Tensegrity structures are distinguished by the way forces are distributed within them.
The members of a tensegrity structure are either in tension or in compression. For the structures I have so far researched; that have been done by others; the tensile members are usually cables or rods, while the compression members are sections of tubing, pipe or rods.
For the tension members I have decided to work with mono line rated at 30lb or 14kg which satisfies my initial criteria for tension capacity.
Compression Members:
This is my primary focus at this time, as I am keen to evolve the definition of what constitutes an acceptable compression strut for the purpose of tensegrity model making. Something that opens up more opportunity for individual expression and provide additional options. It is very tempting to replicate the fine work of artists like Bruce Hamilton, who has developed a series of extraordinary and very elegant models, but that would not satisfy my curiosity for exploration.
What I doing though is looking at compound construction techniques that utilise materials which normally in isolation are ineffective but in conjunction with other material work well together to form strong compression struts.
Design Considerations:
In engineering, buckling is a failure mode characterized by a sudden failure of a structural member subjected to high compressive stress, where the actual compressive stress at the point of failure is less than the ultimate compressive stresses that the material is capable of withstanding. This mode of failure is also described as failure due to elastic instability. source: Wikipedia
Some brief notes on bending due to compression that is an inherent consideration in respect of developing compound compression struts.
Compression members, such as columns, are mainly subjected to axial forces. The failure of a short compression member resulting from the compression axial force looks like:
However, when a compression member becomes longer, the role of the geometry and stiffness becomes more and more important. For a long (slender) column, buckling occurs well before the normal stress reaches the strength of the column material.
In the case of Tensegrity models the struts replace the column in this instance. The tendency to bend under stress can be managed with compound materials and hence satisfy the conditions for structural strength.
Thus the purpose of my research is simply to explore these options.
For more specific details on bending under stress and slenderness ratio with some very good graphics on this subject I would suggest:
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