Is Hemp Really Stronger Than Steel? How?
Let us think of the comparative strength of a metal known to be strong and a hemp plant fiber. Which do you think would be stronger? You’re tempted to say hemp. But is hemp stronger than steel? The comparative strength of steel and a plant fiber, let us say. What would be your common-sense response?
We actually asked this question randomly to a number of people of different age-groups. We simply wanted to check whether our intuitive response matches with theirs. It did. Almost everyone said – steel would be stronger. Only two people refused to answer. They believed there was a trick in the question somewhere.
The common-sense response would be correct in most cases. With one exception: hemp fiber. Fibers from this non-narcotic variety of Cannabis Sativa can be stronger than steel, experts have demonstrated.
By Way of Clarification
You have read right: hemp does belong to the same plant species as the drug cannabis or marijuana: Cannabis Sativa. However, hemp is not a drug. It cannot give you a high. Hemp does not have more than 0.3% tetrahydrocannabinol (THC) to do that.
THC is the substance with psychoactive qualities, present in the narcotic cannabis at a concentration level of 7.5-10% or more. Hence the mind-altering capacity of cannabis or marijuana. Hemp is clean.
Is hemp stronger than steel? The Truth – Revealed
Strength in scientific terms gets calculated in two different ways mainly. Hemp fibers have been studied from both of these ways of measuring strength. Counter-intuitive though it seems, hemp fiber has proven to be stronger than steel from both these angles. Below, we describe in detail how that is possible.
Tensile and Compressive Strength
Tensile strength is the ability to withstand tension. Compressive strength is the ability to endure compression. In other words, how much tension or tautness can something take before it gets permanently deformed? That is the tensile strength of that material.
For example, how much pulling can a rope endure before it tears? That is the rope’s tensile strength. To tear is to get permanently deformed. It could also be measured in terms of weight endurance. For instance, how much weight can a tree branch take before it cracks and breaks?
The weight at which the tree branch cracks and breaks is beyond its tensile strength threshold. The maximum weight it can endure is indicative of its ultimate tensile strength.
Similarly, how much compression can something take before it loses its capacity to mend itself? That is compressive strength.
Think of spring in this context. Normally, a spring will bounce back to its own shape as soon as you remove the pressure you are applying to it. However, it is also possible to keep squeezing a spring until it is no longer able to regain its own shape.
The degree of pressing a spring can take without losing its shape permanently is its compressive strength. In simple terms, the pressure something can withstand before cracking and breaking or tearing is its tensile strength. The force applied takes the form of pulling at both ends.
It can also take the form of piling on increasing amounts of weight on something. till it cracks and breaks. The amount of pressure something can endure without bending and losing its shape permanently is its compressive strength. The force applied in this case takes the form of pushing from both ends.
The Tensile Strength of Steel
Metallurgy, the science of metals, mentions steel to be one of the strongest metals. Strictly speaking, steel is not metal as it is an alloy of iron and other elements, among which carbon is a non-metal. That does not make a difference to the strength of steel, though.
There are different varieties of steel with varying tensile strengths. The weakest form of steel is plain carbon steel with a tensile strength of up to 150 MPa. The strongest variety is ausformed steel with 3000 MPa of tensile strength.
The Tensile Strength of Hemp Fibers
In an article published in 2003 in the Materials Research Innovations, the authors report extensively on the tensile strength of hemp fibers of different diameters. The general rule in the case of synthetic fibers is that a reduction in the diameter of the fiber also decreases the faults.
That implies a lesser diameter of synthetic fibers gives it higher tensile strength. Authors Prasad and Sain demonstrate in their article that this same principle is applicable to hemp fibers also. Hemp fibers with a diameter of 4 μm (micrometer) have a tensile strength of 4200 MPa.
In contrast, the tensile strength of hemp fibers of 66 μm is 250 MPa only. The extensive experiments by Prasad and Sain demonstrate that the thickest hemp fiber with the least tensile strength (250 MPa) has more tensile strength than the variety of steel with the least tensile strength (150 MPa).
Their experiments also demonstrate that the thinnest fibers of hemp with the maximum tensile strength (4200 MPa) is stronger than the steel variety with the highest tensile strength (3000 MPa). The range of tensile strength possessed by hemp fibers of different diameters is, thus, more than the tensile strength range of different varieties of steel.
Is hemp stronger than steel? A Simpler Explanation of the Answer
It is possible to explain the above feature of strength in simpler terms, without using the scientific jargon ‘tensile strength’. It will take a lot more pressure to crack or break composite materials made of hemp fibers than the amount of pressure needed to crack or break things made of steel.
This is true across different varieties of steel and varying diameters of hemp fibers. The weakest hemp fiber needs more pressure to crack and break than the weakest variety of steel. The strongest variety of steel needs less pressure to crack and break than the strongest variety of hemp fiber.
Hemp has the capacity to endure double the weight of steel before it cracks and breaks. That is how much stronger hemp is than steel.
The Compressive Strengths of Hemp and Steel
The ability of hemp not to bend to compression is nearly six times that of steel, experts say. From the angle of compressive strength, therefore, hemp is six times more bend-resistant than steel.
That makes hemp stronger than steel from both aspects of strength measurement. The next time someone asks you – Is hemp stronger than steel? You can confidently answer – hemp, and then educate everyone on ‘how’ it’s stronger.
Strength Measurement in Applications
On June 19, 2017, CNBC reported on an episode from the “Jay Leno’s Garage’ show, where Leno drove a sportscar named Renew. Former Dell executive Bruce Dietzen got this sportscar specially made for himself out of 100 pounds of hemp fibers.
Both Dietzen and Leno punched the car with considerable force several times. Their hands were hurt, but there was no dent in the car, unlike a car with a steel body. According to the owner, his hemp car is 10 times stronger than any car made of steel.
Leno with the hemp car, Source:cnbc.com
A 2018 article in Material Science recommends the use of hemp cables instead of cables made of harmonic steel for roofs with hyperbolic paraboloid cable nets. According to the author, this substitution would be both cost-effective and environment-friendly without involving any compromise in the strength aspect.
News 18 reported on August 26, 2019, that the Canadian Hempheath Group has devised the world’s first aircraft made entirely from hemp. This four-seater plane has everything, from the wings to the body, the seats, and pillows are made from hemp.
The company intends to run it on hemp biofuel also. Hemp’s superior ability to endure more weight than steel and its considerably higher bendability makes it 10 times stronger than steel, says the founder of the company.