CN-121999745-A - Photo-thermal driving reconfigurable liquid crystal elastomer metamaterial and regulating and controlling method thereof

CN121999745ACN 121999745 ACN121999745 ACN 121999745ACN-121999745-A

Abstract

The invention discloses a photo-thermal driving reconfigurable liquid crystal elastomer metamaterial and a regulating and controlling method thereof, and relates to the technical field of acoustic metamaterials. The metamaterial comprises a rigid frame, a liquid crystal elastomer film, a mass block array and an illumination heating device. The rigid frame provides clamping and boundary constraint for the film, the liquid crystal elastomer film is oriented nematic phase at room temperature, is reversibly softened when the temperature rises and spans the phase transition temperature, and realizes adjustable equivalent mechanical property, the mass block array and the film locally form a local resonance unit, anti-resonance modal response is generated in a target low frequency band, and high-efficiency low-frequency sound insulation is realized through surface radiation phase offset. The illumination heating device uniformly irradiates and heats the film, so that the rigidity of the film can be changed reversibly, and further the dynamic characteristics of the local resonance unit can be changed, and the reversible migration and controllable positioning of the sound insulation peak value in the target low-frequency range can be realized. The invention has the advantages of no wiring, no structural geometry change, wireless photo-thermal regulation and control of sound insulation property, light weight and strong working condition adaptability.

Inventors

ZHENG YISHENG
LIU SUIXIN
LUO HUAGENG

Assignees

厦门大学

Dates

Publication Date: 20260508
Application Date: 20260320

Claims (10)

