Abstract:
A shape memory structure includes a plurality of bases directly attached to a composite structure and arranged along a first line at a first edge of the composite structure. A plurality of buckle-shaped shape memory structures are attached to corresponding ones of the plurality of bases, such that first ends of the plurality of buckle-shaped shape memory structures are raised relative to the composite structure. Second ends of the plurality of buckle-shaped shape memory structures are directly attached to the composite structure along a second line at a second edge of the composite structure, the second edge being opposite the first edge. When activated, the shape memory structure changes from a buckled shape to an original shape to cause the composite structure to assume a deployed shape; when deactivated, the shape memory structure to resumes a buckled shape and the composite structure an undeployed shape.

Description:
BACKGROUND INFORMATION 
     1. Field 
     The present disclosure relates generally to aircraft and, in particular, to actuators for aircraft. Still more particularly, the present disclosure relates to a method and apparatus for controlling the shape of a composite structure with a shape memory alloy actuator. 
     2. Background 
     The flight of an aircraft is controlled by airfoil structures. An airfoil structure is a part of an aircraft that may provide aerodynamic performance for the aircraft. An airfoil structure may be, for example, a wing or blade. The design and shape of airfoils may generate lift, control stability, change direction, change drag, or change other suitable aerodynamic parameters for an aircraft. 
     Flight control surfaces on an airfoil structure of an aircraft may be used to change the direction of an aircraft. Different control surfaces such as, for example, an aileron, an elevator, a rotor, a trim, a rudder, a spoiler, a flap, a slat, or other suitable control surfaces may be moved to change the shape of an airfoil structure to provide for different axes of motion for the aircraft. These control surfaces may be used to optimize the aerodynamic surfaces of an airfoil structure. 
     For example, a slat may be located at a leading edge of an airfoil structure in the form of a wing. A slat is an extension to the front of a wing to provide lift augmentation. Further, a slat may reduce a stalling speed by altering airflow over the wing. 
     Movement of this type of control surface, as well as other control surfaces, during flight may be performed to maximize the handling and performance of the aircraft. For example, a wing may be configured to have a sleek leading edge for high-speed flight. The wing may be reconfigured to have a blunt leading edge for low-speed flight. 
     When modifying the shape of an airfoil structure, it is desirable to maintain aerodynamic flow, while minimizing drag and turbulence over the airfoil structure. One manner in which this characteristic may be achieved is to maintain a contiguous surface on the skin of the airfoil structure without disruptions around the airfoil structure in the form of gaps. Current airfoil structure changing systems for leading edge wings include extension or unfolding mechanisms that protrude into the airstream to modify aerodynamic characteristics. These types of systems, however, create voids in the continuity of the skin on the airfoil structure that can generate turbulence. 
     Further, other airfoil structure shape changing systems may allow the changing of the shape of the leading edge. These types of systems, however, use complicated actuator systems and often take more room than desired and weigh more than desired. In some cases, the size and complexity of the actuator system preclude their use with wings that are too thin to provide the room needed for the actuator systems. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues. 
     SUMMARY 
     An embodiment of the present disclosure provides an apparatus comprising a composite structure for an airframe of an aircraft and a shape memory structure associated with the composite structure. The shape memory structure has a buckled shape in a deactivated state such that the composite structure has an undeployed shape. The shape memory structure has an original shape when in an activated state such that the composite structure has a deployed shape. The composite structure applies a load against the shape memory structure. 
     Another embodiment of the present disclosure provides an aerodynamic control system comprising a composite structure on an airfoil structure of an aircraft and a shape memory structure associated with the composite structure. The shape memory structure has a buckled shape when in a deactivated state such that the composite structure is in an undeployed shape. The shape memory structure has an original shape when in an activated state such that the composite structure has a deployed shape. The composite structure applies a load against the shape memory structure. 
     In yet another illustrative embodiment, a method for controlling a shape of a composite structure is presented. A shape memory structure associated with the composite structure is activated. The shape memory structure changes from a buckled shape to an original shape and causes the composite structure to change from an undeployed shape to a deployed shape. The shape memory structure is deactivated. The shape memory structure changes from the original shape to the buckled shape in response to a load from the composite structure and causes the composite structure to change from the deployed shape to the undeployed shape. 
