Stiffness of finished Carbon Fiber part

[RKT]

I have a finished CF sample, a common single-ply weave, that exhibits
extreme stiffness, 'thin-ness' and is very lightweight, it looks dry. I have
molded a part using a similar weave, single ply, and do not get the same
stiffness. I can easily deform the finished part with a press of the thumb.

I am not sure whether this is due to the epoxy type or my humble curing
process. I'm using Fibre Glast System 2000 and 120 minute hardener. I let
the part cure for 12 hours at 110 DegF. The instructions on the can discuss
postcure at 200 DegF and the resulting 'service temperature'.

If it is an Epoxy issue, pls describe and recommend an alternative product.
If it is a postcure issue, when does 'postcure' begin - after my 12 hour
cure cycle? - which was loosely calculated based on instructions on the can.

Any advice appreciated.

[Richard Lamb]

RKT wrote:
>
> I have a finished CF sample, a common single-ply weave, that exhibits
> extreme stiffness, 'thin-ness' and is very lightweight, it looks dry. I have
> molded a part using a similar weave, single ply, and do not get the same
> stiffness. I can easily deform the finished part with a press of the thumb.
>
> I am not sure whether this is due to the epoxy type or my humble curing
> process. I'm using Fibre Glast System 2000 and 120 minute hardener. I let
> the part cure for 12 hours at 110 DegF. The instructions on the can discuss
> postcure at 200 DegF and the resulting 'service temperature'.
>
> If it is an Epoxy issue, pls describe and recommend an alternative product.
> If it is a postcure issue, when does 'postcure' begin - after my 12 hour
> cure cycle? - which was loosely calculated based on instructions on the can.
>
> Any advice appreciated.


It's not about the epoxy, but the layers.

One layer has nothing to lean on.

Two layers pull against each other.

[Checkursix]

I believe that and the possibility of the way you did your lay-up. Did you
use a vacuum bag? That would compact the epoxy/CF!
VS 'Free Air' Lay-up....

Bob
"Richard Lamb" > wrote in message
...
> RKT wrote:
> >
> > I have a finished CF sample, a common single-ply weave, that exhibits
> > extreme stiffness, 'thin-ness' and is very lightweight, it looks dry. I
have
> > molded a part using a similar weave, single ply, and do not get the same
> > stiffness. I can easily deform the finished part with a press of the
thumb.
> >
> > I am not sure whether this is due to the epoxy type or my humble curing
> > process. I'm using Fibre Glast System 2000 and 120 minute hardener. I
let
> > the part cure for 12 hours at 110 DegF. The instructions on the can
discuss
> > postcure at 200 DegF and the resulting 'service temperature'.
> >
> > If it is an Epoxy issue, pls describe and recommend an alternative
product.
> > If it is a postcure issue, when does 'postcure' begin - after my 12 hour
> > cure cycle? - which was loosely calculated based on instructions on the
can.
> >
> > Any advice appreciated.
>
>
> It's not about the epoxy, but the layers.
>
> One layer has nothing to lean on.
>
> Two layers pull against each other.

[jls]

Depending on how they are laid up, CF layups get anywhere from 150k to 800k
psi tensile strength and are a capable according to computer models of 1
million lbs. psi tensile strength. The secret is in the quality of layup
and the orientation of the fibers. Read Andy Marshall's book for details.
"Checkursix" > wrote in message
...
> I believe that and the possibility of the way you did your lay-up. Did you
> use a vacuum bag? That would compact the epoxy/CF!
> VS 'Free Air' Lay-up....
>