Creating Composites to Protect Soldiers

Soldiers worldwide are committed to protecting their nation, and there are dedicated manufacturers working on high quality composite components to protect them. The rising use of composite materials and the advancements in material blends and their fabrication have allowed composite component manufacturers to meet the demanding requirements for military vehicle components.

Using traditional materials such as high quality steel for components and vehicle protection have downfalls in the constantly evolving threats and performance requirements needed to combat those threats. The excessive weight of a material such as steel can severely affect the performance and survivability of vehicles in the field because of the increased vehicle weight and thus necessary modification to the suspension system to support the increased inertial energy. Vehicle maneuverability can be significantly impaired as well, and with the advent of smarter weapons and threats to the soldiers, the ability to get in and out of a hostile situation is paramount.

Through partnerships and cooperative working arrangements, composite manufacturers can take requirements and design parameters and walk a customer through the design, testing and analysis, and eventual fully engineered manufactured end product with the features and qualities required for the application.

Extreme circumstance, extreme benefits

Weight savings is one of the top benefits associated with composite usage in mobile equipment, allowing for increased payload and fuel efficiency, higher speed capability and performance. “Reduced weight of a wheel, for example, improves its acceleration and deceleration, but it also dramatically improves fuel economy and improves the suspension. Areas like that are prime for additional lightweighting,” explains Fiberforge (Glenwood Springs, CO) president and CEO Jon Fox-Rubin.

Composites also have an infinite fatigue life. Steel can go an estimated one billion cycles before fatigue and aluminum an estimated one million cycles. Using aluminum as a replacement for steel offers weight savings, but must have its fatigue life taken into consideration. Something that rotates, such as a driveshaft, goes through a lot of cycles in a short period of time.

Challenging environments also benefit from composites’ corrosion abilities—they simply do not rust.

“Two of the critical design parameters of composites are the stiffness-to-weight ratio and the strength-to-weight ratio. Composites have benefits over metals in both of those categories. With a composite you can orient the fibers along the path that is either stiffness dominant or strength dominant and have an increase in stiffness- or strength-to-weight over a metal,” says Fox-Rubin.

“One thing that most people don’t realize is that most structures that are designed like a frame of a car or a door panel, their design is dominated by the stiffness of the panel, not the strength of the panel. Stiffness-to-weight is the dominant design variable that an engineer is optimizing.”

Designed properties

An advantageous feature of composites is their ability to have their strengths strategically placed. Composite properties are optimal in the direction of the fibers. Since most structures do not have loads in one single direction, stacking multiple layers of composite plies allow fibers to be oriented in multiple directions to bear multi-directional loads and forces.

The most efficient composites accomplish low weight and cost by having most of their fibers oriented in the primary load direction, and just enough fibers oriented in the other directions to carry secondary loads and hold the structure together.

For military vehicle composite components, weight and cost are the targeted properties. “Strength is a given for military applications,” says Brad McPhee, president and CEO, Creative Composites, Rapid River, MI. “In terms of combat vehicles, structurally the vehicles are overdesigned for protection purposes, but that is what makes them heavy. The composites are to make the design and vehicle overall lighter. Many customers have a dollar-per-pound-saved target they are willing to pay, and different industries have different targets.”