Hi All,

I am working on a carbon/glass hybrid laminate (preferably IM-7 and S-2) and was wondering if anyone had experience with multiple fabric weaves in the same laminate and the effect on damage tolerance and/or strength. The fabric types are Twill 2x2 for the carbon and an 8H Satin for the glass. The laminates will be sandwich panel face-sheets with the carbon exterior and glass next to the core. I'm afraid the transition from twill 2x2 to 8H will act as a stress concentration for delamination. The fabrics are simply the easiest/cheapest to get from our supplier so there isn't an issue I'd like to stick with them rather than finding a new supplier for 8H Satin IM-7.

Any thoughts or experiences are appreciated.

There is no reason for concern. While weave styles can have somewhat different mechanical properties (satin weaves generally high than plain weaves) mixing styles is not a problem.

Thanks so much for the quick response.

Well, it really depends on the particular strength and damage tolerance properties of interest. There is (probably) not a lot of difference between 2x2 twill and 8HS IM7 inplane strength properties, however the impact damage resistance and residual strength my be different, as the damage states can be different for different weave types. Also, the strength, impact resistant and residual strength for hybrid glass /carbon laminates can be very different from the properties of an all carbon or all glass laminate using the same materials - you should expect to have to test the actual hybrid laminates; do not use properties derived from all carbon or all glass laminate tests.

SW

Thanks for the advice SW, I'm a big fan of actual, physical testing for that reason. I'll be doing testing on various ply orientations and layups once I can nail down my general materials. The decision to go hybrid was based on this article (http://www.springerlink.com/content/j8814728hux010...) so I'm expecting a much "tougher" final structure (as well as being less expensive) but testing its other properties is a good idea too.