     The features and functions can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments in which further details can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the illustrative embodiments are set forth in the appended claims. The illustrative embodiments, however, as well as a preferred mode of use, further objectives and features thereof, will best be understood by reference to the following detailed description of an illustrative embodiment of the present disclosure when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is an illustration of an aircraft in accordance with an illustrative embodiment; 
         FIG. 2  is an illustration of a block diagram of an aerodynamic environment in accordance with an illustrative embodiment; 
         FIG. 3  is a detailed illustration of a section of a trailing edge of a wing of an aircraft in accordance with an illustrative embodiment; 
         FIG. 4  is an illustration of an aerodynamic control system in accordance with an illustrative embodiment; 
         FIG. 5  is another illustration of an aerodynamic control system in accordance with an illustrative embodiment; 
         FIG. 6  is an illustration of a cross-section of an aerodynamic control system in accordance with an illustrative embodiment; 
         FIG. 7  is an illustration of a cross-section of an aerodynamic control system in accordance with an illustrative embodiment; 
         FIG. 8  is an illustration of a flowchart of a process for controlling a shape of a composite structure in accordance with an illustrative embodiment; 
         FIG. 9  is an illustration of an aircraft manufacturing and service method in the form of a block diagram in accordance with an illustrative embodiment; and 
         FIG. 10  is an illustration of an aircraft in the form of a block diagram in which an illustrative embodiment may be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrative embodiments recognize and take into account one or more different considerations. For example, the illustrative embodiments recognize and take into account that current actuator systems often take more room than desired due to the complexity of the these systems. For example, wires, linkages, connectors, motors and other components may be used to cause the shape of an airfoil structure to change such that control surfaces for the airfoil structure do not need to be separate structures. These systems, however, often take more room than desired. In some cases, the systems may take more room than is available within the airfoil structure. This situation precludes the use of these systems. The illustrative embodiments recognize and take into account that it would be desirable to have an actuator system that can be used in airfoil structures that are thin in shape or have slim profiles, such as aircraft wings or the trailing edge of an aircraft wing. 
     Thus, the illustrative embodiments provide a method and apparatus for controlling the shape of an airfoil structure. An apparatus comprises a composite structure and a shape memory structure. The composite structure is for an airframe of an aircraft. The shape memory structure is associated with the composite structure. The shape memory structure has a buckled shape in a deactivated state such that the composite structure has an undeployed shape. The shape memory structure has an original shape when in an activated state such that the composite structure has a deployed shape. The composite structure applies a load against the shape memory structure. 
     With reference now to the figures, and in particular, with reference to  FIG. 1 , an illustration of an aircraft is depicted in accordance with an illustrative embodiment. In this illustrative example, aircraft  100  has wing  102  and wing  104  attached to body  106 . Aircraft  100  includes engine  108  attached to wing  102  and engine  110  attached to wing  104 . 
     Body  106  has tail section  112 . Horizontal stabilizer  114 , horizontal stabilizer  116 , and vertical stabilizer  118  are attached to tail section  112  of body  106 . 
     Aircraft  100  is an example of an aircraft in which an aerodynamic control system with shape memory structures may be implemented in accordance with an illustrative embodiment. In particular, an aerodynamic control system may use shape memory structures in the form of shape memory alloy structures. 
     For example, the system may be implemented in control surfaces such as flap  120  on wing  102 , elevator  122  on horizontal stabilizer  116 , rudder  124  on vertical stabilizer  118 , slat  126  on wing  104 , as well as other flight control surfaces on aircraft  100 . In this type of implementation, the actuation system may be used to change the shape of a control surface. This change in the shape of a control surface is separate from movement of the control surface as a separate structure relative to aircraft  100 . 
     Additionally, the actuation system may be implemented in airfoil structures in aircraft  100 , such as wing  102 , wing  104 , horizontal stabilizer  114 , horizontal stabilizer  116 , and vertical stabilizer  118 . In this type of implementation, the actuation system may be used to change the shape of the airfoil structure separately from the control surface. 
