Abstract:
A heat shield includes a ceramic composite heat shield panel having a generally concave first surface and a generally convex second surface and a pair of thickened panel edge portions provided in the heat shield panel. A heat shield assembly is also disclosed.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure relates generally to heat shields. More particularly, the disclosure relates to a ceramic heat shield which is suitable for aircraft. 
       BACKGROUND 
       [0002]    Existing aircraft heat shields may be made from titanium, which has an upper temperature limit of about 1100 degrees F. Multiple segments may be built into the titanium heat shield to facilitate thermal expansion and contraction. Aircraft engines may be designed to operate more efficiently by running at idle exhaust temperatures which are higher than the heat capacity of titanium. Therefore, in order to maintain the idle exhaust temperature at a temperature level which is lower than the heat capacity of titanium, the engine may require operation at a higher thrust with a resulting higher fuel consumption level. This may result in an increased level of brake wear. 
         [0003]    Therefore, a heat shield is needed which can withstand temperatures which are higher than the heat capacity of titanium. 
       SUMMARY 
       [0004]    The disclosure is generally directed to a heat shield. An illustrative embodiment of the heat shield includes a ceramic composite heat shield panel having a generally concave first surface and a generally convex second surface and a pair of thickened panel edge portions provided in the heat shield panel. 
         [0005]    The disclosure is further generally directed to a heat shield assembly. An illustrative embodiment of the heat shield assembly includes a heat shield comprising a ceramic composite heat shield panel having a generally concave first surface and a generally convex second surface and a pair of thickened panel edge portions provided in the heat shield panel of the heat shield. A pair of side skins extends from the pair of thickened panel edge portions, respectively. 
     
    
     
       BRIEF DESCRIPTION OF THE ILLUSTRATIONS 
         [0006]      FIG. 1  is a perspective view of an illustrative embodiment of the heat shield. 
           [0007]      FIG. 2  is a perspective view of a heat shield assembly which includes an illustrative embodiment of the heat shield and side skins (one of which is shown) attached to the heat shield assembly. 
           [0008]      FIG. 3  is an enlarged sectional perspective view, illustrating a pair of nut plates attaching a side skin to an illustrative embodiment of the heat shield in a heat shield assembly. 
           [0009]      FIG. 4  is a sectional view of an illustrative embodiment of the heat shield, more particularly detailing attachment of each nut plate to a side skin in the heat shield assembly. 
           [0010]      FIG. 5  is a transverse sectional view, taken along section lines  5 - 5  in  FIG. 1 , of an illustrative embodiment of the heat shield. 
           [0011]      FIG. 6  is an enlarged sectional view, taken along section line  6  in  FIG. 5 , of an illustrative embodiment of the heat shield. 
           [0012]      FIG. 7  is a longitudinal sectional view of an alternative illustrative embodiment of the heat shield. 
           [0013]      FIG. 8  is a flow diagram of an aircraft production and service methodology. 
           [0014]      FIG. 9  is a block diagram of an aircraft. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The disclosure is generally directed to a composite matrix ceramic (CMC) heat shield lower surface which may have a heat capacity higher than that of titanium. The ceramic heat shield may provide a one-piece (no segmented gaps) construction which may undergo minimal thermal expansion during aircraft engine thermal cycling and may have a high temperature capacity to thermally isolate structure and systems above the heat shield from engine exhaust on an aircraft. Consequently, an aircraft engine on which the heat shield is assembled may be operated at a lower idle thrust and higher temperature, resulting in decreased fuel consumption and brake wear. 
         [0016]    Referring initially to FIGS.  1  and  5 - 7 , an illustrative embodiment of the heat shield is generally indicated by reference numeral  2 . The heat shield  2  may include a heat shield panel  3  which may include a wide panel end  5  and a narrow panel end  6  and have a generally elongated, conical shape when viewed from above or below. The heat shield panel  3  may have a generally concave lower surface  3   a  and a generally convex upper surface  3   b . Multiple stiffening ribs  4  may be shaped in the heat shield panel  3  in generally spaced-apart, parallel relationship with respect to each other for structural reinforcing purposes. 
         [0017]    As shown in  FIGS. 5 and 6 , thickened panel edge portions  9  may be provided in the opposite longitudinal edges of the heat shield panel  3 . A panel side flange  10  may extend outwardly from each panel edge portion  9 . A side skin attachment flange  11  may extend from each panel edge portion  9  at a generally acute angle with respect to the heat shield panel  3 . Therefore, each panel edge portion  9  may define the junction between the heat shield panel  3 ; each side flange  10 ; and the corresponding side skin attachment flange  11 . As shown in  FIG. 1 , the panel edge portions  9  and side skin attachment flanges  11  may converge and meet at the narrow panel end  6  of the heat shield panel  3 . 
