Method and apparatus for fabrication of lattice composite fuselage for commercial aircraft employing steered fiber lay up

Abstract

A system for fabrication of an aerospace structure incorporates a mold having a surface and at least one unidirectional SFL head adapted to lay down a plurality of collimated tows in a predetermined laminated pattern on the mold surface to produce a fuselage skin. At least one cross plied laminate SFL head is adapted to lay down a cross plied laminate base interface on the fuselage skin to establish a lattice rib shape for each of a plurality of lattice ribs. The cross plied laminate SFL head has a band placement head steerable to avoid structural design features and to maintain spacing from adjacent steered lattice ribs. The unidirectional SFL head is further adapted to lay down a plurality of collimated tows on the base interface of each of the plurality of lattice ribs for a first plurality of unidirectional tow plies in each lattice rib. The unidirectional SFL head has a fiber placement head steerable to match the lattice rib shape to avoid structural design features and to maintain spacing from adjacent steered lattice ribs.

1 . A method for fabrication of an aerospace structure comprising:
 employing at least one unidirectional steered fiber layup head to lay down a plurality of collimated tows in a predetermined laminated pattern on a mold surface to produce a fuselage skin;   employing at least one cross plied laminate steered fiber layup head to lay down a cross plied laminate base interface on the fuselage skin to establish a lattice rib shape for each of a plurality of lattice ribs;   steering a band placement head in the at least one cross plied laminate steered fiber layup head laterally diverging from a baseline geodesie lattice to avoid structural design features and to maintain spacing from adjacent steered lattice ribs;   employing the at least one unidirectional steered fiber layup head to lay down a plurality of collimated tows on the base interface of each of the plurality of lattice ribs for a plurality of unidirectional tow plies in each lattice rib;   steering a fiber placement head in the at least one unidirectional steered fiber layup head to match the lattice rib shape laterally diverging from the baseline geodesie lattice to avoid structural design features and to maintain spacing from adjacent steered lattice ribs;   employing the at least one cross plied laminate steered fiber layup head to lay a cap over the plurality of unidirectional tow plies in each of the plurality of lattice ribs; and   steering a band placement head in the at least one cross plied laminate steered fiber layup head to track the lattice rib shape and position the cap over the plurality of unidirectional tow plies.   
     
     
         2 . canceled 
     
     
         3 . canceled 
     
     
         4 . The method as defined in  claim 2  wherein steering of the fiber placement head additionally includes rotating the fiber placement head about a nominal axis perpendicular to a mold surface to maintain fiber alignment with a direction of travel. 
     
     
         5 . The method as defined in  claim 3  wherein steering of the band placement head additionally includes rotating the band placement head about a nominal axis perpendicular to a mold surface to maintain band alignment with the direction of travel. 
     
     
         6 . The method as defined in  claim 1  wherein the step of employing at least one unidirectional steered fiber layup head to lay down a plurality of collimated tows in a predetermined laminated pattern on a mold surface to produce a fuselage skin further includes employing a tow cutter and clamp mechanism in a fiber placement head to terminate and restart the collimated tows at the design features. 
     
     
         7 . The method as defined in  claim 1  wherein the step of employing the at least one cross plied laminate steered fiber layup head to lay a cap over the plurality of unidirectional tow plies further comprises draping of the cap over the plurality of tow plies. 
     
     
         8 . The method as defined in  claim 7  further comprising extending the draped cap over a surface of the skin adjacent the lattice rib. 
     
     
         9 . A system for fabrication of an aerospace structure comprising:
 a mold having a surface;   at least one unidirectional steered fiber layup head adapted to lay down a plurality of first collimated tows in a predetermined laminated pattern on the mold surface to produce a fuselage skin;   at least one cross plied laminate steered fiber layup head adapted to lay down a cross plied laminate base interface on the fuselage skin to establish a lattice rib shape for each of a plurality of lattice ribs in a lattice layup, said at least one cross plied laminate steered fiber layup head having a band placement head steerable to diverage from a baseline geodesie lattice pattern to avoid structural design features and to maintain spacing from adjacent steered lattice ribs; and,   said at least one unidirectional steered fiber layup head further adapted to lay down a plurality of second collimated tows on the base interface of each of the plurality of lattice ribs for a first plurality of unidirectional tow plies in each lattice rib, said at least one unidirectional steered fiber layup head having a fiber placement head steerable to match the lattice rib shape to avoid the structural design features and to maintain spacing from the adjacent steered lattice ribs.   
     
