Talk Composites - The Forum for Advanced Composites

Cumbersome surface layer *product request*

http://www.talkcomposites.com/Topic7571.aspx

By cpkielycua - 8/26/2013 8:41:03 AM

I have perfected my use of the surface and backing layers of your prepreg, but see room for improvement.  Even with the highest continuous run vacuum there are still some pinholes.  Also Id like to have a slight buffer to be able to wet sand and polish after molding.  Lastly the stray fiber from the surfacing layer can ruin the otherwise perfect surface.  

If you offered your standard prepreg backing layer with the 'surface layer film' on top it would be perfect.  A very resin rich (even if not the perfect ratio) would solve all my layup issues.  Essentially taking your backing layers and adding the film making it a double rich layer.  This would solve the pinhole problem, the stray fiber problem, and the wet sanding allowance problem.  

Please let me know if you are able to carry, order, or modify from a supplier, Im sure it will be hit with many orders!
By morepower - 1/27/2014 12:10:58 AM

20_rc51_00 (25/01/2014)
what is your oven ramp temps, ultimate temp and dwell time?

I would assume that with a slow/proper ramp (even lengthened might not hurt but help) the resin can decrease in visc and flow gradually with even saturation and air removal. maintaining the proper temp will allow the resin to cure and set at a reasonable pace for all this to happen as well. If the temp is too much too soon the resin might go through these phases too quick and cause air entrapment instead of gradual escape and saturation which might be the result of pinholes. 

Morepower, should he  not extend the breather over the surface layer that is sitting on the flange? This porvides the only exit path for air if he has carbon>nonperf release> breather, since the breather isnt' really doing much if if it's sitting over an impervious release film without direct contact through a peel ply on the flanges or over a portion of perforated release film. Where is he going to get the air migration out of the stack?  I will try and draw a pic to describe this.

I wrap breather over the whole part. Front and back of the mould. I do try and avoid bunching or more than one layer of breather anywhere on the actual part though as you lose surface pressure of the bag pushing down into the part.  I do ramp up slowly and I dwell at the lower temperature for a while OR cure fully at the lower temp as it gives the maximum flow time for the resin....