calculated according to formula (4).

6.2.4.2 The density of carbon fiber reinforced plastics shall be determined according to GB/T 1463, and the density of carbon fiber shall be determined according to GB/T 30019.Carbon fiber reinforced plastics The fiber volume content is calculated according to formula (5) or formula (6).

7.Experimental Results Calculate the arithmetic mean of each group of samples and round it to 3 significant figures.