WO2021261676A1

WO2021261676A1 - Elastic shape-memory polymer composite skin having zero poisson's ratio

Info

Publication number: WO2021261676A1
Application number: PCT/KR2020/015251
Authority: WO
Inventors: 권오현; 노진호; 배재성
Original assignee: 한국항공대학교산학협력단
Priority date: 2020-06-23
Filing date: 2020-11-03
Publication date: 2021-12-30
Also published as: DE112020007338T5; KR102343337B1

Abstract

Disclosed is an elastic shape-memory polymer composite skin having a zero Poisson's ratio. The elastic shape-memory polymer composite skin comprises: a body formed of conductive fibers; a plurality of metal frames that are disposed on a lower portion of the body and deliver electrical power to the body; and a plurality of reinforcement members that are coupled to the lower portion of the body so as to be spaced from the plurality of metal frames, wherein the body may change temperature on the basis of the electrical power delivered from the plurality of metal frames. Accordingly, low-power, long-duration flight in a morphing aircraft can be maintained due to low aerodynamic loss.

Description

Stretchable Shape Memory Polymer Composite Skin with Zero Poisson Ratio

Various embodiments relate to a stretchable shape memory polymer composite skin having a zero Poisson ratio.

As a solution to improve aircraft efficiency and satisfy various operating conditions, research on variable geometry aircraft or morphing structure aircraft is being actively conducted.

In particular, the skin of the morphing structure, which can change shape according to flight conditions, should be able to have flexible rigidity in the direction in which the shape is changed and strong rigidity in the direction in which aerodynamic forces are generated.

A typical morphing skin manufacturing method includes a method using a thin elastomer, a method using a corrugated structure, and a method using a cellular structure. These conventional methods have a characteristic that it is not easy to manufacture because the structure is complicated, or the required load is rapidly increased at a strain rate above a certain level.

Various embodiments of the present invention provide a stretchable shape memory polymer composite skin having a zero Poisson ratio that does not have a complex structure and does not rapidly increase the load required for deformation to solve the problems of the prior art.

The technical problems to be achieved in this document are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. There will be.

A stretchable shape memory polymer composite skin having a zero Poisson ratio according to various embodiments of the present disclosure includes a body made of conductive fibers, a plurality of metal frames disposed under the body to transmit power to the body, and the plurality of metals and a plurality of reinforcing materials coupled to a lower portion of the main body at a distance from the frame, and the main body may change in temperature based on electric power transmitted from the plurality of metal frames.

The plurality of metal frames and the plurality of reinforcing materials according to various embodiments of the present disclosure may be formed to cross the width of the main body along the width direction of the main body, respectively.

The length of the main body according to various embodiments of the present disclosure is increased by an external force applied to the main body at a reference temperature or higher, and when there is no external force, the original length of the main body may be restored.

The length of the body according to various embodiments of the present disclosure may be maintained in a deformed state below the reference temperature.

Each of the body and the plurality of metal frames according to various embodiments of the present disclosure may be formed in a 'C' shape with one side open.

Each of the plurality of metal frames according to various embodiments of the present disclosure may be connected to a wire for receiving power from the outside.

An adhesive layer for bonding to a morphing aircraft wing may be formed on one side of each of the plurality of metal frames according to various embodiments of the present disclosure.

According to various embodiments of the present disclosure, both ends of the main body in the width direction may be bent to cover the lower portion of the morphing aircraft wing.

The skin proposed in the present disclosure is a shape memory polymer composite skin in which a shape memory polymer is impregnated into a stretchable and conductive fabric. have.

Based on such easy deformation, the skin proposed in the present disclosure may be used as a skin of a morphing wing having a variable shape and a sheet material of a space structure having a variable shape.

In addition, the skin proposed in the present disclosure can maintain a deformed shape without external force, and since it has a zero-Poisson ratio, it has less aerodynamic loss compared to the existing morphing skin, so that when applied to a morphing aircraft, low power and long flight time can be maintained. can do.

Effects obtainable in the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present disclosure belongs from the description below. will be.

1 is a diagram schematically illustrating a process of manufacturing the body 110 of the stretchable shape memory polymer composite skin 100 having a zero Poisson ratio according to an embodiment of the present invention.

2 is a perspective view of a stretchable shape memory polymer composite skin 100 having a zero Poisson ratio according to an embodiment of the present invention.

3 is a view showing a rear view of the stretchable shape memory polymer composite skin 100 having a zero Poisson ratio according to an embodiment of the present invention.

4 is a view showing a stretchable shape memory polymer composite skin 100 having a zero Poisson ratio in which the overall length is deformed, according to an embodiment of the present invention.

5A and 5B are views illustrating a rear view of the stretchable shape memory polymer composite skin 100 having a zero Poisson ratio according to an embodiment of the present invention.