         [0018]    The heat shield panel  3  and each panel edge portion  9 , side flange  10  and side skin attachment flange  11  may be a ceramic composite material having a high temperature capacity such as composite matrix ceramic (CMC), for example and without limitation. As shown in  FIG. 6 , the heat shield panel  3  and each side flange  10  and each side skin attachment flange  11  may include multiple laminated CMC plies  7 . A radius filler or “noodle”  12  may fill the interface between the plies  7  at the joint between the heat shield panel  3 , each side flange  10  and the corresponding side skin attachment flange  11  in each panel edge portion  9 , as is known to those skilled in the art. As shown in  FIG. 7 , in some embodiments an insulation coating  14  may be provided on the heat shield panel  3  and may additionally be provided on the panel side portions  9 , shown in  FIG. 6 , side flanges  10  and side skin attachment flanges  11  of the heat shield  2 . 
         [0019]    Referring next to  FIGS. 2-4  of the drawings, the heat shield  2  may be a part of a heat shield assembly  1 . In the heat shield assembly  1 , a side skin  16  may be attached to each side skin attachment flange  11  of the heat shield  2 . Each side skin  16  may be diffusion-bonded SPF (superplastic forming) titanium, for example and without limitation and may be a continuous piece having no split line. Each side skin  16  may be attached to the corresponding side skin attachment flange  11  according to any suitable technique which is known to those skilled in the art. As shown in  FIG. 3 , in some embodiments multiple side skin fasteners  17  may extend through respective registering pairs of fastener openings (not shown) provided in the side skin attachment flange  11  and the side skin  16 , respectively. Securing nuts  18  may be provided on the respective side skin fasteners  17  and threaded against the interior surface of the side skin  16 . 
         [0020]    As further shown in  FIGS. 2-4 , in some embodiments a nut plate  22  is attached to each stiffening rib  4  in the heat shield panel  3  and to the side skin  16 . Each nut plate  22  may be titanium, for example and without limitation and may include a generally rectangular nut plate panel  23 . A reinforcing lip  24  may extend from one or multiple edges of the nut plate panel  23 . A rib notch  25  may be provided in the reinforcing lip  24  to receive and engage the stiffening rib  4  in a snap-fit. 
         [0021]    In typical application of the heat shield  2 , the heat shield panel  3  of the heat shield assembly  1  is attached to an aft pylon fairing (not shown) and wing structure (not shown) on a jet passenger aircraft according to the knowledge of those skilled in the art. In operation of the aircraft, exhaust gases (not shown) from the jet engine contact the generally concave lower surface  3   a  of the heat shield panel  3 , which thermally insulates structures and systems (not shown) above the heat shield assembly  1  from the heat. Because the heat shield panel  3  may be capable of withstanding temperatures which are higher than the temperature capacity of titanium, the jet engine may be operated at a lower idle thrust and higher temperature, resulting in decreased fuel consumption and aircraft brake wear. Furthermore, because it may undergo minimal thermal expansion and contraction during thermal cycling of the jet engine, the heat shield  2  may be constructed in one piece as was noted hereinabove. Consequently, the jet engine can be designed with thermal cycles which are not limited by material restrictions. 
         [0022]    Referring next to  FIGS. 8 and 9 , embodiments of the disclosure may be used in the context of an aircraft manufacturing and service method  78  as shown in  FIG. 8  and an aircraft  94  as shown in  FIG. 9 . During pre-production, exemplary method  78  may include specification and design  80  of the aircraft  94  and material procurement  82 . During production, component and subassembly manufacturing  84  and system integration  86  of the aircraft  94  takes place. Thereafter, the aircraft  94  may go through certification and delivery  88  in order to be placed in service  90 . While in service by a customer, the aircraft  94  may be scheduled for routine maintenance and service  92  (which may also include modification, reconfiguration, refurbishment, and so on). 
         [0023]    Each of the processes of method  78  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
         [0024]    As shown in  FIG. 9 , the aircraft  94  produced by exemplary method  78  may include an airframe  98  with a plurality of systems  96  and an interior  100 . Examples of high-level systems  96  include one or more of a propulsion system  102 , an electrical system  104 , a hydraulic system  106 , and an environmental system  108 . Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry. 
         [0025]    The apparatus embodied herein may be employed during any one or more of the stages of the production and service method  78 . For example, components or subassemblies corresponding to production process  84  may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft  94  is in service. Also, one or more apparatus embodiments may be utilized during the production stages  84  and  86 , for example, by substantially expediting assembly of or reducing the cost of an aircraft  94 . Similarly, one or more apparatus embodiments may be utilized while the aircraft  94  is in service, for example and without limitation, to maintenance and service  92 . 
         [0026]    Although the embodiments of this disclosure have been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of skill in the art.