     With using an actuation system in airfoil structures in accordance with an illustrative embodiment, the use of control surfaces as separate structures may be reduced or eliminated for aircraft  100 . For example, the actuation system may be used to change the shape of trailing edge  128  of wing  102 . In other illustrative examples, the actuation system may be used to cause a bump, ridge, or other change in shape on surface  130  of wing  102 . These and other types of changes may be made to airfoil structures on aircraft  100 , as well as on any part of aircraft  100  during operation of aircraft  100 . 
     A more detailed illustration of section  132  on wing  102  is shown in  FIG. 3 . The description of this section below in  FIG. 3  is an illustrative example of one implementation of an aerodynamic control system in accordance with an illustrative embodiment. 
     Turning next to  FIG. 2 , an illustration of a block diagram of an aerodynamic environment is depicted in accordance with an illustrative embodiment. In aerodynamic environment  200 , aerodynamics  201  of vehicle  202  is controlled by aerodynamic control system  204 . In this illustrative example, vehicle  202  takes the form of aircraft  206 . 
     In the illustrative example, aerodynamic control system  204  includes a number of different components. As depicted, aerodynamic control system  204  includes composite structure  208 , shape memory structure  210 , and activation system  212 . In this example, shape memory structure  210  is an example of an actuator system. 
     Composite structure  208  is aerodynamic composite structure  214 . For example, composite structure  208  may be selected from one of an airfoil, a control surface, a skin panel, a flap, an aileron, a wing tip, a trailing edge of the wing, a leading edge of the wing, a horizontal or vertical stabilizer, an engine nacelle, engine nozzles, spoilers, vortex generators, a winglet, or some other suitable composite structure. In the illustrative example, these composite structures may be thin composite materials. In the illustrative example, a thin composite material is a material forming a structure that has a form that is sufficiently thin to allow deformation of the structure between the original shape and the deformed shape without damage to the composite material. The thickness of these materials also may be sufficiently thin that connection to the composite material cannot be achieved using discrete fastener features. Further, the material may be too thin for using fasteners because the material is unable to handle the concentrated loading of the individual fasteners or the material is not sufficiently thick to allow countersinking to maintain a smooth airflow surface. 
     In this illustrative example, shape memory structure  210  is a structure that remembers original shape  220  for shape memory structure  210  such that shape memory structure  210  returns to original shape  220  from deformed shape  219  when heated by a sufficient amount. As depicted, shape memory structure  210  is associated with composite structure  208 . 
     When one component is “associated” with another component in the illustrative examples, the association is a physical association in the depicted examples. For example, a first component, shape memory structure  210 , may be considered to be physically associated with a second component, composite structure  208 , by at least one of being secured to the second component, bonded to the second component, mounted to the second component, welded to the second component, fastened to the second component, or connected to the second component in some other suitable manner. The first component also may be connected to the second component using a third component. The first component may also be considered to be physically associated with the second component by being formed as part of the second component, extension of the second component, or both. 
     In this illustrative example, shape memory structure  210  is associated with composite structure  208  by being at least one of bonded to composite structure, fastened to composite structure  208 , or formed as part of composite structure  208 . For example, shape memory structure  210  may be formed as part of composite structure  208  by being placed within layers of composite material that are then cured to form composite structure  208 . 
     Also, composite structure  208  may take different forms depending on the particular implementation. For example, composite structure  208  may be a carbon fiber composite, a fiberglass composite, or some other suitable type of composite suitable for use in vehicle  202 . 
     In this illustrative example, shape memory structure  210  is elongate member  215  and has shape  216 . Shape  216  for shape memory structure  210  may be buckled shape  218  and original shape  220 . In these illustrative examples, shape  216  may transition or move between these two shapes. Buckled shape  218  is deformed shape  219  for shape memory structure  210 . 
     As depicted, shape memory structure  210  has buckled shape  218  when shape memory structure  210  is in deactivated state  222 . Shape memory structure  210  has original shape  220  when shape memory structure  210  is in activated state  224 . 
     As depicted, shape memory structure  210  in the form of elongate member  215  may have various forms of shape  216  when in original shape  220 . For example, elongate member  215  may be a rod, a sheet, or some other suitable form that may be deformed into buckled shape  218  when in deactivated state  222  and may return to original shape  220  when in activated state  224 . For example, elongate member  215  may have a shape selected to allow a controlled and reversible transition between original shape  220  and buckled shape  218 . In this example, the deformation is a bending of shape memory structure  210 . 
     In this illustrative example, when shape memory structure  210  has buckled shape  218  in deactivated state  222 , composite structure  208  has undeployed shape  226 . When shape memory structure  210  has original shape  220  in activated state  224 , composite structure  208  has deployed shape  228 . 
     In these illustrative examples, composite structure  208  applies load  230  against shape memory structure  210 . Load  230  may take various forms such as compressive load  232  and bending load  234 . 
     As depicted, composite structure  208  applies load  230  on shape memory structure  210  as compressive load  232  when shape memory structure  210  is in activated state  224  and has original shape  220 . Compressive load  232  occurs when shape memory structure  210  is in activated state  224  and returns to original shape  220 . Activated state  224  may occur when shape memory structure is heated to or above a transition temperature for shape memory structure  210 . 
     Composite structure  208  applies load  230  on shape memory structure  210  as bending load  234  when shape memory structure  210  is in deactivated state  222 . For example, when shape memory structure  210  cools below a transition temperature, shape memory structure  210  may be deformed. In other words, load  230  applied by composite structure  208  against shape memory structure  210  causes shape memory structure  210  to bend. As a result, load  230  is bending load  234  that may cause the bending of shape memory structure  210  into buckled shape  218 . 
     Shape memory structure  210  may take various forms. Further, shape memory structure  210  may be comprised of different types of materials. For example, shape memory structure  210  may be comprised of a material selected from a shape memory metal alloy, a shape memory polymer, copper-aluminum-nickel, nickel-titanium, or some other suitable material. The material selected may depend on the particular application or implementation and is selected as one that allows shape memory structure  210  to be deformed when in deactivated state  222  and return to original shape  220  when in activated state  224 . 
     In this illustrative example, shape memory structure  210  is unitary structure  236 . In other words, shape memory structure  210  may be a single piece or component. 
     In an illustrative example, shape memory structure  210  may aid in controlling movement of aircraft  206  when in original shape  220  such that composite structure  208  moves from undeployed shape  226  to deployed shape  228 . For example, shape memory structure  210  in original shape  220  causes composite structure  208  to have a group of desired values  238  for a group of parameters  240  in deployed shape  228 . As depicted, the group of parameters  240  is selected from at least one of rigidity, stability, airflow, noise, vibration, lift, drag, angle of attack, or other suitable parameters. 
     In this illustrative example, activation system  212  is a component in aerodynamic control system  204  that controls the state of shape memory structure  210 . For example, activation system  212  causes shape memory structure  210  to shift from deactivated state  222  to activated state  224 . 
     This change in state is caused by activation system  212  applying heat to shape memory structure  210 . In other words, activation system  212  includes one or more heat sources. As depicted, activation system  212  includes at least one of a wire, a resistive element, a heating unit, a bleed air system, an electromagnetic induction unit, an infrared emitter, a bleed air conduit from an aircraft engine, a laser unit, or some other suitable component that may generate heat in shape memory structure  210  sufficient to cause a change in state. 
     The illustration of an aerodynamic environment  200  in  FIG. 2  is not meant to imply physical or architectural limitations to the manner in which an illustrative embodiment may be implemented. Other components in addition to or in place of the ones illustrated may be used. Some components may be unnecessary. Also, the blocks are presented to illustrate some functional components. One or more of these blocks may be combined, divided, or combined and divided into different blocks when implemented in an illustrative embodiment. 
     For example, although vehicle  202  has been described with respect to aircraft  206 , vehicle  202  may take other forms. For example, vehicle  202  may be selected from one of a mobile platform, an aircraft, a surface ship, a tank, a personnel carrier, a train, a spacecraft, a submarine, a bus, an automobile, or some other suitable type of vehicle. 
     As another example, activation system  212  may be omitted or may not be part of aircraft  206 . For example, the activation and deactivation of shape memory structure  210  may occur as a result of changes in the temperature in the environment to which shape memory structure  210  is exposed. For example, the temperature may change during different phases of flight. 
