One of my recent projects involved the repair of a 1993 International Medium-Duty truck hood made from SMC. There were several areas needing attention, and one of them was the driver’s side inner fender. This piece had formerly been attached with button-head pop rivets. This design is common to composites, and allows for easy replacement of the separate fiberglass pieces. The pop rivets had come loose over time, allowed to move around, and cause severe damage to the extent that the riveting flange was broken off. My only solution was to bond the two pieces together.
The loose panel flexed so much and for so long that it fatigued the material and failed in the corner of the inner fender next to the attachment to the rest of the hood. To repair this, I removed the area with the rivets, ground down the surfaces of both pieces on both sides, and reattached them with fiberglass and epoxy resin.
I wanted to place epoxy and fiberglass on both sides of the repair area to ensure a good, solid bond that would hold very well.
After the area was prepared, I applied epoxy resin to the surface to ensure good adhesion. I had a low spot that was a gap, so I mixed some microfiber and epoxy to make a paste and fill this gap. A stronger bond is produced when the fiberglass is not spanning an open gap between the two pieces. I placed two layers of 3oz Chopped Strand Mat over the paste and worked the air out to make a nice consistent repair. I then ground down the surface to make a nice-looking, consistent repair.
The rear of the inner fender had similar problems. A hole had emerged in the black SMC piece. I ground down both surfaces and placed some fiberglass across the area to bond it together.