1. A photo-thermally driven reconfigurable liquid crystal elastomer metamaterial, comprising: a rigid frame for providing peripheral clamping and boundary constraint to the liquid crystal elastomer film; The liquid crystal elastomer film is clamped and fixed on the rigid frame and is used as a sound insulation functional layer, the liquid crystal elastomer film is in a nematic phase at room temperature and has a preset orientation, and the liquid crystal elastomer film is reversibly softened when the temperature rises to cross a nematic phase-isotropic phase transition temperature T Ni , so that the equivalent mechanical property of the film is changed; The mass blocks are fixed on the liquid crystal elastomer film to form a mass block array, each mass block and a local area of the liquid crystal elastomer film below the mass block form a local resonance unit together, and the local resonance unit is used for generating anti-resonance modal response in a target low-frequency range, so that surface radiation phase offset is realized, and the aim of low-frequency sound insulation is fulfilled; The illumination heating device is arranged on one side of the liquid crystal elastomer film and is used for carrying out integral irradiation on the liquid crystal elastomer film and generating photo-thermal uniform heating so that the temperature of the liquid crystal elastomer film reaches or exceeds T Ni , and thus the reversible change of the rigidity of the liquid crystal elastomer film is caused, the dynamic characteristic of the local resonance unit is further changed due to the rigidity change, and the sound insulation peak value is reversibly moved and controllably positioned in a target low-frequency range.
2. The photo-thermal driving reconfigurable liquid crystal elastomer metamaterial according to claim 1, wherein the liquid crystal elastomer film is prepared by a two-step crosslinking method, and comprises the following steps: firstly, forming an initial cross-linked network through an addition reaction to obtain a liquid crystal elastomer multi-domain film; and secondly, applying uniaxial mechanical stretching to the liquid crystal elastomer multi-domain film to realize mesogenic orientation, and performing ultraviolet curing under the stretching state to fix a mesogenic orientation structure, so as to obtain the liquid crystal elastomer film.
3. The photo-thermal driven reconfigurable liquid crystal elastomer metamaterial according to claim 1, wherein the rigid frame comprises a plurality of periodically arranged hollowed-out units; The liquid crystal elastomer film is covered and clamped on the rigid frame, so that the liquid crystal elastomer film is divided into a plurality of independent film vibration areas which are in one-to-one correspondence with the hollowed-out units by the solid part of the rigid frame; the mass blocks are fixed on the liquid crystal elastomer film in the same periodic arrangement mode, and each mass block is positioned at the center of one vibration area of the film, so that a mass block array corresponding to the hollowed-out unit array is formed.
4. The photo-thermally driven reconfigurable liquid crystal elastomer metamaterial according to claim 1, wherein the light heating means is a power adjustable light source comprising one of a continuous laser, a pulsed laser, an LED array or a halogen lamp.
5. The photo-thermal driven reconfigurable liquid crystal elastomer metamaterial according to claim 1, wherein the liquid crystal elastomer film has photo-thermal responsiveness, the liquid crystal elastomer film is in a high-modulus state under no illumination condition, the metamaterial has a first sound insulation characteristic, the liquid crystal elastomer film is softened under effective illumination of the illumination heating device to reduce modulus, the metamaterial is converted into a second sound insulation characteristic, and a sound insulation amount difference between the first sound insulation characteristic and the second sound insulation characteristic at a preset frequency is larger than a preset difference.
6. The photo-thermally driven reconfigurable liquid crystal elastomer metamaterial according to claim 5, further comprising: the temperature sensor is arranged on the surface of the liquid crystal elastomer film or embedded in the liquid crystal elastomer film; the control unit is in signal connection with the temperature sensor and the illumination heating device; The control unit is configured to control the working state of the illumination heating device according to the film temperature fed back by the temperature sensor so that the liquid crystal elastomer film temperature reaches and maintains a target temperature range corresponding to the first sound insulation characteristic or the second sound insulation characteristic.
7. The photo-thermally driven reconfigurable liquid crystal elastomer metamaterial according to claim 5, wherein the liquid crystal elastomer film is a nematic liquid crystal elastomer film, and the interior of the nematic liquid crystal elastomer film comprises an adjustable cross-linked network structure; the cross-linked network structure is configured such that the liquid crystal elastomer film has a first storage modulus in a first operating state corresponding to the first sound insulation characteristic and a second storage modulus in a second operating state corresponding to the second sound insulation characteristic, and a ratio of the first storage modulus to the second storage modulus is greater than M.
8. A method for regulating and controlling a photo-thermal driving reconfigurable liquid crystal elastomer metamaterial, which is characterized by comprising the following steps of: S1, providing a rigid frame and preparing a liquid crystal elastomer film, wherein the liquid crystal elastomer film is prepared by the following steps: S11, forming a liquid crystal elastomer multi-domain body with an initial cross-linked network through an addition reaction; S12, applying uniaxial mechanical stretching to the multi-domain body to induce mesogen to orient along the stretching direction; S13, ultraviolet light curing is carried out under the state of maintaining stretching so as to lock the mesogenic alignment structure, and a nematic liquid crystal elastomer film with preset alignment is formed; The method comprises the steps of regulating the ratio of a liquid crystal monomer to a cross-linking agent, and regulating and controlling the cross-linking network density of the liquid crystal elastomer film, so that the initial rigidity of the liquid crystal elastomer film at room temperature and the softening amplitude of the liquid crystal elastomer film when the liquid crystal elastomer film is heated to cross a nematic phase-isotropic phase transition temperature T Ni are preset; S2, clamping and fixing the liquid crystal elastomer film prepared in the step S1 on the rigid frame, fixing a plurality of mass blocks on the surface of the liquid crystal elastomer film in a preset array mode, wherein each mass block and a local area of the film below the mass block form a local resonance unit together, and the mass blocks, the distribution and the cross-linked network density of the liquid crystal elastomer film are cooperatively designed according to the target frequency of a target low-frequency sound insulation peak value so that the initial characteristic frequency of the local resonance unit falls into a range near the target frequency; S3, arranging an illumination heating device on one side of the liquid crystal elastomer film, irradiating the liquid crystal elastomer film through the illumination heating device in an operation stage to generate a photo-thermal effect so as to enable the liquid crystal elastomer film to be heated uniformly, enabling the liquid crystal elastomer film to be softened reversibly when the temperature of the film reaches or exceeds T Ni of the film, enabling the characteristic frequency of the local resonance unit to migrate to a low frequency direction due to the reduction of equivalent stiffness of the liquid crystal elastomer film, and enabling the sound insulation peak value of the metamaterial in a target low frequency range to achieve reversible migration and controllable positioning by controlling illumination parameters to adjust the characteristic frequency of the local resonance unit reversibly.
9. The method of conditioning a photo-thermally driven reconfigurable liquid crystal elastomer metamaterial according to claim 8, wherein the conditioning method further comprises the steps of: A temperature detection module is arranged and used for monitoring the temperature of the liquid crystal elastomer film in real time; And taking the nematic phase-isotropic phase transition temperature T Ni as a criterion of state switching, and dynamically stabilizing the temperature of the liquid crystal elastomer film in a preset temperature interval above T Ni by controlling the illumination parameters of the illumination heating device through feedback so as to realize and maintain a heating softening state.
10. The method of conditioning a photo-thermally driven reconfigurable liquid crystal elastomer metamaterial according to claim 8, wherein the conditioning method further comprises the steps of: In step S11, the content of unreacted liquid crystal monomer in the system is controlled by adjusting the initial feeding ratio of the liquid crystal monomer and the cross-linking agent; In the uv curing process of step S13, the unreacted liquid crystal monomer further undergoes a crosslinking reaction to form additional liquid crystal-liquid crystal chemical bonds, so as to increase the effective crosslinking density of the liquid crystal elastomer film on a molecular scale, thereby presetting a higher initial stiffness at room temperature.