6 is a perspective view of a stretchable shape memory polymer composite skin 100 having a zero Poisson ratio coupled to a morphing aircraft wing 200 according to an embodiment of the present invention.

7A to 7C are cross-sectional views illustrating a stretchable shape memory polymer composite skin 100 having a zero Poisson ratio coupled to a morphing aircraft wing 200 according to an embodiment of the present invention.

In connection with the description of the drawings, the same or similar reference numerals may be used for the same or similar components.

Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in describing the embodiment of the present invention, if it is determined that a detailed description of a related known configuration or function interferes with the understanding of the embodiment of the present invention, the detailed description thereof will be omitted. In addition, the embodiments of the present invention will be described below, but the technical spirit of the present invention is not limited thereto and may be variously implemented by those skilled in the art.

Throughout the specification, when a part is "connected" with another part, this includes not only the case of being "directly connected" but also the case of being "indirectly connected" with another element interposed therebetween. . Throughout the specification, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated. In addition, in describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the component from other components, and the essence, order, or order of the component is not limited by the term.

Referring to FIG. 1 , the body 110 of the stretchable shape memory polymer composite skin 100 is impregnated with a shape memory polymer (SMP) liquid in which a conductive powder is mixed with a fabric such as nylon fiber having stretchability and conductive properties. can be manufactured by

The shape memory polymer (SMP) has the characteristic of memorizing the initial shape of the main body 110 by thermo-mechanical properties, so that it becomes flexible when the glass temperature (Tg) or higher, and the shape before deformation is remembered to be restored. Conversely, below the glass transition temperature (Tg), it may have a characteristic to maintain a deformed shape. That is, the body 110 may change the strength of the fabric depending on the properties of the shape memory polymer (SMP) above the glass transition temperature (Tg), and may be freely deformed in shape using this. In addition, the body 110 can maintain a deformed shape below the glass transition temperature (Tg) due to the properties of the shape memory polymer (SMP).

In one embodiment, the body 110 may be made of a fabric of heat-generating fibers that generate heat using electric power applied from the outside. For example, the temperature of the body 110 may increase or decrease depending on the amount of power applied from the outside, and the shape may be deformed or maintained at a specific temperature by the properties of the shape memory polymer (SMP). . In this case, the body 110 is filled with a shape memory polymer (SMP) solution mixed with conductive powder, or a shape memory polymer (SMP) composite material using a metal mesh is formed, or heating paint. can be applied.

The stretchable shape memory polymer composite skin 100 having a zero Poisson ratio according to an embodiment of the present invention is coupled to a wing of a morphing aircraft having a variable shape, a space structure having a variable shape, etc. to affect the deformation of each structure The main feature is to maintain a zero-Poisson's ratio without affecting Here, Poisson's ratio refers to the rate at which a material expands or contracts in another axial direction with respect to an axial stress, and a zero Poisson's ratio has no deformation in another axial direction due to an axial strain applied by the stress. can mean Hereinafter, the stretchable shape memory polymer composite skin 100 capable of solving problems such as deformation of a structure and loss of aerodynamic force based on such a zero Poisson ratio will be described in more detail.

2 and 3 show a perspective view and a rear view, respectively, of the stretchable shape memory polymer composite skin 100 having a zero Poisson ratio according to an embodiment of the present invention.

2 and 3, the stretchable shape memory polymer composite skin 100 having a zero Poisson ratio is a body 110 and a metal frame 120 and a reinforcing material 130 coupled to the lower portion of the body 110, respectively. can be configured.

As described above, the body 110 may be manufactured by impregnating a liquid shape memory polymer (SMP) liquid in which a conductive powder is mixed with a fabric such as nylon fiber having elasticity and conductivity. In an embodiment, the temperature of the body 110 may increase or decrease by power supplied from the outside, and the shape may be deformed or maintained at a specific temperature.

For example, when the body 110 becomes above a preset glass temperature (Tg) by electric power supplied from the outside, the shape may be easily deformed by the properties of the shape memory polymer (SMP). . That is, the body 110 may be deformed in a direction in which a load acts by decreasing the stiffness (or strength) of the fabric above the glass transition temperature (Tg).

Conversely, when power is not supplied to the main body 110 , when the main body 110 is below the glass transition temperature (Tg), the deformed shape may be maintained. In addition, when power is supplied from the outside and the main body 110 becomes above the glass transition temperature (Tg), the main body 110 restores to the initial shape by the property of the shape memory polymer (SMP) to return to the memorized shape. can be

The metal frame 120 may transmit power supplied from the outside to the body 110 . For example, the metal frame 120 may be made of a metal aluminum material that transmits power to the body 110 made of conductive fiber, and the lower portion of the body 110 corresponds to the width in the horizontal direction of the body 110 . can be coupled to In this case, a wire for receiving power from the outside may be connected to both ends of the metal frame 120 .