     
         10 . The system as defined in  claim 9  wherein said at least one cross plied laminate steered fiber layup head is further adapted to lay a cap over the plurality of unidirectional tow plies in each of the plurality of lattice ribs, said band placement head further steerable to track the lattice rib shape and position the cap over the plurality of unidirectional tow plies. 
     
     
         11 . The system as defined in  claim 9  wherein the band placement head is laterally translatable relative to a baseline geodesic lattice. 
     
     
         12 . The system as defined in  claim 11  wherein the band placement head is rotatable about a nominal axis matinained perpendicular to the surface of the mold to maintain band alignment with a direction of travel. 
     
     
         13 . The system as defined in  claim 9  wherein the fiber placement head is laterally translatable relative to a baseline geodesic lattice. 
     
     
         14 . The system as defined in  claim 13  wherein the fiber placement head is rotatable about a nominal axis maintained perpendicular to the surface of the mold to maintain fiber alignment with a direction of travel. 
     
     
         15 . The system as defined in  claim 9  wherein the at least one unidirectional steered fiber layup head further comprises a plurality of spindles each carrying tows of structural fiber, said tows of structural fiber dispensed from the spindles with controlled tension to the fiber placement head as individual tows. 
     
     
         16 . The system as defined in  claim 15  further comprising:
 a band collimator in the fiber placement head adapted to combine the individual tows into the first or second collimated tows; 
 tow restart rollers receiving the first or second collimated tows from the band collimator, 
 a compaction roller adapted to press the first or second collimated tows from the tow restart rollers initially onto the surface of the mold and subsequently on prior laid first collimated tows, laminate interface or second collimated tows to produce multiple layer structures; and 
 a controlled heat source proximate the compaction roller for adhering the first or seocnd collimated tows; and, a band cutter and clamp mechanism adapted to terminate each fiber band along a direction of head travel. 
 
     
     
         17 . The system as defined in  claim 9  wherein the at least one cross plied laminate SFL head further comprises a plurality of cassettes each cassette having rolled cross plied fiber laminate bands of determined widths for the caps and base layer, each cross plied laminate band fed under controlled tension to the band placement head. 
     
     
         18 . The system as defined in  claim 17  further comprising:
 band restart rollers receiving cross plied laminate band; 
 a compaction roller adapted to press initially each cross plied laminate band onto the skin as the laminate base interface or prior laid unidirectional tow plies; and, 
 a controlled heat source proximate the compaction roller for adhering each cross plied laminate band; 
 a band cutter and clamp mechanism adapted to terminate a run of each cross plied laminate band along a direction of head travel. 
 
     
     
         19 . A damage tolerant lattice rib structure comprising:
 a skin having a plurality of collimated tows in a predetermined laminated pattern;   a cross plied laminate base interface laid on the skin to establish a lattice rib shape for each of a plurality of lattice ribs, said lattice ribs steered for lateral displacement from features in the skin;   a first plurality of collimated tows laid on the base interface of each of the plurality of lattice ribs for a first plurality of unidirectional tow plies in each lattice rib;   a first cap laid over the plurality of unidirectional tow plies in each of the plurality of lattice ribs;   a second plurality of collimated tows laid on the first cap of each of the plurality of lattice ribs for a second plurality of unidirectional tow plies in each lattice rib; and,   a second cap laid over the second plurality of unidirectional tow plies in each of the plurality of lattice ribs.   
     
     
         20 . The damage tolerant lattice rib structure as defined in  claim 19  wherein the first cap has a width relative to a width of the first plurality of unidirectional tow plies sufficient to drape over the first plurality of unidirectional tow plies to a surface of the skin. 
     
     
         21 . The damage tolerant lattice rib structure as defined in  claim 19  wherein the second cap has a width relative to a width of the first plurality of unidirectional tow plies sufficient to drape over the first plurality of unidirectional tow plies and second plurality of unidirectional tow plies to a surface of the skin.