What is the recommended vacuum pressure in inches of mercury for curing a repair?

The recommended vacuum pressure for curing a repair in low observable aircraft structural maintenance is 15-28 inches of mercury. This pressure range is essential because it ensures that the curing process is effective, allowing for optimal bonding of the materials being used.

At this level of vacuum pressure, air is adequately removed from the repair area, significantly enhancing the consolidation of the resin and fibers in composite materials. This prevents the formation of air pockets that could weaken the structure and ensures a uniform distribution of the resin, leading to improved mechanical properties of the cured material.

Vacuum pressures below 15 inches may not provide enough force to properly remove all the air from the system, potentially leading to insufficient cure quality, while pressures above 28 inches can introduce complications such as excessive resin draw-out and inadequate wetting of fabrics. Thus, operating within the 15-28 inch range strikes a balance that facilitates optimal repair conditions.