Matrix Heating Blanket and Controller System

The Matrix Heating Blanket and Controller System is used for repairing the leading edge of a helicopter rotor blade. It consists of three thirty-zone, 8-ft silicone blankets. Each blanket has built-in electronics to digitize the blanket temperature for individual PID calculations. The three blankets are networked together to form a single ninety-zone, 22-ft heating blanket that maintains 275 F +/- 3 F across the entire blanket. (The conventional blanket has up to 100 F spread.) A central computer, located outside the pressurized and heated autoclave, controls the ramp rate and temperature set points via an RS-485 bus.

The Matrix Heating Blankets being installed on a test blade.

Three heater blankets, each with its dedicated controller, are used to accurately and uniformly control the cure temperature across a 22-foot span.

The 90-zone heater blankets can be controlled to +/- 1 degree F on an uniform surface. When installed on the rotor blade, part temperature can be maintained to well within the specified +/- 10 degrees F. Tests have yielded +3/-2 degrees F.

Breather cloth is used to insulate the heaters and to allow the removal of volatile vapors under vacuum.

Installation of blade into an autoclave. The matrix controllers and heaters with embedded electronics must operate inside the pressurized and heated autoclave. (25 PSI and 150 degrees F, respectively.)

A vacuum is pulled on the Matrix Heater Blanket to put the heaters in close contact with the repair part and to remove volatile vapors.

An actual temperature plot of production run during the installation. All temperature readings across the entire 22 ft. blade are +/- 3 degrees F – well inside the required +/- 10 F.

The Matrix Heater Blankets and Controllers inside the 12-ft. diameter, 50-foot long autoclave.

The Matrix Controllers are fully integrated with existing autoclave software to function as one seamless user interface.

CPU board from one of the three Matrix Blanket Controller boxes. Mil Spec, thru-hole parts are used to ensure long-term reliability inside the 25-PSI and 150 F auto-clave environment. MTBF calculations showed a life expectancy of over 20 years!

Thermocouple digitizer boards: Two boards are embedded in one thirty-zone heater blanket. Each board digitizes up to 16 thermocouple signals and transmits the data via RS485 serial link to its corresponding controller.