Abstract:
An energy absorbing apparatus and system for leading edge structures includes an impact member, such as a “bird-band”, of a plastically deformable material of a predetermined configuration positioned with the structure in an area of the leading edge of the structure to absorb energy of an impact of a projectile with the leading edge of the structure, and to redistribute the energy of the impact to the structure, and can break up the projectile, and can increase the impact area. The structure can have one or more sheet members, such as a single sheet, or an inner face sheet and an outer face sheet with a core positioned between the inner face sheet and the outer face sheet. One or more impact members of the plastically deformable material can be positioned with one or more of the single sheet, the inner face sheet, the outer face sheet or the core.

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to energy absorbing impact apparatus and methods to minimize damage incurred for impact events. More particularly, the disclosure pertains to energy absorbing impact members, or bands, and methods to minimize damage from high velocity impact events, such as projectile impacts, including, for example, bird impacts, with an aircraft. 
     BACKGROUND 
     Aircraft are susceptible to high velocity impact events with birds, or bird strikes. To reduce the damage and effects of impacts, certain parts or areas of aircraft, such as those with blunt leading edges, for example, wings and stabilizers of the aircraft, are designed and/or sized to withstand such an impact event to assure safety of flight. 
     Referring to  FIGS. 4A and 4B , for example,  FIG. 4A  is a perspective cross section of a conventional wing arrangement  70  and  FIG. 4B  is a perspective cross section of the leading edge  72  of the conventional wing arrangement  70  of  FIG. 4A , with an apex of the leading edge  72  being designated by the numeral  74 . The conventional wing arrangement  70  of  FIG. 4A  can include an outer face sheet  76 , a core  77  and an inner face sheet  78  of suitable material. The conventional wing arrangement  70  also can include exemplary first and second spars  79   a  and  79   b,  respectively, with the portion of the wing arrangement  70  including the leading edge  72  and the first and second spars  79   a  and  79   b  being indicated by the ellipse  72   a , the ellipse  72   a  also indicating the area of the leading edge  72 . 
     Prior approaches to address reducing the damage and effects of impacts typically involved the thickening of structure, such as one or more of the inner face sheet  78  and the outer face sheets  76  or the core  77 , or the addition or sizing of secondary structure, such as one or more spars, such as the spars  79   a  and  79   b , to the aircraft wings. However, thickening or addition of structure for the purpose of preventing damage to critical structure or systems components results in an increase of the weight of the structure, as well as an increase in weight of the aircraft. Moreover, the additional weight, while addressing the effects of potential impacts, can add to the manufacturing and operating costs of the aircraft or other vehicle. 
     The geometry of the leading edge, such as a leading edge of a wing or stabilizer, typically has significant curvature. Impacts that are away from the apex of the leading edge have a tendency to be re-directed, thus potentially imparting less damage to the leading edge or subsequent structure behind the leading edge. 
     Accordingly, it is desirable to provide a method and apparatus capable of overcoming the disadvantages described herein at least to some extent. 
     SUMMARY 
     The foregoing needs are met, to a great extent, by the present disclosure, wherein, in one respect, apparatus, systems and methods are provided that beneficially resist projectile impacts, such as bird or debris impacts, but without the significant weight penalties that can be associated with conventional sizing methods. 
     The present disclosure provides various benefits related to improving tolerance to projectile impacts, such as bird or debris impacts. One benefit associated with the disclosure is providing an increased tolerance with less of a weight penalty to reduce the overall weight of the air, or other type, vehicle, which can provide improved efficiency throughout the service life of the air, or other type, vehicle. Another benefit, among others, is stopping the projectile, such as a bird or debris, sooner and allowing less penetration into the structure, which will facilitate simpler repairs and reduced repair costs in the event of an impact. 
     The energy absorbing impact member, or “bird-band”, such as a wire, band, tubular structure, composite structure, or other suitable configuration or structure, according to aspects of the present disclosure, enables deflecting a projectile, such as a bird or debris, upon impact, and absorbing the energy of the impact through deformation and redistributing the load into the surrounding structure. The energy absorbing impact member, according to aspects of the present disclosure, can enable the projectile, such as a bird or debris, to break up and spread out, thus increasing the impacted surface area and reducing subsequent damage from the impact. 
