Investigation on adaptive wing structure based on shape memory polymer composite hinge Yuemin Yu *a,b ,Xinbo Li c, Wei Zhang c, Jinsong Leng a Centre for Composite Materials and Structures, P.O. Box 3011, No. 2 Yi Kuang Street ,Science Park of HIT, Harbin Institute of Technology (HIT), Harbin 150080, P.R. China; b Dept. of Mathematics and Mechanics, Heilongjiang Institute of Science and Technology, Harbin 150027, P.R. China c. Hafei Aviation Industry Co. LTD, Harbin 150066, P.R. China a
ABSTRACT This paper describes the design and investigation of the SMP composite hinge and the morphing wing structure. The SMP composite hinge was based on SMP and carbon fiber fabric. The twisting recoverability of it was investigated by heating and then cooling repeatedly above and below the Tg. The twisting recoverability characterized by the twisting angle. Results show that the SMP composite hinge have good shape recoverability, Recovery time has a great influence on the twisting recoverability. The twisting recovery ratio became large with the increment of recovery time. The morphing wing can changes shape for different tasks. For the advantages of great recovery force and stable performances, we adopt SMP composite hinge as actuator to apply into the structure of the wing which can realize draw back wings to change sweep angle according to the speed and other requirements of military airplanes. Finally, a series of simulations and experiments are performed to investigate the deformations of morphing wings have been performed successfully. It can be seen that the sweep angle change became large with the increment of initial angle. The area reduction became large with the increment of initial angle, but after 75° the area reduction became smaller and smaller. The deformations of the triangle wing became large with the increment of temperature. The area and the sweep angle of wings can be controlled by adjusting the stimulate temperature and the initial twisting angle of shape memory polymer composite hinge. Keywords: shape memory polymer composite hinge; actuator ; twisting
1. INTRODUCTION Shape memory material has the property to return mechanically induced strains upon heating or application of an electric field. The typical shape memory materials are shape memory alloy and shape memory polymer (SMP). For most of the SMP, their characterizations such as shape recovery and/or shape fixation may appear at the temperatures above and/or below the glass transition temperature (Tg ) [1–2]. Shape memory effect (SME) of SMP in a thermomechanical cycle is illustrated as shown in Fig.1. 1. SMP is easily deformed at a temperature above Tg . Only a small force is required for maintaining the deformed shape. 2. After cooling to below Tg (the deformed shape is fixed during cooling) the deformed shape is remained. 3. This deformed shape can be held until the shape recovery is activated by reheating SMP to over Tg . The SMP shows the typical SME by fully regaining the original shape upon heating. The SME cycle can be repeated for many times.
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[email protected] [email protected] ; phone 0451-88036308; fax 0451-86402328
International Conference on Smart Materials and Nanotechnology in Engineering edited by Shanyi Du, Jinsong Leng, Anand K. Asundi Proc. of SPIE Vol. 6423, 64231D, (2007) · 0277-786X/07/$18 · doi: 10.1117/12.779394 Proc. of SPIE Vol. 6423 64231D-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 03/15/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
II' O1gII
Ii
tTg
I*
Ii
ill
Fig . 1 Illustration of SME.
Although SMP materials already have some applications in the engineering industry, they are far from the technological potential of SMP. The main reason for this is the significant weaknesses in mechanical strength and stiffness. In this paper, for design of the wing frame , SMP composite hinge based on SMP and carbon fiber fabric were developed. The dynamic mechanical analysis (DMA) was investigated. The original shape of SMP composite hinge can recovered by changing the temperature above Tg. New advances in smart materials and adaptive structures have made possible the idea of morphing wing shapes in-flight in order to adapt the aircraft configuration to all flight conditions [3-4].The goal is to create a wing that will be able to reconfigure itself to give optimal performance at all stages of flight. Several morphing concepts for aircraft wings have been proposed [5-6] to change chord and span .Adaptive materials, such as shape memory materials, can be used to accomplish this purpose efficiently. Structural health monitoring of the wing can using the Extrinsic Fabry-Perot Interferometer and Fiber Bragg Grating sensors [7]. The paper brings forward a wing structure based on the smart materials and the require of military affairs[8-9], which can adjust the parameter of wings by controlling actuator deformations .The design adopts SMP composite hinge as actuator to drive the wing to deform . The links are attached to one another using pin joints as shown in the sketches below. The Fig.2 displays the linkage of the triangle wing. Span
Fig. 2 The design of the triangle wing structure
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2. PROPERTY ANALYSIS OF SMP COMPOSITE HINGE 2.1 Dynamic mechanical property Dynamic mechanical analysis (DMA) test was used to investigate the dynamic mechanical properties of the SMP composite. In the DMA test, the storage modulus, the loss modulus and tangent delta can be recorded against the temperature. The storage modulus is the modulus of elastic portion of material while the loss modulus is the modulus of viscous portion. Tangent delta is defined as the ratio of the loss modulus over the storage modulus indicating the damping capability of a material. The sample dimension is 60 ×10 ×5 mm is shown in Fig.3. DMA tests were carried out in the three-point bending mode at a heating rate of 5°C/min and a constant frequency of 1 Hz. Temperature rang was set from 0 to 120 . The DMA property of SMP composite with carbon fiber fabric is shown in Fig.4 It is clear that there existed the temperature dependency of storage modulus E′, and loss factor tan δ for the SMP composite. The temperature corresponding to the peak of tangent delta is an alternative definition of Tg . Tg of SMP composite was 64 .
