I recently had the
opportunity to examine some weathered composites in the form of fiberglass pipe. There are some very important observations to be made from visual clues. One of the difficulties with too much analysis is the unknown history with the original manufacturing process, materials, and intended application. We also do not know much about the actual use and environmental exposure history. These factors would be great to have, and could probably give us additional data regarding the degradation of materials.
Here is the picture showing the pipe in an outdoor setting where it has rested for at least twenty years.
The exposed pattern is showing that the outer layer of resin has weathered away, leaving the white strands of fiberglass exposed. It is pretty minimal loss, likely just a few thousandths of resin is missing. The weathering has nicely exposed the crosshatch pattern of the filament winding process to see the angles and directions that were used. An old pipe joint can also be seen at the top of the picture.
Many physical properties could be tested on this fiberglass today, but would be pretty useless without a baseline for comparison. Armed with data as to the original strength, materials, and processing characteristics, it would be interesting to test the loss of properties such as impact resistance, shear strength, load fatigue, etc. Many products undergo aging and weathering testing before final design approval, but do so in an accelerated fashion.