The Green Aspects of SMC
Sheet Molding Compound (SMC) is used to create many composite parts especially for the transportation industry, and contributes heavily to a positive environmental impact. SMC has been developed over the last 25 years to replace steel/sheet metal mostly in transportation applications. It is widely used in many heavy duty semi truck hoods, agricultural equipment, and pickup trucks, SUV’s and muscle cars.
The main goal of this substitution is to reduce weight, which improves fuel efficiency. Other positive side effects include fewer assembly operations, additional design freedom, dent and impact resistance, and the elimination of corrosion. Several “green” resin formulations have been introduced that make use of bio resins, which use much more renewable resources such as soy products. The fillers and reinforcements in this material can also be made from recycled and renewable materials.
SMC has overcome several hurdles in order to get to its present use and application. General acceptance and education had to be proven to the OEM manufacturers and consumers. Paint application and adhesion was one large consideration that had to be proven out. There were issues with popping and blistering from the SMC surface. Making sure the SMC parts held dimensions and aesthetics was also an important milestone.
SMC has become widely used today for many applications, and will find its way into many more. The weight saving aspects are paramount for reducing fuel consumption. The anti-corrosion and dent resistance are loved by consumers.
Composite Utility Poles
Composite Utility Poles have been under development for a number of years. Replacing the existing wooden poles with fiberglass composites have many long-term advantages and yet have many obstacles to implementation. These poles are pultruded and use polyester resin and E-glass reinforcement. UV additives are employed to minimize one of the Achilles heels of composites resin.
Advantages of composite poles over wood are numerous. Composite poles have a lifespan of roughly 80 years versus the 25-30 years for wood, due to rotting issues. These rotting issues with wooden poles are combatted with chemical additives that are sometimes corrosive and toxic. Composite poles have a weight advantage, as they weigh about two-thirds less than a wooden pole, which allows for easier transportation to the jobsite and reduced equipment requirements for installation. Due to their controlled and known construction, composite poles have physical properties that are more stable and reliable over the duration. Composites are intrinsically non-conductive, which is ideal in this application.
Replacing an existing material in a current application always brings hurdles and challenges for acceptance. The wooden poles are known by purchasing, engineering, installation, and line utworker crews. Composite poles have a higher upfront cost, though long-term savings are significant. As the educational resources reach those affected, the transition will take place and composite utility poles will become widespread.
Composites in the Military
The military has been using composite materials for decades. Mostly applied to the aerospace segment, composites are now finding more uses to the traditional armed forces.
One of the uses for military ground forces is in the segment of armored vehicles. Metal armor competes with composite armor with metal being less expensive but heavier. This weight advantage has required the use of composite armor for the “up armoring” of vehicle systems that were already near their max payload. This minimizes the amount of other weight sacrifices being made in order to add armor.
Weight and performance are becoming more important as military tactics transition towards fast and nimble. This will create many future applications for composite materials as acceptance and testing open new opportunities.
Composite Bridge Decks
The application of fiberglass composite bridge decks has been under development for some time. The technology has been applied at several sites around the country and engineers and designers are getting comfortable with the technology. It basically combines resin-infused decking panels that are placed over fiberglass composite or steel bridge beams. Sometimes the attachment is mechanical, and sometimes the use of high-strength adhesives carries the load.
Replacing steel and concrete, composite bridge decks claim several advantages. They can be built in a factory as opposed to onsite (better quality control) transported and lifted rather easily, and should be much more resistant to the natural elements of freeze/thaw. One of the big savings is on installation time. The on-site construction time is much less, which allows for cost savings from road closures, detours, and site crews.
There has been TONS of Research and Development money spent by several federal, state, and private entities in developing the technology, testing, and specification criteria for this application of composites to the real world. Hurdles that need to be overcome include the acceptance by engineering professionals, infrastructure managers, and the public.
As a Composites Engineer, it sure is neat to see new applications of composites. And as a taxpayer, if it can save some money, I am very excited. As a driver, it sure would be nice to see some of these road projects shortened up!
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