Fig.3 The sample of SMP composite
Fig.4 Dynamic mechanical properties of the SMP composite
2.2 Twisting recoverability Before doing twisting recovery tests, the specimen was pasted with the resistance film and twisted at a specified angle .The samples with dimensions of 80 ×20 × 5 mm were taken from SMP composite. One end of the specimen was fixed with 20 mm length on the jig and the other end was deformed with the length of 60 mm. The sample was heated by 20volt alternating current. The recovering curve of the specimen was recorded. The time dependency of twisting recovery property was investigated. The specimen was heated for 2 min, 4min, 6 min and 8 min, respectively. In order to examine the twisting recovery ability of SMP composite hinge with carbon fiber fabric, the twisting recovery ratio was defined by the parameter, R =φ0/φ, where φ was defined as the recovery angle and φ0 was the initial angle. The time dependency of the twisting recovery property of the SMP composites was investigated. The relationship between the twisting recovery ratios and recovery time was shown in Fig. 5.
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Recovery ratio (%)
120 100 80 60 0
2
4
6
8
10
Recovery time (min) Fig. 5 The relationship between the recovery ratios and recovery time
From Fig.5, it is clear that the SMP composite developed have good shape recoverability. As for the influence of recovery time, the recovery ratio increased with increments of recovery time. 2.3 The torsion of twisting recoverability From the dynamic mechanical properties of the SMP composite, the recovery torsions of the SMP composite hinge are calculated and shown in table 1. Table 1The recovery torsion Initial twisting angle / °
45 60 75 90
Torsion / kNm
0.11 0.15 0.18 0.22
3. SIMULATIONS The models of the four configurations were developed. All of the models were created by automatic dynamic analysis of mechanic system (ADAMS) . Fig.6 shows the models of the four configurations with different initial angle. The regulations of deformations are shown in Fig. 7. The relationship between the sweep angle change and the initial angle of SMP composite hinge are shown in Fig. 8. The relationship between the area reduction and the initial angle of SMP composite hinge are shown in Fig.9.
(a)
(b)
(c)
(d)
Fig.6 The ADAMS models : (a) 45° (b) 60° (c) 75° (d) 90°
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5.0
450.0
:
.
-3553
—
— -
—. .——.—————
30053 — — — —
-45.0
-550
2500 00
1000
2000
3000
4000
5000
6000
00
1000
2000
3000
(a)
4000
5000
6000
(b)
Fig.7 The deformations of the triangle wing : (a) The sweep angle change (b) The span change
Sweep angle change (°)
30 25 20 15 10 5 0 30
45
60
75
90
105
Initial angle of SMP composite hinge (°) Fig.8 The relationship between the sweep angle change and the initial angle of SMP composite hinge
Area reduction (%)
16 14 12 10 8 6 30
45
60
75
90
105
Initial angle of SMP composite hinge (°) Fig.9 The relationship between the area reduction and the initial angle of SMP composite hinge
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4. EXPERIMENTS A working prototype of the wing structure was created to demonstrate the wing how to morph. The SMP composite hinge was heated for 10 min. The wings deform when the SMP composite hinge begin to twist recovery that is shown in Fig. 10. The sweep angles change of the triangle wing are shown in Fig. 11 when the SMP composite hinge with different initial angles. The relationship between the area reduction and initial angle of SMP composite hinge are shown in Fig.12.
(a)
(b)
Sweep angle change (°)
Fig.10 Prototype of the Wing Structures : (a) Unmorphed (b) Morphed
30 25 20 15 10 5 0 30
45
60
75
90
105
Initial angle of SMP composite hinge (°) Fig.11 The sweep angles change of the triangle wing
Area reduction (%)
16 14 12 10 8 6 30
45
60
75
90
105
Initial angle of SMP composite hinge (°) Fig.12 The relationship between the area reduction and initial angle of SMP composite hinge
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5. CONCLUSION In the paper , the SMP composite hinge were developed. The deformations of the wing structure are tested. The results obtained are remarked as follows: (1) The developed SMP composites hinge have excellent shape recoverability. Recovery time has a great influence on the twisting recoverability. The recovery ratio became large with the increment of recovery time. (2) Initial angle has a great influence on the twisting recoverability of SMP composite hinge. The sweep angle change and the area reduction of the wing structure became large with the increment of initial angle, but after 75° the area reduction became smaller and smaller. (3) Because the twisting recovery ratios of SMP composite hinge became large with the increment of temperature, the deformations of the triangle wing became large with the increment of temperature. (4) Compared and analyzed the deformations from experiment and simulation analyses. Results obtained indicate the good agreement between the experiment and simulation suggests that the design enable the triangle wing to alter its configuration in flight by heating the SMP composite hinge.
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