Advanced guide - Working with pre-pregs

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Advanced guide - Working with pre-pregs

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mawgan

posted 12 Years Ago

Group: Forum Members
Posts: 12, Visits: 32

I am new here and have had a quick look through the forums and on the easy composites website/videos and I have yet to see any real advanced techniques shown (please correct me if I'm wrong and there is in fact advanced tutorials somewhere that state the techniques that I am referring to).

I have personally had over 10 years experience working with all aspects of advanced composites and the family run company that I own has been in the business for over 30 years. We have worked mostly in marine but have covered all aspects along the way from F1 through to aerospace.

I thought that I would list just a few things here and people can maybe carry this on and extend any knowledge/tips they may have learnt along the way.

To start with, no matter what composite project you are working on, it is all in the preparation, it is the most important thing. I.e, cutting materials correctly and all consumables ready to go before you even think about getting started. Working cleanly is also very important and something you learn working professionally within the industry. I will post some of my top tips of preparation and working cleanly later on this thread.

For now a couple of advanced pre-preg tips:

Spike rollers - I have not seen these listed anywhere on this forum or the main site, if you do not know what I refer to, it is basically a roller with spikes sticking out. It is important to spike roller each layer of pre-preg that you put down in the stack as this creates small holes within the otherwise solid resin structure for any air pockets to escape during debulking.

Debulking - As a general rule of thumb you should always debunk every 2 layers, along with the spike roller this gets rid of air pockets trapped in the stack and helps 'set' the pre-preg in place as you go.

Breather tows - A breather toe is simple a short tow of fibreglass placed around the edge of the laminate (in the area to be trimmed), you should place one tow roughly every 250-500mm for large panels/mouldings and smaller distances apply for smaller jobs. This is more important with infusion and Sprint system pre-pregs as it enables the air to escape more easily between layers but also applies to pre-preg as well if you want to do a professional job.

Pre-preg curing - I have had a quick look through the easy composites pre-preg offering and was surprised to find fairly basic information regarding the resin systems used and the cure process. Not anywhere mentioned is the recommended ramp rate for cure which is extremely important. As a general rule of thumb anywhere from 0.3C to 2C per minute is acceptable but this really depends on the application and should be specified by the manufacturer. Ramp rates allow the resin to flow correctly eliminating pin holes and voids and it allows the cured resins tg1 to stay ahead of the 'cure'.

Dwell times - A dwell is a temperature hold for a set period of time in order for the stack and mould to catch up with the rest of the cure, this all depends on the oven and should be analysed using oven test before curing any pre-preg. Once you have learnt your oven you can apply this to all future cures and can set an appropriate dwell time.

That concludes just a few things that I have noticed were never mentioned thus far. I am working on a very detailed pre-preg guide which will include many tips and goes into extreme detail in order to achieve results seen in the most advanced racing yachts/f1/aerospace applications. Please let me know if you are interested in this.

Please feel free to add any other advanced suggestions on working with pre-pregs and I will post more up when I have time.

Thanks and I hope this helps anyone interested.

Airship-Jim

posted 12 Years Ago

Group: Forum Members
Posts: 27, Visits: 111

Hi Morepower.

I make up a box to suit my parts... It can be anything from 2 double wall cardboard boxes inside each other (Good insulator) or a brand new Wheelie bin for slightly larger parts.. My biggest parts have been done in a friends oven but when I have time I am going to line an unused outside toilet, which is in my garage at home, with sheets of Kingspan insulation and make a forced air circulation system which can be used with my portable heater and controller.

Here is my basic heater set up....
http://www.ebay.co.uk/itm/261248875323?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
http://www.ebay.co.uk/itm/221069382477?var=520098955846&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
http://www.ebay.co.uk/itm/3kw-Industrial-Heater-Electric-Thermostat-Fan-Heater-Portable-Blow-Cooler-Warm-/190734861601?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item2c68af0521
http://www.ebay.co.uk/itm/261257736361?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
http://www.ebay.co.uk/itm/190836999056?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

I have had to alter the heater to keep the fan running and bypass the thermal over rides which turn it off at 65 degrees C and run the heating elements directly through the controller and 40amp SSR. The fan runs continually that way.

This is the type of fan I am going to use with the full size oven as you want to get air circulating as fast as possible to get an even heat through the oven..
http://www.ebay.co.uk/itm/Rexon-DE-1000A-Portable-Dust-Extractor-/330999205929?pt=LH_DefaultDomain_3&hash=item4d11171029
The way the air will be ducted has not been sorted out yet as it will need to be done once the oven case has been made up.

Post #7551

I like the details you are providing for the equipment to make up an oven for working with pre-pregs, I am hoping you will be putting up some pics of your finished oven designs and hope you are open to a pm to discuss helping me build my own in the near future when I am ready to have a try at pre-preg carbon production.

