Patent Application: US-201313864127-A

Abstract:
preforms for open structured composite truss structures manufactured from large prepreg yarns on a conventional maypole braiding machine , and subsequently cured to produce fiber reinforced composites of high strength and light weight .

Description:
the structures of this invention are tubular structures ( 101 ) produced on a maypole braiding machine ( 103 ) utilizing very large prepreg yarns ( 102 ) with filament counts from 20 , 000 ( 20k ) up to 100 , 000 ( 100 k ) or more . the prepreg yarns are jacketed by braiding , yarn wrapping or extrusion of a thermoplastic sheath . fig1 is a diagram of a typical maypole braiding machine ( 103 ), although it will be appreciated by one skilled in the art that such braiding machines are available in a variety of sizes — both physically and in the number of carriers on the machine . typical carrier numbers on a machine range from 4 up to 1000 . bobbins ( 104 ) for the carriers range from 3 inches up to 3 feet and more . so the structures ( 101 ) that can be made using this invention can be scaled up in size from the examples produced to illustrate this patent . the structures ( 101 ) in the following reduction to practice are all produced on a 32 - carrier or 64 - carrier wardwell maypole horizontal braiding machine ( 103 ). fig2 shows a side view of an open structured truss ( 101 ) in cylindrical form having eight axial yarns ( 105 ) and eight helical braided yarns ( 106 ), four in each direction . the structure ( 101 ) was braided on a cylindrical mandrel ( 108 ) and after curing was removed prior to insertion of four “ z ” prepreg reinforcing yarns ( 107 ), also commonly referred as cross yarns , strut yarns , or through - the - thickness yarns , which were subsequently cured in place . fig3 is a drawing of the cross section of the structure ( 101 ) in fig2 . fig4 is a perspective drawing of the same structure . fig5 shows a picture of the prepreg yarns ( 102 ) as they transition from the carrier yarn packages to the braid consolidation point ( fell point ) of the structure . one skilled in the art will immediately understand that the size and shape of the braid openings as well as the diameter of the structure are determined by the number of yarns , the speed of the braiding head , the speed of the take up , and the size of any mandrel ( 108 ) inserted into the center of the forming structure ( 101 ). it will also be understood that the mandrel cross section can be any polygon shape ( fig6 ) or any convex curved elongate shape . the mandrel may also vary in cross sectional size along its length . an open structured cylinder ( 101 ) was made according to the teaching of this invention , but similar in size and weight per unit length to an energy drink can and similar in size and weight to a prepreg braided sleeve constructed of carbon fiber and epoxy resin . the structure was made from a 36k assembled prepreg carbon yarn ( 102 ) ( from tcr composites ) core with eight helical yarns in the jacket . the jacket yarns were 200 denier vectran ™ yarns which were braided around the 32 prepreg tow carrier jacket . the jacket consists of eight helical yarns and eight axial yarns arranged in a true triaxial configuration . the open structured composite ( 101 ) was made on a 32 - carrier maypole braider ( 103 ) with four helical yarns ( 106 ) and four axial yarns ( 105 ) in the true triaxial structure ( as shown in fig7 ). in the true triaxial structure , the axial yarns ( 105 ) interlace with the helical yarns . the crossover joints in this structure ( 101 ) were reinforced with additional epoxy resin . both the aluminum can and the cured prepreg could be easily crushed by hand , but the cured open truss structure ( 101 ) could not be crushed by hand . open structured cylinders ( 101 ) similar to that disclosed in example 1 may be assembled into larger structures like that shown in fig6 . fig6 is a drawing of a framework for a human powered vehicle for a student “ moonbuggy ” competition at nasa &# 39 ; s marshall space flight center . the framework was constructed of cylindrical open structured trusses ( 101 ) produced in accordance with the teachings of this invention using the z direction reinforcement ( 107 ) of yarn intersection joints shown in fig2 , 3 , and 4 . an open truss structure was constructed using jacketed 36k carbon prepreg yarns ( 102 )— namely , three axial ( 105 ) and eight helical ( 106 ) prepreg yarns — in a true triaxial configuration . a mandrel ( 108 ) of triangular cross section was used . each helical prepreg yarn ( 106 ) was flanked by 2 kevlar ™ 1000 denier yarns . the structure was cured on the mandrel ( 108 ) to set the shape and then the smaller kevlar ™ flanker yarns ( 109 ) and the joints were coated with resin before curing again . the kevlar ™ yarns ( 109 ) were on either side of the cured yarns ( 102 ). the flanking yarns ( 109 ) helped to stabilize the joints . the geometry of the structure ( 101 ) is shown in fig9 and in enlarged view ( fig1 ). an open truss structure ( 101 ) was constructed using 8 axial ( 105 ) and 8 helical ( 106 ) jacketed 36k prepreg carbon tows on a maypole braiding machine ( 103 ) set up for true triaxial braiding . the mandrel ( 108 ) was a 1 . 5 inch diameter pipe with a 1 . 5 inch diameter sleeve of braided fiberglass covering the pipe . the open structured tube ( 101 ) and sleeve was painted with liquid resin and then cured . the structure had significantly greater strength than the same structure ( 101 ) without the added sleeve . the structure ( 101 ) of example 4 was taken before painting with resin and was covered with a 1 . 5 inch diameter braided fiberglass sleeve . the mandrel ( 108 ) with its 3 layers was vacuum bagged and vacuum infused with liquid epoxy resin before curing . the composite structure ( 101 ) was very strong and supported a 200 pound person standing and jumping on the side of the structure ( 101 ). in this configuration , as in example 4 , the lattice truss ( 101 ) with a sleeve can be viewed as rib stiffened cylindrical structure which on larger scale might be useful as a pipe , tank or rocket motor . an open structured truss structure ( 101 ) was constructed using jacketed prepreg carbon yarns ( 102 ) on a maypole braiding machine ( 103 ). the structure used 4 - 36k axials ( 105 ) and 16 - helicals ( 106 ) ( 8 - 36k and 8 - 72k ). the helical yarns ( 106 ) were arranged in sets of 4 with the smaller two in the center and the larger 2 flanking either side . the yarns ( 102 ) were braided on a 2 . 5 inch diameter mandrel ( 108 ). the joints were strengthened and reinforced by painting with additional epoxy resin before curing . the product was used as a drive shaft by a student team in a formula style race car for intercollegiate competition . the axials ( 105 ) and helicals ( 106 ) were interlaced into a titanium gear to transmit the power . the structure had a 75 % weight saving over the metal drive shaft it replaced . hou , a ., gramoll , k ., compressive strength of composite lattice structures , journal of reinforced plastics and composites march 1998 17 : 462 - 483 hou , a ., gramoll , k ., fabrication and compressive strength of the composite attachment fitting for launch vehicles , j of advanced materials , 2000 , vol . 32 , no 1 , pp . 39 - 45 jensen , m . j ., jensen , d . w ., howcroft , a . d ., continuous manfacturing of cylindrical composite lattice structures , texcomp10 recent advances in textile composites , edited by christophe binetruy , francois boussu , 2010 , p . 80 - 87 mouritz a ., gellert , e ., burchill , p ., challis , k ., review of advanced composite structures for naval ships and submarines , composite structures , 2001 zhang , q ., beale , d ., adanur , s ., broughton , r . & amp ; 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