Improved High Voltage Encapsulants through In Situ Fiber Reinforcement.
Final rept. 24 Sep 79-1 Mar 81,
HUGHES AIRCRAFT CO CULVER CITY CA AEROSPACE GROUPS
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This report describes an engineering development program which was conducted to evaluate the benefits of using in situ formed fibers as a reinforcement for the solid encapsulant of production high voltage electronic devices. The devices used were the diode bridge module of a Travelling Wave Tube amplifier circuit both ends of the Travelling Wave Tube itself. The fibers were produced via flow induced crystallization by agitation of the electronic component in a polymer solution. The fiberization process was optimized to produce uniform coverage with thin high strength polypropylene fibers. The fiberized devices and unfiberized controls were encapsulated with an epoxy resin, EPON 825, crosslinked with a Hughes-developed amine catalyst system designated HV. A small number of additional devices were encapsulated with another material, Stycast 2850 cured with catalyst 11. The devices were subjected to thermal cycling from -73 C to 143 C with Corona Inception Voltage CIV measurements done at the low temperature after each cycle. The CIV data showed no significant difference between fiberized and unfiberized control devices. However, failure analysis of selected devices after cycling and thermal shock did reveal fracture patterns which were influenced by the presence of the fibers. In particular, crack initiation appeared to take place in resin rich areas and cracks may have been arrested or forced to change direction in regions of high fiber concentration. Author
- Laminates and Composite Materials