Patent Publication Number: US-2020291812-A1

Title: Multiple layer structure

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/805,467 filed Nov. 7, 2017, which is incorporated herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     An aircraft engine, for example a turbine engine, air is drawn into the front of the engine through an inlet, compressed by a compressor, and mixed with fuel in a combustor. The mixture is burned and passes through a turbine. The flow of combustion gas expands through the turbine which in turn spins the shaft and provides power to the compressor. The hot exhaust gases are further expanded through nozzles at the back of the engine, generating powerful thrust, which drives the aircraft forward. 
     A fan casing can define the inlet and a fan formed by a plurality of blades. Variable conditions exist in which an engine operates. Foreign objects, such as birds, hailstones, ice, sand, and rain may be entrained in the inlet of the engine where impact with portions of the engine can occur, including impact with an interior of the fan casing. In some cases impact may cause a portion of the blade to become torn out which is commonly known as fan blade out. The loose fan blade can impact the interior of the fan casing as well. 
     The fan casing can be formed in part by composite materials formed to withstand impacts caused by foreign objects or fan blade outs. Depending on the thickness and of the composite material in the fan casing, the composite material can add a significant amount of weight to the engine. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, the present disclosure relates to a multiple layer structure having a sub-portion defining an impact zone, the multiple layers comprising an inner composite fiber layer, an outer composite fiber layer overlying the inner composite fiber layer; and a woven glass layer sandwiched between the inner and outer composite fiber layers made from fibers having a higher puncture resistance than the fibers used in the inner composite fiber layer or the outer composite fiber layer; wherein the inner composite fiber layer, outer composite fiber layer, and the woven glass layer overly the impact zone, and the outer composite fiber layer abuts the inner composite fiber layer beyond the impact zone. 
     In another aspect the present disclosure relates to a multiple layer structure having a sub-portion defining an impact zone, the multiple layers comprising an inner composite fiber layer formed from a woven fiber with a weave oriented such that the warp weave direction is in a first direction with respect to the multiple layer structure and the weft weave direction is in a second direction perpendicular to the first direction, an outer composite fiber layer overlying the inner composite fiber layer, and a woven glass layer sandwiched between the inner and outer composite fiber layers, wherein the inner composite fiber layer, outer composite fiber layer, and the woven glass layer overly the impact zone, and the outer composite fiber layer abuts the inner composite fiber layer beyond the impact zone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic cross-sectional view of a turbine engine. 
         FIG. 2  is an enlarged view of a fan casing for the turbine engine of  FIG. 1 . 
         FIG. 3A  is a cross-sectional view of a middle portion of the fan casing taken along line IIIA of  FIG. 2 . 
         FIG. 3B  is a cross-sectional view of an aft portion of the fan casing taken along line IIIB of  FIG. 2 . 
         FIG. 4  is a variation of the cross-sectional view of  FIG. 3A  according to another aspect of the disclosure described herein. 
         FIG. 5  is an enlarged view of the fan casing of  FIG. 2  illustrating a method of fabricating the fan casing according to an aspect of the disclosure described herein. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure is related to a fan casing circumscribing a fan for a turbine engine and having multiple layers and including a sub-portion defining a blade impact zone. For purposes of illustration, the aspects of the disclosure discussed herein will be described with respect to the fan casing for an aircraft turbine engine. It will be understood, however, that the disclosure as discussed herein is not so limited and may have general applicability within an engine, including compressors, as well as in non-aircraft applications, such as other mobile applications and non-mobile industrial, commercial, and residential applications. 
     As used herein, the term “forward” or “upstream” refers to moving in a direction toward the engine inlet, or a component being relatively closer to the engine inlet as compared to another component. The term “aft” or “downstream” used in conjunction with “forward” or “upstream” refers to a direction toward the rear or outlet of the engine relative to the engine centerline. Additionally, as used herein, the terms “radial” or “radially” refer to a dimension extending between a center longitudinal axis of the engine and an outer engine circumference. Furthermore, as used herein, the term “set” or a “set” of elements can be any number of elements, including only one. 
