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Composite Materials and Avalanche Shovels

Written by Jim Frankenfield, Avalanche Center Director and Engineer/Physicist

This article offers a brief explanation of composite materials, which some avalanche shovels are now made of. It explains what a composite is and why it is different from polycarbonate ("plastic") and metal. It is not intended to evaluate or recommend any particular product.

What is a "Composite" ?

A composite material combines two or more constituent materials in such a way that they remain distinguishable. This is in contrast to materials such as metal alloys, where two or more constituents are blended in a way that leaves them indistinguishable.

Composite materials can be engineered to specific requirements for specific applications by choosing appropriate components and combining them in a way that takes advantages of the best properties of each.

"Traditional" Composite Materials

One of the oldest examples of a composite is a mud brick with straw in it. A brick without straw can be broken easily by bending, which pulls one side apart in tension. Straw has a high tensile strength, and adding it to a mud brick makes it much more resistant to such a bending failure. But the straw itself has only tensile strength. So the composite brick takes advantage of the tensile strength of the straw and the compression strength of the mud, as well as the ability to form a shape out of the mud. In composite terminology the straw is a reinforcement and the mud is a matrix.

Another example of a composite material which has been used for a long time is concrete. In this case the matrix is cement and the reinforcement is gravel, and the reinforcement is not directional. If we wish to make concrete even stronger in certain directions we can add rebar. Now we have two reinforcements in one matrix.

Aerospace Applications

Modern high-strength low-weight composites were initially developed largely for aerospace applications. Parts in airplanes, rockets, and satellites can be made very light and also very strong. Stronger than the older metal components had been. Composites may have replaced many materials, but often it was metal and not plastic that was being replaced. In addition to the weight and strength advantages they can also be designed with thermal advantages for applications such as jet engine components.

Recreation

When composites were still primarily a high-tech advanced material they were expensive. But with time the materials became more commonplace and easier to design and manufacture for a wide variety of applications.

One of the first was bicycle frames on high-end bikes. Especially mountain bikes where the low weight and the ability to take much abuse are both important. These are still the more expensive bikes, but they are not uncommon today.

Avalanche Shovels

A few years ago LifeLink came out with a line of composite shovels which is similar in shape and appearance to the polycarbonate models, which are also still available. The composite is supposed to be much stronger, and they once told me that in their testing the handle would break off where it enters the blade before the blade would break. (Pry with enough leverage, especially on an extended handle, and anything will fail in some way.) Given that composites can be designed with specific properties for specific applications this isn’t surprising.

However, there are some people who insist that this is no better than polycarbonate and is essentially the same thing. For an example, this statement was made on a forum:

The term "composite" sounds so high tech, doesn't it? Add a bunch of short, chopped glass fibers into the plastic resin for more stiffness, along with a dash of grey pigment to make the new shovel "carbon colored" (in the words of one bold e-talier) and what do you know? Those rainbow colored polycarbonate plastic shovels with the bad reputation are suddenly the latest and greatest "composite" backcountry models, "designed to chop ice & stubborn snow."

This is like claiming a mud brick with straw is no better than one without or that concrete with rebar is no better than without.

Whether or not a composite shovel is a good shovel, or one you are comfortable with, depends on more than strength. The blade is thicker than metal is, and there may be more “bounce” to it. Basically it may feel and handle different. But it does not lack strength and durability, and it is not the same thing as polycarbonate.

Incidentally, on the same forum you find people going off endlessly about how the polycarbonate blades are no good. These are offered by both LifeLink and Ortovox and both stand behind them. If you do a search on the internet you’ll find pros as well as cons. I found comments from a patroller who had used the “plastic” blades in numerous situations including avalanche rescue and found them to be fine. So there are conflicting opinions out there. Inform yourself, consider your own preferences and experiences, and make your own decision.

Conclusion

The intent here is not to review shovels of suggest any particular kind, but to explain what a composite is and why it’s different from polycarbonate. It’s simply wrong to say it’s nothing more than plastic which is dressed up a bit for marketing.

www.avalanche-center.org