     For example, original shape  220  is present during a first phase of flight for aircraft  206  and buckled shape  218  is present during a second phase of flight for aircraft  206 . In one illustrative example, the first phase of flight is take-off of aircraft  206  and the second phase of flight is cruising of aircraft  206 . In this example, the activation of shape memory structure  210  occurs during take-off and the deactivating of shape memory structure  210  occurs during cruising of aircraft  206 . Additionally, original shape  220  is present during a third phase of flight, such as landing of aircraft  206 . 
     With reference to  FIG. 3 , a detailed illustration of a section of a trailing edge of a wing of an aircraft is depicted in accordance with an illustrative embodiment. As depicted, a more detailed illustration of section  132  of wing  102  is shown in this figure. As depicted, aerodynamic control system  300  is shown as being implemented in trailing edge  128  of wing  102  in this exposed view of wing  102 . In this example, trailing edge  128  in wing  102  is shown in an undeployed shape. 
     As depicted, aerodynamic control system  300  may be used to change the shape of trailing edge  128  and wing  102 . A more detailed view of aerodynamic control system  300  in section  304  is shown in  FIG. 4  below. 
     With reference now to  FIG. 4 , an illustration of an aerodynamic control system is depicted in accordance with an illustrative embodiment. In this figure, a more detailed view of aerodynamic control system  300  in section  304  in trailing edge  128  is shown. In this illustration, aerodynamic control system  300  is depicted in a deactivated state with trailing edge  128  of wing  102  from  FIG. 3  being in an undeployed shape. 
     In this illustrative example, aerodynamic control system  300  has a number of different components that can be seen in this exposed view. As depicted, shape memory structures  406  and composite structure  408  are illustrated in trailing edge  128  of wing  102 . In this illustrative example, shape memory structures  406  are comprised of nickel-titanium alloy. Shape memory structures  406  include shape memory structure  410 , shape memory structure  412 , shape memory structure  414 , and shape memory structure  416 , which are in the form of elongate members in this depicted example. Shape memory structures  406  also include shape memory structure  418 , shape memory structure  420 , shape memory structure  422 , and shape memory structure  424 . 
     As depicted, first end  426  of shape memory structure  410  is associated with composite structure  408 , and first end  428  of shape memory structure  412  is associated with composite structure  408 . First end  430  of shape memory structure  414  is associated with composite structure  408 , and first end  432  of shape memory structure  416  is associated with composite structure  408 . 
     In the illustrative example, second end  434  of shape memory structure  410  is associated with mounting base  436 , and second end  438  of shape memory structure  412  is associated with mounting base  440 . Second end  442  of shape memory structure  414  is associated with mounting base  444 , and second end  446  of shape memory structure  416  is associated with mounting base  448 . 
     As depicted, shape memory structure  418 , shape memory structure  420 , shape memory structure  422 , and shape memory structure  424  assist in the continuity of the deployed shape of composite structure  408 . These shape memory structures produce a local curvature in the area of composite structure  408  around these shape memory structures. 
     In the illustrative example, shape memory structure  418 , shape memory structure  420 , shape memory structure  422 , and shape memory structure  424  are secondary shape memory structure elements. These structures affect a shape change by generating internal stresses in the composite and shape memory structure assembly that leads to curvature of that assembly. 
     As shown in this deactivated state for shape memory structures  406 , composite structure  408  applies a load in the form of a bending load on shape memory structure  410 , shape memory structure  412 , shape memory structure  414 , and shape memory structure  416 . This load is shown in the direction of arrow  450 . This deformation is caused by composite structure  408  in this illustrative example. 
     In the deactivated state, composite structure  408  has an undeployed shape at trailing edge  128  of wing  102 . Undeployed shape of composite structure  408  is the shape of composite structure  408  that is present when shape memory structures  406  do not apply a force against composite structure  408 . 
     Turning next to  FIG. 5 , another illustration of an aerodynamic control system of an aircraft is depicted in accordance with an illustrative embodiment. In this example, trailing edge  128  of wing  102  shown in  FIG. 3  is shown in a deployed shape. In this depicted example, trailing edge  128  of wing  102  is shown as bent or curved in the direction of arrow  500  to form a shape. 
     With reference now to  FIG. 6 , an illustration of a cross-section of an aerodynamic control system is depicted in accordance with an illustrative embodiment. In this figure, an illustration of a cross-sectional view of aerodynamic control system  300  is shown taken along lines  6 - 6  in  FIG. 4 . 
