# Experiment and Modeling on Macro Fiber Composite Stress-Induced Actuation Function Degradation
## 2 Experiment Set Up and Procedures
### Actuation Function Degradation Test of MFC Actuator Undergoing Cyclic Load
By adjusting the input excitation voltage amplitude, the excitation force of this shaker can be adjusted to control the stress (strain) amplitude of  
Figure 1: Flow diagram for the actuation function degradation test procedure of the Macro Fiber Composite (MFC) actuator. the cyclic loads imposed upon the MFC actuator. Cyclic loads with different stress amplitudes can be applied to the MFC actuator via the beam specimen under the excitation of a shaker, and the stress (strain) amplitude of the cyclic load imposed on the MFC actuator is measured by a foil strain gauge, which has been bonded onto the surface of MFC actuator. A dynamic strain gauge is used to measure the dynamic strain of the MFC actuator under the action of cyclic loads, and the stress amplitude of the cyclic load will be measured and recorded by the strain gauge during the whole process of the cyclic loading test. In the present study only the cyclic load is imposed on the MFC actuator without an external electric field. During the experiment, cyclic loading will be paused by every 50,000 cycles for an actuation function degradation test. The actuation function index \(A\) of the MFC actuator will be measured immediately, and then cyclic loading will be continued for another 50,000 cycles. For the actuation function test of the MFC actuator, a laser displacement sensor is used to measure the free end resonant \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**MFC (M2814-P1)**} \\ \hline Full size (mm) & \(60\times 32\times 0.3\) \\ Active size (mm) & \(56\times 28\times 0.3\) \\ Fiber Material & PZT-5A \\ d\({}_{33}\) (pm/V) & 400 \\ E\({}_{1}\) (GPa) & 30.34 \\ E2 (GPa) & 15.85 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of the MFC actuator [15]. Figure 3: Photograph of the cyclic loading system for the MFC actuator. (**a**) Amplifier of shaker; (**b**) Dynamic strain gauge; (**c**) Steel beam with MFC; (**d**) Shaker; (**e**) Signal Acquisition System (**f**) PC. Figure 2: Test specimens of a steel beam bonded with the MFC (M2814-P1) actuator, and a foil strain gauge bonded on the surface of the MFC actuator. displacement response time history of the MFC piezoelectric beam actuated by the attached MFC actuator, and the resonant amplitude \(A_{t}\)\((\sigma,N)\) will be obtained for this specific stress amplitude and cycles of the cyclic load. The experiment set up for actuation function test system of the MFC actuator is shown in Figure 4.  
For the measurement of the two amplitudes \(A_{0}\) and \(A_{t}\), which are used to calculate the actuation function index \(A\), the amplitude and frequency of the driving voltage for the MFC actuator should be ensured to be consistent. In the present test, the frequency of the driving voltage for MFC is 13.67 Hz, which is the first natural mode frequency of the MFC piezoelectric beam under the corresponding boundary condition. Three different amplitudes of driving voltage are chosen as 160 V, 200 V and 240 V for the actuation function degradation test of MFC actuator.