Abstract:
Disclosed herein is a composite pressure vessel with a liner having a polar boss and a blind boss a shell is formed around the liner via one or more filament wrappings continuously disposed around at least a substantial portion of the liner assembly combined the liner and filament wrapping have a support profile. To reduce susceptible to rupture a locally disposed filament fiber is added.

Description:
This disclosure was made with Government support under Contract no. DE-FC36-04GO14010, awarded by the Department of Energy. The Government has certain rights in this disclosure. 
    
    
     BACKGROUND 
     Field 
     This disclosure relates to high pressure storage devices and processes of manufacture. More particularly, this disclosure relates to improved methods of fabricating composite pressure vessels with internal liners for storage of hydrogen, natural gas, or other gases or liquids, specifically with respect to improvements in high-weight and high-cost efficiency manufacturing methodology. 
     SUMMARY 
     According to at least some aspects of some implementations, disclosed is a composite pressure vessel, comprising: a liner assembly having a non-homogenous support profile; and a shell, further comprising: at least one continuous and general layer of a filament wrap disposed around the liner assembly; and at least one non-continuous and local fiber segment. 
     The location of the at least one fiber segment may correspond to an area of the liner assembly that is more susceptible to rupture than other areas of the liner assembly, according to the non-homogenous support profile. The at least one at least one continuous and general layer of a filament wrap and the at least one non-continuous and local fiber segment may be disposed in alternating layers on the liner assembly. 
     Complementary pairs of fiber segments may be disposed with respective angles of ±φ relative to a principal axis extending through the composite pressure vessel. The complementary pairs of fiber segments may be configured to address a non-homogenous stress distribution profile of the composite pressure vessel. 
     The at least one fiber segment may form a hoop disposed axially about a principal axis extending through the composite pressure vessel, wherein each portion of the hoop may be substantially perpendicular to the principal axis. The hoop may be configured to address a non-homogenous stress distribution profile of the composite pressure vessel. 
     The filament wrap may comprise a filament wound fiber and a resin. The filament wound fiber may comprise at least one inorganic or organic fiber. The inorganic or organic fiber may comprise at least one of carbon, glass, basalt, boron, aramid, Kevlar, high-density polyethylene (HDPE), and nylon. 
     The fiber segment may comprise a dry fiber impregnated with a resin. The dry fiber comprises at least one inorganic or organic fiber. The inorganic or organic fiber may comprise at least one of carbon, glass, basalt, boron, aramid, Kevlar, high-density polyethylene (HDPE), PP, PE, PET, PEN, zylon, and nylon. The resin may comprise at least one of a thermoset polymer resin and a thermoplastic polymer resin. 
     Each of the at least one layer of a filament wrap and the at least one fiber segment may be disposed with axial symmetry about a principal axis. 
     According to at least some aspects of some implementations, disclosed is a composite pressure vessel, comprising: a liner assembly, further comprising: a liner; at least one of a polar boss and a blind boss; and a shell, further comprising: at least one layer of a filament wrap continuously disposed around at least a substantial portion of the liner assembly, wherein the liner assembly and the filament wrap combined have a non-homogenous support profile; and at least one fiber segment locally disposed on an area of the liner assembly and the at least one layer of a filament wrap that is more susceptible to rupture than other areas of the liner assembly, according to the non-homogenous support profile. 
     The liner may be at least one of a plastic liner and a metal liner configured as a gas barrier. The polar boss may be a metal fitting directly attached to the liner and is configured to provide a connection to a valve system. The composite pressure vessel may be configured for storage of gas or liquid and further configured for any on-board or stationary application. 
    
    
     
       DRAWINGS 
       The above-mentioned features and objects of the present disclosure will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein like reference numerals denote like elements and in which: 
         FIG. 1  shows a cross-sectional view of an implementation of a pressure vessel with composite wrapped around the liner assembly; 
         FIG. 2  shows a cross-sectional view of an implementation of a pressure vessel with liner assembly with polar boss on one dome and blind boss on another dome; 
         FIG. 3  shows a cross-sectional view of an implementation of a pressure vessel with Tank inside which the liner assembly has polar boss on both domes; 
         FIG. 4  shows a cross-sectional view of an implementation of a dome region of a pressure vessel having a blind boss; 
         FIG. 5  shows a cross-sectional view of an implementation of a dome region of a pressure vessel having a polar boss; 
         FIG. 6  shows a view of an implementation of a cylinder and dome region of a pressure vessel with AFP placed fiber segments only in the dome region; 
         FIG. 7  shows a view of an implementation of a cylinder and dome region of a pressure vessel with AFP placed fiber segments in both the dome region and cylinder region; 
         FIG. 8  shows a view of an implementation of a cylinder and dome region of a pressure vessel with AFP placed fiber segments only in the cylinder region; 
         FIG. 9  shows a view of an implementation of a cylinder and dome region of a pressure vessel with AFP placed fiber segments having the same or different angles relative to the principal axis; 
         FIG. 10  shows a view of an implementation of a cylinder and dome region of a pressure vessel with AFP placed fiber segments wound in hoop direction in the cylinder region, the dome region, or both; and 
         FIG. 11  shows a representation of conditions at a dome region of an implementation of a pressure vessel. 
     
