Experiment-Based Sensitivity Analysis of Scaled Carbon-Fiber-Reinforced Elastomeric Isolators in Bonded Applications
Abstract
:1. Introduction
2. Manufacturing Test Specimens
C-FREI | Plan Size of Supporting Plates (mm × mm) | Plan Size of Reinforcement (mm × mm) | H (mm) | ts (mm) | te (mm) | tf (mm) | ne | nf | S |
---|---|---|---|---|---|---|---|---|---|
A1 | 150 × 150 | 70 × 70 | 26.5 | 6.35 | 1.5 | 0.25 | 8 | 7 | 11.7 |
B1 | 150 × 150 | 70 × 70 | 33.5 | 6.35 | 1.5 | 0.25 | 12 | 11 | 11.7 |
A3 | 150 × 150 | 70 × 70 | 40.5 | 6.35 | 1.5 | 0.25 | 16 | 15 | 11.7 |
B4 | 150 × 150 | 70 × 70 | 42.4 | 6.35 | 1.5 | 0.25 | 17 | 16 | 11.7 |
D1 | 150 × 150 | 70 × 70 | 36.7 | 6.35 | 3 | 0.50 | 7 | 6 | 5.8 |
E1 | 150 × 150 | 70 × 70 | 38.2 | 6.35 | 3 | 0.75 | 7 | 6 | 5.8 |
3. Experimental Tests
3.1. Pressure Sensitivity Test
3.2. Rate Sensitivity Test
4. Results and Discussion
4.1. Effect of Vertical Pressure
C-FREI | P (MPa) | KH (kN/mm) | β (%) | |||||
---|---|---|---|---|---|---|---|---|
γ (%) | 1 | 2 | 3 | 1 | 2 | 3 | ||
A1 | 25 | 0.375 | 0.380 | 0.375 | 11.7 | 11.9 | 11.7 | |
50 | 0.287 | 0.289 | 0.287 | 10.3 | 10.4 | 10.3 | ||
100 | 0.239 | 0.240 | 0.239 | 9.1 | 9.2 | 9.1 | ||
B1 | 25 | 0.226 | 0.244 | 0.233 | 13.0 | 13.0 | 13.2 | |
50 | 0.177 | 0.188 | 0.181 | 12.6 | 12.3 | 12.5 | ||
100 | 0.128 | 0.141 | 0.137 | 12.7 | 11.9 | 11.6 | ||
D1 | 25 | 0.203 | 0.211 | 0.203 | 11.1 | 11.0 | 11.1 | |
50 | 0.165 | 0.169 | 0.165 | 10.3 | 10.2 | 10.3 | ||
100 | 0.132 | 0.132 | 0.132 | 9.3 | 9.3 | 8.9 | ||
E1 | 25 | 0.212 | 0.223 | 0.212 | 11.6 | 11.4 | 11.6 | |
50 | 0.170 | 0.176 | 0.170 | 10.5 | 10.3 | 10.5 | ||
100 | 0.135 | 0.136 | 0.135 | 9.7 | 9.7 | 9.8 | ||
A3 | 25 | 0.209 | 0.171 | 0.165 | 12.5 | 12.6 | 12.6 | |
50 | 0.153 | 0.132 | 0.128 | 11.2 | 11.6 | 11.7 | ||
100 | 0.095 | 0.096 | 0.094 | 13.2 | 11.2 | 11.2 | ||
B4 | 25 | 0.213 | 0.173 | 0.166 | 12.8 | 12.9 | 13.1 | |
50 | 0.158 | 0.133 | 0.129 | 11.4 | 11.8 | 12.0 | ||
100 | 0.099 | 0.099 | 0.097 | 12.3 | 10.7 | 10.9 |
4.1.1. Effective Horizontal Stiffness
4.1.2. Equivalent Viscous Damping
4.2. Effect of Lateral Cyclic Rate
C-FREI | VH (mm/s) | fH (Hz) | KH (kN/mm) | β (%) |
---|---|---|---|---|
A1 | 20 | 0.27 | 0.284 | 10.5 |
30 | 0.40 | 0.293 | 10.5 | |
75 | 1.00 | 0.317 | 9.9 | |
B1 | 20 | 0.18 | 0.171 | 14.1 |
30 | 0.27 | 0.176 | 13.5 | |
75 | 0.66 | 0.187 | 12.2 | |
D1 | 20 | 0.15 | 0.165 | 10.3 |
30 | 0.23 | 0.167 | 10.1 | |
75 | 0.57 | 0.174 | 9.6 | |
E1 | 20 | 0.15 | 0.171 | 10.6 |
30 | 0.23 | 0.173 | 10.5 | |
75 | 0.57 | 0.181 | 10.1 | |
A3 | 20 | 0.13 | 0.128 | 12.2 |
30 | 0.20 | 0.130 | 11.9 | |
75 | 0.50 | 0.134 | 11.5 | |
B4 | 20 | 0.12 | 0.129 | 12.1 |
30 | 0.19 | 0.131 | 11.8 | |
75 | 0.47 | 0.135 | 11.4 |
4.2.1. Effective Horizontal Stiffness
4.2.2. Equivalent Viscous Damping
4.3. Effect of Number of Rubber Layers
4.4. Effect of Thickness of Fiber-reinforced Layers
5. Conclusions
- In order to make the manufacturing process fast and easy, long rectangular laminated pads were subjected to a uniform pressure of 4 MPa for 24 h at the room temperature (around 23 °C) without using a mold. Then, they were cut to the required size.