     Additionally, when integrated into a leading edge structure, the energy absorbing impact member, according to aspects of the present disclosure, enables distribution of the impact load along the leading edge, absorbing more of the projectile&#39;s energy, with the energy absorbing impact member typically deforming plastically to minimize damage from the impact to the subsequent portions of the structure behind the leading edge. 
     According to aspects of the present disclosure, placing an energy absorbing impact member, such as a strip of high strength/high strain material, for example, along the apex of the leading edge, damage to the structure can be reduced. Specifically, the energy absorbing impact member enables increased protection of relatively more vulnerable areas of a structure, such as a wing or stabilizer, by causing the projectile, such as a bird or debris, to slow down, such as by converting kinetic energy of the projectile, into a plastic strain and to enable break-up or “splatter” of the projectile prior to impacting the subsequent portions of the structure. 
     An embodiment of the present disclosure pertains to an energy absorbing apparatus including an impact member of a plastically deformable material of a predetermined configuration, the impact member being positioned with a structure in an area of the leading edge of the structure to absorb energy of an impact of a projectile with the leading edge of the structure and to redistribute the energy of the impact to the structure. 
     Yet another embodiment of the present disclosure relates to an energy absorbing system including a structure having a leading edge, and an impact member, such as a “bird-band”, of a plastically deformable material of a predetermined configuration, the impact member, or “bird-band”, being positioned with the structure in an area of the leading edge of the structure to absorb energy of an impact of a projectile with the leading edge of the structure and to redistribute the energy of the impact to the structure. The structure can include a single sheet, a composite single sheet, a plurality of sheets, a plurality of composite sheets, a plurality of sheets with a core between one or more sheets, or other suitable structure, for example, according to aspects of the present disclosure. 
     A further embodiment of the present disclosure relates to an energy absorbing system including a sheet means for forming a structure having a leading edge, and a means for absorbing an impact positioned with the structure in an area of the leading edge of the structure to absorb energy of an impact of a projectile with the leading edge of the structure and to redistribute the energy of the impact to the structure. 
     Additionally, another embodiment of the present disclosure relates to an energy absorbing method including forming a structure having a leading edge, and positioning an impact member, such as a “bird-band”, of plastically deformable material with the structure in an area of the leading edge of the structure to absorb energy of an impact of a projectile with the leading edge of the structure and to redistribute the energy of the impact to the structure. 
     There has thus been outlined, rather broadly, certain embodiments that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments that will be described below and which will form the subject matter of the claims appended hereto. 
     In this respect, before explaining at least one embodiment in detail, it is to be understood that embodiments are not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. In addition to the embodiments described, the various embodiments are capable of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the disclosure. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of an exemplary aircraft illustrating various structures having leading edges, such as the wings, vertical stabilizer and horizontal stabilizers, to which the present disclosure is applicable. 
         FIG. 1B  is a perspective view of a helicopter, as an exemplary aircraft, illustrating rotor blades, horizontal and vertical stabilizers, and payload wings as structures having leading edges to which the present disclosure is applicable. 
         FIG. 1C  is a perspective view illustrating exemplary propeller blades for a vehicle, such as an aircraft, as structures having leading edges to which the present disclosure is applicable. 
         FIG. 2A through 2I  are diagrammatic, exemplary cross sectional views to illustrate the leading edge of the various structures of  FIGS. 1A through 1C  incorporating an energy absorbing impact member according to aspects of the present disclosure. 
         FIG. 3A and 3B  are illustrations of simulations of a horizontal stabilizer for an aircraft, such as the aircraft of  FIG. 1A , impacted by a projectile, such as a bird or debris, with the horizontal stabilizer of  FIG. 3A  incorporating an energy absorbing impact member according to aspects of the present disclosure, and with the horizontal stabilizer of  FIG. 3B  not incorporating an energy absorbing impact member according to aspects of the present disclosure. 
         FIG. 4A  is a perspective cross section of a conventional wing arrangement including support spars and a leading edge. 
         FIG. 4B  is a perspective cross section of the leading edge of the conventional wing arrangement of  FIG. 4A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Various embodiments of the present disclosure will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. As shown in  FIG. 1A ,  FIG. 1A  is a perspective view of an airplane  10 , as an example of a vehicle, such as an aircraft, to which the present disclosure is applicable, illustrating various structures having leading edges, such as wings  12 , horizontal stabilizers  16  and vertical stabilizer  20 . The airplane  10  also has a body or fuselage  11  to which the wings  12  and the horizontal and vertical stabilizers  16  and  20  are attached. Engines  13  are attached, for example, to the wings  12  of the airplane  10 . 
