Longitudinal load carrying method for fiber reinforced filament wound structures

Abstract

A lightweight composite fiber wound tubular member or casing, such as a rocket motor case, has one or more openings formed through one end portion of the wall thereof by orienting the filaments or fibers around each opening to provide reinforcement for loads applied to fasteners passing through said openings. The orientation of the filaments or fibers is such as to receive and transfer loads applied to the walls of the openings in the tubular member in a direction substantially parallel to the axis of the tubular member. A method of manufacturing the tubular member is disclosed which includes winding the filaments or fibers along a helical path and around the area defining each opening, together with the apparatus for performing the method.

I claim: 
     
       1. In a method of manufacturing a lightweight filament wound casing having connector openings at one end comprising the steps of: (1) preparing a cylindrical mandrel by inserting a predetermined number of radially projecting, spaced-apart pegs near one end portion thereof,   (2) rotating said mandrel as it is moved longitudinally in one direction,   (3) feeding a continuous resin impregnated filament to the surface of said mandrel to lay the filament up in a helical form,   (4) controlling the speed of the longitudinal movement so as to decrease the angle the filament makes with respect to the longitudinal axis of the mandrel as the fiber approaches the area of the pegs and increase the angle as the filament leaves the area of the pegs, said filament being passed around one of said pegs as the direction of longitudinal movement is reversed, the filament being laid up along a helical path around the mandrel back to a starting point, each layer of filaments including at least one pass around each peg in said mandrel;   (5) curing the wound casing,   (6) removing the pegs from the mandrel; and,   (7) removing the casing from the mandrel.   
     
     
       2. In the method of manufacture of claim 1 wherein the longitudinal movement of the mandrel is such as to produce an angle between the filament and the axis of the mandrel of 27°. 
     
     
       3. In the method of manufacture of claim 1 wherein the longitudinal movement of the mandrel is such as to produce an angle between the filament and the axis of the mandrel varying from 27° to 47°. 
     
     
       4. In the method of manufacture of claim 1 wherein the longitudinal movement of the mandrel is such that each filament of the first layer of filaments will have an angle of approximately 27° with respect to the longitudinal axis of the mandrel, each filament of each successive layer of filaments having a slightly increased angle with respect to the longitudinal axis until a maximum angle of approximately 47° is reached. 
     
     
       5. In a method of manufacturing a lightweight filament wound casing having connector openings at one end comprising the steps of: (1) preparing a cylindrical mandrel by inserting a predetermined number of radially projecting, circumferentially equally spaced-apart pegs therein,   (2) rotating said mandrel as it is moved longitudinally first in one direction and then in reverse,   (3) connecting a continuous resin coated filament to said mandrel, said rotating and longitudinal movement of the mandrel will lay the filament up in a helical path so that the angle of the filament to the longitudinal axis of the mandrel is relatively small as the filament approaches one of said pegs,   (4) controlling the speed of the longitudinal movement so as to decrease the angle the filament makes with respect to the longitudinal axis of the mandrel as the filament approaches the area of the pegs and increases the angle as the filament leaves the area of the pegs and, said filament being passed around said peg as said longitudinal movement of the mandrel is reversed, the filament being laid up along a helical path around the mandrel back to a starting point, each layer of filaments including at least one pass around each peg in said mandrel,   (5) wrapping said filament along a helical path around the mandrel back toward the area where the winding was initially started, each layer of filaments including at least one pass around each peg in said mandrel, each successive layer of filaments having the filaments approach each peg at an angle slightly greater than the angle of the previous layer until said angle is a predetermined maximum, thereafter each layer of filaments is laid up with a smaller angle than the previous layer until a predetermined minimum angle is reached,   (6) curing the wound casing,   (7) removing the pegs and then casing from the mandrel.   
     
     
       6. In a method of manufacturing as claimed in claim 5 wherein said maximum angle is approximately 47° and said minimum angle is approximately 27°. .Iadd. 
     
     
       7.  In a method of manufacturing a lightweight filament wound casing having connector openings in at least one end comprising the steps of: (1) preparing a casing core having an axis by inserting a predetermined number of projecting pegs spaced apart about said axis near an end portion of said core to form said connector openings;   (2) rotating said core about said axis as said core is moved in one direction substantially parallel to said axis;   (3) feeding a continuous resin impregnated filament to the surface of said core to lay the filament up in a helical form at an angle with respect to said axis;   (4) controlling the speed of the movement of the core so as to decrease the angle the filament makes with respect to said axis of the core as the fiber approaches the area of the pegs and increase the angle as the filament leaves the area of the pegs, said filament being passed around one of said pegs as the direction of the movement of the core relative to its axis is reversed, the filament being laid up along a helical path around the core back to a starting point, each layer of filament including at least one pass around each peg in said core to orient said filaments in a formed and cured casing so as to receive and transfer loads applied to the walls of said openings in a direction substantially parallel to said axis;   (5) curing the wound casing;   (6) removing the pegs from the core; and   (7) removing the casing from the core. .Iaddend. .Iadd.   
     
     
       8.  In the method of manufacture of claim 7 wherein the movement of the core is such as to produce an angle between the filament and the axis of the core of 27°. .Iaddend. .Iadd.9. In the method of manufacture of claim 7 wherein the movement of the core is such as to produce an angle between the filament and the axis of the core varying from 27° to 
     
     
        47°. .Iaddend. .Iadd.10.  In the method of manufacture of claim 7 wherein the movement of the core is such that each filament of the first layer of filaments will have an angle of approximately 27° with respect to the axis of the core, each filament of each successive layer of filaments having a slightly increased angle with respect to the axis until a maximum angle of approximately 47° is reached. .Iaddend. 
     