     In this view, shape memory structure  412  is shown as being in a buckled shape when this structure is in a deactivated state. In this deactivated state, shape memory structure  412  is in a state in which shape memory structure  412  may be deformed. In this example, deformation is a bending of shape memory structure  412  that forms the buckled shape of shape memory structure  412 . Further, the undeployed shape for composite structure  408  is also seen in this view. 
     In this view, different sections of shape memory structure  412  are illustrated. As depicted, base section  600 , middle section  602 , and attachment section  604  are shown for shape memory structure  412 . 
     Base section  600  is part of second end  438  and is associated with mounting base  440 . Attachment section  604  is part of first end  428 . 
     As can be seen in this illustrative example, middle section  602  has a buckled shape from being bent by composite structure  408 . Composite structure  408  applies a bending load when shape memory structure  412  is in a deactivated state. 
     In the illustrative example, base section  600  may be associated with mounting base  440  in a number of different ways. As depicted in this illustrative example, base section  600  is bonded to mounting base  440 . In other examples, base section  600  may be fastened to the composite structure, formed as part of mounting base  440 , or connected to mounting base  440  in some other manner. Further, some combination of mechanisms also may be used to associate base section  600  with mounting base  440 . 
     In the illustrative example, attachment section  604  is bonded to composite structure  408 . In other illustrative examples, attachment section  604  may be associated with composite structure  408  using other mechanisms. For example, attachment section  604  may also be fastened to the composite structure, formed as part of mounting base  440 , or connected to mounting base  440  in some other manner. 
     Further, some combination of mechanisms also may be used to associate attachment section  604  with composite structure  408 . For example, attachment section  604  may be placed between with layers in composite structure  408 . These layers may be cured such that attachment section  604  is considered to be formed as part of composite structure  408 . Additionally, adhesive also may be included to bond attachment section  604  to the layers of composite structure  408 . 
     In the illustrative example, the shape and thickness of base section  600  is designed to allow for a desired attachment to a structure such as mounting base  440 . In an illustrative example, base section  600  may also be designed to allow for some adjustment in the mounting to “tune” the performance of the actuator. 
     In the illustrative example, tuning involves adjusting the amount of compressive pre-load in the actuator by moving the end of the actuator. Increasing the pre-load can result in more shape change in the deployed state and vice versa. 
     As depicted in the illustrative example, the shape and thickness of middle section  602  is designed to allow for a controlled and reversible transition between the original shape and the buckled shape. Curve  606  at trailing edge  608  of middle section  602  is designed to transform the compressive loading in middle section  602  of the actuator to a moment load at trailing edge  608  at the connection to the skin, composite structure  408 , to induce additional curvature in the trailing edge  608  during actuation. In this depicted example, the actuator is shape memory structure  412 . This resultant moment also helps initiate buckling in middle section  602  during relaxation, promoting the overall buckling and “collapse” of shape memory structure  412 . The shape and thickness of attachment section  604  is designed to induce a curvature at the trailing edge of composite structure  408  through the generation of internal stresses when actuated. 
     In this illustrative example, composite structure  408  and attachment section  604  are formed with opposite curvatures and constrained together during bonding. Actuation and relaxation of attachment section  604  of this bonded assembly changes the internal stress distribution, leading to a straight shape when relaxed and a curved shape when actuated. 
     With reference now to  FIG. 7 , an illustration of a cross-section of an aerodynamic control system is depicted in accordance with an illustrative embodiment. In this figure, an illustration of a cross-sectional view of aerodynamic control system  300  is shown taken along lines  7 - 7  in  FIG. 5 . 
     In this view, shape memory structure  412  is shown as being in an original shape when this structure is in an activated state. In this activated state, shape memory structure  412  is in a state in which shape memory structure  412  returns to a pre-deformed shape if shape memory structure  412  has been deformed. In other words, shape memory structure  412  remembers its original shape and returns to its original shape when heated in this illustrative example. Further, the deployed shape for composite structure  408  is also seen in this view. 
     As shown in this view, shape memory structure  412  is straightened out in this original shape. Shape memory structure  412  in the original shape may be, for example, a beam that may create a truss-type configuration between shape memory structure coordinates and composite structure  408 . In this manner, this arrangement may be insensitive or reduced in sensitivity to other types of loads that may be applied to this configuration. 
