| 摘要 |
In one example, the voids 208 comprise one or more gas (e.g., air) bubbles in the solid material 206 . In another example, the voids 208 comprise a structure that preserves a space in the solid material 206 . In a further example, the voids 208 comprise hollow elastomeric bubbles, for example, hollow elastomeric microspheres. The hollow elastomeric microspheres comprise microballoons with tin walls that encapsulate a gas to allow for easy compression. For example, the walls of the hollow elastomeric microspheres are strong enough to avoid breakage under pressure, but thin enough to easily compress. In a further example, once cured in the solid material 206 , the hollow elastomeric microspheres comprise substantially similar compressibility characteristics as gas bubbles. The voids 208 in one example are added to a resin of the solid material 206 in a substantially uniform distribution. For example, the hollow elastomeric microspheres are stirred into the resin of the solid material 206.
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