Mechanics of shape-locking-governed R2G adhesion with shape memory polymers
Shape memory polymers (SMPs), with unique properties such as tunable elastic modulus, temporary shape locking and shape recovery upon external stimulation, are emerging as a new class of smart materials with switchable adhesion capabilities. A prominent feature of the adhesion between SMP and a sphe...
| Main Authors: | , , , , , |
|---|---|
| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
| Published: |
2023
|
| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/164647 |
| _version_ | 1811689907468369920 |
|---|---|
| author | Linghu, Changhong Yang, Xudong Liu, Yangchengyi Li, Dong Gao, Huajian Hsia, K. Jimmy |
| author2 | School of Mechanical and Aerospace Engineering |
| author_facet | School of Mechanical and Aerospace Engineering Linghu, Changhong Yang, Xudong Liu, Yangchengyi Li, Dong Gao, Huajian Hsia, K. Jimmy |
| author_sort | Linghu, Changhong |
| collection | NTU |
| description | Shape memory polymers (SMPs), with unique properties such as tunable elastic modulus, temporary shape locking and shape recovery upon external stimulation, are emerging as a new class of smart materials with switchable adhesion capabilities. A prominent feature of the adhesion between SMP and a spherical indenter is the so-called R2G adhesion, defined as making contact in the rubbery state to a certain indentation depth followed by detachment in the glassy state. While it has been demonstrated that the R2G adhesion with SMPs can achieve orders of magnitude higher adhesive strength compared to conventional elastic adhesive systems with similar geometrical and adhesion parameters, the fundamental mechanics of R2G adhesion and why it leads to such tremendous adhesion enhancement remain largely mysterious at this point. Here, combined experimental testing, theoretical analysis, and finite element analysis (FEA) based on a thermomechanical constitutive model of SMP are performed to investigate the mechanics of R2G adhesion with a rigid spherical indenter. It is shown that the orders of magnitude enhancement of R2G adhesion over conventional elastic adhesion systems is mostly governed by the shape locking effect during the transition from the rubbery to glassy states. The shape locking effect freezes the deformed configuration of the SMP substrate, resulting in nearly conformal contact between the spherical indenter and the glassy-state SMP substrate, thus greatly increases the effective radius of curvature of the contact surface. Our experimental measurements and FEA analysis demonstrate that the net effect of shape locking leads to a pull-off force of a sphere nearly the same as that of a flat punch on an elastic half-space with the same contact radius. An explicit expression of the pull-off force for R2G adhesion is proposed based on flat-punch adhesion. Our results from combined experimentation, modeling and simulations reveal the fundamental mechanics of R2G adhesion. Such understanding provides guidance for the design of SMP smart adhesives. |
| first_indexed | 2024-10-01T05:55:34Z |
| format | Journal Article |
| id | ntu-10356/164647 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T05:55:34Z |
| publishDate | 2023 |
| record_format | dspace |
| spelling | ntu-10356/1646472023-02-07T06:21:27Z Mechanics of shape-locking-governed R2G adhesion with shape memory polymers Linghu, Changhong Yang, Xudong Liu, Yangchengyi Li, Dong Gao, Huajian Hsia, K. Jimmy School of Mechanical and Aerospace Engineering School of Chemical and Biomedical Engineering Engineering::Mechanical engineering Shape Memory Polymers R2G Adhesion Shape memory polymers (SMPs), with unique properties such as tunable elastic modulus, temporary shape locking and shape recovery upon external stimulation, are emerging as a new class of smart materials with switchable adhesion capabilities. A prominent feature of the adhesion between SMP and a spherical indenter is the so-called R2G adhesion, defined as making contact in the rubbery state to a certain indentation depth followed by detachment in the glassy state. While it has been demonstrated that the R2G adhesion with SMPs can achieve orders of magnitude higher adhesive strength compared to conventional elastic adhesive systems with similar geometrical and adhesion parameters, the