Rub tolerant fan case

Abstract

A case apparatus for a gas turbine engine includes an annular case having an interior surface with annular recess formed therein; and an annular bumper disposed in the recess, the bumper comprising a frangible material and having a low-friction contact surface, wherein the bumper is configured to permit elastic radial deflection in response to applied forces below a predetermined threshold.

What is claimed is: 
     
         1 . A case apparatus for a gas turbine engine, comprising:
 an annular case having an interior surface with annular recess formed therein; and   an annular bumper disposed in the recess, the bumper comprising a frangible material and having a low-friction contact surface, wherein the bumper is configured to permit elastic deflection in response to applied forces below a predetermined threshold.   
     
     
         2 . The apparatus of  claim 1  wherein the bumper includes a web defining the contact surface, and a pair of spaced-apart parallel legs extending from the web, wherein the web and the legs cooperatively define a channel. 
     
     
         3 . The apparatus of  claim 2  wherein the web is convex-curved. 
     
     
         4 . The apparatus of  claim 2  wherein the bumper includes a pair of flanges extending in opposite directions from distal ends of the legs. 
     
     
         5 . The apparatus of  claim 1  wherein the bumper comprises carbon-epoxy composite. 
     
     
         6 . The apparatus of  claim 5  wherein the composite includes at least one layer of glass fiber at the contact surface. 
     
     
         7 . The apparatus of  claim 2  further comprising a filler disposed in the channel of the bumper. 
     
     
         8 . The apparatus of  claim 7  wherein the filler comprises a honeycomb structure. 
     
     
         9 . The apparatus of  claim 1  further comprising an abradable material disposed in the recess adjacent the bumper, such that the abradable material, the contact surface, and the interior surface cooperatively define a flowpath surface. 
     
     
         10 . The apparatus of  claim 9  wherein the abradable material comprises a phenolic resin. 
     
     
         11 . A fan apparatus for a gas turbine engine comprising:
 an annular fan case having an interior surface with annular recess formed therein; and   an annular bumper disposed in the recess, the bumper comprising a frangible material and having a low-friction contact surface; and   a rotor carrying an array of blades mounted for rotation within the case such that the bumper is in axial alignment with tips of the blades, wherein the bumper is configured to permit elastic radial deflection in response to contact between the blades and the bumper generating applied forces below a predetermined threshold.   
     
     
         12 . The apparatus of  claim 11  wherein the bumper includes a web defining the contact surface, and a pair of spaced-apart parallel legs extending from the web, wherein the web and the legs cooperatively define a channel. 
     
     
         13 . The apparatus of  claim 12  wherein the web is convex-curved. 
     
     
         14 . The apparatus of  claim 12  wherein the bumper includes a pair of flanges extending in opposite directions from distal ends of the legs. 
     
     
         15 . The apparatus of  claim 11  wherein the bumper comprises carbon-epoxy composite. 
     
     
         16 . The apparatus of  claim 15  wherein the composite includes at least one layer of glass fiber. 
     
     
         17 . The apparatus of  claim 12  further comprising a filler disposed in the channel of the bumper. 
     
     
         18 . The apparatus of  claim 17  wherein the filler comprises a honeycomb structure. 
     
     
         19 . The apparatus of  claim 11  further comprising an abradable material disposed in the recess adjacent the bumper, such that the abradable material, the contact surface, and the interior surface cooperatively define a flowpath surface. 
     
     
         20 . The apparatus of  claim 19  wherein the abradable material comprises a phenolic resin.