Composite parts are widely used due to their unique properties, including durability. Unfortunately, even the best designed and best made parts can be damaged by unforeseen circumstances either at the OEM or in service. The following steps cover best practices for repair of anything from gel coat gouges or scratches to damage penetrating through the entire laminate. Before starting, put on the appropriate personal protective equipment for the task, including protective clothing, safety glasses, gloves and a respirator.
Step 1: Evaluate the work area.
Make sure the work area is well lit, but not in direct sunlight. The temperature of the work area, part and all repair materials should be 75 to 80 F. Temperatures below 75 F extend cure times of repair materials and can result in under cure. Elevated temperatures speed up cure, reducing work time.
For cool conditions, heat guns or heat lamps can be carefully used to warm parts and repair materials. The area is too hot if you can’t hold your hand on it. Patching materials are flammable, so be careful.
Step 2: Determine the type and extent of the repair.
Inspect the part to determine the extent of damage and type of repair needed, which will also dictate your materials and tools. For minor defects, determine if any repair is needed by standing a reasonable distance away from the part. If you can’t see the defect, a repair may not be needed. If a minor defect requires repair, a spot or dab patch with gel coat may be sufficient. Deeper defects may need to be filled with putty prior to covering with gel coat. For defects penetrating into or through the laminate, laminate reinforcements and resin must be replaced. Any remaining voids must be filled with putty. For gel coated parts, the area should also be spray patched.
Step 3: Set up the equipment and obtain materials.
Gather your equipment and tools. Inspect all equipment before use to ensure operator safety as well as part quality. If anything is missing or broken, repair or replace it before proceeding.
Obtain all necessary materials. Make sure gel coats and resins have been thoroughly mixed prior to removing samples for repair. For repairs requiring gel coat, use the same batch originally used to spray the part whenever possible to achieve the best color match. When patching an older part, weathering may have occurred, so a tinting kit may be necessary. You can lightly sand and buff an area to see the true color.
Step 4: Prepare the repair area.
Remove the damaged material. For minor defects, hand sanding with a sanding block or a dual action sander may be sufficient. For laminate repairs, use a saw to cut away the damaged portion. Make sure to remove all damaged material so that the remaining material is structurally sound.
Once the damaged material has been removed, prepare the repair area by grinding or sanding to facilitate adhesion of repair materials. Remove all dust, oils, waxes and other contaminates. Keep the repair area as small as possible to minimize finishing work. Mask off the repair area to prevent damage to surrounding areas.