     All directional references (e.g., radial, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the disclosure, and do not create limitations, particularly as to the position, orientation, or use thereof. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and can include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order, and relative sizes reflected in the drawings attached hereto can vary. 
     A turbine engine  10  is illustrated in  FIG. 1 . The disclosure as discussed herein is not limited to use in a specific turbine engine, and the engine shown in  FIG. 1  is for illustrative purposes only. The turbine engine  10  includes a fan assembly  11  and a core engine  13  including a high-pressure compressor  14 , a combustor  16 , a high-pressure turbine  18 , a low-pressure turbine  20 , and a booster  22 . The fan assembly  11  is surrounded by a multiple layer fan casing  23  and includes a fan  12  having an array of fan blades  24  extending radially outward from a rotor disc  26 . The fan assembly  11  can define an axial length (L) of an annular shell  25  comprising an inner composite fiber layer  27  surrounding the fan  12 . The engine  10  has an intake side  28  and an exhaust side  30 . The fan assembly  11  and the low-pressure turbine  20  are coupled by a first rotor shaft  31 , and the high-pressure compressor  14  and the high-pressure turbine  18  are coupled by a second rotor shaft  32 . 
     During operation, air flows through the fan assembly  11 , along a central axis  34 , and compressed air is supplied to the high-pressure compressor  14 . The highly compressed air is delivered to the combustor  16 . Airflow (not shown in  FIG. 1 ) from the combustor  16  drives the fan assembly  11  by way of the first rotor shaft  31 . 
       FIG. 2  is an enlarged partial cross-sectional view of the multiple layer fan casing  23  from  FIG. 1 . The multiple layer fan casing  23  can at least in part define the axial length (L) of the fan assembly  11 . More specifically, the length (L) circumscribes a sub-portion of the fan casing defining a blade impact zone  40  of the fan assembly  11 . The blade impact zone  40  can be larger or smaller than illustrated and is defined as an axially extending region most likely to receive an impact from fan blade  24  in the event of a fan blade out (FBO). An FBO is when a portion of the fan blade  24  becomes torn out or dislodged from the fan assembly  11 , travels along a blade trajectory path  42 , and impacts the multiple layer fan casing  23 . A blade trajectory path  42  is a path along which a portion of the fan blade  24  would most likely travel in the event of an FBO. 
     The inner composite fiber layer  27  of the multiple layer fan casing  23  can be co-extensive with the fan casing such that it extends axially through the full length (L). The inner composite fiber layer  27  can extend radially between an inner surface  44  and an outer surface  46  maintaining a constant thickness (T) throughout. A non-limiting example for the inner composite layer  27  is use of a woven fiber. When the inner composite fiber layer  27  is made out of a woven fiber, there can be a constant number of weave layers across the whole length (L). More specifically all wraps extend across the entire length (L), and the weave is oriented such that the warp weave, fibers held stationary in tension, direction is in the circumferential direction of the case and the weft weave, fibers drawn through and inserted over and under the warp weave, direction is in the axial direction of the case. In such a case, thickness changes in the composite fiber layer  27  can be achieved by adding or subtracting warp fibers. The thickness (T) affects the capability, or strength and stiffness, of the inner composite fiber layer  27 . An inner composite fiber layer  27  having a greater thickness (T) decreases the axial capability of the annular shell  25  and increases the hoop capability while a lesser thickness (T) increases the axial capability but decreases the hoop capability. A thickness (T) with a warp to weft fiber ratio of between 1:2 and 2:1 optimizes both the axial and hoop capabilities. 
     Multiple layers  52  form the multiple layer fan casing  23 . The inner composite fiber layer  27  is wrapped in additional layers to form an annular casing wrap  50  circumscribing the annular shell  25  along at least a portion of the outer surface  46  of the annular shell  25 inner composite fiber layer  27 . The annular casing wrap  50  includes an outer composite fiber layer  54  overlying the inner composite fiber layer  27  with a woven glass layer  56  sandwiched therebetween. Each of the additional layers  54 ,  56  can be wrapped about the annular shell  25  to form areas of varying thickness in the radial direction with an area of maximum thickness (T MAX ) located within the blade impact zone  40  where the blade trajectory path  42  intersects the inner surface  44  of the inner composite fiber layer  27 . 
