pre preg , resin not covering whole part "help please"

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pre preg , resin not covering whole part "help please"

Author	Message
ice2T	ice2T posted 11 Years Ago HOT Topic Details
Group: Forum Members Posts: 7, Visits: 159	Hello to all, I'm still at a very early learning stage with composites , but would grateful of some professional advice or guidance to help me along the way. I am useing 1 layer of easy preg for what is seeming to be a very awkward part to get Wright . As the description says for use of the easy preg is to oven cure for ten hours at 100c ' I have followed this instructions but 5 parts later I am still getting generally the same outcome of the parts. I have been looking on the forum for information of people with the same problems . What keeps popping up is a lot of people are talking about ramping up and down in the curing process. So this is what I did I cured the part for 6 hours instead of ten , I started at 30c 1hr/50c1hr/75c1hr/60c1hr/ and you wouldn't believe it from the pictures but it actually came out better. As I am at loss now of what to do next please could anyone "Or everyone...lol help .....
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Hanaldo	Hanaldo posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	I'm possibly not the best person to comment as I haven't personally used pre-preg before, but from what I understand, your ramp rate could still be an issue. Ideally you want to ramp temperature up at 1-2 degrees per minute. What oven are you using, just a household one? They won't have the precise temperature control really needed for pre-preg, they are designed to heat up quite quickly. Otherwise, are you leaving your vacuum pump connected for the duration of the cure? Or are you disconnecting it? You may find if you are disconnecting it that you either have a small leak in your bag or you are getting outgassing of solvents that are reducing your vacuum and affecting the finish.
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Brian_s	Brian_s posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 99, Visits: 2.5K	Again, I am not an expert but I don't think your ramp up/down time should be taken away from the cureing time. You still need 10 hours at 100c. Brian.
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Matthieu Libeert	Matthieu Libeert posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 955, Visits: 3.4K	as above, are you leaving your vacuum on? You need to keep the pump running for better results. As well do you have a perfect sealed bag? Without a well sealed bag you dont even have to start the curing because you'll keep getting bad results. How is the surface of your mould? as for the curing cycle try following: 3hours 65°C, 2hours 85°C, 2hours 105 °C, 1hour 115°C. as above the change between temperatures should be slow and steady, if you are working with a kitchen oven this will be more difficult Matthieu Libeert Founder MAT2 Composites X Sports website: www.mat2composites.com
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ice2T	ice2T posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 7, Visits: 159	Hi my friend thankyou for your reply which is very welcome , What you're saying about the conventional oven is making sense ' I'm looking into how quick the oven heats up and to see if I can control it more accurately. I have no problems with full vacume and the bag is holding full vacume all the way through the process. I have come up with an idea of trying to digitally to control with a pid temperature controler to get it more accurate . Because as you say it seems about ramping the temperature slower and steadily " I thank you very much for your advice which very valued and will post back on the site of how it goes.
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ice2T	ice2T posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 7, Visits: 159	Hi this is the sursurface of the the mold which is constructed useing the uni mold system and seems to have a a good finish , I also had thoughts that because having full vacume all way through the curing cycle that the vacume could be pulling the resin off the part before being able to set....?
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ice2T	ice2T posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 7, Visits: 159	Hi my friend thanks for your reply it is very welcome , I'm going to try and control the ramping via a pid temperature controler' when ive figured out to use it...lol but as for your other advice about the vacume and degassing solvents" I do fortunetly have full vacume all through the cure process but I'm not sure what u mean about the solvents, anymore info would be appreciated. ...
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ice2T	ice2T posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 7, Visits: 159	Thanks my friend for advice, yes I'm going to try putting it back up to the ten hours but slow the whole ramp time down and even it out amongst the ten hours ....thanks
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ChrisR	ChrisR posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 363, Visits: 3K	When using prepreg you typically use a non perforated release film so it doesn't bleed the resin out of the fabric. The slow ramp rate and dwell periods are pretty important if you want a decent finish, the 1st lower temperature dwell period allows the resin to reduce in viscosity so it flows but doesn't cure then the higher temperature does the curing. Ideally you also need to control the cooling period too so it doesn't distort, but normally you can just leave it in the oven until it's reached close to room temp.
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Warren (Staff)	Warren (Staff) posted 11 Years Ago HOT Post Details
Group: Administrators Posts: 2.5K, Visits: 8.5K	You don't mention which pre-preg you are using our Easy-Preg Surface layer or normal Vari-preg? With normal pre-preg it is very hard to get a very good cosmetic finish out of autoclave. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
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