     The wings  12  of the exemplary airplane  10  have a respective leading edge  14  that extends along the area indicated by the ellipse  14   a . Also, the horizontal stabilizers  16  of the airplane  10  have a respective leading edge  18  that extends along the area indicated by the ellipse  18   a . Additionally, the vertical stabilizer  20  of the exemplary airplane  10  has a corresponding leading edge  22  that extends along the area indicated by the ellipse  22   a.    
     Continuing with reference to  FIG. 1B ,  FIG. 1B  is a perspective view of a helicopter  30 , as another exemplary aircraft, illustrating main rotor blades  32 , tail rotor blades  36 , payload wings  23   a  (for carrying cargo or for lift), horizontal stabilizers  24   a  and  25   a , and vertical stabilizer  26   a  as exemplary structures having leading edges to which the present disclosure is applicable. The main rotor blades  32  have a respective a leading edge  34  and a respective trailing edge  35 , referenced from a clockwise rotation direction for the blades  32  indicated by the circular arrow headed line A 1 , for example. Also, the tail rotor blades  36  have a respective a leading edge  37  and a respective trailing edge  38 , referenced from a clockwise rotation direction for the blades  36  indicated by the circular arrow headed line A 2 , for example. The helicopter can also include one or more of the payload wings  23   a  having leading edges  23 , the horizontal stabilizers  24   a  having leading edges  24 , the horizontal stabilizers  25   a  having leading edges  25 , and the vertical stabilizer  26   a  having leading edge  26 , for example. The helicopter  30  also has a body  31  that supports a main rotor assembly  33   a  that communicates with the main rotor blades  32 . The body  31  also supports a tail rotor assembly  33   b  that extends from the body  31  and communicates with the tail rotor blades  36 . 
     Referring now to  FIG. 1C ,  FIG. 1C  is a perspective view illustrating an exemplary propeller  40  having blades  42  for a vehicle, such as an aircraft, hovercraft, or other propeller driven vehicle or device, as an exemplary structure having leading edges to which the present disclosure is applicable. The propeller blades  42  have a respective a leading edge  43  and a respective trailing edge  44 , referenced from a clockwise rotation direction for the propeller blades  42  indicated by the circular arrow headed line A 3 , for example. As evident from the various vehicles identified with reference to  FIGS. 1A through 1C , while aircraft, such as the airplane  10  and the helicopter  30 , are example of vehicles to which the present disclosure is applicable, the present disclosure is not limited in this regard. 
       FIG. 2A through 2I  are diagrammatic, exemplary cross sectional views illustrating leading edges  50   a  through  50   i  of the various structures of  FIGS. 1A through 1C , or other structures, incorporating an energy absorbing impact member according to aspects of the present disclosure. In  FIGS. 2A through 2I , cross sections of leading edges  50   a  through  50   i , such as the leading edges  14 ,  18 ,  22  through  26 ,  34 ,  37 , and  43  of the wings  12 , horizontal stabilizers  16 , vertical stabilizer  20 , payload wings  23   a , horizontal stabilizers  24   a  and  25   a , vertical stabilizer  26   a , main rotor blades  32 , tail rotor blades  36 , and propeller blades  42 , respectively, illustrate various embodiments of the present disclosure, although the present disclosure is not limited in this regard. Also, while the leading edge cross sections  50   a  through  50   i , are primarily directed to illustrate the present disclosure for incorporation in airplane wings and stabilizers, they are also illustrative for other applications of the present disclosure, such as for incorporation in blades or propellers, for various other vehicles that move through or on the air, water, or land, or other propeller driven devices. 
     In this regard, for example, the energy absorbing impact members and methods of the present disclosure can be applied to aircraft nose cones, such as to minimize damage or breach of the cabin by a projectile. Also the energy absorbing impact members and methods of the present disclosure can be applied to watercraft, such as hydrofoils, catamarans, or boat hulls, such as to minimize damage from projectiles, such as logs or other debris, or can be applied to submarines or other submersible craft, such as to minimize damage to control surfaces. Further, for example, the energy absorbing impact members and methods of the present disclosure can be applied to windmill blades, such as to minimize damage by a projectile impact, such as by a bird. 