- The equivalent viscous damping, which is a ratio of the dissipated energy to the restored elastic energy, increased from 9.1% to 13.2% when the total thickness of rubber increased from 12 mm to 24 mm. This range of damping ratio shows that the commercial high-quality neoprene has a higher effective damping capability compared to the low-damping natural rubber.
- Increasing the vertical pressure from 1 MPa to 3 MPa showed that, within this range, the manufactured C-FREIs are almost insensitive to the compressive pressure regardless of the level of shear strain (25% to 100%).
- For all C-FREIs, increasing the rate of the lateral displacement increased the effective horizontal stiffness. The maximum amount of increase was 10.4% when the rate changed from 20 mm/s to 75 mm/s. By increasing the rate of the lateral cyclic loading, the elastomeric layers were stiffened, and, as a result, the rubber bearings showed a lower flexibility in the horizontal direction.
- Increasing the lateral cyclic rate from 20 mm/s to 75 mm/s reduced the equivalent viscous damping (from 14.1% to 12.2%). The reason is that the stiffness of the rubber layers increases at high lateral cyclic rates. Consequently, the elastomeric isolator restores more energy, and the capability of the device in dissipating the earthquakes’ energy degrades. Another point is that, compared to the high damping rubber, which has a highly nonlinear behavior, the neoprene used in the C-FREIs has a low sensitivity to the rate of the cyclic lateral displacements.
- At 100% shear-strain amplitude, when the number of rubber layers was doubled (from 8 to 16), the effective horizontal stiffness decreased by 60% and the equivalent viscous damping increased by 22%. At the same shear-strain level, increasing the thickness of fiber-reinforced layers from 0.5 mm to 0.75 mm slightly increased the lateral stiffness. This is because the fiber-reinforced layers become stiffer when their thickness increases. However, compared to the rubber layers, the effect of the reinforcement on the lateral flexibility was negligible. Some level of flexibility remains in the reinforcement after curing the bi-directional carbon fiber fabric impregnated by the adhesive. As a result, fiber-reinforced layers can slightly contribute to the energy dissipation and be considered as a minor source of energy damping.
6. Future Recommendations
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Hedayati Dezfuli, F.; Alam, M.S. Experiment-Based Sensitivity Analysis of Scaled Carbon-Fiber-Reinforced Elastomeric Isolators in Bonded Applications. Fibers 2016, 4, 4. https://doi.org/10.3390/fib4010004
Hedayati Dezfuli F, Alam MS. Experiment-Based Sensitivity Analysis of Scaled Carbon-Fiber-Reinforced Elastomeric Isolators in Bonded Applications. Fibers. 2016; 4(1):4. https://doi.org/10.3390/fib4010004
Chicago/Turabian StyleHedayati Dezfuli, Farshad, and M. Shahria Alam. 2016. "Experiment-Based Sensitivity Analysis of Scaled Carbon-Fiber-Reinforced Elastomeric Isolators in Bonded Applications" Fibers 4, no. 1: 4. https://doi.org/10.3390/fib4010004