    
    
     DETAILED DESCRIPTION 
     One of the primary issues associated with implementation of gaseous fueled vehicles and the like is in manufacturing components at cost and weight that can be borne by the consumer and industry. A significant portion of the cost of the vessel is taken by raw material cost. 
     High-pressure storage vessels may be made by wrapping fiber composites around a liner assembly  20 , which is used as a mandrel. To support high pressure (3,000 to 10,000 or greater PSI service pressure) within the storage vessel, and to maintain safety of operation, greater amounts of material must be used to provide greater support. An increase in the amount of material used results in the penalty of increased weight and material cost. 
     According to at least some aspects of some implementations, pressure vessel  10  comprises liner assembly  20  configured to enclose a gas or liquid and a shell  40  to provide support to liner assembly  20 . Pressure vessel  10  may have one of a variety of shapes, including cylindrical, spherical, or combinations thereof. Pressure vessel  10  may be axially symmetric about a principal axis  52  extending along a longitudinal length of pressure vessel  10 . According to at least some aspects of some implementations, as shown in  FIG. 1 , pressure vessel  10  may comprise cylindrical region  30  and two dome regions  32 . Other shapes are contemplated and considered within the current disclosure. 
     According to at least some aspects of some implementations, liner assembly  20  comprises liner  22 , and at least one of polar boss  24  and blind boss  26 . Liner  22  may be composed of plastic, metal, or other materials to contain a gas or liquid. According to at least some aspects of some implementations, liner  22  may be impermeable with respect to selected contents of pressure vessel  10 . According to at least some aspects of some implementations, the shape of liner assembly  20  may contribute to the shape of pressure vessel  10 . 
     At least one of polar boss  24  and blind boss  26  may be disposed near at least one end of liner assembly  20 . For example, as shown in  FIG. 1 , polar boss  24  may be disposed at one end and blind boss  26  may be disposed at an opposite end. For example, as shown in  FIG. 3 , one polar boss  24  may be disposed at each of two ends. As shown in  FIG. 5 , polar boss  24  may provide selective access to the interior portion of liner assembly  20  for providing or discharging the contents of pressure vessel  10 . Polar boss  24  may be configured to provide a connection to a valve system. Polar boss  24  may be made of metal or other durable material. As shown in  FIG. 4 , blind boss  26  may provide support to liner  22 . Polar boss  24  and blind boss  26  may allow liner assembly  20  to be supported and rotated about its principal axis  52  as a mandrel. 
     According to at least some aspects of some implementations, pressure vessel  10  comprises shell  40 . Shell  40  provides support to liner assembly  20  against deformation and rupture due to pressure from within liner assembly  20 . Shell  40  may comprise at least one of filament wrap  42  and fiber segment  44 . According to at least some aspects of some implementations, shell  40  may comprise alternating layers of filament wrap  42  and fiber segments  44 . Either one of filament wrap  42  and fiber segment  44  may provide an innermost layer or an outermost layer. 
     According to at least some aspects of some implementations, filament wrap  42  may form a continuous wrap around more than one full rotation of liner assembly  20  about its principal axis  52  or along more than one longitudinal length of liner assembly  20 . Filament wrap  42  may form a general layer around liner assembly  20 , such that a substantial portion of liner assembly  20  may be covered by filament wrap  42 . 
     According to at least some aspects of some implementations, at least one of liner assembly  20 , filament wrap  42 , and fiber segments  44  may have a non-homogenous support profile. A support profile may be defined as an evaluation at every point on the surface of a structure such as a liner assembly  20  (or a wound liner) of the protection against deformation and rupture due to pressure from within the structure. A non-homogenous support profile implies that certain points are more or less susceptible to deformation and rupture than other points on the surface of the structure. Such points are determinable using, at least in part, computational or experimental means discussed herein. 