     In the illustrative embodiments, shape memory structure  412  in an activated state results in a truss configuration formed by shape memory structure  412  and composite structure  408 . This truss configuration has an increased resistance to deformation. When shape memory structure  412  is a deactivated state, shape memory structure  412  in the truss configuration undergoes structural collapse through buckling. This change, reducing the stiffness of the shape memory structure  412 , allows shape memory structure  412  to deform to a buckled shape and allows composite structure  408  to return to its base shape. Further, when composite structure  408  is in a deployed shape when moved to the deployed shape by shape memory structure  412 , the deployed shape of composite structure  408  and the original shape of shape memory structure  412  are independent of the exterior loading on the composite structure  408 . 
     The illustration of the different components in the aerodynamic control system illustrated in  FIG. 1  and  FIGS. 3-7  are not meant to limit the manner in which different illustrative embodiments may be implemented. For example, although aerodynamic control system  300  is shown as being implemented in trailing edge  128  of wing  102  for aircraft  100 , aerodynamic control system may be implemented in other locations or for other portions of aircraft  100 . For example, and aerodynamic control system may be implemented in a leading edge of wing  102 , on body  106  of aircraft  100 , in a faring, as part of the control surface, or in some other suitable manner. 
     In other illustrative examples, shape memory structure  418 , shape memory structure  420 , shape memory structure  422 , and shape memory structure  424  may be omitted. Also, the illustrations did not show an activation system. The activation system used depends on the particular implementation. For example, wires or traces may be formed on or within the shape memory structures. In other examples, the heat may be supplied through an infrared emitter, a bleed air conduit from an aircraft engine, on in some other manner. 
     The different components shown in  FIG. 1  and  FIGS. 3-7  may be combined with components in  FIG. 2 , used with components in  FIG. 2 , or a combination of the two. Additionally, some of the components in  FIG. 1  and  FIGS. 3-7  shown in block form in  FIG. 2  can be implemented as physical structures. 
     With reference now to  FIG. 8 , an illustration of a flowchart of a process for controlling a shape of a composite structure is depicted in accordance with an illustrative embodiment. The process illustrated in  FIG. 8  may be implemented in aerodynamic environment  200  in  FIG. 2 . For example, the process may be implemented using aerodynamic control system  204 . The process begins with the shape memory structure in a deactivated state and the composite structure in an undeployed shape in this illustrative example. 
     The process begins by determining whether to change the shape of the composite structure to a deployed shape (operation  800 ). If the composite structure is not to be changed to the deployed shape, the process returns to operation  800 . If the composite structure is to be changed to the deployed shape, the process activates the shape memory structure associated with the composite structure (operation  802 ). In operation  802 , the shape memory structure changes from a buckled shape to an original shape and causes the composite structure to change from an undeployed shape to a deployed shape. The composite structure applies a load in the form of a compressive load on the shape memory structure when in the deployed shape. The undeployed shape is the shape of the composite structure when the shape memory structure is not applying a force on the composite structure to place the composite structure in the deployed shape. 
     A determination is made as to whether to change the shape of the composite structure back to the undeployed shape (operation  804 ). If the composite structure is to remain in the deployed shape, the process returns to operation  804 . 
     Otherwise, the process then deactivates the shape memory structure (operation  806 ). In operation  806 , the shape memory structure bends from the original shape to a buckled shape in response to a load from the composite structure and the composite structure changes from the deployed shape to the undeployed shape. In this example, the load applied by the composite structure is a bending load. The process then returns to operation  800  as described above. 
     In these illustrative examples, the activating and deactivating of the shape memory structure may be controlled by an activation system. The activation system may apply heat to the shape memory structure through a device in the aircraft. In other illustrative examples, the activation system may not be a device, but may be the environment around the shape memory structure. For example, the activating step and the deactivating step occur during different phases of flight of the aircraft. The activating step occurs during take-off of the aircraft and the deactivating step occurs during cruising of the aircraft. This activation and deactivation may be caused by the temperature in the environment to which the shape memory structure is exposed. For example, a first temperature during a take-off causes the shape memory structure to be in the activated state and a second temperature during cruising causes the shape memory structure to be in the deactivated state. 