In an embodiment, a plurality of metal frames 120 may be provided. The plurality of metal frames 120 may be disposed with a predetermined interval across the width of the body 110 , and preferably may be respectively coupled to the lower portion of the body 110 . In this case, the magnitude of the power supplied to the plurality of metal frames 120 may be set differently, and the tensile strength of the main body 110 may be set differently for each region using this.

The reinforcing material 130 may be coupled to the body 110 at a distance from the metal frame 120 . For example, the reinforcing material 130 may be made of a light and strong material of synthetic resin or plastic material (eg, FRP material, ABS material, etc.). In an embodiment, a plurality of reinforcing materials 130 may be provided and disposed under the body 110 in parallel to the metal frame 120 .

In addition, in an embodiment, the thickness of the reinforcing material 130 may be formed to be thicker than the thickness of the metal frame 120 . For example, when the shape of the body 110 is deformed by an external force at the glass transition temperature (Tg), the reinforcing material 130 does not affect the maximum strain of the body 110, and the transverse strain of the body 110 The main body 110 can be fixed and supported more firmly so as to minimize this.

Referring to FIG. 4 , when electric power is applied from the outside, the stretchable shape memory polymer composite skin 100 is deformed in shape due to a decrease in stiffness (or strength) above a preset reference temperature (eg, glass transition temperature). Alternatively, it may be restored to its initial shape. At this time, a plurality of reinforcing materials 130 in the width (W) direction of the stretchable shape memory polymer composite skin 100 may be coupled to the lower portion of the stretchable shape memory polymer composite skin 100 at regular intervals, through which the stretchable shape The memory polymer composite skin 100 may be made only by tensile deformation in the length (L) direction without deformation in the width (W) direction. That is, the stretchable shape memory polymer composite skin 100 may have an overall length (L+ΔL) increased without a sharp increase in the load above the glass transition temperature (Tg).

Conversely, when power is not supplied from the outside, the stretchable shape memory polymer composite skin 100 becomes below a preset reference temperature (eg, glass transition temperature), and in this case, the shape is changed due to the shape memory polymer (SMP) properties. can be maintained In addition, when electric power is supplied from the outside and the stretchable shape memory polymer composite skin 100 becomes above a preset reference temperature (eg, glass transition temperature) again, the stretchable shape memory polymer composite skin 100 has a memorized shape Due to the nature of the shape memory polymer (SMP) to return to its original shape, it can be restored to its initial shape.

Meanwhile, the same components in FIGS. 1 to 5B refer to the same terms and reference numerals, and in order to avoid repeated description, reference is made to the descriptions of FIGS. 1 to 4 described above. Hereinafter, only differences between the embodiments will be described.

5A and 5B, the body 110 constituting the stretchable shape memory polymer composite skin 100 has a metal frame 120 and a reinforcing material 130 across the width of the body 110, the body 110 may be coupled to the lower surface of the In this case, the metal frame 120 and the reinforcing material 130 may be formed in plurality.

For example, as shown in FIG. 5A , the first metal frame 120-1 to the fifth metal frame 120-5, and the first reinforcing material 130-1 and the second reinforcing material 130-2 Each may be disposed to be spaced apart from the lower surface of the main body 110 at regular intervals. At this time, the first metal frame 120-1 to the fourth metal frame 120-4 may be sequentially disposed from one end to the other end direction of the body 110 and coupled thereto, and the fourth metal frame 120-4 may be coupled thereto. A first reinforcing material 130 - 1 and a second reinforcing material 130 - 2 may be respectively disposed between and coupled to the fifth metal frame 120 - 5 .

For example, by applying power to the first metal frame 120-1 to the fourth metal frame 120-4 to form a temperature at one end of the body 110 higher than the temperature at the other end of the body 110, It is possible to reduce the load for increasing the length in the direction of one end of the body 110 .

In addition, according to another embodiment of the present invention, as shown in FIG. 5B , the first reinforcing material 130-1 is disposed between the first metal frame 120-1 and the second metal frame 120-2. The second reinforcing material 130-2 is positioned between the second metal frame 120-2 and the third metal frame 120-3, and the second metal frame 120-3 and the fourth metal frame ( 120-4) may be coupled such that the third reinforcing member 130-3 and the fourth reinforcing member 130-4 are disposed between them. Through this, a load required to increase the length of the main body 110 may be formed differently for each region of the main body 110 . However, the embodiment of the present invention is not limited thereto, and the plurality of metal frames 120 and the plurality of reinforcing materials 130 may be coupled to the lower portion of the body 110 in various forms.

6 is a perspective view of a stretchable shape memory polymer composite skin 100 having a zero Poisson ratio coupled to a morphing aircraft wing 200 according to an embodiment of the present invention, and FIGS. 7A to 7C are According to an embodiment of the present invention, it is a view showing a cross-sectional view of a stretchable shape memory polymer composite skin 100 having a zero Poisson ratio coupled to a morphing aircraft wing 200 .