     According to at least some aspects of some implementations, liner assembly  20  with at least one layer of filament wrap  42  may have a non-homogenous support profile. While filament wrap  42  may provide generally increased support against rupture, the support profile may nonetheless have absolute or relative deficiencies. According to at least some aspects of some implementations, because some regions on liner assembly  20  with at least one layer of filament wrap  42  have variable radius of curvature, and the stress condition changes as the radius of curvature changes, one layer of filament wrap  42  may not be able to reinforce all of the regions it covers. 
     According to at least some aspects of some implementations, at least one fiber segment  44  may be included in shell  40 . Fiber segments  44  may be present in shell  40  in non-continuous segments, such that the segments do not wrap around substantially more than one full rotation of liner assembly  20  about its principal axis  52  or along substantially more than one longitudinal length of liner assembly  20 . Fiber segments  44  may be present locally within shell  40 , such that each fiber segment  44  does not cover a substantial portion of liner assembly  20 . Rather, the locality of fiber segment  44  may correspond to an area in which support provided by filament wrap  42  alone is insufficient for a desired purpose or relatively insufficient compared to other areas, according to the general and continuous coverage of filament wrap  42 . Such absolute or relative deficiency is determinable by computational or experimental methods and may correspond to a non-homogenous support profile of liner assembly  20  alone or a non-homogenous support profile of liner assembly  20  with filament wrap  42 . 
     According to at least some aspects of some implementations, at least one of liner assembly  20 , filament wrap  42 , and fiber segments  44  may have a non-homogenous stress distribution profile. A stress distribution profile may be defined as an evaluation at every point on the surface of a structure such as a liner assembly  20  (or a wound liner) of a direction in which stress is distributed due to pressure from within the structure. The direction in which stress is distributed may be attributable to the geometry of the structure, and may be expressed as having a multiplicity of contributing components. A non-homogenous stress distribution profile implies that at least one point has a distinct direction in which stress is distributed. Such a profile is determinable based on computational or experimental means, as discussed herein. 
     According to at least some aspects of some implementations, a stress distribution may have multiple contributing components. A representation of certain conditions at dome region  32  of an implementation of pressure vessel  10  is shown in  FIG. 11 . For example, at any given point on dome region  32 , a radius of curvature in a meridional direction is defined by R m . The meridional direction corresponds to an arc on the surface of principal axis  52  that intersects principal axis  52  at the tip of dome region  32 , intersects tangent line  50  at two points, and has bilateral symmetry across principal axis  52 . At any given point on dome region  32 , a radius of curvature in a parallel direction and disposed axially about principal axis  52  is defined by R p . The parallel direction corresponds to an arc on the surface of dome region  32  that is perpendicular to principal axis  52  at any given point and is disposed axially about principal axis  52 . Tangent line  50  is an example of an arc of a parallel direction (see  FIGS. 6-10 ). 
     The stress balance, p, of a given point on the vessel inner surface may be expressed as: 
                     N   α       R   m       +       N   β       R   P         =   p     ,         
where N α  and N β  represent the stress of that point in the meridional and parallel directions, respectively.
 