fundamental mechanics of R2G adhesion and why it leads to such tremendous adhesion enhancement remain largely mysterious at this point. Here, combined experimental testing, theoretical analysis, and finite element analysis (FEA) based on a thermomechanical constitutive model of SMP are performed to investigate the mechanics of R2G adhesion with a rigid spherical indenter. It is shown that the orders of magnitude enhancement of R2G adhesion over conventional elastic adhesion systems is mostly governed by the shape locking effect during the transition from the rubbery to glassy states. The shape locking effect freezes the deformed configuration of the SMP substrate, resulting in nearly conformal contact between the spherical indenter and the glassy-state SMP substrate, thus greatly increases the effective radius of curvature of the contact surface. Our experimental measurements and FEA analysis demonstrate that the net effect of shape locking leads to a pull-off force of a sphere nearly the same as that of a flat punch on an elastic half-space with the same contact radius. An explicit expression of the pull-off force for R2G adhesion is proposed based on flat-punch adhesion. Our results from combined experimentation, modeling and simulations reveal the fundamental mechanics of R2G adhesion. Such understanding provides guidance for the design of SMP smart adhesives. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University The authors acknowledge financial support by the Ministry of Education of Singapore under Academic Research Fund Tier 2 (T2EP50122-0005). C-H.L. acknowledges a Graduate Research Scholarship supported by the Ministry of Education of Singapore. Y.L. acknowledges the scholarship support as Visiting PhD Student from the China Scholarship Council. K.J.H. acknowledges a research start-up grant (002271-00001) from Nanyang Technological University. H.G. acknowledges a research start-up grant (002479-00001) from Nanyang Technological University and the Agency for Science, Technology and Research (A*STAR), and the use of the A*STAR Computational Resource Centre, Singapore (ACRC) and National Supercomputing Centre, Singapore (NSCC). H.G. and D.L. also acknowledge support from the Singapore Ministry of Education (MOE) AcRF Tier 1 (Grant RG120/21). 2023-02-07T06:21:27Z 2023-02-07T06:21:27Z 2023 Journal Article Linghu, C., Yang, X., Liu, Y., Li, D., Gao, H. & Hsia, K. J. (2023). Mechanics of shape-locking-governed R2G adhesion with shape memory polymers. Journal of the Mechanics and Physics of Solids, 170, 105091-. https://dx.doi.org/10.1016/j.jmps.2022.105091 0022-5096 https://hdl.handle.net/10356/164647 10.1016/j.jmps.2022.105091 2-s2.0-85139855977 170 105091 en T2EP50122-0005 NTU-SUG 002271-00001 NTU-SUG 002479-00001 RG120/21 Journal of the Mechanics and Physics of Solids © 2022 Elsevier Ltd. All rights reserved. |
| spellingShingle | Engineering::Mechanical engineering Shape Memory Polymers R2G Adhesion Linghu, Changhong Yang, Xudong Liu, Yangchengyi Li, Dong Gao, Huajian Hsia, K. Jimmy Mechanics of shape-locking-governed R2G adhesion with shape memory polymers |
| title | Mechanics of shape-locking-governed R2G adhesion with shape memory polymers |
| title_full | Mechanics of shape-locking-governed R2G adhesion with shape memory polymers |
| title_fullStr | Mechanics of shape-locking-governed R2G adhesion with shape memory polymers |
| title_full_unstemmed | Mechanics of shape-locking-governed R2G adhesion with shape memory polymers |
| title_short | Mechanics of shape-locking-governed R2G adhesion with shape memory polymers |
| title_sort | mechanics of shape locking governed r2g adhesion with shape memory polymers |
| topic | Engineering::Mechanical engineering Shape Memory Polymers R2G Adhesion |
| url | https://hdl.handle.net/10356/164647 |
| work_keys_str_mv | AT linghuchanghong mechanicsofshapelockinggovernedr2gadhesionwithshapememorypolymers AT yangxudong mechanicsofshapelockinggovernedr2gadhesionwithshapememorypolymers AT liuyangchengyi mechanicsofshapelockinggovernedr2gadhesionwithshapememorypolymers AT lidong mechanicsofshapelockinggovernedr2gadhesionwithshapememorypolymers AT gaohuajian mechanicsofshapelockinggovernedr2gadhesionwithshapememorypolymers AT hsiakjimmy mechanicsofshapelockinggovernedr2gadhesionwithshapememorypolymers |