     The exemplary cross sections of the leading edges  50   a  through  50   i,  such as leading edges  14 ,  18  and  22  have areas  51   a  through  51   i  in which energy absorbing impact members, or “bird bands”,  53   a  through  53   i   2 , according to aspects of the present disclosure, can be positioned. The energy absorbing impact members  53   a  through  53   i   2  can be positioned selectively, variably, continuously, intermittently or periodically along the length, or course, of the leading edge, such as within the areas  51   a  through  51   i  of the leading edges  50   a  through  50   i , of various structures, such as the leading edges  14 ,  18  and  22 , for example, depending upon the particular use or application, according to aspects of the present disclosure, although the present disclosure is not limited in this regard. 
     Also, the energy absorbing impact members  53   a  through  53   i   2  can be of any suitable shape or configuration, dependent upon the particular use or application, such as of a generally “C” shape or generally parabolic shape illustrated in  FIGS. 2A through 2I , or other suitable configuration, although the present disclosure is not limited in this regard. The width, thickness and curvature of the strip, piece or pieces forming one or more energy absorbing impact members  53   a  through  53   i   2  can be tailored for a particular application, such as taking into account the curvature of the leading edge, pre-existing structural and aerodynamic sizing, and a projectile, such as bird or debris, strike requirement to create the optimal, or suitable, design, typically by analysis and/or testing. Additionally, the energy absorbing impact member, such as the energy absorbing impact members  53   a  through  53   i   2  can be integrated into new leading edge designs, or used as an improvement on existing leading edges, such as to provide additional bird strike resistance capabilities. 
     The energy absorbing impact members  53   a  through  53   i   2  improve the bird, or other projectile, strike resistance of a structure, such as an aircraft, or other structure, susceptible to high energy impacts from projectiles, such as birds or debris, or other types of projectiles. The energy absorbing impact members, or “bird-bands”,  53   a  through  53   i   2  can be formed of a strip, piece or pieces of one or more configurations of high strength/high strain material positioned with a structure in the area  51   a  through  51   i  of the leading edge, such as the leading edges  14 ,  18  and  22  of wings  12  or stabilizers  16 ,  20 , which typically are relatively more vulnerable to bird, or other projectile, strikes or impacts. 
     The energy absorbing impact members  53   a  through  53   i   2  can also be positioned with a structure in the area  51   a  through  51   i  of the leading edge, such as the leading edges  23  through  26 ,  34 ,  37 , and  43 , of payload wings  23   a , horizontal stabilizers  24   a  and  25   a , vertical stabilizer  26   a , main rotor blades  32 , the tail rotor blades  36  or the propeller blades  42 , which can also be susceptible to projectile, such as bird, debris, or other projectile, strikes or impacts. However, placement of the energy absorbing impact members, such as energy absorbing impact members  53   a  through  53   i   2 , positioned with, such as on or within a structure, such as wing or stabilizer, is typically a function of bond strength, structural configuration and manufacturing considerations, according to aspects of the present disclosure. 
     Alloys such as 301% hardened and  314  annealed stainless steels are typically highly suitable materials for energy absorbing impact members  53   a  through  53   i   2 . However, other high strength/high strain materials (metallic, composite, or other), alloys, such as nickel alloys, titanium alloys or steel alloys (non-stainless), or plastic type materials, such as KEVLAR®, are suitable, with varied amount and type of benefit, for the composition of the energy absorbing impact members  53   a  through  53   i   2 , depending on the use, application or protection level, according to aspects of the present disclosure. 
     The outer face sheet  52   a  through  52   e  and  52   g  through  52   i  and the inner face sheet  56   a  through  56   e  and  56   g  through  56   i , and the single sheet  52   f  are typically formed of aluminum alloys, or a suitable composite material, such as of fiberglass, for example. Further, a core, to provide face sheet stability, such as cores  54   a  through  54   e  and  54   g  through  54   i , can be sandwiched between all or portions of the outer face sheet  52   a  through  52   e  and  52   g  through  52   i  and all or portions of the inner face sheet  56   a  through  56   e  and  56   g  through  56   i . The core, such as cores  54   a  through  54   e  and  54   g  through  54   i , is typically affixed to the outer face sheet  52   a  through  52   e  and  52   g  through  52   i  and the inner face sheet  56   a  through  56   e  and  56   g  through  56   i , such as by a suitable glue or adhesive. The core  54   a  through  54   e  and  54   g  through  54   i  is typically formed of a lightweight material and of a honeycomb type structure or other suitable type structure, such as formed of aluminum alloys, titanium alloys, foam, NOMEX®, or other suitable material. 
