GB/T 15780-2026Test methods for the physical and mechanical properties of bamboo (English PDF)

4.1 Selection of Sample Bamboo

4.1.1 The selection of sample bamboo should be representative, reflecting the population represented by the test results, and conforming to the objectives of the experimental plan. For any For specific types of bamboo, select according to the following requirements.

a) To obtain the basic properties of a particular bamboo species, test materials should be collected from representative bamboo-producing areas. For widely distributed bamboo species, the following should be followed. Collect samples from different regions based on varying climates, geographical locations, soil conditions, and other natural factors.

b) In the bamboo forest of the collection area, select representative, mature bamboo samples from no fewer than 100 bamboo plants with a diameter at breast height of 50mm or more. There should be no fewer than 15 mature, defect-free sample bamboo plants.

c) Before felling the bamboo, mark the north direction above breast height.

4.1.2 After felling the sample bamboo, record the diameter at breast height (DBH), height below the branch, and bamboo height. For each bamboo, cut a section approximately 2.0m long upwards from a node about 1.5m above the ground. A section was cut off at a whole node to serve as test material. For bamboo species with lower branch height and smaller diameter at breast height, the section could be cut upwards from a whole node approximately 1.0m above the ground. Take a section of bamboo about 2.0m long and cut it off at the joint to use as the test material. The test material should be clearly numbered.

4.1.3 After the bamboo samples are harvested, they should be transported in a timely manner to prevent discoloration, cracking, rotting, and insect infestation.

4.2 Sampling

4.2.1 From each bamboo segment approximately 2m long, select two bamboo segments without obvious defects or damage to the bamboo shoots, with an internode length of over.200mm. Tube. The lower section of the bamboo tube is split into one 15mm wide strip and one 30mm wide strip in the east, south, west and north directions, respectively, as shown in Figure 1. 15mm wide bamboo strips are used to prepare samples for testing shrinkage, density, bending strength, and bending modulus of elasticity. 30mm wide bamboo strips are used for... Prepare samples for compression and shearing along the grain. Using the top section of bamboo, split it into 15mm wide sections in the east, south, west, and north directions, as shown in Figure 2. One bamboo strip each, for making parallel tensile test specimens.

4.2.2 Test sections for preparing shrinkage test specimens should be soaked in room temperature water until their dimensions are basically stable before specimen preparation. Other splitting methods... After drying, the test strips should be air-dried indoors, with the bamboo pith facing down. The top layer should be weighed down with a heavy object to prevent the test strips from warping or deforming. The unit is millimeters. Figure

1.Method for preparing split test strips for shrinkage, density, flexural strength, compressive strength, and shear strength along the grain. Figure

2.Method for preparing tensile test strips along the grain.

5.1 Sample Preparation and Preservation

5.1.1 Bamboo segments shall be cut according to the test requirements, and the bamboo segments shall be free from obvious defects and damage. Unless otherwise specified in the test method, the samples shall not have any defects. Defects. Each sample should be clearly labeled.

5.1.2 Specimen preparation accuracy. Unless otherwise specified in the test methods, the permissible error for specimen length is ±

1.0 mm, and the permissible error for width is... The difference is ±0.5mm, but the relative deviation of the width over the entire length of the sample should not exceed 0.2mm.

5.1.3 The processed sample should be placed in a constant temperature and humidity environment at (20±2)°C and (65±5)% to achieve humidity equilibration. The difference between two weighing results 24 hours apart should not exceed 0.1% of the mass of the last weighing of the sample.

5.2 Sample Testing Environment The test environment for the samples should be maintained at a temperature of (20±2)°C and a relative humidity of (65±5)%. If the environmental conditions do not meet the test requirements, [further action may be taken]. Furthermore, the sample after the moisture content has been adjusted should be stored in a sealed container and only taken out during the test.

5.3 Calculation of Sample Quantity

5.3.1 The number of test specimens can be calculated according to the formula specified for the results of various physical and mechanical properties.

5.3.2 When processing test results, the relevant statistics should be calculated according to the following formulas.

5.3.3 To approximate the minimum number of samples required for the experiment, the average coefficient of variation of the following main properties of bamboo can be used, as shown in Table 1. As shown.

6.1 Moisture content

6.1.1 Principle The ratio of the mass of water contained in the sample to the mass of the completely dry sample, expressed as a percentage.

6.1.2 Sample Select from specimens or specimens after physical and mechanical tests. Bamboo shavings and fragments adhering to the specimen surface should be thoroughly cleaned.

