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similar techniques for the most common types of face sheet materials, such as fiberglass, carbon, and Kevlar$^{®}$. Kevlar ® is often repaired with fiberglass.  [Figure 7-54] 

## Damage Classification 

A temporary repair meets the strength requirements, but is limited by time or flight cycles. At the end of the repair’s life, the repair must be removed and replaced. An interim repair restores the required strength to the component. However, this repair does not restore the required durability to the component. Therefore, it has a different inspection interval and/or method. A permanent repair is a repair that restores the required strength and durability to the component. The repair has the same inspection method and interval as the original component. 

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## Sandwich Structures 

## Minor Core Damage (Filler and Potting Repairs) 

A potted repair can be used to repair damage to a sandwich honeycomb structure that is smaller than 0.5 inches. The honeycomb material could be left in place or could be removed and is filled up with a potting compound to restore some strength. Potted repairs do not restore the full strength of the part. 

Potting compounds are most often epoxy resins filled with hollow glass, phenolic or plastic microballoons, cotton, flox, or other materials. The potting compound can also be used as filler for cosmetic repairs to edges and skin panels. Potting compounds are also used in sandwich honeycomb panels as hard points for bolts and screws. The potting compound is heavier than the original core and this could affect flight control balance. The weight of the repair must be calculated and compared with flight control weight and balance limits set out in the SRM. 

## Damage Requiring Core Replacement and Repair to One or Both Faceplates 

Note: the following steps are not a substitution for the aircraft specific Structural Repair Manual (SRM). Do not assume that the repair methods used by one manufacturer are applicable to another manufacturer. 

## Step 1: Inspect the Damage 

Thin laminates can be visually inspected and tap tested to map out the damage. [Figure 7-55] Thicker laminates need more in-depth NDI methods, such as ultrasonic inspection. Check in the vicinity of the damage for entry of water, oil, fuel, dirt, or other foreign matter. Water can be detected with X-ray, back light, or a moisture detector. 

## Step 2: Remove Water From Damaged Area 

Water needs to be removed from the core before the part is repaired. [Figure 7-56]  If the water is not removed, it boils 

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