Electrically conductive composite heater and method of manufacture

DETAILED DESCRIPTION This invention relates to heater elements intended for use in applications requiring high reliability in harsh environments.
Such heaters would be suitable for ice protection systems on aerospace structures, windmill blades or other like structures where the operating life and performance of the heater is of significant concern.
According to the present invention, the foregoing and other objects are attained by a heater assembly that consists of a resistive heater subassembly integrated with a laminated composite protective carrier.
The resistive heater subassembly comprises a generally co-planar resistive heater element and structural and bonding layers.
The resistive heater element may be any substantially porous, woven or non-woven, electrically conducting web, such as a metalized fabric.
In the most preferred embodiment, the resistive heater element is a non-woven fabric consisting of chopped nickel-coated carbon fibers (NCCF).
The fibers provide the conducting means for the electrical current which provides heat to the aircraft surface in an ice protection application.
The composite carrier provides mechanical integrity and resistance stability to the heater subassembly.
The thickness and composition of the composite carrier will vary with the application.
Typically the composite carrier includes multiple mechanical structural layers, bonding layers and electrical insulation layers for improved dielectric strength, mechanical and erosion protection and thermal insulation.
The resistive heater layer is connected to an external power source by way of conductors and a conductive adhesive.
Alternatively, the composite carrier may contain additional layers of electrical shielding to provide ground fault protection to the heater assembly as disclosed in U.
S.
Pat.
No.
5,361,183 entitled "Ground Fault Protection for Electrothermal De-Icing Applications", issued to co-applicant E.
G.
Weise and assigned to the same assignee, the disclosure of which is hereby incorporated by reference