remnant deflection of the wing due to hysteresis for each configuration. The 15
, segmented configuration displayed a
maximum residual deflection of 2.65 mm, whereas more restricted structural models exhibited deflections less than 1.60 mm.
It is evident that the effects of hysteresis are mitigated with increased boundary stiffness and surface complexity. On the other
hand, freeing the restrictive boundaries enables increased residual deformation with respect to increased actuation curavature.
The next conducted study observed the time-dependent profile of the MFC hysteresis curve at the tip of the patch. The
MFC was actuated so that the tip deflection would cycle in a periodic motion from its neutral position. Specified time periods
were inputted into the waveform generator to cycle the MFCs using a sinusoidal signal. Periods of 100 and 500 seconds were
selected. Experiments were performed using the configuration presented in Fig. 15.5c. Note that 3-D deflections towards the
camera were considered positive and vise versa. Figure 15.8 presents the out-of-plane tip displacement of the MFC patch
against the actuation percent signaled by the waveform generator.
The time-dependent nature of the hysteresis curve is a direct correspondent of the “creep” behavior exhibited by
piezoelectrics. The hysteresis curve in Fig. 15.8 shows a narrower profile when a longer period was specified. It is postulated
by Setchell that the electric current generation rate of a piezoelectric under a compressive load is subject to the its
microstructural behavior [18]. Here, the opposite of this statement may also be true. Subjecting the MFCs to an electric
field may create delay in movement of the microstructure due to friction between grain boundaries. By increasing the wash
time of the MFCs under an electric field, an increased number of ferroelectric domains in the material will deform at
concurrent rates, which is evident in Fig. 15.8. However, this statement cannot be concluded without measuring the
mechanical strains corresponding to this phenomenon. Thus, further work is required.
Fig. 15.5 Post-DIC imagery of a fabricated wing model in the following configurations: (a) continuous wing section at 60
ply orientation, (b)
scalped/segmented wing section at 60
ply orientation, (c) continuous wing section at 15
ply orientation and (d) segmented/scalped wing section at
15
ply orientation. MFC bimorphs were positioned 60
globally at identical locations in each image
15 Applying Macro Fiber Composite Patches to Morph Complex Aircraft Structure
103
, segmented configuration displayed a
maximum residual deflection of 2.65 mm, whereas more restricted structural models exhibited deflections less than 1.60 mm.
It is evident that the effects of hysteresis are mitigated with increased boundary stiffness and surface complexity. On the other
hand, freeing the restrictive boundaries enables increased residual deformation with respect to increased actuation curavature.
The next conducted study observed the time-dependent profile of the MFC hysteresis curve at the tip of the patch. The
MFC was actuated so that the tip deflection would cycle in a periodic motion from its neutral position. Specified time periods
were inputted into the waveform generator to cycle the MFCs using a sinusoidal signal. Periods of 100 and 500 seconds were
selected. Experiments were performed using the configuration presented in Fig. 15.5c. Note that 3-D deflections towards the
camera were considered positive and vise versa. Figure 15.8 presents the out-of-plane tip displacement of the MFC patch
against the actuation percent signaled by the waveform generator.
The time-dependent nature of the hysteresis curve is a direct correspondent of the “creep” behavior exhibited by
piezoelectrics. The hysteresis curve in Fig. 15.8 shows a narrower profile when a longer period was specified. It is postulated
by Setchell that the electric current generation rate of a piezoelectric under a compressive load is subject to the its
microstructural behavior [18]. Here, the opposite of this statement may also be true. Subjecting the MFCs to an electric
field may create delay in movement of the microstructure due to friction between grain boundaries. By increasing the wash
time of the MFCs under an electric field, an increased number of ferroelectric domains in the material will deform at
concurrent rates, which is evident in Fig. 15.8. However, this statement cannot be concluded without measuring the
mechanical strains corresponding to this phenomenon. Thus, further work is required.
Fig. 15.5 Post-DIC imagery of a fabricated wing model in the following configurations: (a) continuous wing section at 60
ply orientation, (b)
scalped/segmented wing section at 60
ply orientation, (c) continuous wing section at 15
ply orientation and (d) segmented/scalped wing section at
15
ply orientation. MFC bimorphs were positioned 60
globally at identical locations in each image
15 Applying Macro Fiber Composite Patches to Morph Complex Aircraft Structure
103