WO2021021034A2

WO2021021034A2 - Tensile testing method of small bamboo

Info

Publication number: WO2021021034A2
Application number: PCT/TH2020/000050
Authority: WO
Inventors: Phanawisittha NATCHRUNGSUNKH
Original assignee: Natchrungsunkh Phanawisittha
Priority date: 2019-07-26
Filing date: 2020-07-20
Publication date: 2021-02-04
Also published as: WO2021021034A3

Abstract

This invention is related to the tensile testing process of small bamboo, such as Thyrsostachys siamemis Gamble, etc. Its characteristics differ from the previously apparent methods of tensile testing of bamboo as follows: the testing technique using a small bamboo strip as a specimen including both the skin and the innermost area of bamboo culm, the tensile testing technique for small bamboo using a testing machine that can adjust its compression force of sample clamping, the tensile testing technique for small bamboo using a manual clamp that can adjust its damping force manually, the tensile testing technique for small bamboo using a sample as a small bamboo strip which its node is positioned at the center of the test, the tensile testing technique for small bamboo using a sample as a small bamboo strip which the testing uses the slowest pulling speed or the slowest speed of adding weight or testing using a fixed hanging weight for a long time.

Description

Title of Invention

TENSILE TESTING METHOD OF SMALL BAMBOO

Technical Fields

Civil Engineering

Forestry

Background Art

In the field of engineering, bamboo’s problems are fire and wood-eating insect, which can be solved using the methods specified in the patents "Method of solving the separation problem of concrete and reinforced bamboo in bamboo-reinforced concrete by using waterproof concrete" (Phanawisittha NATCHRUNGSUNKH, World Intellectual Property Organization: Patent No. WO2019135720) and/or "Method of prestressing concrete with bamboo" (Phanawisittha NATCHRUNGSUNKH, World Intellectual Property Property Organization: Patent No. W02Q19135719)

The problem directly related to this patent is that the current industrial standard of bamboo tensile testing “ISO-TR-22157-2: 2004. Bamboo - Determination of physical and mechanical properties - part 2 - laboratory manual” can not be used for small bamboo, especially Thyrsostachys siamensis Gamble. Thyrsostachys siamensis Gamble and Thyrsostachys oliveri Gamble have been found to be the most suitable bamboo species for concrete reinforcement (Natchrungsunkh, 2018). The tensile testing in accordance with the mentioned testing standards can not be undertaken due to the inability to prepare test samples from small bamboo. Additionally, general tensile testings such as those from Ghavami reports (2007) or ISO-TR-22157-2: 2004 do not represent the tensile strength of entire cross-sectional area of bamboo. Those tests only select a part of cross-sectional area of bamboo culm. In fact, tensile strength of bamboo is diffirent across its cross-sectional area. The area near the surface of the bamboo culm is strong and yields high tensile strength. The area near the hollow core of bamboo culm is the weakest and has the least tensile strength. Therefore, in application using full area of bamboo, the tensile testing using samples in accordance with existing standards is not able to represent strength of all cross-section area. From the inventor’s research, the tensile test of small bamboo - Thyrsostachys siamensis Gamble - was experimented. In order to acquire the representative tensile strength of entire cross-sectional area of bamboo culm, following testing methods ware undertaken:

1. Tensile testings of cut whole bamboo culm glued at both ends

2. Tensile testings of cut whole bamboo culm bolted at both ends

3. Tensile testings of cut whole bamboo culm fixed at both ends with screw nails

4. Test of small pieces of bamboo Without having to enlarge the area at the end of the sample

The result showed that the test method 4. was the most appropriate for tensile test of small bamboo.

References:

Natchrungsunkh, P. 2018. Suitable Bamboo Species for Concrete Reinforcement to replace reinforcing Steel. Proceedings of the 9^th National Academic Conference of Si Ayutthaya Group Rajabhat Universities - Research and Innovation for Society, Pathum Thani, Thailand, 18-19 October 2018. pp. 529- 541.

Ghavami, K. 2007 . Bamboo: Low cost and energy saving construction materials.

Modem Bamboo Structures: Proceedings of first international Conference on Modem Bamboo Structures ( ICBS-2007) , Changsha, China, 28-30 October 2007

Description and Purpose of the Invention

This invention relates to the tensile testing methods of small bamboo, such as Thyrsostachys siamensis Gamble. Brief Description of Drawings

Figure 1 Selection of a bamboo culm which its length is more than 2

internodes

Figure 2. A Bamboo clum which was cut at a determinded length

Figure 3 A bamboo sample which was radial cut (sectional cut)

Figure 4 Tensile strength testing of a bamboo sample

Disclosure of Invention

The technical characteristics developed in this patent are

1. Using full sectional area of bamboo samples, including inner area and outer area of bamboo culm. This shape of sample represents the real application bamboo as concrete reinforcement, which yields the real tensile strength. Additional, it solves former problems, that sample had to be cut into dog-bone resulting loss of area near outer and inner sides of bamboo culm.

