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Created: 5/21/97 |
Updated: 8/05/98 |
The primary objective of this research is to subject the new composite material, distributed filament contacts (DFC), to a battery of environmental tests and then benchmark the capabilities and limitations of DFCs with conventional metal contacts. Other objectives include modeling of the redundant contact interface and defining dominant failure modes. The results from this study will be used to construct a generic, industry wide specification for DFCs and to help pin point new applications which can benefit from the unique properties they have.
It is well known that metallic contacts can suffer electric failure as the result of contamination and long term environmental corrosion. A new composite material which can be fabricated into Distributed Filament Contacts or DFCs is being invented by Xerox as a more robust alternative to metal contacts for certain applications. DFCs are carbon fiber filled polymeric composites that are processed into contacts rich in highly oriented, conductive carbon fiber. While these contacts have somewhat higher contact resistance than metals, the multiple redundancy of many thousands of fibers coupled with excellent corrosion resistance and thermal properties indicate that DFCs will have exceptional stability and reliability.
CALCE-EPRC and Xerox have launched into an empirical study to probe into the fundamental contact physics and the performance reliability of DFCs under adverse conditions.
1) Contact Resistance vs. Normal Force
Objective: Characterize baseline performance
The first test to perform is the contact resistance versus normal force. This must be established to relate increases in contact resistance to any variations in the hold-down mechanism in a connector that employs DFCs. The expected range of normal forces that this technology would see in an application have been supplied by Xerox.
2) Temperature Rise/Current Rating
Objective: Determine current handling capacity
Current and voltage ratings for the technology must be established. Typical industry values to be met include a temperature rise of 30 degrees C maximum, with a current rating of 1 ampere for signal contacts.
3) Durability Testing
Objective: Determine effects of repeated cycling
The next test to perform is a durability test. In clean conditions the DFC should be mated and unmated at least hundreds of times to illustrate its stability in field conditions. The interface should be examined prior to and after wear cycling under the electron microscope for any visible clues of wear related failure mechanism.
4) Temperature Life Testing
Objective: Determine effects of operation at elevated temperature
The temperature life test will be performed to analyze any effects that long term high temperature exposure has on the DFC technology. The contact pairs will be exposed to 100 hours at 85 deg.C and then tested to determine any change in the contact resistance.