Vacuum Bagging - Problem with surface finish

Talk Composites - The Forum for Advanced Composites

Back

Home
»
Advanced Composites Forum
»
Resin Infusion
»
Vacuum Bagging - Problem with surface finish

Vacuum Bagging - Problem with surface finish

Author	Message
Ashutosh	Ashutosh posted 8 Years Ago HOT Topic Details
Group: Forum Members Posts: 2, Visits: 28	Hi I am doing Vacuum Bagging and in the final part there are gaps/voids where the warp and wept intersect. Here is an image of it. Can anyone help please? Attachments IMG_20160224_221923626_HDR.jpg (2.1K views, 1.00 MB) Tags Gaps Surface finish Vacuum Bagging Voids
	Reply Like 3
scottracing	scottracing posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 460, Visits: 5.2K	Could be caused by numerous things. What method and material are you using? When you vacuum bag how good is the vacuum and is there enough bag so you don't get any bridging or wrinkling. The photo looks like not enough consolidation so probably a vac leak?
	Reply Like 3
Dravis	Dravis posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 592, Visits: 1.9K	Not enough consolidation + resin starved (severely!) -- Vacuum leak or not enough vacuum? Not enough resin (Wet-lay with Vac-bagging?) To give you really useful advice we need complete info on materials used and process/technique -- "Sapere Aude"... Dare to KNOW! The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind... 103% of all people do not understand statistics... Do not adjust our mind, theres a fault in reality :-)
	Reply Like 3
Ashutosh	Ashutosh posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 2, Visits: 28	We use 200 gsm 3k plain weave Carbon Fiber and an epoxy resin system. The Vacuum Bagging materials are peel ply, breather/bleeder, and vacuum bag is standard 75 micron polyester. We wet the fabric layer by layer, with an initial layer of resin on the mould. And then the standard vacuum bagging procedure of fabric + peel ply + breather/bleeder + Vac bag. The ratio of fibre to resin for wet layup is almost 40:60 (fibre to resin) to make sure that the fiber is soaked properly in the resin pool and thinking the excess will be soaked up by the bleeder/breather (which is true as our fibre weight is 55:45 of total after curing). The vacuum bagging is done in our university's composite lab. we ensure the vacuum is maintained while we leave our parts there overnight for curing. But returning next day the vacuum is not maintained, and we cant leave the vacuum pump on overnight as per lab regulations. So the parts are not entirely cured in vacuum. Regards Tags Pin holes Edited 8 Years Ago by Ashutosh
	Reply Like 3
Chris Scott	Chris Scott posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 20, Visits: 235	Yea I would say that is almost definitely due to not maintaining a full vacuum. Also if you are wet laying it up, even if you have the overall fibre/resin ratio correct, that doesn't mean you won't have localized resin starved/rich areas. I would wait until the early morning to wet layup/vacuum bag so that you can keep it under vacuum as long as possible. Since you don't have the luxury of doing a leak test once the part is bagged like you do with vacuum infusion (prior to infusing), I would also take your time with the bagging tape to make sure that it is perfectly sealed and leak-free. Vacuum infusion will minimize these errors, but if you're limited to just vacuum bagging you can still improve on this.
	Reply Like 3
Hanaldo	Hanaldo posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	Are you not using a perforated release film between the peel ply and the breather?
	Reply Like 5
Dravis	Dravis posted 8 Years Ago HOT Post Details
Group: Forum Members Posts: 592, Visits: 1.9K	If you are not using a perforated release film between peel-ply and breather material, a lot of the resin will end up in the breather material, especially with a poor vacuum. If your Vac-bag is completely sealed, it should hold vacuum for at least the time it takes for the initial cure of the epoxy .. even when turning off the pump -- also do ensure that you clamp the vac-hose form your bag to the pump.. In my experience a lot of laboratory vac-pumps have no stop valve .. so air will leak back through the pump .. "Sapere Aude"... Dare to KNOW! The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind... 103% of all people do not understand statistics... Do not adjust our mind, theres a fault in reality :-)
	Reply Like 4