     R m  and R P  can be derived and expressed as: 
               R   m     =     -         (     1   +       (     z   ′     )     2       )       3   /   2         z   ″                   and               R   P     =     -         r   ⁡     (     1   +       (     z   ′     )     2       )         1   /   2         z   ′               
where r, z′, and z″ are determinable polar coordinates corresponding to the given point.
 
     N α  and N β  can be derived and expressed as: 
               N   α     =       -   Q     ⁢         1   +       (     z   ′     )     2           rz   ′                   and                 N   β     =       -         1   +       (     z   ′     )     2           z   ′         ⁢     (     pr   -       Qz   ″         z   ′     ⁡     (     1   +       (     z   ′     )     2       )           )         ,         
where Q is axial stress. Mathematical expressions and derivations are further set forth in Appendix A, the entirety of which is incorporated by reference, as if set forth herein in its entirety.
 
     On pressure vessel  10 , near the transition region between cylinder region  30  and dome region  32 , there is a sudden change of R m  and R P ; also, along the surface of dome region  32 , R m  and R P  are constantly varying, therefore the stress condition in these regions is complicated. At each location, for example location A, certain amount and type of reinforcement needs to be placed locally at certain angles; another location, B, even if very close to location A, may require different amount and type of reinforcement placed at different angles to support. 
     According to at least some aspects of some implementations, WFW is a winding process (i.e. it introduces continuous reinforcement wound into the structure). Therefore if we introduce some material over location A on dome region  32 , in order to support the load there to address a non-homogenous support profile, the reinforcement must also cover other regions, such as cylinder region  30 , simply because of the continuous nature, even though some of these reinforcement materials are parasitic at other locations except location A. 
     According to at least some aspects of some implementations, at least one non-continuous fiber segment  44  may be locally disposed at or near dome region  32  of pressure vessel  10 . According to at least some aspects of some implementations and as shown in  FIG. 6 , tangent line  50  defines the transition between cylinder region  30  and dome region  32 . 
     According to at least some aspects of some implementations, at least one non-continuous fiber segment  44  is locally disposed at or near dome region  32  of pressure vessel  10 . According to at least some aspects of some implementations, pairs of fiber segments  44  may be disposed with bilateral symmetry across principal axis  52 , as shown in  FIGS. 6-9 . As shown in  FIG. 6 , at least one pair of fiber segments  44  may be disposed entirely on dome region  32 . As shown in  FIG. 7 , a pair of fiber segments  44  may be disposed so as to cross tangent line  50 . As shown in  FIG. 8 , a pair of fiber segments  44  may be disposed entirely on cylinder region  30 . As shown in  FIG. 9 , fiber segments  44  may form a substantially linear shape from which an angle φ relative to principal axis  52  may be determined. Complementary pairs of fiber segments  44  may be disposed with respective angles of ±φ relative to principal axis  52 . Pairs of fiber segments  44  may intersect or may provide bilateral symmetry across principal axis  52  without intersecting. 
     According to at least some aspects of some implementations, fiber segment  44  may be configured to address a non-homogenous stress distribution profile. Angles ±φ may be determined to address a non-homogenous stress distribution profile, where pressure, p, at a given point has a meridional stress component N α  and a parallel stress component N β . For example, relatively smaller angles for ±φ (approaching φ=0°) may address a relatively larger meridional stress component N α . Relatively larger angles for for ±φ (approaching φ=90°) may address a relatively larger parallel stress component N β . Ideal values for ±φ depend on the geometry of dome region  32 , vary across the surface of dome region  32 , and are determinable. 
     According to at least some aspects of some implementations, hoops of fiber segments  44  may be disposed around pressure vessel  10  with axial symmetry around principal axis  52 , as shown in  FIG. 10 . For example, a hoop may be placed primarily to address a parallel stress component N β . 
     According to at least some aspects of some implementations, filament wrap  42 , individual fiber segments  44 , pairs of fiber segments  44  having angles ±φ, hoops of fiber segments  44 , or combinations thereof are used to address both a non-homogenous support profile and a non-homogenous stress distribution profile. 
     Wet filament winding (WFW) processes, may be used to manufacturer gas or liquid storage high pressure vessels. Filament winding processes generally involve winding filaments around a mold or mandrel. Filament materials may include fiber tows impregnated with liquid resin just before it is integrated into the structure or a pre-preg fiber tow, i.e., a filament tow with pre-impregnated resins. 
     According to at least some aspects of some implementations, at least one filament winding process may be used to form shell  40  onto liner assembly  20 . According to at least some aspects of some implementations, WFW may be performed to contribute filament wrap  42  to shell  40  of pressure vessel  10 . In WFW, liner assembly  20  may act as a mandrel as it rotates about its principal axis  52  while a carriage moves parallel to the principal axis  52  and applies filament wrap  42 . The carriage may travel parallel to the principal axis  52  in one or more directions and subsequently travel in an opposite direction while applying a single continuous filament wrap  42  or multiple continuous filament wraps  42 . This process may be repeated as desired with one continuous filament wrap  42 . The resulting contribution is a filament wrap  42  in helical layers, polar layers, or hoop layers. 