6.1.3 Instruments and Equipment

6.1.3.1 Balance. accuracy is 0.001g.

6.1.3.2 Oven. It should be able to maintain (103±2)°C.

6.1.4 Test Procedure

6.1.4.1 Weigh the sample immediately after selection, accurate to 0.001g.

6.1.4.2 The samples were kept at (103±2)°C in the oven for 4 hours. After drying, 1 to 2 samples were weighed, with a interval of not less than Record the sample mass every 2 hours. The sample is considered completely dry when the difference between the last two weighings does not exceed 0.5%. Record the mass of the sample when it is completely dry. Quantity, accurate to 0.001g.

6.1.4.3 Remove the sample from the oven and place it in a weighing bottle inside a glass desiccator containing desiccant. Seal the weighing bottle and desiccator lids. After the sample has cooled to room temperature, remove it from the weighing bottle and weigh it to an accuracy of 0.001g.

6.1.5 Result Calculation

6.1.5.1 The moisture content of the sample shall be calculated according to formula (7), accurate to 0.1%.

6.1.5.2 During the test, the weighing values should be entered into the moisture content determination record table in Appendix A at any time, and the moisture content calculation results should also be entered.

6.2 Shrinkage rate and shrinkage coefficient

6.2.1 Principle Bamboo with a moisture content below the fiber saturation point shrinks in size and volume as the moisture content decreases. The change in bamboo size and volume occurs from wet to air-dried or fully dried. The difference between the dimensions and volume of the bamboo when air-dried and the ratio of the dimensions and volume of the bamboo when wet indicates the linear shrinkage and volumetric shrinkage of the bamboo when air-dried or fully dried.

6.2.2 Sample Prepare the test material to a saturated moisture state, and take a saturated moisture sample according to the requirements of 5.1, with dimensions of 10mm × 10mm × tmm (tangential width × longitudinal length × bamboo wall thickness). This should not be tested using the same sample as density measurement.

6.2.3 Instruments and Equipment

6.2.3.1 Oven. It should be able to maintain (103±2)°C.

6.2.3.2 Vernier caliper. accuracy is 0.1mm.

6.2.4 Test Procedure

6.2.4.1 Immerse the sample in distilled water at (20±2)°C, and measure the wall thickness every (72±0.5) h until two consecutive measurements are taken. The difference in test results should not exceed

0.02 mm.

6.2.4.2 Mark the geometric center of each face of the specimen, and measure the radial, tangential, and longitudinal directions of the wet specimen through the geometric centers of the opposite faces. The dimensions should be accurate to

0.01 mm, and the sample should be kept moist during the measurement process.

6.2.4.3 After measurement, the sample is placed in the environment specified in

5.2 for air drying. During the air drying process, 2 to 3 samples are tested every 6 hours. The wall thickness at a single mark is considered air-dried when the difference between two consecutive test results does not exceed

0.02 mm. The air-drying of the sample is then measured. The radial, chordal, and longitudinal dimensions at the time mark are accurate to

0.01 mm, and the weighing mass is accurate to

0.001 g.

6.2.4.4 After the sample is measured, it is dried at a temperature of (103±2)°C until its mass is constant. The mass changes are not significant when weighed twice, 2 hours apart. A weight greater than 0.002g indicates the sample is completely dry. After drying, the sample should be immediately placed in a desiccator to cool. Once cooled to room temperature, it should be weighed for accuracy. Accurate to 0.001g. Measure the radial, tangential, and longitudinal dimensions of the sample at the marked point when it is completely dry, accurate to 0.01mm, and weigh it, accurate to 0.001g. 0.001g.

6.2.4.5 During the measurement process, any sample that cracks or becomes distorted in shape should be discarded. Discarding samples during the test will result in a significant loss of data. If the quantity is insufficient, additional samples need to be added and tested.

6.2.5 Result Calculation

6.2.5.1 When the sample is dried from wet material to completely dry, the radial or tangential shrinkage rate of the dry line shall be calculated according to formula (8) respectively, accurate to 0.1%.

6.2.5.2 When the sample is dried from wet material to air dry, the radial or tangential shrinkage rate of the air drying line shall be calculated according to formula (9) respectively, accurate to 0.1%.

6.2.5.3 The volume shrinkage rate of the sample from wet material to completely dry material shall be calculated according to formula (10) and accurate to 0.1%.

6.2.5.6 Based on the mass of the sample when it is air-dried and fully dried, calculate the moisture content of the sample when it is air-dried according to 6.1.

6.2.5.7 During the experiment, all measured values should be entered into the Drying Shrinkage Rate Measurement Record Table in Appendix B, along with the air-dried moisture content and dry weight. The result of the reduction ratio calculation.

6.3 Density

6.3.1 Principle The ratio of the mass to the volume of the sample is the density of the bamboo.

6.3.2 Sample Prepare a 10mm × 10mm × tmm sample (tangential width × longitudinal length × bamboo wall thickness) according to the requirements of 5.1.It should not be affected by drying shrinkage. The rate determination uses a single sample.

