Here are some photos of the material testing I completed. The photos of the bending were taken at the maximum amound of curvature before the material failed. The photos of the twisting show the maximum amount of torque I could exert on the material, but I believe the material was close to failure. Please let me know if there are any other specific tests that would be helpful.
Material:
5mm Lauan Plywood 1m in length at various widths (50mm, 75mm, 100mm). This was the only Lauan plywood I could find. The material was labelled as 5.2mm but also 1/4" which is 6.35mm, however it measured 5mm. The material was cut so that the grain of the outer layers ran legthwise along the piece of material (parallel to bending force)
Conclusions:
- maximum bending does not change with width of material.
- maximum twisting is inversly related to width of the material (the narrower material twisted the most). The max twisting decreased more when the width of the material increased (50mm - 75mm = -30 degrees, 75mm-100mm = -60 degrees), meaning that a smaller increase of width has a greater effect on max twisting as the width increases.
Notes:
- Due to material imperfections and the nature of the wood, rate of bending along the length of the material was sometimes not constant, creating an uneven curve. Also, this caused the material to sometimes fail unexpectedly at lower levels of stress
- The maximum bending was most easily acheived after 'warming up' the material by flexing it several times at lower levels of stress. I believe this can be attributed to breaking the bonds between layers and the rigidness of the wood grains (in the inner layer)
- Due to the the length of the clamp holding the material, the effective length being twisted was 820mm. However, I would assume that one would not want to use the material under maximum stress in the project, so perhaps using the same amount of torque at the 1m length would provide an adequate safety factor.
I cannot edit this post for some reason, but the data under the BENDING photos should read:
ReplyDeleteHeight of Arch = ~290mm
Length of Arch = ~750mm
Excellent work!
ReplyDeleteI want to use the material properties as bend and twist to strengthen up structure like pre-tensioning system.
yes, one thing to think about is how to create stiffness in structural components from such a flexible material. This may depend on the design concept.. but we also might think of ways to create vertical and horizontal members that can act as a skeleton if need be.
ReplyDeleteOutstanding work. I think this is very helpful for moving the design forward.
ReplyDeleteAs far as stiffness, I am hoping that that can be achieved through twisting and bending.
The next step might be to understand an assembly of twisted elements and/or understanding how a variable width strip might 'twist' differently along the access which could result in an assembly that has variable visual and lighting effects.