     The outer composite fiber layer  54  abuts the inner composite fiber layer  27  beyond the blade impact zone  40 . The outer composite fiber layer  54  can extend axially forward of the blade impact zone  40  to define a forward portion (F) of the annular casing wrap  50 . The forward portion (F) extends forward from a contact point (Fp) where the woven glass layer  56  terminates and the composite fiber layer  54  abuts the inner composite fiber layer  27 . It is further contemplated that the outer composite fiber layer  54  can extend axially aft from the blade impact zone  40  to define an aft portion (A) of the annular casing wrap  50 . The aft portion (A) extends aft from a contact point (Ap) where the woven glass layer  56  terminates and the composite fiber layer  54  abuts the inner composite fiber layer  27 . It is contemplated that the forward portion (F) and the aft portion (A) of the multiple layer fan casing  23  include only the inner and outer composite fiber layers  27 ,  54 . The outer composite fiber layer  54  can co-extend with the fan casing  23  such that it is equal to the axial length (L) but greater than the axial extent of the blade impact zone  40 . It is further contemplated that the outer composite fiber layer  54  is less than the axial length (L). The outer composite fiber layer  54  can include multiple wraps of layers of carbon fiber material. 
     Turning to  FIG. 3A , an enlarged view of the blade impact zone  40  is illustrated to more clearly distinguish the multiple layers  52  that form the multiple layer fan casing  23 . The woven glass layer  56  can be any type of woven glass fiber, by way of non-limiting example an S 2  class fiberglass. It is contemplated that any fiber having a higher puncture resistance than the fibers used in the inner composite fiber layer  27  or the outer composite fiber layer  54 , for example R-glass, can be used. A list of such fibers can be found in the ASM Handbook, Vol. 21 Composites. The outer composite fiber layer  54  can be, by way of non-limiting example, an intermediate modulus, IM, type 7 graphite. The outer composite fiber layer  54  can be any carbon fiber suitable for a casing and is not meant to be limited. Both the woven glass layer  56  and the outer composite fiber layer  54  can be formed with varying thickness within the blade impact zone  40  such that the thickness is increased toward the maximum thickness (T MAX ) while tailoring the hoop and axial capabilities of the multiple layer fan casing  23 . 
     The inner composite fiber layer  27  can be formed by wrapping a woven fiber preform material around the circumference of the case with the woven layer extending across the entire axial length of the case. The layer can be infused with resin and cured using a resin transfer mold (RTM) process to achieve a composite material of a constant thickness (T). By way of non-limiting example, the inner composite fiber layer  27  can be made from carbon fiber that has been woven to form a network of fibers with most fibers in the plane of the weave, but having some fibers extending through the thickness to interlock the fiber layers of the weave. The through-thickness fibers could either extend fully through the thickness to achieve a 3D weave or partially through the thickness to achieve a 2.5 D weave as is described in Structure and Mechanics of Textile Fibre Assemblies, P. Schwartz, Elsevier, 2008. It is also contemplated that the inner composite fiber layer  27  is any textile composite material having a woven, braided, non-crimp fabric for example, but not limited to graphite fiber, glass fiber, ceramic fiber, or aramid polymer fiber. 
     Turning to  FIG. 3B , an enlarged view of the aft portion (A) is illustrated to more clearly distinguish the outer composite fiber layer  54  annular shell  25 . It should be understood that this enlarged view can also represent the forward portion (F). The inner composite fiber layer  27  has the same thickness (T) as illustrated in  FIG. 3A  while the annular casing wrap  50  only includes the outer composite fiber layer  54  within the forward portion (F) and aft portion (A). 