6.3.3 Instruments and Equipment

6.3.3.1 Oven. It should be able to maintain (103±2)°C.

6.3.3.2 Vernier caliper. accuracy is 0.1mm.

6.3.3.3 Balance. accuracy is 0.001g.

6.3.4 Test Procedure

6.3.4.1 At the center of each opposite surface of the sample, measure the chordal width, longitudinal length, and bamboo wall thickness (radial width), accurate to [value missing].

0.01 mm. For irregular specimens, the volume can be measured using the water displacement method, according to GB/T 1927.5.Weigh the specimen. Mass, accurate to 0.001g.

6.3.4.2 Dry the sample as described in 6.1.4.2, and weigh the sample when it is completely dry. Immediately after drying, measure the mass at the center of each opposite surface of the sample. The tangential width, longitudinal length, and bamboo wall thickness (radial width) are accurate to

0.01 mm.

6.3.4.3 When calculating the basic density, the sample should be brought to a state of saturated moisture as per 6.2.4.1, and the chord width and longitudinal width of the sample should be measured as per 6.3.4.1. The length and bamboo wall thickness (radial width) should be accurate to

0.01 mm. The sample should be kept moist. Dry the sample according to 6.1.4.2, and weigh the entire sample. Quality when dry.

6.3.5 Result Calculation

6.3.5.1 The air-dry density of the sample when the moisture content is W is calculated according to formula (13), accurate to

0.001 g/cm3.

6.3.5.2 The air-dry density of the sample with a moisture content of 12% is calculated according to formula (14), and the result is accurate to

0.001 g/cm3.

6.3.5.5 During the experiment, all measured values should be recorded in Appendix C (Air-dry Density and Total Dry Density Measurement Record Table) and Appendix D. Fill in the basic density measurement record table and enter the above three density calculation results.

6.4 Parallel compressive strength

6.4.1 Principle The compressive strength of bamboo along the grain is determined by applying pressure at a uniform speed until failure.

6.4.2 Sample Prepare the specimens according to the requirements of 5.1.Cut one specimen from each test strip, with a specimen size of 20mm × 20mm × tmm (bamboo wall). Thickness), and adjust the moisture content of the sample.

6.4.3 Instruments and Equipment

6.4.3.1 Mechanical testing machine. The indication error is not greater than ±1.0%.

6.4.3.2 Oven. It should be able to maintain (103±2)°C.

6.4.3.3 Vernier caliper. accuracy is 0.1mm.

6.4.3.4 Balance. accuracy is 0.001g.

6.4.4 Test Procedure

6.4.4.1 At the midpoint of the sample's length and width, measure the bamboo wall thickness as the sample thickness, taking the tangential dimension near the green and yellow parts of the bamboo. The value is the width, accurate to 0.1mm.

6.4.4.2 Place the specimen at the center of the spherical sliding support of the testing machine, with the force applied in a direction parallel to the longitudinal direction.

6.4.4.3 During the test, the load is applied at a uniform rate, causing the specimen to fail within (1 ± 0.5) min. The failure load is recorded in Appendix E, Compressive Strength Test. In the verification record form.

6.4.4.4 Immediately after the sample is destroyed, weigh the entire sample to an accuracy of

0.001 g. Determine the moisture content of the sample according to 6.1.

6.4.5 Result Calculation

6.4.5.1 The compressive strength shall be calculated according to formula (17) and accurate to

0.1 MPa.

6.4.5.3 During the test, all measured values should be entered into the compression strength test record table in Appendix E at any time, and the compression strength along the grain should be entered. Degree calculation results.

6.5 Bending strength

6.5.1 Principle Using a simply supported beam method, a concentrated load is applied at a uniform speed at the center of the specimen length until failure, and the bending of the bamboo is determined. strength.

6.5.2 Sample Prepare internode samples and adjust the moisture content of the samples according to the requirements of 5.1.Sample size. 160mm × 10mm × tmm (bamboo wall thickness).

6.5.3 Instruments and Equipment

6.5.3.1 Mechanical testing machine. The indication error is not greater than ±1.0%.

6.5.3.2 Oven. It should be able to maintain (103±2)°C.

6.5.3.3 Dial indicator. with an accuracy of

0.01 mm, and should be equipped with a dial indicator holder.

6.5.3.4 Vernier caliper. accuracy is 0.1mm.

6.5.3.5 Balance. accuracy is 0.001g.

6.5.4 Test Procedure

6.5.4.1 To determine the tangential bending strength and flexural modulus of bamboo, the bamboo wall thickness and tangential dimension are measured at the midpoint of the sample length. The thickness of the bamboo wall is the width, and the tangential dimension is the height, accurate to 0.01mm.

6.5.4.2 Using a central single-point loading method, the specimen is placed on two supports of the testing apparatus, with a span of 120 mm. Loading is applied uniformly along the chord of the spe...