     
        .Iadd.     In a method of manufacturing a lightweight filament wound casing having connector openings in at least one end comprising the steps of: (1) preparing a casing core having an axis by inserting a predetermined number of projecting pegs spaced equally about said axis in said core;   (2) rotating said core about said axis as said core is moved first in one direction relative to its axis and then in the opposite direction;   (3) connecting a continuous resin coated filament to said core, said rotation and movement of the core laying the filament up in a helical path at an angle with respect to said axis of the core so that the angle is relatively small as the filament approaches one of said pegs;   (4) controlling the speed of the movement of the core so as to decrease the angle the filament makes with respect to the axis of the core as the filament approaches the area of the pegs and increase the angle as the filament leaves the area of the pegs, said filament being passed around one of said pegs as the direction of the movement of the core relative to its axis is reversed;   (5) wrapping said filament along a helical path around the core back toward the area where the winding was initially started, each layer of filaments including at least one pass around each peg in said core, each successive layer of filaments having the filaments approach each peg at an angle relative to said axis of the core slightly greater than the angle of the previous layer until said angle is a predetermined maximum, thereafter each layer of filaments being laid up with a smaller angle than the previous layer until a predetermined minimum angle is reached to thereby orient said filaments to receive and transfer loads applied to the walls of said openings in a direction substantially parallel to said axis in a fully formed and cured casing;   (6) curing the wound casing; and   (7) removing the pegs and then the casing from the core. .Iaddend.   
     
     
        .Iadd.     In a method of manufacturing as claimed in claim 11 wherein said maximum angle is approximately 47° and said minimum angle is approximately 27°. .Iaddend. .Iadd. 13. In a method of manufacturing a liqhtweight filament wound casing having connector openings in at least one end comprising the steps of: (1) preparing a mandrel having an axis by inserting a predetermined number of projecting pegs spaced about said axis near one said portion of said mandrel to form said connector openings;   (2) feeding a continuous resin impregnated filament to lay the filament up in a helical form at an angle with respect to said axis of the core beginning at a starting point on said mandrel and progressing in the direction of said axis toward said pegs;   (3) decreasing the angle said filament makes with respect to said axis as said filament approaches said pegs and increasing the angle said filament makes with respect to said axis as said filament leaves said pegs, said filament being passed around one of said pegs and the direction of relative movement between said filament and said mandrel in relation to the axis of the core being reversed so that said filament is laid up along a helical path around said mandrel back to said starting point to form said wound casing and to orient said filaments so as to receive and transfer loads applied to the walls of said openings in a direction substantially parallel to said axis in a formed and cured casing;   (4) curing said wound casing on said mandrel;   (5) removing said pegs from said mandrel; and   (6) removing said wound casing from said mandrel. .Iaddend. .Iadd. 14. The method of manufacture as defined in claim 13 wherein the movement of the mandrel is such as to produce an angle between the filament and the axis of the mandrel of 27°. .Iaddend..Iadd. 15. The method of manufacture as defined in claim 13 wherein the movement of the mandrel is such as to produce an angle between the filament and the axis of the mandrel varying from 27° to 47°. .Iaddend..Iadd. 16. The method of manufacture as defined in claim 13 wherein the movement of the mandrel is such that each filament of the first layer of filaments will have an angle of approximately 27° with respect to the axis of the mandrel, each filament of each successive layer of filaments having a slightly increased angle with respect to the axis of the mandrel until a maximum angle of approximately 47° is reached. .Iaddend..Iadd. 17. The method of manufacture as defined in claim 13 wherein said axis of said mandrel is the longitudinal axis thereof and wherein said filament and said mandrel undergo relative longitudinal movement. .Iaddend. .Iadd. 18. In a method of manufacturing a lightweight filament wound casing having connector openings in at least one end comprising the steps of:   (1) preparing a casing core having an axis by inserting at least one projecting peg near one end portion thereof to form a connector opening;   (2) feeding a continuous resin impregnated filament to the surface of said core to lay the filament up in a helical form at an angle with respect to said axis of the core beginning at a starting point on said core and progressing in the direction of said axis toward said peg;   (3) decreasing the angle said filament makes with respect to said axis as said filament approaches said peg and increasing the angle said filament makes with respect to said axis as said filament leaves said peg, said filament being passed around said peg and the direction of relative movement between said filament and said core in relation to said axis of the core being reversed so that said filament is laid up along a helical path around said core back to said starting point to form said wound casing and to orient said filament so as to receive and transfer loads applied to the wall of said opening in a direction substantially parallel to said axis in a formed and cured casing;   (4) curing said wound casing on said core;   (5) removing said peg from said core; and   
     
     
       (6) removing said wound casing from said core. .Iaddend. .Iadd. 19.  The method of manufacturing as defined in claim 18 wherein the relative movement between said filament and said core is such as to produce an angle between said filament and said axis of said core varying between a maximum angle of approximately 47° and a minimum angle of approximately 27°. .Iaddend..Iadd. 20. The method of manufacturing as defined in claim 18 wherein said axis of said core is the longitudinal axis thereof and wherein said filament and said core undergo relative longitudinal movement. .Iaddend.