How long is the curing time here for pre-preg and did it need to go into the oven? Kinda wish they did this ep the whole way through w/ the final result as well like they did w/ the infusion ep~
Typical cure time for prepreg is 3hrs @ elevated temps. Most commercial epoxy prepregs cure at 250F while some Aerospace prepregs cure at 350F. The results would indeed have been interesting to show (debagging and plate inspection). I'll let the guys know next time they need to go through the whole process :-)
I noticed no pleats, assuming you guys use them when needed based on part geometry to control how taught the vacuum bag is? Noticed many other videos with a similar sheet part use pleats. Glad to know they aren't necessary for something so simple, way cleaner vacuum bag laydown.
You hit the nail on the head. Rarely can you get away without them but in some cases, the size and simplicity of the geometry allows one to bypass pleating.
Dear Sir thank for interesting video , I have question , can we cut the prepreg in longitudinal (along 0 direction) direction on in the transverse direction (along 90 direction) to make it fit with dimension requirements?.
Prepreg is easily cut with utility knives or scissors in any direction you need. Prepregs can be cut in very complex shapes to fit your needs. This is one the benefits of prepreg, it holds it's shape without fraying or changing shape, unlike dry fabric.
Well, not so much. Vacuum is essentially negative pressure, and the more you can pull, the better off you will be. Here in Utah, the best we can get is ~26 to 29 Hg.
All the vacuum does is remove the air which is at roughly 1020hpa and once the air is removed, the atmosphere creates even pressure on the Part instead of using clamps etc.
We can't speak for other companies, but most prepreg hand layup is done in this fashion. Of course, if you have some profile to your part, the layup will be slightly different as you place the materials on the mold.
aviation composites are usually woven and places at 90's and vacuum bagged with a heating blanket. so, anyone working around composite aircraft use this or similar.
In most cases, and especially if you are only curing with an oven, the vacuum is connected before the part is cured and left connected through the cure and until the part has cooled down to below 130°F. That's about the point that you can touch it without burning your skin. If you are curing with an autoclave, some requirements want to vent the vacuum as soon as the autoclave pressure reaches a set point, usually around 30 psi. but most times the vacuum is left connected throughout the cure cycle.
@@RockWestComposites So to be clear. After what is shown in this video, the entire part (still attached to the vacuum line) is moved into an oven (or autoclave). The part will NOT cure with vacuum alone. The video implies the part will cure with vacuum only.
Correct. Prepreg requires an elevated temperature cure cycle in order for the epoxy resin to crosslink and become a solid. While prepreg will eventually harden at room temperature, it will take months or years, and will never exhibit it's full mechanical properties. Vacuum or pressure of some sort must be used throughout the entire cure to ensure proper compaction while the resin cures.
I could see how an air bubble could get trapped then expand causing delam when put in the oven during the curing process. maybe a roller or squeegee might help
It's understandable how this could be perceived, but the vacuum bag is very powerful and provides up to about 14 psi of external pressure. The vacuum bag eliminates trapped air when the air is evacuated. The prepreg is porous and allows air to travel though it while is cures. It's also common practice to "debulk" or add vacuum bagging steps every few plies if you are laminating very thick layups. Adding an autoclave cure and the trapped air will be forced into the vacuum system with pressure during cure. A roller is rarely used as it can distort the fibers, but a squeegee is used regularly to push the prepreg into tight spots and to remove large pockets while laying the fiber down.
Been in the industry for almost 20 years and it’s nice to know this info is getting out to people.
THANK YOU. I'm a student and there aren't any nicely packed answers with a bow on top.
How long is the curing time here for pre-preg and did it need to go into the oven? Kinda wish they did this ep the whole way through w/ the final result as well like they did w/ the infusion ep~
Typical cure time for prepreg is 3hrs @ elevated temps. Most commercial epoxy prepregs cure at 250F while some Aerospace prepregs cure at 350F. The results would indeed have been interesting to show (debagging and plate inspection). I'll let the guys know next time they need to go through the whole process :-)
I noticed no pleats, assuming you guys use them when needed based on part geometry to control how taught the vacuum bag is?
Noticed many other videos with a similar sheet part use pleats. Glad to know they aren't necessary for something so simple, way cleaner vacuum bag laydown.
You hit the nail on the head. Rarely can you get away without them but in some cases, the size and simplicity of the geometry allows one to bypass pleating.
Dear Sir thank for interesting video , I have question , can we cut the prepreg in longitudinal (along 0 direction) direction on in the transverse direction (along 90 direction) to make it fit with dimension requirements?.
Prepreg is easily cut with utility knives or scissors in any direction you need. Prepregs can be cut in very complex shapes to fit your needs. This is one the benefits of prepreg, it holds it's shape without fraying or changing shape, unlike dry fabric.
@@RockWestComposites Thank you so much for your kind information
When you coonect the vacuum hose to vacuum pump, do you set any pressure?
Well, not so much. Vacuum is essentially negative pressure, and the more you can pull, the better off you will be. Here in Utah, the best we can get is ~26 to 29 Hg.
All the vacuum does is remove the air which is at roughly 1020hpa and once the air is removed, the atmosphere creates even pressure on the Part instead of using clamps etc.
What companies in America use this laminating technique?
We can't speak for other companies, but most prepreg hand layup is done in this fashion. Of course, if you have some profile to your part, the layup will be slightly different as you place the materials on the mold.
aviation composites are usually woven and places at 90's and vacuum bagged with a heating blanket. so, anyone working around composite aircraft use this or similar.
How long do you leave the vacuum connected?
In most cases, and especially if you are only curing with an oven, the vacuum is connected before the part is cured and left connected through the cure and until the part has cooled down to below 130°F. That's about the point that you can touch it without burning your skin.
If you are curing with an autoclave, some requirements want to vent the vacuum as soon as the autoclave pressure reaches a set point, usually around 30 psi. but most times the vacuum is left connected throughout the cure cycle.
@@RockWestComposites So to be clear. After what is shown in this video, the entire part (still attached to the vacuum line) is moved into an oven (or autoclave). The part will NOT cure with vacuum alone. The video implies the part will cure with vacuum only.
Correct. Prepreg requires an elevated temperature cure cycle in order for the epoxy resin to crosslink and become a solid. While prepreg will eventually harden at room temperature, it will take months or years, and will never exhibit it's full mechanical properties. Vacuum or pressure of some sort must be used throughout the entire cure to ensure proper compaction while the resin cures.
It's really good to see content like these. Greetings from R&D lab ;-)
Thanks Pete! We'll keep em coming!
I could see how an air bubble could get trapped then expand causing delam when put in the oven during the curing process. maybe a roller or squeegee might help
It's understandable how this could be perceived, but the vacuum bag is very powerful and provides up to about 14 psi of external pressure. The vacuum bag eliminates trapped air when the air is evacuated. The prepreg is porous and allows air to travel though it while is cures. It's also common practice to "debulk" or add vacuum bagging steps every few plies if you are laminating very thick layups. Adding an autoclave cure and the trapped air will be forced into the vacuum system with pressure during cure. A roller is rarely used as it can distort the fibers, but a squeegee is used regularly to push the prepreg into tight spots and to remove large pockets while laying the fiber down.
Prepreg can be sticky and wet? Funny...Sticky and Wet was the name of my all girl metal band in college! What a coincidence!
Make a new roll wrapping video please
What particular elements of Roll Wrapping are you most interested in?