Description

Photo-thermal driving reconfigurable liquid crystal elastomer metamaterial and regulating and controlling method thereof Technical Field The invention belongs to the field of acoustic metamaterials and intelligent high polymer materials, and particularly relates to a photo-thermal driving reconfigurable liquid crystal elastomer metamaterial and a regulating and controlling method thereof. Background Rotor systems, transmission systems, engines, and accessory systems in aerospace equipment can generate significant low frequency noise. The low-frequency noise has the characteristics of long wavelength and slow attenuation, and is difficult to effectively control by a conventional structural means, and the traditional sound insulation method generally depends on increasing the surface density or thickness, so that the weight and space cost are high, and the lightweight design of the structure is limited. In addition, the noise spectrum in the field of equipment tends to fluctuate significantly with changes in operating conditions. For example, the dominant noise band may drift during different rotational speeds, climb, cruise, or hover conditions, and during start-stop of accessory devices (e.g., fans, pump valves). Once the existing passive sound insulation structure is prepared, the sound insulation frequency band of the existing passive sound insulation structure is usually fixed, and the existing passive sound insulation structure cannot be flexibly adapted to the change of the working conditions. Therefore, on the premise of not changing the geometric constitution of the structure, the sound insulation performance of equipment noise is actively regulated and controlled, dynamic adaptive sound insulation is realized according to the change of working conditions, and meanwhile, the light weight of the structure is ensured, so that the current key technical problem is solved. On the other hand, the aviation equipment has two requirements of audible/shielding at the positions of cabin skins, equipment cabins, avionics cabinets and the like, namely noise needs to be effectively shielded to improve passenger comfort and communication definition in an operation stage, and certain audibility needs to be carried out for acoustic diagnosis or abnormal alarm identification in a maintenance or state monitoring stage. The existing passive sound insulation scheme is difficult to simultaneously consider light weight and working condition adaptation, the existing active sound insulation scheme generally depends on complex wiring and actuators, and the systems generally need to be provided with sensors, actuators and controllers, and the sound insulation effect is regulated through electric signals. Because of the cooperation of the multiple components, the system has a complex structure and high maintenance cost of wiring and an actuator, so that the system faces technical challenges in practical application. Therefore, the light acoustic metamaterial based on the liquid crystal elastomer has a simple structure, does not need wiring, can be remotely triggered and can switch sound insulation states between different working conditions, and has important engineering application value for effectively controlling low-frequency noise of aviation equipment. The liquid crystal elastomer is used as a core component, and can realize a reconfigurable sound insulation effect through the unique adjustable performance of the liquid crystal elastomer on the premise of not changing the geometric shape of the structure, thereby meeting the sound insulation requirements under different working conditions and simultaneously keeping the advantages of light weight and simplified structure. Disclosure of Invention The invention provides a photo-thermal driving reconfigurable liquid crystal elastomer metamaterial, which aims at solving the problem that light weight and suitability are difficult to be compatible in low-frequency noise control of existing aviation equipment. The metamaterial has the advantage of wiring-free regulation and control, can realize reversible migration and controllable positioning of sound insulation peaks in a target low-frequency range so as to adapt to drift of main noise frequency bands under different working conditions, and can realize reversible switching between high and low sound insulation states of a specific frequency band through photo-thermal triggering, thereby meeting the shielding/audible requirements of operation and maintenance stages. The second object of the invention is to provide a regulating method of the liquid crystal elastomer metamaterial. The molecular network crosslinking degree of the liquid crystal elastomer film is programmed by adjusting the excess ratio of the liquid crystal monomers, so that the sound insulation spectrum shape is preset and the adjustable range of the sound insulation spectrum shape is expanded in the manufacturing stage. In order to achieve the above purpose, the