     The energy absorbing impact members, or “bird-bands”,  53   a  through  53   i   2  can be positioned with the leading edges, such as leading edges  14 ,  18  and  22 , by being bonded or affixed, as by being adhesively bonded with an adhesive, such as an epoxy or other suitable adhesive, or as by being affixed, such as by rivets or other suitable fasteners, to one or more surfaces, such as the inner or outer surfaces, of the leading edge. Also, the energy absorbing impact members, or “bird-bands”,  53   a  through  53   i   2  can be positioned with the leading edges, such as leading edges  14 ,  18  and  22 , by being integrated or embedded within a sheet member, such as within a laminate or within the plies of a composite material, forming a structure. 
     Referring first to  FIGS. 2A through 2D , for example, as illustrated in  FIGS. 2A through 2D , the energy absorbing impact members  53   a  through  53   d  are positioned with the leading edges, such as leading edges  14 ,  18  and  22 , by being adhesively bonded or secured, for example, to a surface of the outer face sheet  52   a  and  52   b , respectively, or to a surface of the inner face sheet  56   c  and  56   d,  respectively. 
     Referring to  FIG. 2A , in the cross section of the leading edge  50   a , such as leading edges  14 ,  18  and  22 , the leading edge  50   a  is formed by a plurality of sheet members including the outer face sheet  52   a  having an outer surface  52   a   1  and an inner surface  52   a   2  and the inner face sheet  56   a  having an outer surface  56   a   1  and an inner surface  56   a   2 . The inner face sheet  56   a  of  FIG. 2A  includes two portions  56   ap   1  and  56   ap   2  that are separated from each other in the apex  51   a  of the area  50   a   1  of the leading edge  50   a . The area  50   a   1  is the area including and within the entire leading edge  50   a . The core  54   a  within the area  50   a   1  of the leading edge  50   a  is sandwiched and affixed between the inner surface  52   a   2  of the outer face sheet  52   a  and the outer surface  56   a   1  of corresponding portions  56   ap   1  and  56   ap   2  of the inner face sheet  56   a , with the core  54   a  and the inner face sheet  56   a  not being included within the apex  51   a  of the area  50   a   1  of the leading edge  50   a , as illustrated in  FIG. 2A . The energy absorbing impact member  53   a  is positioned with the structure by being adhesively secured, or otherwise affixed, to the inner surface  52   a   2  of the outer face sheet  52   a  within the apex  51   a  of the area  50   a   1  of the leading edge  50   a , although the present disclosure is not limited in this regard. Also, the embodiment of the leading edge  50   a  of  FIG. 2A  illustrates an example of a single sheet member embodiment, according to aspects of the present disclosure, by removing the two portions  56   ap   1  and  56   ap   2  of the inner face sheet  56   a  and the core  54   a , providing a structure for the leading edge  50   a  that includes the outer face sheet  52   a , as a single sheet member, positioned with the energy absorbing impact member  53   a.    
     Further, referring to  FIG. 2B , for example, in the cross section of the leading edge  50   b , such as leading edges  14 ,  18  and  22 , the leading edge  50   b  is formed by a plurality of sheet members including the outer face sheet  52   b  having an outer surface  52   b   1  and an inner surface  52   b   2  and the inner face sheet  56   b  having an outer surface  56   b   1  and an inner surface  56   b   2 . The core  54   b  within the area  50   b   1  of the leading edge  50   b  is sandwiched and affixed between the inner surface  52   b   2  of the outer face sheet  52   b  and the outer surface  56   b   1  of the inner face sheet  56   b . The area  50   b   1  is the area including and within the entire leading edge  50   b . The energy absorbing impact member  53   b  is positioned with the structure by being adhesively secured, or otherwise affixed, to the inner surface  52   b   2  of the outer face sheet  52   b  adjacent the core  54   b  within the apex  51   b  of the area  50   b   1  of the leading edge  50   b , although the present disclosure is not limited in this regard. 
