Spawn Aerodynamics - Bullittes CF build thread.

[njmike]

Originally Posted by CCCLXXZ

I am assuming you have never made a carbon fiber hood before because you have not mentioned making two molds for the hood. One mold provides the exterior contours and the latter the interior contours and structural rigidity. Once both molds are complete the two parts need to be bonded with carbon specific structural adhesive for wet layup, if dry carbon was used you could reintroduce heat and the two pieces would bond together in an autoclave.

Completely untrue. Once a thermoset polymer is cured, it can not be reheated to bond to other matricies.

Read up on thermoset v. thermoplastic polymers. All structural resins are thermosets.

There are specialized adhesives used to bond cured composite components.

[CCCLXXZ]

Originally Posted by njmike

Completely untrue. Once a thermoset polymer is cured, it can not be reheated to bond to other matricies.

Read up on thermoset v. thermoplastic polymers. All structural resins are thermosets.

There are specialized adhesives used to bond cured composite components.

The prepreg is partially cured which means that it is in B-Stage. It can be trimmed, pleated and formed using a knife or a pair of scissors. The prepreg handles very easily and because of its tackiness, it will lay tightly into your mold.* You might still have relief cuts or pleats to contend with just like you would with a dry fabric.*

After placing the layers in the mold, the prepreg must be compressed to allow bonding, to remove any trapped air between the layers and to squeeze out any excess resin. Although there will be very little excess, the resin will naturally become thinner as the temperature is raised and there will be resin flow prior to a full cure of the resin.* **

The needed compression can be accomplished using a press but unless the part is perfectly flat, a press is not an option.* Consequently, the part is generally vacuum bagged.* *

With prepreg fabric, there is a benefit in having plenty of time to build your bag and get the part ready for the oven.* You are not fighting the natural pot life of the resin.* However, the more layers you have laid, the more likely that there will be air trapped between the layers.* You should really have perfected your vacuum bagging technique before laying multiple layers of prepreg for a single curing.

A big advantage of prepregs is that after curing and cooling, additional layers can be laid onto the part without scuffing or additional surface preparation.* Again, up to ¼” can be laid at a single time with the same consideration of not trapping air between layers.

After the layup is complete, the vacuum bag is built and sealed, and you are ready to pull vacuum and begin the heat cycle.* There are 3 recommended cure cycles for Fibre Glast prepregs.* All 3 will produce similar properties.

There is an unconventional new prepreg out that can be stored at room temperature and can be layed up in stages. This is not consistent with traditional thermoset resin prepreg that requires handling and storage at sub temperatures.

[njmike]

Originally Posted by CCCLXXZ

The prepreg is partially cured which means that it is in B-Stage. It can be trimmed, pleated and formed using a knife or a pair of scissors. The prepreg handles very easily and because of its tackiness, it will lay tightly into your mold.* You might still have relief cuts or pleats to contend with just like you would with a dry fabric.*

After placing the layers in the mold, the prepreg must be compressed to allow bonding, to remove any trapped air between the layers and to squeeze out any excess resin. Although there will be very little excess, the resin will naturally become thinner as the temperature is raised and there will be resin flow prior to a full cure of the resin.* **

The needed compression can be accomplished using a press but unless the part is perfectly flat, a press is not an option.* Consequently, the part is generally vacuum bagged.* *

With prepreg fabric, there is a benefit in having plenty of time to build your bag and get the part ready for the oven.* You are not fighting the natural pot life of the resin.* However, the more layers you have laid, the more likely that there will be air trapped between the layers.* You should really have perfected your vacuum bagging technique before laying multiple layers of prepreg for a single curing.

A big advantage of prepregs is that after curing and cooling, additional layers can be laid onto the part without scuffing or additional surface preparation.* Again, up to ¼” can be laid at a single time with the same consideration of not trapping air between layers.

After the layup is complete, the vacuum bag is built and sealed, and you are ready to pull vacuum and begin the heat cycle.* There are 3 recommended cure cycles for Fibre Glast prepregs.* All 3 will produce similar properties.

There is an unconventional new prepreg out that can be stored at room temperature and can be layed up in stages. This is not consistent with traditional thermoset resin prepreg that requires handling and storage at sub temperatures.

Yes, everything you posted is correct. (it should be, it was copy/pasted directly from Fiberglast's site).

About Prepregs - Fibre Glast Developments

your plagiarized work starts about 2/3rds down the page.

Yes, a prepreg system (like any other epoxy resin) allows laying up in multiple stages, provided proper debulking, etc as described in the link, but you're original statement that the OP could layup a hood skin, and the underlaying support separately, then simply clamp them together and place them in a autoclave to bond them is preposterous. Clearly you're misinformed.

There is very limited use of thermoplastic matrices used with carbon fiber, and non of them in a laminated structural part.

Again, read up on thermoplastics vs. thermosets. All epoxies (and poly/vinylesters for that matter) are thermoset resins and once cured, can not be melted and recured.