     In this manner, autonomous activation of the shape memory structure may occur through different phases of flight. In other illustrative examples, the activation and deactivation may be through controlling the operation of the activation system that applies heat to the shape memory structure. 
     The flowcharts and block diagrams in the different depicted embodiments illustrate the architecture, functionality, and operation of some possible implementations of apparatuses and methods in an illustrative embodiment. In this regard, each block in the flowcharts or block diagrams may represent at least one of a module, a segment, a function, or a portion of an operation or step. 
     In some alternative implementations of an illustrative embodiment, the function or functions noted in the blocks may occur out of the order noted in the figures. For example, in some cases, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be performed in the reverse order, depending upon the functionality involved. Also, other blocks may be added in addition to the illustrated blocks in a flowchart or block diagram. 
     Illustrative embodiments of the disclosure may be described in the context of aircraft manufacturing and service method  900  as shown in  FIG. 9  and aircraft  1000  as shown in  FIG. 10 . Turning first to  FIG. 9 , an illustration of an aircraft manufacturing and service method is depicted in the form of a block diagram in accordance with an illustrative embodiment. During pre-production, aircraft manufacturing and service method  900  may include specification and design  902  of aircraft  1000  in  FIG. 10  and material procurement  904 . 
     During production, component and subassembly manufacturing  906  and system integration  908  of aircraft  1000  in  FIG. 10  takes place. Thereafter, aircraft  1000  in  FIG. 10  may go through certification and delivery  910  in order to be placed in service  912 . While in service  912  by a customer, aircraft  1000  in  FIG. 10  is scheduled for routine maintenance and service  914 , which may include modification, reconfiguration, refurbishment, and other maintenance or service. 
     Each of the processes of aircraft manufacturing and service method  900  may be performed or carried out by a system integrator, a third party, an operator, or some combination thereof. In these examples, the operator may be 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, a leasing company, a military entity, a service organization, and so on. 
     With reference now to  FIG. 10 , an illustration of an aircraft is depicted in the form of a block diagram in which an illustrative embodiment may be implemented. In this example, aircraft  1000  is produced by aircraft manufacturing and service method  900  in  FIG. 9  and may include airframe  1002  with plurality of systems  1004  and interior  1006 . Examples of systems  1004  include one or more of propulsion system  1008 , electrical system  1010 , hydraulic system  1012 , and environmental system  1014 . Any number of other systems may be included. Although an aerospace example is shown, different illustrative embodiments may be applied to other industries, such as the automotive industry. 
     Apparatuses and methods embodied herein may be employed during at least one of the stages of aircraft manufacturing and service method  900  in  FIG. 9 . In one illustrative example, components or subassemblies produced in component and subassembly manufacturing  906  in  FIG. 9  may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft  1000  is in service  912  in  FIG. 9 . 
     For example, aerodynamic control system in accordance with an illustrative embodiment may be manufactured during component and subassembly manufacturing  906 . The aerodynamic control system may be implemented into aircraft  1000  during system integration  908 . Further, the aerodynamic control system may be used in operation of aircraft  1000  during certification and delivery  910  and in service  912 . 
     As another illustrative example, aerodynamic control system may be manufactured and added to aircraft  1000  during maintenance and service  914 . For example, the aerodynamic control system may be added during upgrades, routine maintenance, refurbishment, and other operations performed on aircraft  1000  during maintenance and service  914 . 
     Thus, the illustrative examples provide a method and apparatus for controlling the shape of a composite structure. In the illustrative examples, the system used to actuate or change the shape of the composite structure is implemented using shape memory structures. The shape memory structures in the illustrative examples are designed for use in locations in a vehicle, such as an aircraft that has limited clearance. For example, an illustrative embodiment may be implemented in an area such as a trailing edge of a wing of an aircraft. In this manner, the composite structure may be implemented to allow for a change in shape that reduces or eliminates gaps. As a result, the change in shape at the trailing edge of the wing may occur without airflow disturbing features such as discrete hinges, gaps, fasteners, or other undesired features. Further, the shape memory structures may be selected with a desired stiffness to maintain the shape of the composite structure. 
     The description of the different illustrative embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different illustrative embodiments may provide different features as compared to other desirable embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.