     According to at least some aspects of some implementations, filament wrap  42  is applied in a desired pattern onto the outer surface of liner assembly  20 . For example, filament wrap  42  may be applied in helical layers, polar layers, or hoop layers around liner assembly  20  and along the length of liner assembly  20 . The pattern may be applied in a regular repeating manner to provide symmetrical distribution of support against high pressures. The pattern may also be varied so that successive layers are plied or oriented differently, to provide diverse and comprehensive coverage. The angle at which material is applied during WFW contributes to the properties of the final product. These properties may be determined from analytical and numerical stress analysis. From stress analysis, it may become clear where the material needs to be placed at given angles in order to reinforce a given region. WFW is well suited to automation. 
     According to at least some aspects of some implementations, the placement during WFW is general, in that a substantial portion of liner assembly  20  may be covered by WFW. According to at least some aspects of some implementations, the placement during WFW is continuous, in that a single phase of WFW may be used to wrap around more than one full rotation of liner assembly  20  about its principal axis  52  or along more than one longitudinal length of liner assembly  20 . 
     According to at least some aspects of some implementations, filament wrap  42  comprises a filament wound fiber, such as either inorganic or organic fiber. Examples include carbon, glass, basalt, boron, aramid, Kevlar, high-density polyethylene (HDPE), zylon, PP, PE, PET, PEN, PBT, and nylon. Other inorganic and organic fibers are contemplated by the present disclosure. According to at least some aspects of some implementations, filament wrap  42  further comprises a resin. The resin may be impregnated onto the filament wound fiber before or as the filament wound fiber is wound onto liner assembly  20 . 
     According to at least some aspects of some implementations, the resin of filament wrap  42  may have a low-viscosity or be in a liquid state as it is impregnated onto the filament wound fiber and applied to liner assembly  20 . The resin may be based on Di-Glycidyl Ether of Bisphenol-A (DGEBA), undiluted and non-toughened epoxy resin cured by a mixture of propyl oxide amine and cyclo-aliphatic amine. The low-viscosity may provide flexibility and ease during application. For example, a continuous and automated WFW process may be operated at a more efficient rate where the resin is in a liquid state. According to at least some aspects of some implementations, once the winding process is finished, the whole assembly is placed in an oven to solidify the resin. According to at least some aspects of some implementations, liner assembly  20  is pressurized as the resin is heated and solidified. For example, a pressure within liner assembly  20  may be relatively higher than the pressure outside liner assembly  20 , such that liner assembly  20  is expanded and filament wrap  42  is compressed, thereby removing air bubbles during the heating process. 
     According to at least some aspects of some implementations, the repetitive nature of some filament winding processes may result in parasitic fiber tows in places where they are not needed. For example, filament winding may result in a non-homogenous support profile, where some regions having higher support needs may require greater support. Where filament winding processes are continuous and automated, they do not selectively apply additional materials where greater support is needed. If the amount of material is increased generally to support such regions requiring greater support, then the amount of material overall is increased, including in regions not requiring such additional support. These parasitic materials increase the weight and cost significantly. 
     According to at least some aspects of some implementations, automated fiber placement (AFP) is used in combination with WFW, to locally introduce non-continuous fiber segments  44  to individual locations. Through computational, experimental, or other stress analysis, locations having absolute or relatively insufficient support via filament winding processes may be determined. 
     According to at least some aspects of some implementations, fiber segments  44  used in AFP may comprise a dry fiber impregnated with a high-viscosity resin in a gel state. The dry fiber may comprise one or more inorganic or organic materials. Examples include carbon, glass, basalt, boron, aramid, Kevlar, high-density polyethylene (HDPE), zylon, PP, PE, PET, PEN, PBT, and nylon. Other inorganic and organic fibers are contemplated by the present disclosure. The resin may be either thermoset or thermoplastic. The range of viscosities for the high-viscosity resin include any viscosity that is conducive to the placement of the fiber segments  44 . For example, the placement during AFP may be made more precise where the resin is in a gel state. According to at least some aspects of some implementations, fiber segment  44  further comprises a toughening agent. 
     According to at least some aspects of some implementations, fiber segments  44  are heated, applied with pressure, and consolidated on any surface by at least one roller medium. The process causes adhesion of fiber segments  44  to the surface with the resin of fiber segments  44 . According to at least some aspects of some implementations, fiber segments  44  are selectively provided at desired locations. Fiber segments  44  may be in the form of single or multiple narrow, slit tapes or tows to make up a given total prepreg band width. According to at least some aspects of some implementations, a fiber segment  44  forms a hoop disposed axially about principal axis  52 , wherein each portion of fiber segment  44  is substantially perpendicular to the principal axis  52 , as shown in  FIG. 10 . According to at least some aspects of some implementations, pairs of fiber segments  44  are placed with respective angles of ±φ relative to principal axis  52 , as shown in  FIGS. 6-9 . The pairs provide bilateral symmetry across principal axis  52 , resulting in balanced support. 
     According to at least some aspects of some implementations, pressure vessel  10  is configured to store a gas or a liquid. Pressure vessel  10  may be configured to store a fuel for a vehicle. Vehicles include, but are not limited to, any means of conveyance across marine, surface, terrestrial, or other medium. Pressure vessel  10  may be configure for stationary application or on-board vehicle application. 
     While the apparatus and method have been described in terms of what are presently considered to be the most practical and preferred implementations, it is to be understood that the disclosure need not be limited to the disclosed implementations. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures. The present disclosure includes any and all implementations of the following claims.