2. Using force-adjustable manual clamp or machine’s clamp to hold bamboo’s ends. This solves the cracking problem of bamboo samples. General testing machines, which can not adjust the compression force of sample clamp, causes the bamboo to break at the edge of clamps from overcompression. Hence unadjustable-automatic-clamp testing machings can not be used to test the tensile strength of small bamboo, which is too small to be prepared into a dog-bone shape sample. 3. The position of tensile failure in bamboo sample is occured only at a node during the tensile test. Therefore the bamboo node must present in every sample and must be placed at the middle of the tetsing. In the past, there wes no report about this technique for small bamboo. The tensile test of bamboo samples without node results in the higher tensile strength than reality. This was reported from inventor’s research showing that the bamboo node had less tensile strength than the bamboo intemode.

4. Testing at higher pulling speed results a higher tensile breaking value as well. The testing in this patent has been improved to use the least pulling speed that the machine can be operated or use the hanging weight. These methods yield the correct tensile strength, which is less than those values obtained from prior test for the tensile strength of small bamboo.

Tensile testing process of small bamboo specified in this patent has the following steps:

1. Prepare bamboo that its length is longer than 2 internodes, as shown in Figure 1.

2. Determine the positions of the centers of intemodes (1).

3. Determine the cutting point (2), which extends from the point (1) plus the end clamping length. Try to maximize the length from (1) to (2). 4. Cut the bamboo at position (2). We will get bamboo as shown in figure 2.

5. Radial cut the bamboo into (might be 6-8) strips. We will get bamboo as shown in figure 3.

6. Measure the cross-sectional area of the node of the bamboo strip (3). Use the measurable largest area.

7. Bring the bamboo example in figure 3 into the Universal Testing Machine that can adjust its clamping force (4) as shown in Figure 4 or use the manual clamp (4) that can adjust its clamping force.

8. From 7., insert bamboo into the clamps (4) so that the bamboo sample will be compressed by full length of clamps. 9. Try to maximize the gripping forces of the clamps so that the bamboo sample does not break and does not slip from the clamps (4). However, the bamboo sample may allow having some cracks.

10. For the tensile test with a tensile testing machine, grasp both ends of the bamboo sample with the machine’s clamps (4). 11. For the manual tensile test with a manual clamp, hold the top end of bamboo sample with the clamp. Attach the lower end of bamboo sample with a dead weight, which can be increase its hanging weight later by adding more dead weights.

12. Set the bamboo sample so that the node is positioned at the center of the length of the test as shown in Figure 4.

13. Increase the tensile testing load. For the testing with a machine, use the slowest tensile loading speed or the smallest tension increment at one or both ends of bamboo (5) that the machine can operate, for example 0.00001 mm/s or 0.0001 N/s until the bamboo sample is broken. For the manual tensile test with a manual clamp and the hanging weight (4) + (5), gradually increase the fixed weight when the bamboo sample has not been broken in a specified time period, until the bamboo sample is broken.

14. Record the maximum tensile force (5) when testing with a machine or record the maximum hanging load at the ends of bamboo (4) + (5) for manual testing.

15. Divide the maximum recorded tensile force from 14. by the cross-sectional area from 6. The result will be the ultimate tensile strength of this bamboo spicemen.

Best Mode of Carrying out the Invention

The same as described in the topic“Disclosure of Invention”.

Claims

1. The tensile testing method for small bamboo which has following characteristics:

1.1. The testing technique uses a small bamboo strip as a specimen. This specimen includes both the skin and the innermost area of bamboo culm. This specific characteristics of testing differs from prior testing methods. Prior methods chose samples from some area of the bamboo cross-section, that did not represent the strength of all bamboo cross-sections. Actually, bamboo strips as in this patent have been used as concrete reinforcement without outer/inner-skin trimming.

1.2. The tensile testing technique for small bamboo uses a testing machine that can adjust its compression force of sample clamping. This specific characteristics of testing differs from prior testing methods. Prior methods used testing machines that its‘clamp compression force could not be adjusted or did not specify/clarify about adjustment of sampling clamping forces. Automatic clamping of machine leaded to breaking of bamboo sample from excessive bearing force.

1.3. The tensile testing technique for small bamboo uses a manual clamp that can adjust its clamping force manually. This specific characteristics of testing differs from prior testing methods. Prior methods used testing machines that its clamp compression force could not be adjusted or did not specify/clarify about adjustment of sampling clamping forces. Automatic clamping of machine leaded to breaking of bamboo sample from excessive bearing force.

1.4. The tensile testing technique for small bamboo uses a sample as a small bamboo strip which its node is positioned at the center of the test. When any nodes present in a tensile test, the bamboo sample will always be torn/broken from the tension at node(s). This specific characteristics of testing differs from prior testing methods. Prior methods did not specify that a bamboo sample had to contained a node and that node had to be at the center. Thus, any prior tensile tests yielded higher results than thoes of the reality.

1.5. The tensile testing technique for small bamboo uses a sample as a small bamboo strip which the testing uses the slowest pulling speed or the slowest speed of adding weight or testing using a fixed hanging weight for a long time. This specific characteristics of testing differs from prior testing methods. Prior methods did not specify that the test should be performed with the lowest speed or with long-term hanging weight Therefore the prior results were higher than the the tensile strength of bamboo in practical applications as concrete reinforcement requireing a service life of several decades.