# Steel vs Bamboo strength types/ weight and in various directions & orientations? Specific, Tensile, Compressive, Shear, Lateral etc?

How are their comparative strengths in various directions and orientations?

I've been reading a lot online but can't seem to find definitive comparison that talks numbers and specific comparison of numbers in various directions.

Are there specific experiment(s) or research whose findings can be outlined here?

• Look carefully at what is actually compared. In your second link it says "Our [bamboo composite] material is only a quarter of the weight of steel. In terms of strength to weight, it performs better than steel." So it's not tensile strength that is compared there, but the specific strength, which is an important material parameter in civil engineering. Jun 27 '16 at 9:18
• @Robin - Do share more of that in an answer if possible. I can't remember all diff specific strengths/ stresses/ strain varieties from my Engg college days Nov 16 '17 at 3:21
• In my opinion the main point is that you have to look at the application. It does not make sense do compare steel against bamboo just for the sake of it. They are too different. This is also the core of what starrise wrote. Therefore I'm afraid I'm unable to write more about the topic. Nov 17 '17 at 7:36
• You mention "bamboo". But what type of bamboo? Because there are many type of bamboo, and so it depends the strength. May 2 '19 at 19:15
• @Lavinia there’s many types of bamboo as well as steel. Given the content & context above I’m open to any that were studied comparatively for building materials May 6 '19 at 12:07

The highest strength steels have isotropic strength near $2\ \textrm{GPa}$, and have ductilities of $3\%$ to $10\%$. Kevlar fibers are near $3\ \textrm{GPa}$ but only along their length. Their transverse strength is closer to $50\ \textrm{MPa}$, and they have limited extensibility, closer to $1\%$. All of these values are available with some internet sleuthing and in many textbooks. Bamboo fiber data is harder to find, but the sources here and here (both links end at ScienceDirect, and are peer-reviewed journal articles) have interesting results. The former link has either $350\ \textrm{MPa}$ or $550\ \textrm{MPa}$ depending on preparation method, with no reported variance (though there is probably considerable variance, it was not reported). The latter link gives $650\pm175\ \textrm{MPa}$ and $800\pm100\ \textrm{MPa}$ for different preparation methods. Note that these values are all along the fiber lengths. No values were found for transverse strength, though it is probably an order of magnitude lower than longitudinal strength if the mechanisms are similar to those of non-biological polymers. And, at any rate, the fiber strengths are misleading since the fibers must be mixed into a polymer-matrix composite to be of any use (except perhaps as ropes), which will result in strength values lower than those of the fibers alone.