Which material addition provides strength for the repair of damaged fastener holes in composite panels?

The strengthening of damaged fastener holes in composite panels primarily involves the use of flox and chopped fibers. This combination effectively enhances the structural integrity of the repair area.

Flox, a type of fibrous filler, offers superior mechanical properties when mixed with resin, allowing it to bridge gaps created by the damage and distribute loads across the repaired section. Chopped fibers additionally provide reinforcement, improving shear and tensile strength. The combination of these two materials allows for a more robust and durable repair, making it ideal for restoring the functionality of the composite panels where fastener holes have been compromised.

Other materials such as microballoons are primarily used for lightweight filling and do not contribute to strength in the same way. Resin and fillers can assist in the repair process but lack the specific reinforcing properties required for damaged fastener holes. Fiberglass strands are valuable for other applications but may not be as effective as flox and chopped fibers in addressing the specific structural needs in this context.