Jim

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Advanced guide - Working with pre-pregs

mawgan - 12 Years Ago

[quote][b]mawgan (17/08/2013)[/b][hr]I am new here and have had a quick look through the forums and...

wozza - 12 Years Ago

Hi Warren Many thanks for your response. I appreciate the service that is currently offered...

mawgan - 12 Years Ago

[quote][b]mawgan (17/08/2013)[/b][hr]Hi Warren Many thanks for your response. I appreciate the...

wozza - 12 Years Ago

Hi Warren As I stated in my report, I am merely talking about pre-preg here that is why I posted...

mawgan - 12 Years Ago

Are you really only 23?

compositepro - 12 Years Ago

Notwithstanding the name of the forum, this is for discussion with the odd chip in from EC... They...

andygtt - 12 Years Ago

The best thing anyone can do is read about boat building and the techniques involved iam quite...

Shaneer22 - 12 Years Ago

nothing wrong with the OP's tips and they sure do have thier places in the higher levels of advanced...

Warren (Staff) - 12 Years Ago

I agree with much of what Warren has said... I have never put glass tows on the flange area under...

morepower - 12 Years Ago

Breather tows are not necessary with VTF, and probably not with the easypreg surface layer, as this...

carboncactus - 12 Years Ago

[quote][b]carboncactus (20/08/2013)[/b][hr]Breather tows are not necessary with VTF, and probably...

morepower - 12 Years Ago

[quote][b]morepower (20/08/2013)[/b][hr][quote][b]carboncactus (20/08/2013)[/b][hr]Breather tows are...

wozza - 12 Years Ago

320c TG are you sure its not from Tencate your description of no tack sounds very familiar and we...

compositepro - 12 Years Ago

Its horses for courses at the end of the day. Sure no ones doubting that pre-preg parts are the...

Warren (Staff) - 12 Years Ago

[quote][b]Warren (Staff) (22/08/2013)[/b][hr]Its horses for courses at the end of the day. Sure no...

morepower - 12 Years Ago

[quote][b]morepower (22/08/2013)[/b][hr]...

carboncactus - 12 Years Ago

[quote][b]carboncactus (23/08/2013)[/b][hr] I like that carbon kevlar chain guard / side...

morepower - 12 Years Ago

[quote][b]morepower (22/08/2013)[/b][hr][quote][b]Warren (Staff) (22/08/2013)[/b][hr]Its horses for...

andygtt - 12 Years Ago

I got an 8 foot commercial freezer for £230.00 lol... Making an oven is not hard but it does take up...

morepower - 12 Years Ago

I regularly have customers asking for parts in pre-preg (which I also do) but when you actually ask...

wozza - 12 Years Ago

Either way, infusion or pre-preg needs some form of clear coat to protect from UV. The time it would...

morepower - 12 Years Ago

and what baking machine you use any advise and cost?>

TomDesign - 12 Years Ago

[quote][b]TomDesign (24/08/2013)[/b][hr]and what baking machine you use any advise and...

morepower - 12 Years Ago

Any images of your construction autoclave? so can imagine all that stuff connected ? that would help...

TomDesign - 12 Years Ago

I will get you a photo of my simple box oven for the small parts with everything connected when I...

morepower - 12 Years Ago

[quote][b]TomDesign (25/08/2013)[/b][hr]Any images of your construction autoclave? so can imagine...

morepower - 12 Years Ago

ye but give me an idea so i can try to build ;)

TomDesign - 12 Years Ago

[quote][b]mawgan (17/08/2013)[/b][hr]I am new here and have had a quick look through the forums and...

fgayford - 12 Years Ago

Hi Fred, Thanks for your question. I will take a photo of the spike rollers that we use and put it...

mawgan - 12 Years Ago

[quote][b]mawgan (01/09/2013)[/b][hr]Hi Fred, Thanks for your question. I will take a photo of the...

fgayford - 12 Years Ago

Hi Morepower. I make up a box to suit my parts... It can be anything from 2 double wall...

Airship-Jim - 12 Years Ago

Hi Mawgan. I see from you post that you advise us all here on the forum about your expertise...

Airship-Jim - 12 Years Ago

Part made using my cheap and quick controller... I didnt use one of my best moulds as I didnt want...

morepower - 12 Years Ago

interesting where cutting is neaded of hard angles and to much material go into one place after...

TomDesign - 12 Years Ago

[quote][b]TomDesign (03/09/2013)[/b][hr]interesting where cutting is neaded of hard angles and to...

morepower - 12 Years Ago

Hi everyone, I currently have some top of the range carbon fibre twill pre-preg for sale. Priced...

mawgan - 11 Years Ago

Given this is a thread on pre-preg usage I wonder if the OP (or anyone else) can give some tips on...

FLD - 11 Years Ago

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