     Continuing with reference to  FIG. 2C , for example, in the cross section of the leading edge  50   c , such as leading edges  14 ,  18  and  22 , the leading edge  50   c  is formed by a plurality of sheet members including the outer face sheet  52   c  having an outer surface  52   c   1  and an inner surface  52   c   2  and the inner face sheet  56   c  having an outer surface  56   c   1  and an inner surface  56   c   2 . The core  54   c  within the area  50   c   1  of the leading edge  50   c  is sandwiched and affixed between the inner surface  52   c   2  of the outer face sheet  52   c  and the outer surface  56   c   1  of the inner face sheet  56   c.  The area  50   c   1  is the area including and within the entire leading edge  50   c . The energy absorbing impact member  53   c  is positioned with the structure by being adhesively secured, or otherwise affixed, to the inner surface  56   c   2  of the inner face sheet  56   c  within the apex  51   c  of the area  50   c   1  of the leading edge  50   c , although the present disclosure is not limited in this regard. 
     Also, referring to  FIG. 2D , for example, in the cross section of the leading edge  50   d , such as leading edges  14 ,  18  and  22 , the leading edge  50   d  is formed by a plurality of sheet members including the outer face sheet  52   d  having an outer surface  52   d   1  and an inner surface  52   d   2  and the inner face sheet  56   d  having an outer surface  56   d   1  and an inner surface  56   d   2 . The core  54   d  within the area  50   d   1  of the leading edge  50   d  is sandwiched and affixed between the inner surface  52   d   2  of the outer face sheet  52   d  and the outer surface  56   d   1  of the inner face sheet  56   d . The area  50   d   1  is the area including and within the entire leading edge  50   d . The energy absorbing impact member  53   d  is positioned with the structure by being adhesively secured, or otherwise affixed, to the outer surface  56   d   1  of the inner face sheet  56   d  adjacent the core  54   d  within the apex  51   d  of the area  50   d   1  of the leading edge  50   d , although the present disclosure is not limited in this regard. 
     Referring now to  FIGS. 2E through 2I , for composite leading edges, such as leading edges  14 ,  18  and  22 , the energy absorbing impact members, or “bird-bands”, can also be positioned with a structure by being integrated with the structure, such as by being embedded within a laminate forming the structure. The energy absorbing impact member can be embedded within a laminate forming the outer face sheet, such as illustrated in  FIGS. 2E and 2H . The energy absorbing impact member can be embedded within a laminate forming a single sheet, such as illustrated in  FIG. 2F . The energy absorbing impact member can be embedded within a laminate forming the inner face sheet, such as illustrated in  FIG. 2G . The energy absorbing impact member can also be embedded both within a laminate forming the inner face sheet and within a laminate forming the outer face sheet, such as illustrated in  FIG. 2I , according to aspects of the present disclosure, although the present disclosure is not limited in this regard. For example, the energy absorbing impact members  53   e  through  53   i   2  can be sandwiched between plies of a composite material, such as fiberglass or other suitable composite material. 
     Referring to  FIG. 2E , in the cross section of the leading edge  50   e , such as leading edges  14 ,  18  and  22 , the leading edge  50   e  is formed by a plurality of sheet members including the outer face sheet  52   e  having an outer surface  52   e   1  and an inner surface  52   e   2  and the inner face sheet  56   e  having an outer surface  56   e   1  and an inner surface  56   e   2 . The inner face sheet  56   e  of  FIG. 2E  includes two portions  56   ep   1  and  56   ep   2  that are separated from each other within the apex  51   e  of the area  50   e   1  of the leading edge  50   e . The core  54   e  within the area  50   e   1  of the leading edge  50   e  is sandwiched and affixed between the inner surface  52   e   2  of the outer face sheet  52   e  and the outer surface  56   e   1  of corresponding portions  56   ep   1  and  56   ep   2  of the inner face sheet  56   e , with the core  54   e  not being included within the apex  51   e  of the area  50   e   1  of the leading edge  50   e . The area  50   e   1  is the area including and within the entire leading edge  50   e . The energy absorbing impact member  53   e  is positioned with the structure by being integrated with the structure by being embedded within the laminate, such as within the plies of the composite material, within the outer face sheet  52   e  in the apex  51   e  of the area  50   e   1  of the leading edge  50   e.    
