What does "Low strength but good strength-to-weight ratio" mean?

In summary, spider silk is incredibly strong and has a strength to density ratio that is similar to steel.
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I am studying the properties of polymers, I understand they are low strength but I do not understand what is meant by "good strength-to-weight ratio". What does that mean?
Good strength-to-weight-ratio
 
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I assume it means that an ant has low strength compared to e.g. our strength in absolute values, but compared to its own weight, the ant is incredibly stronger than we are. Spider webs are another example, or folded paper.
 
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It’ll depend on exactly what you mean by strength, but it’s generally either tensile, compressive, or shear strength. So taking elastic tensile strength as an example, the strength to weight ratio will be the Young’s modulus divided by the density of the material:
https://en.m.wikipedia.org/wiki/Specific_strength
Polymers have a significantly lower density than, e.g., most metals, so that even though their Young’s modulus isn’t particularly high, their strength to weight ratio is.
 
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Copied from
https://www.treehugger.com/captivating-facts-about-spider-silk-4868351

"Spider silk is lighter than cotton and up to 1,000 times thinner than human hair, yet it's also incredibly strong for such a wispy material. This outsized strength is vital for spiders, who need their silk to withstand an array of destructive forces, from the frantic flapping of trapped insects to powerful blasts of wind and rain.

Still, for animals of our size, it's hard to grasp the proportional strength of spider silk unless we frame it in familiar terms. Comparing it with steel might sound absurd, for example, but on a per-weight basis, spider silk is stronger. It may lack the stiffness of steel, but it has similar tensile strength and a higher strength-to-density ratio.

"Quantitatively, spider silk is five times stronger than steel of the same diameter," explains a fact sheet from the University of Bristol School of Chemistry. It also draws comparisons with Kevlar, which has a higher strength rating but a lower fracture toughness than certain spider silks, according to the American Chemical Society (ACS). Spider silk is highly elastic, too, in some cases stretching four times its original length without breaking, and retains its strength below minus 40 degrees Celsius.

It has even been suggested — but not tested, obviously — that a pencil-width strand of spider silk could stop a Boeing 747 in flight. In a more natural flex, however, the Darwin's bark spider of Madagascar can stretch its dragline silk up to 25 meters (82 feet) across large rivers, forming the world's largest-known spiderwebs."
 
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FAQ: What does "Low strength but good strength-to-weight ratio" mean?

What is strength-to-weight ratio?

The strength-to-weight ratio is a measure of how much strength a material can withstand per unit of weight. It is calculated by dividing the material's ultimate strength (the maximum stress it can handle before breaking) by its density (mass per unit volume).

Why is a low strength but good strength-to-weight ratio desirable?

A low strength but good strength-to-weight ratio means that a material is relatively lightweight but can still withstand a significant amount of stress. This makes it ideal for applications where weight is a critical factor, such as in aerospace or automotive industries.

How is strength-to-weight ratio different from just strength?

Strength-to-weight ratio takes into account the weight of the material, while strength alone does not. This means that a material with a high strength but also a high density may not be as desirable as a material with a lower strength but a lower density and a better strength-to-weight ratio.

What are some examples of materials with a low strength but good strength-to-weight ratio?

Some examples include aluminum, titanium, and carbon fiber. These materials are commonly used in lightweight structures such as aircraft, bicycles, and sporting equipment.

How is strength-to-weight ratio measured?

Strength-to-weight ratio is typically measured in units of stress per unit of weight, such as pounds per square inch (psi) or newtons per kilogram (N/kg). It can also be represented as a ratio, such as 100:1, which means that the material can withstand 100 units of stress for every 1 unit of weight.

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