TY  - JOUR
A1  - Kollosche, Matthias
A1  - Zhu, Jian
A1  - Suo, Zhigang
A1  - Kofod, Guggi
T1  - Complex interplay of nonlinear processes in dielectric elastomers
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - A combination of experiment and theory shows that dielectric elastomers exhibit complex interplay of nonlinear processes. Membranes of a dielectric elastomer are prepared in various states of prestretches by using rigid clamps and mechanical forces. Upon actuation by voltage, some membranes form wrinkles followed by snap-through instability, others form wrinkles without the snap-through instability, and still others fail by local instability without forming wrinkles. Membranes surviving these nonlinear processes are found to attain a constant dielectric strength, independent of the state of prestretches. Giant voltage-induced stretch of 3.6 is attained.
Y1  - 2012
U6  - https://doi.org/10.1103/PhysRevE.85.051801
SN  - 1539-3755
VL  - 85
IS  - 5
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Laflamme, S.
A1  - Kollosche, Matthias
A1  - Connor, Jerome J.
A1  - Kofod, Guggi
T1  - Soft capacitive sensor for structural health monitoring of large-scale systems
JF  - Structural control & health monitorin
N2  - Structural integrity of infrastructures can be preserved if damage is diagnosed, localized, and repaired in time. During the past decade, there has been a considerable effort to automate the process of structural health monitoring, which is complicated by the inherent large size of civil structures. Hence, a need has arisen to develop new approaches that enable more effective health monitoring.
 In this paper, a new sensing technique for damage localization on large civil structures is proposed. Specifically, changes in strain are detected using a capacitance sensor built with a soft, stretchable dielectric polymer with attached stretchable metal film electrodes. A change in strain causes a measurable change in the capacitance of the sensor, which can be directly monitored when the sensor is fixed to a structure.
 The proposed method is shown here to permit an accurate detection of cracks. The proposed system deploys a layer of dielectric polymer on the surface of a structural element, and regularly monitors any change in capacitance, giving in turn information about the structural state. The smart material is composed of inexpensive silicone elastomers, which make the monitoring system a promising application for large surfaces. Results from tests conducted on small- scale specimens showed that the technology is capable of detecting cracks, and tests conducted on large- size specimens demonstrated that several sensor patches organized on a sensor sheet are capable of localizing a crack. The sensor strain also exhibits a high correlation with the loss of stiffness.
KW  - large-scale system
KW  - structural health monitoring
KW  - strain monitoring
KW  - capacitive sensor
KW  - dielectric polymer
KW  - stretchable sensor
Y1  - 2012
U6  - https://doi.org/10.1002/stc.426
SN  - 1545-2263
VL  - 19
IS  - 1
SP  - 70
EP  - 81
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Zhu, Jian
A1  - Kollosche, Matthias
A1  - Lu, Tongqing
A1  - Kofod, Guggi
A1  - Suo, Zhigang
T1  - Two types of transitions to wrinkles in dielectric elastomers
JF  - Soft matter
N2  - A membrane of a dielectric elastomer coated with compliant electrodes may form wrinkles as the applied voltage is ramped up. We present a combination of experiment and theory to investigate the transition to wrinkles using a clamped membrane subject to a constant force and a voltage ramp. Two types of transitions are identified. In type-I transition, the voltage-stretch curve is N-shaped, and flat and wrinkled regions coexist in separate areas of the membrane. The type-I transition progresses by nucleation of small wrinkled regions, followed by the growth of the wrinkled regions at the expense of the flat regions, until the entire membrane is wrinkled. By contrast, in type-II transition, the voltage-stretch curve is monotonic, and the entire flat membrane becomes wrinkled with no nucleation barrier. The two types of transitions are analogous to the first and the second order phase transitions. While the type-I transition is accompanied by a jump in the vertical displacement, type-II transition is accompanied by a continuous change in the vertical displacement. Such transitions may enable applications in muscle-like actuation and energy harvesting, where large deformation and large energy of conversion are desired.
Y1  - 2012
U6  - https://doi.org/10.1039/c2sm26034d
SN  - 1744-683X
VL  - 8
IS  - 34
SP  - 8840
EP  - 8846
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -