by stede52 » Wed Apr 12, 2017 1:10 pm
Ken,
I have not done any kind of testing in that area for two reasons, 1: I'm no structural engineer and 2: all certified aircraft use acrylic for windshields. The structural properties of polycarbonate versus acrylic are quit different and what I know about the two is that if each were the same thickness the polycarbonate (lexan) is a tougher material. The acrylic is a harder material which allows you to polish it and remove scratches, however, being harder also makes it more brittle and will break using less force then polycarbonate. I've had pilots tell me that they will never put polycarbonate windows in an airplane because if they were in an accident and needed to punch out a window or windshield to escape the aircraft its nearly impossible to do so with polycarbonate, where acrylic they could. I can't imagine a 1/16" polycarbonate material under load (which compromises its structural integrity) like it is on the Highlander being that much stronger then an 1/8" molded windshield which is not under load and therefore will maintain its structural integrity. The gradual bend of the 1/16" poly ok on the Highlander however at the upper corners of the windshield it is under extreme load and is bend far beyond what the specs say it should be for that thickness of material. That is one reason cracking occurs down the windshield at those areas along with the constant vibrating and flexing of that thinner material in flight.
Steve D N419LD