Tuesday, March 30, 2010

Wind Turbine Interference on Radar


Wind farm development has seen resistance from a variety of people/groups. Some environmentalists fear the safety of bats and birds caught in the path of the blades. Local residents of potential developments fear blocked views, noise, and even flickering of shadows.

Another concern, is the disruption wind turbines can have on radar. Here is a recent ABC News article discussing the Pentagon's concern that wind farms may disrupt radar systems, and could be a homeland security threat.


If wind turbines stood still, there would be no problem. Modern radar is programed to ignore stationary objects. However, with tip speeds over 200 mph, large wind turbines create a signature that can be reported on radar. Above is an image from the NOAA, the star represents a Doppler radar tower, and the circled area is the disruption from a local wind farm. Looks like a thunder storm is moving in right? According to the NOAA:
"The rotating turbines also impact the velocity base data as you can see from the below image.  This velocity data is used by radar operators and by a variety of algorithms in the radar's data processors to detect certain storm characteristics such as mesocyclones, tornado vortex signatures, and relative storm motion."
With the National Weather Service, there is a concern as a severe weather event such as a flash flood could roll through undetected as it is passed off as wind turbine interference. Here are a couple more interesting images.



Photo Credits: NOAA National Weather Forecast Office Buffalo, NY

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Monday, March 29, 2010

Composites vs Metal


Above is a helpful material property comparison of composites and metals. Below is an interesting graph comparing the fatigue strength of composites vs metal. Enjoy...



Source: Advanced Composite Materials Technology Research Centre at The Hong Kong University of Science and Technology.


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Wednesday, March 24, 2010

Life Cycle Assessment


We have talked before about life cycle assessment (LCA) of products manufactured with composite materials. Here is a paper discussing the life cycle of a surfboard. A surfboard is more or less a composite sandwich structure. The core is either a polyurethane foam core or eps foam core. A wood stringer is added down the center for stiffness. The skins are generally woven 4oz fiberglass, often 2 layers on top and one on the bottom. Resin is epoxy or more commonly polyester.

In the life cycle analysis paper, the author cites more carbon emissions are created driving to and from the beach then the life of the surfboard will ever produce. Recently, companies have been experimenting with greener surfboard materials. In particular, bio-based resins, fabric, and foam. However, at least from a greenhouse emissions point of view, the composite construction of the board is a moot point in comparison to the emissions surfers generate driving to the beach.

I imagine similar studies for other products manufactured with composite materials will find similar statistics. It also exemplifies that we need greener transportation, and composites will play a role in reducing automotive weight and increasing fuel efficiency.

Photo Credit: Hot Tamale Surfboards

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Monday, March 22, 2010

DARPA Composite Armor Development

Some great warfighter technologies come out of the DARPA. Here is a synopsis for the development of composite armor with private company Hardwire.
"In collaboration with the U.S. Army, the Hardwire® DARPA Armor program exploited unique hybrid composite materials in innovative geometries and systems to provide improved military vehicle armor protection at a significantly reduced weight compared to other technologies. This approach to armor design has provided a suite of armor solutions that can be tailored to meet mission and vehicle-specific weight and performance requirements in response to specific and emerging threats. New insights and infrastructure for armor manufacturing has changed hybrid, composite armor production from a labor-intensive, small-quantity process to a quality-controlled, high-throughput operation. The program applied automated high-precision production fabrication technologies to adaptively and rapidly produce panels to specification and at a cost comparable to that of traditional armor. These changes in the composite armor design and production paradigm have made life-saving armor systems available for warfighter vehicles"
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Thursday, March 18, 2010

Recycled Plastic as a Building Material



There are a few building materials already using recycled plastic; some composite decking products use recycled polyethylene grocery bags. The video above describes a whole new building product. Here, it appears the variety of ground up plastics are held together by a thermoset. If this is the case, the plastic will act as the reinforcement in the new composite material...

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