Martin Fraser (15/10/2014)
Hi Warren,
It's twin twill glass and epoxy that I'm using on my scale heli project. I've just done a test lamination on the tail section using 1@ 100g and 3@ 200g. The gauge of the layup seems to be about right 0.9mm but it's very flexible. I've pigmented the resin (no more that 5%) could this be the cause or is it down to curing temperature?
Also, I've got some air trapped under the first layer(see attached), despite using a bristle roller after the layup. In future, should lay down the first lamination, roller it, let it tack off a bit and then lay the remainder of layers consecutively?
Many thanks, Marty Hi Marty, temperature (or lack of) is probably the main issue for it remaining flexible, and it being a bit resin shy. Much depends on what hardener (fast/slow or a mixture) you are using and how quickly you get the layers down. It looks like the first layer (mould side) may have started to gel before you finished the remaining layers. If that happens it is very difficult to remove any trapped air even with a bristle roller. Most epoxy resins need curing at 60 degrees c to reach their best mechanical properties. Has it cured just at ambient temperature?
Not sure how big the part you have done is. You could try wrapping it in an electric blanket and post curing it that way. Just keep a close eye on it for safety reasons and see if that improves the stiffness (it should)
You could also try orientating the layers. Make a template from some paper, place that on the cloth and mark around it. Then flip the template over and mark the second layer and so on. That should give you 90 degree orientation of the weave once placed in the mould. If stiffness is still a concern you could look at using a biaxial cloth.
P.S Sorry should have said if your going to try post curing put the part back in the mould if that's practical to help prevent distortion of the part.
Warren
Carbon Copies Ltd