Uncompromising Composites

By Steve Robbins

I have owned the same fiberglass sailboat, a Southern Cross 31, for more than 25 years. It was built in 1983 out of glass fiber and polyester resin with an Airex foam core. The challenge of building with composites, even 30 years ago, was to build the boat to be as light as possible without comprising its structural integrity. Without the simulation and mechanical testing tools we have today, my sailboat, designed to be used for offshore cruising, was overbuilt for toughness and stability. It weighs a lot.

You really don’t want your sailboat hull oil canning 300 miles offshore in the middle of the Atlantic Ocean in 12-ft. seas. But weight doesn’t matter in a boat like it does in an aircraft or even a car. Whether in an automobile, spacecraft, or the cellphone in your pocket, composite materials need to perform to the specified requirements of particular products. Fatigue, puncture, delamination, and tensile strength are key factors in using the right composite.

A Lighter, Stronger Future
Today, there are many tools to help design composite parts and structures. They fall into two areas: simulation tools used during the design phase and mechanical testing tools that are used during the prototyping phase. Composite simulation has become a hot topic in the design engineering world as more engineers are using it to great advantage.

Composite materials are a great, lightweight way to improve stiffness and strength.
In recent issues of DE, we have covered applications where lightweight structures are very important. In aerospace and automotive, for instance, fuel efficiencies improve greatly as weight is jettisoned. As materials and manufacturing processes continue to improve, composites will continue to make their mark in designs that will change the way we live. In the future, one of the greatest advantages to using composites, aside from its inherent strength and reduced weight, is the ability to easily manufacture them into complex shapes. This ability has been used in military aircraft to build stealth contour surfaces and in consumer aircraft to add strength. The new Boeing 787, for example, is made of approximately 60% composite materials.

The uses of these materials in current designs has been facilitated by the increased availability of the right materials for the right jobs, and a decreased overall cost of the materials. But the key factor to using composites is being able to test the designs in a cost effective and accurate manner.

Simulate and Test
Being able to simulate the lifecycle of a design using composite material will save companies time and money, and they will be able to build better products. Although simulation is getting a lot of attention, mechanical testing will not diminish in this area. Have you noticed how composite test equipment looks a lot like torture machines from the Inquisition? That’s because they are designed to torture composite materials until they break!

Composite simulation and mechanical testing has come a long way from the day my sailboat was launched. In 1983, boat builders didn’t know the durability and strength of the materials they were using. Polyester resin was relatively new and vacuum bagging the laminate was almost unheard of, so they just added a few more inches of material to stress areas, like compression posts and hull-to-deck joints. The foam core in my boat added tremendous strength. It was cutting edge. Most builders were using solid fiberglass layups. 

But today, using the appropriate software and test equipment, designers can build aerodynamic, lightweight vessels, vehicles and aircraft—from composite tractor-trailer trucks that will double their mileage to larger planes that use less fuel. I haven’t flown in a 787 yet, but when I do, I will look out the window at the composite wing and remember the night I spent offshore sailing from Bimini to Lake Worth, FL, in 25-knot winds from the northeast, directly opposite the direction of the Gulf Stream. Crashing into 12-ft. waves, I was comforted by the strength of Ananda’s hull, and I will marvel at the engineering accomplishments made possible with the composites we now experience in our lives.

 Steve Robbins is the CEO of Level 5 Communications and executive editor of DE. Send comments about this subject to de-editors@digitaleng.news.