     Turning to  FIG. 4 , it is further contemplated that another layer  60 , which can be by way of non-limiting example a woven layer, overlies the outer composite fiber layer  54  to form three distinct layers of materials within the annular casing wrap  50 . The other layer  60  can be formed from the same material as the woven glass layer  56 , by way of non-limiting example S 2  Fiberglass. It is contemplated that the other layer  60  is a different material than the woven glass layer  56 , by way of non-limiting example a material with higher elongation capability than carbon such as S-glass, E-glass, Kevlar, or Dyneema. It is further contemplated that the other layer  60  extends along the entire axial length (L1) of the annular ramp such that it is the same length as outer composite fiber layer  54 . It is also contemplated that other layer  60  extends into one of the forward portion (F) or aft portion (A) such that the annular casing wrap  50  includes two layers within the forward portion (F) or aft portion (A), where the two layers are the other layer  60  and the inner composite fiber layer  54 . 
     A method  200  of fabricating the multiple layer fan casing  23  is described below with reference to  FIG. 5 . The method  200  includes at  202  fabricating the annular shell  25  out of an inner composite fiber layer  27  with a constant thickness (T). At  204 , the annular shell  25  is wrapped with the additional layers to form the annular casing wrap  50  including at least one carbon layer, by way of non-limiting example the outer composite fiber layer  54  and at least one woven glass layer, by way of non-limiting example, the woven glass layer  56 . It should be understood that forming the multiple layers  52  can include forming another layer  60 , as described herein, where the other layer  60  overlays the outer composite fiber layer  54 . At  206  the at least one woven glass layer  56  is confined to just the blade impact zone  40 . The method further includes at  208  producing a maximum thickness (T MAX ) of annular casing wrap  50  at a point (P) along the annular shell  25  within the blade impact zone  40 . The point (P) is defined as the point where the blade trajectory path  42  intersects the multiple layer fan casing  23 . 
     The method  200  can further include at  210  abutting the at least one carbon layer with the annular shell  25 , by way of non-limiting example abutting the inner composite fiber layer  27  with the outer composite fiber layer  54  outside the blade impact zone  40 . Finally, the method can also include at  212  tapering at least one of the carbon layer  54  or glass layer  56  from the point (P) to where the outer composite fiber layer  54  abuts the inner composite fiber layer  27 . By way of non-limiting example, as illustrated, the woven glass layer  56  of glass is tapered in both the forward and aft direction such that the annular casing wrap  50  forms a substantially trapezoidal shape within the blade impact zone  40 . 
     When compared to a layered casing without additional woven glass layer(s), the annular casing wrap  50  can minimize or eliminate back-side fiber failure. In other words, through holes from blade impacts do not occur in the middle portion of the annular casing wrap  50 . During testing, impacts to areas with and without the additional layers are compared to form a baseline damage amount on the inner surface  44 . This baseline damage amount is the amount of damage sustained in both areas until the damage beings to increase in one of the areas when compared to each other. Even with kinetic energy increases up to 20% above the baseline damage amount, zero through holes were formed in the blade impact zone  40  of the annular casing wrap  50 . Tailoring the annular casing wrap  50  to cover these areas minimizes weight for the multiple layer fan casing  23  and maximizes performance of the multiple layer fan casing  23  during an FBO. 
     Benefits associated with the fan casing as described herein include a lightweight annular shell conducive to automated manufacturing due to the constant thickness and homogeneous material. Including the plurality of layers within the annular casing wrap facilitates the ability to tailor the thickness of the annular casing wrap to locations where more thickness is needed. The wrapping aspect also enables rapid modification in terms of the placement of the layers. Wrapping the annular shell minimizes any excess weight and localizes necessary thickness in the annular casing wrap. 
     To the extent not already described, the different features and structures of the various aspects can be used in combination with each other as desired. That one feature cannot be illustrated in all of the aspects is not meant to be construed that it cannot be, but is done for brevity of description. Thus, the various features of the different aspects can be mixed and matched as desired to form new examples, whether or not the new examples are expressly described. Combinations or permutations of features described herein are covered by this disclosure. Many other possible embodiments and configurations in addition to that shown in the above figures are contemplated by the present disclosure. 
     This written description uses examples to disclose aspects of the invention, including the best mode, and also to enable any person skilled in the art to practice aspects of the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.