>>2. Point: Only that there is no problem with the bonding of carbon to glass.<<

 

If you mean by this that one will stick to the other and nothing more, then I completely agree with you.

If you are suggesting that adding 50 lbs of tensile strength in carbon to  50 lbs of tensile strength in glass will result in a combined tensile strength of 100 lbs then you are dangerously mistaken.

 

>>3. I do not believe that the carbon is designed to carry the whole load.  However, as we approach destructive distortional discombobulation (technical term), the carbon may shatter before the glass. <<

 

While I can't speak for the engineer who designed the spar to which you refer, I think it entirely possible that the contribution of the glass wrap on the spar cap was completely ignored in calculting the capacity of the spar cap. Certainly its contribution is minimal.

 

While you are correct that the carbon spar cap will fail before the the glass wrap, the time difference will be measured in milliseconds.

 

 

>>5. One may design for terminal collapse at ultimate strength but, as a practical matter, one operates within the 50% of that boundary of ultimate discombobulation - thus taking advantage of the budgeted give to carry the everyday load.  Note: I do not like the word "terminal."<<

 

This perfectly illustrates the danger in mixing high modulus materials with low modulus materials in a composite structure. If one hasn't taken the difference in modulus into account, the component may fail at 2/3's or less of what was expected. If you normaly operate at up to 50% of the expected failure, then I wish you extremely smooth air and extremely uniform materials.

 

My point is simply that one needs to have his thinking cap on when he starts modifying structural components with materials having significantly different modulii. There are situations where this works very well and there are others where it makes no sense at all. Most importantly, in the situations where it makes little to no sense, it is very easy to overlook the problems and create a part of substantially less strength than expected.

 

 

Rob Harshman