First, referring to FIGS. 6 and 7A , the body 110 and the metal frame 120 of the stretchable shape memory polymer composite skin 100 are bent at both ends to form a 'C'-shaped structure in cross section. For example, the body 110 may be coupled to closely contact the outer surface of the metal frame 120 coupled from one open side. That is, the body 110 may be coupled while surrounding the outside of the metal frame 120 . In this case, the adhesive layer 121 may be applied to the inner surface of the metal frame 120 to strengthen the bonding with the morphing aircraft structure.

In one embodiment, when a plurality of metal frames 120 are respectively disposed at predetermined intervals along the length of the morphing aircraft wing 200, the metal frame ( 120 may be a metal frame 120 disposed in the middle region A in the longitudinal direction of the front and rear of the morphing aircraft wing 200 .

That is, as shown in FIG. 6 , the adhesive layer 121 is applied to the inner surface of the metal frame 120 coupled to the lower portion of the body 110 corresponding to the middle region A of the morphing aircraft wing 200 . can be formed. However, the embodiment of the present invention is not limited thereto, and the adhesive layer 121 is applied and formed on the inner surface of each of the plurality of metal frames 120 disposed under the main body 110, so that the morphing aircraft wing 200 is formed. ) and the bonding state can be maintained more firmly.

In one embodiment, the external force acting on the stretchable shape memory polymer composite skin 100 may be applied along the longitudinal direction of the stretchable shape memory polymer composite skin 100 while the morphing aircraft wing 200 is deformed. For example, when the morphing aircraft wing 200 is stretched and unfolded above the glass transition temperature (Tg), an external force is applied to both ends of the stretchable shape memory polymer skin 100 coupled to the morphing aircraft wing 200 in the longitudinal direction. can That is, according to the external force acting by the deformation of the morphing aircraft wing 200, the length of the stretchable shape memory polymer composite skin 100 may be varied.

Conversely, when an external force does not act on the stretchable shape memory polymer composite skin 100 above the glass transition temperature (Tg), the stretchable shape memory polymer composite skin 100 has the original length due to the properties of the shape memory polymer (SMP). It can be restored to its initial shape with. Next, referring to 7b and 7c, both ends of the main body 110 of the stretchable shape memory polymer composite skin 100 wrap around and support the lower part of the morphing aircraft wing 200 . It may be formed to extend to be curved in the inward direction so as to be able to do so. For example, the morphing aircraft wing 200 may be implemented as a structure in which a hollow is formed therein, as shown in FIG. 7C , and in this case, the body 110 of the stretchable shape memory polymer composite skin 100 is a morphing aircraft In order to support the wing 200 more stably, both ends may be formed to be bent toward the inside.

As described above, the skin proposed in the present disclosure increases or decreases the temperature of the skin in a simple way of controlling the power flowing through the conductive fabric as a shape memory polymer composite skin by impregnating the stretchable and conductive fabric with a shape memory polymer. It can be easily deformed.

As described above, an optimal embodiment has been disclosed in the drawings and the specification. Although specific terms are used herein, they are used only for the purpose of describing the present invention, and are not used to limit the meaning or scope of the present invention described in the claims. Therefore, it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Claims

A stretchable shape memory polymer composite skin having a zero Poisson ratio, comprising:

a body made of conductive fibers;

a plurality of metal frames disposed under the main body to transmit power to the main body; and

and a plurality of reinforcing materials coupled to the lower portion of the body at intervals from the plurality of metal frames, respectively;

The body is a stretchable shape memory polymer composite skin whose temperature changes based on the electric power transmitted from the plurality of metal frames.
According to claim 1,

The plurality of metal frames and the plurality of reinforcing materials are each formed across the width of the body along the width direction of the body, a stretchable shape memory polymer composite skin.
According to claim 1,

The body is above the reference temperature, the length is increased by an external force applied to the body, and restored to the length of the body in the absence of an external force, stretch-improving memory polymer composite skin.
According to claim 1,

The body is a stretchable shape memory polymer composite skin in which the shape is maintained in a state with a deformed length below the reference temperature.
According to claim 1,

The body and the plurality of metal frames are each formed in a 'C' shape with one open side, a stretchable shape memory polymer composite skin.
According to claim 1,

The plurality of metal frames are each connected to a wire for receiving power from the outside, a stretchable shape memory polymer composite skin.
According to claim 1,

A stretchable shape memory polymer composite skin having an adhesive layer formed on one side of each of the plurality of metal frames for bonding with a morphing aircraft wing.
8. The method of claim 7,

A stretchable shape memory polymer composite skin that is formed by bending both ends of the body in the width direction to cover the lower portion of the morphing aircraft wing.