: Sam,

: I have checked Sweet Composites page. According to the Fabric
: Finishes section, it is not reasonalbe to use glass fiber, 3 or
: 5 years after production date without testing. Could please
: clarify what kind of tests should be done in this regard?

: Reza

Reza,

If we assume good storage conditions, the potential shelf life affects are with respect to the finish (sizing). So, one would want to select a test for which the results are dominated by the finished fiber to matrix bond strength. The most direct way to do that is with a single fiber pull-out test. Off-axis tensile or short beam bending may also work. Of course, testing to demonstrate that material is "still good" requires acceptance/rejection criteria. There is some discussion of this topic at: http://www.compositesworld.com/articles/fiber-matrix-interfacial-bond-test-methods.

Controlled quantitative testing is expensive, so it would likely only be used in a manufacturing quality control program that affects critical applications and or large volumes of material. The DIY enthusiast would not benefit from it, unless the main objective was to learn more about testing than about a roll of leftover glass in the garage. Typically, DIY kayak builders aren't adversely impacted by using materials with a wide range of properties, even properties that have degraded over time. This works fine in most cases. Just like eating old food from the fridge - some individuals may prefer to pickup a carton of fresh milk rather than drink the old stuff.

Sam