     Continuing with reference to  FIG. 2F , for example, in the cross section of the leading edge  50   f , such as leading edges  14 ,  18  and  22 , the leading edge  50   f  is formed by a sheet member including a single sheet  52   f  having an outer surface  52   f   1  and an inner surface  52   f   2  The energy absorbing impact member  53   f  is positioned with the structure by being integrated with the structure by being embedded within a laminate, such as within the plies of a composite material, within the single sheet  52   f  within the apex  51   f  of the area  50   f   1  of the leading edge  50   f , although the present disclosure is not limited in this regard. The area  50   f   1  is the area including and within the entire leading edge  50   f.    
     Also, referring to  FIG. 2G , for example, in the cross section of the leading edge  50   g , such as leading edges  14 ,  18  and  22 , the leading edge  50   g  is formed by a plurality of sheet members including the outer face sheet  52   g  having an outer surface  52   g   1  and an inner surface  52   g   2  and the inner face sheet  56   g  having an outer surface  56   g   1  and an inner surface  56   g   2 . The core  54   g  within the area  50   g   1  of the leading edge  50   g  is sandwiched and affixed between the inner surface  52   g   2  of the outer face sheet  52   g  and the outer surface  56   g   1  of the inner face sheet  56   g . The area  50   g   1  is the area including and within the entire leading edge  50   g.  The energy absorbing impact member  53   g  is positioned with the structure by being integrated with the structure by being embedded within a laminate, such as within the plies of a composite material, within the inner face sheet  56   g  within the apex  51   g  of the area  50   g   1  of the leading edge  50   g , although the present disclosure is not limited in this regard. 
     Further, referring to  FIG. 2H , for example, in the cross section of the leading edge  50   h , such as leading edges  14 ,  18  and  22 , the leading edge  50   h  is formed by a plurality of sheet members including the outer face sheet  52   h  having an outer surface  52   h   1  and an inner surface  52   h   2  and the inner face sheet  56   h  having an outer surface  56   h   1  and an inner surface  56   h   2 . The core  54   h  within the area  50   h   1  of the leading edge  50   h  is sandwiched and affixed between the inner surface  52   h   2  of the outer face sheet  52   h  and the outer surface  56   h   1  of the inner face sheet  56   h . The area  50   h   1  is the area including and within the entire leading edge  50   h . The energy absorbing impact member  53   g  is positioned with the structure by being integrated with the structure by being embedded within a laminate, such as within the plies of a composite material, within the outer face sheet  52   h  within the apex  51   h  of the area  50   h   1  of the leading edge  50   h , although the present disclosure is not limited in this regard. 
     Continuing with reference to  FIG. 2I , for example, in the cross section of the leading edge  50   i , such as leading edges  14 ,  18  and  22 , the leading edge  50   i  is formed by a plurality of sheet members including the outer face sheet  52   i  having an outer surface  52   i   1  and an inner surface  52   i   2  and the inner face sheet  56   i  having an outer surface  56   i   1  and an inner surface  56   i   2 . The core  54   i  within the area  50   i   1  of the leading edge  50   i  is sandwiched and affixed between the inner surface  52   i   2  of the outer face sheet  52   i  and the outer surface  56   i   1  of the inner face sheet  56   i . The area  50   i   1  is the area including and within the entire leading edge  50   i . In  FIG. 2I , a plurality of energy absorbing impact members  53   i   1  and  53   i   2  are illustrated. The energy absorbing impact member  53   i   1  is positioned with the structure by being integrated with the structure by being embedded within a laminate, such as within the plies of a composite material, within the outer face sheet  52   i  within the apex  51   i  of the area  50   i   1  of the leading edge  50   i . The energy absorbing impact member  53   i   2  is positioned with the structure by being integrated with the structure by being embedded within a laminate, such as within the plies of a composite material, within the inner face sheet  56   i  within the apex  51   i  of the area  50   i   1  of the leading edge  50   i , although the present disclosure is not limited in this regard. 
     Thus, according to aspects of the present disclosure, protecting a relatively small portion of the leading edge, such as within the apex of the area of the leading edge, with the energy absorbing impact member(s), or “bird-band(s)”,  53   a  through  53   i   2 , enables an increased level of protection to be concentrated in a relatively critical area of the structure, while substantially reducing or minimizing a weight penalty associated with providing the enhanced level of protection. 
