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Tunable dry adhesion is a crucial mechanism in compliant manipulation. The gripping force can be controlled by reversibly varying the physical properties (e.g., stiffness) of the composite via external stimuli. The maximal gripping force Fmaxand its tunability depend on, among other factors, the stress distribution on the gripping interface and its fracture dynamics (during detaching), which in turn are determined by the composite microstructure. Here, we present a computational framework for the modeling and design of a class of binary smart composites containing a porous low-melting-point alloy (LMPA) phase and a polymer phase, in order to achieve desirable dynamically tunable dry adhesion. We employ spatial correlation functions to quantify, model, and represent the complex bi-continuous microstructure of the composites, from which a wide spectrum of realistic virtual 3D composite microstructures can be generated using stochastic optimization. A recently developed volume-compensated lattice-particle method is then employed to model the dynamic interfacial fracture process, where the gripper is detached from the object, to compute Fmaxfor different composite microstructures. We focus on the interface defect tuning mechanism for dry adhesion tuning enabled by the composite, and find that for an optimal microstructure among the ones studied here, a tenfold dynamic tuning of Fmaxbefore and after the thermal expansion of the LMPA phase can be achieved. Our computational results can provide valuable guidance for experimental fabrication of the LMPA–polymer composites.
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Robust Bicontinuous Elastomer–Metal Foam Composites with Highly Tunable Stiffness
Herein, a new class of robust bicontinuous elastomer–metal foam composites with highly tunable mechanical stiffness is proposed, fabricated, characterized, and demonstrated. The smart composite is a bicontinuous network of two foams, one metallic made of a low melting point alloy (LMPA) and the other elastomeric made of polydimethylsiloxane (PDMS). The stiffness of the composite can be tuned by inducing phase changes in its LMPA component. Below the melting point of the LMPA, Young's modulus of the smart composites is ≈1 GPa, whereas above the melting point of the LMPA it is ≈1 MPa. Thus, a sharp stiffness change of ≈1000× can be realized through the proposed bicontinuous foam composite structure, which is higher than all available robust smart composites. Effective medium theory is also used to predict the Young's modulus of the bicontinuous smart composites, which generates reasonable agreement with experimentally measured Young's modulus of the smart composites. Finally, the use of these smart materials as a smart joint in a robotic arm is also demonstrated.
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- PAR ID:
- 10372014
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Engineering Materials
- Volume:
- 24
- Issue:
- 8
- ISSN:
- 1438-1656
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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