Which type of seal fills a void such as a cavity, hole, or channel?

The correct answer is injection seal. Injection seals are specifically designed to fill voids such as cavities, holes, or channels in various materials, thereby providing a barrier against fluids, contaminants, and environmental factors. The process typically involves injecting a fluid or material that expands or cures within the void to create a complete seal. This is particularly useful in aerospace applications, where ensuring the integrity of structures is critical for safety and performance.

In comparison, the remaining options serve different functions. Cap seals are generally used to cover or close off openings rather than filling voids, and they do not provide the same filling capability. Sealants, while effective in creating airtight and watertight barriers by covering surfaces, do not specifically target voids in the same manner as injection seals. Bonding refers to the process of adhering two surfaces together, which does not involve filling voids but rather creating a strong connection between structural components. Understanding these distinctions is crucial for proper application in aerospace assembly and maintenance.