     Also, according to aspects of the present disclosure, in view of the reduced coverage area for the energy absorbing impact member, or “bird-band”, to provide an increased level of protection, a denser but higher strength, higher strain material, such as various stainless steels, for example, can be used to form the energy absorbing impact member, or “bird-band”. Moreover, there is an added benefit of utilizing a ductile material for the energy absorbing impact member, or “bird-band”, according to aspects of the present disclosure. In this regard, typically aircraft materials are high stiffness/high strength materials with minimal ductility. Providing an energy absorbing impact member of a material with significant plastic deformation capability can increase the energy absorption characteristics of the structure, as well as reducing or minimizing potentially damaging kinetic energy of the impact by the projectile, such as a bird or debris. 
     Finite element analysis by simulating bird impacts while utilizing the energy absorbing impact member, or “bird-band”, according to aspects of the present disclosure, have shown a significant improvement in projectile strike resistance, such as bird strike resistance, with a minimal weight effect on the structure. Further, use of an energy absorbing impact member, or “bird-band”, such as a stainless steel impact member, or “bird-band”, is typically lighter, thereby minimizing a weight penalty, and also relatively more effective than increasing the gage of the first and second spars  79   a  and  79   b  ( FIG. 4A ) for stopping the penetration of a projectile, such as a bird or debris, into the horizontal and vertical stabilizer structures, for example. However, actual weight benefit of the energy absorbing impact member, or “bird-band”, according to aspects of the present disclosure, typically depends on the specific application. 
       FIG. 3A and 3B  are illustrations of simulations of a horizontal stabilizer for an aircraft, such as the aircraft of  FIG. 1A , impacted by a projectile, such as a bird or debris, with the horizontal stabilizer of  FIG. 3A  incorporating an energy absorbing impact member, or “bird-band”, according to aspects of the present disclosure, and with the horizontal stabilizer of  FIG. 3B  not incorporating an energy absorbing impact member, or “bird-band”, according to aspects of the present disclosure. The simulated impact analyses illustrated in  FIGS. 3A and 3B  were performed using the LS-DYNA finite element software package. The simulated analyses of  FIGS. 3A and 3B  were also performed based upon an 8 lb bird, as the projectile, impacting the horizontal stabilizer of an aircraft at a speed of 350 knots. 
       FIG. 3A  illustrates a simulation of an impact with a horizontal stabilizer  60   a  such as for the airplane  10  of  FIG. 1A , incorporating an energy absorbing impact member, or “bird-band”, according to aspects of the present disclosure. The horizontal stabilizer  60   a  includes a first spar  66   a , a second spar  64   a  and a third spar  62   a . The simulated area of impact is indicated by  68   a  with the damage from the impact indicated by  68   a   1 . For the simulated analysis, a 20% thinner first spar  66   a  was used to offset the weight penalty of incorporating the energy absorbing impact member, or “bird-band”, according to aspects of the present disclosure. Running the simulation on the structure of  FIG. 3A , the horizontal stabilizer  60   a  with the 20% thinner first spar  66   a , and incorporating the energy absorbing impact member, or “bird-band”, according to aspects of the present disclosure, showed no visible damage or penetration of the second spar  64   a  and the third spar  62   a.    
       FIG. 3B  illustrates a simulation of an impact with a horizontal stabilizer  60   b , such as for the airplane  10  of  FIG. 1A , that does not incorporate an energy absorbing impact member, or “bird-band” of the present disclosure. The horizontal stabilizer  60   b  includes a first spar  66   b , a second spar  64   b  and third spar  62   b . The simulated area of impact is indicated by  68   b  with the damage from the impact indicated by  68   b   1 . Portions of the horizontal stabilizer  60   b  dislodged by the simulated impact are indicated by  69   b . Running the simulation on the structure of  FIG. 3B , the horizontal stabilizer  60   b  that did not incorporate the energy absorbing impact member, or “bird-band”, of the present disclosure, resulted in damage to and failure of the second spar  64   b  and the third spar  62   b.    
     The many features and advantages of the various embodiments are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages that fall within the true spirit and scope of the embodiments. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the embodiments to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the various embodiments.