Post Curing Composites

I am looking for some advise regarding "Post Curing of Epoxy Composites".

The sailplane composite repairs have been completed regarding my salvaged ASW-27. The tail boom has a new 3'long intermediate section that has been scarfed and glassed into position. The fuselage pod had some radial cracks and the seat pan had some fractures that were all scarfed and glassed. All of the composite repairs were done at room temperature using OEM materials and MGS epoxy.

What temperature is recommended and for what duration should I be using for post curing the repaired areas. Is there a temperature ramp up and ramp down time that I need to work with. I plan to build a foam insulation box around the repair areas and use a fan with a number of light bulbs to regulate the temperature.

Any advise is greatly appreciated,
Thanks,
Chris

If my memory is correct. It is 55 C for 15 hours. I’ll confirm when I get back home this week. It is on most Schemp fiber plans.

On Monday, December 31, 2018 at 3:45:51 PM UTC-5, wrote:
I am looking for some advise regarding "Post Curing of Epoxy Composites".

The sailplane composite repairs have been completed regarding my salvaged ASW-27. The tail boom has a new 3'long intermediate section that has been scarfed and glassed into position. The fuselage pod had some radial cracks and the seat pan had some fractures that were all scarfed and glassed. All of the composite repairs were done at room temperature using OEM materials and MGS epoxy.

What temperature is recommended and for what duration should I be using for post curing the repaired areas. Is there a temperature ramp up and ramp down time that I need to work with. I plan to build a foam insulation box around the repair areas and use a fan with a number of light bulbs to regulate the temperature.

Any advise is greatly appreciated,
Thanks,
Chris

The manual calls for 60 degrees C for minimum of 12 hours. You won't go wrong by going longer. It takes a couple hours for the structure to come up to temperature. Longer curing also helps reduce future shrinks showing up.
Make sure you monitor the temperature in a couple of spots.
I usually have a couple blankets to throw over everything if temp doesn't quite come up to target.
Good Luck
UH

It all depends om what Epoxysystem is used. I would be very carfull of post curing with heat without knowing what epoxies that is used. You can ruin the whole glider by overheating the structure.

Am 02.01.2019 um 13:42 schrieb Per Carlin:
It all depends om what Epoxysystem is used. I would be very carfull of post curing with heat without knowing what epoxies that is used. You can ruin the whole glider by overheating the structure.



Yes, it depents on the Epoxy Systems (and all other materials in the
area). To make sure please refer to the data sheet of the systems in use.

As a guideline composite gliders are certified to temperatures up to 54
deg C.
Without specific background info of all materials in use I would post
cure at 50 deg C for 15-24h. You may ramp up the temperature to avoid
problems with only paritial cured epoxy (10h 30 deg C + 15h 50 deg C).

Paula

Hi Chris,

I build a cellotex box (building insulation material) and then use a
small bar heater placed low in the box. The Control is achieved using
a commercial Kiln controller which achieves the required temperature
from a thermocouple placed somewhere appropriate in the heat box,
and then controls the temperature to +/- about 1 degree by turning
the bar heater on and off. You can program the cure time and it cuts
it off at the end. I use a separate USB temperature monitor to get
the date to support the cure. Done about 25 cures with this system
now and no problems.... I have done most cures at temperatures of
55C but also done some specialist cures as high as 80C....

I think a fan approach might struggle into a sealed box....

Craig

At 20:45 31 December 2018, wrote:
I am looking for some advise regarding "Post Curing of Epoxy
Composites".=
=20

The sailplane composite repairs have been completed regarding my
salvaged
A=
SW-27. The tail boom has a new 3'long intermediate section that
has been
s=
carfed and glassed into position. The fuselage pod had some radial
cracks
=
and the seat pan had some fractures that were all scarfed and
glassed. All
=
of the composite repairs were done at room temperature using OEM
materials
=
and MGS epoxy.=20

What temperature is recommended and for what duration should I
be using
for=
post curing the repaired areas. Is there a temperature ramp up
and ramp
do=
wn time that I need to work with. I plan to build a foam insulation
box
ar=
ound the repair areas and use a fan with a number of light bulbs to
regulat=
e the temperature.=20

Any advise is greatly appreciated,
Thanks,
Chris

On Wednesday, January 2, 2019 at 11:00:06 AM UTC-6, Craig Lowrie wrote:
Hi Chris,

I build a cellotex box (building insulation material) and then use a
small bar heater placed low in the box. The Control is achieved using
a commercial Kiln controller which achieves the required temperature
from a thermocouple placed somewhere appropriate in the heat box,
and then controls the temperature to +/- about 1 degree by turning
the bar heater on and off. You can program the cure time and it cuts
it off at the end. I use a separate USB temperature monitor to get
the date to support the cure. Done about 25 cures with this system
now and no problems.... I have done most cures at temperatures of
55C but also done some specialist cures as high as 80C....

I think a fan approach might struggle into a sealed box....

Craig

At 20:45 31 December 2018, wrote:
I am looking for some advise regarding "Post Curing of Epoxy
Composites".=
=20

The sailplane composite repairs have been completed regarding my
salvaged
A=
SW-27. The tail boom has a new 3'long intermediate section that
has been
s=
carfed and glassed into position. The fuselage pod had some radial
cracks
=
and the seat pan had some fractures that were all scarfed and
glassed. All
=
of the composite repairs were done at room temperature using OEM
materials
=
and MGS epoxy.=20

What temperature is recommended and for what duration should I
be using
for=
post curing the repaired areas. Is there a temperature ramp up
and ramp
do=
wn time that I need to work with. I plan to build a foam insulation
box
ar=
ound the repair areas and use a fan with a number of light bulbs to
regulat=
e the temperature.=20

Any advise is greatly appreciated,
Thanks,
Chris


Craig,

Are you using an infrared bar heater or something different. What size and type has been working for you. Have you had any problems with the overheat cut off protection.

Thanks,
Chris

Hi Chris - you can find some technical date sheets that show the T-glass, E, and strengths that are available as a pull down in most of the MGS supplier sites (AC spruce, Wicks, etc). There can see the material changes when cured at both elevated temperatures and for different time durations. Really, do go with what a few others have said - the manufactures temp. At some point - refer to graphs, the increase in time will have very little effect at a constant temp. What you should pay attention to is not going to the extreme cure temps that the resin is capable of - then you could end up with a section of the boom with strengths and flex characteristics that vary from the original build. Basically a very stiff section between the original boom sections that will cause stress problems. And then it is a repair - easy to make stronger without much effort! I assume you have it in an alignment jig - it would be wise to keep it aligned as repaired and supported during the cure time.
Regards, Mark

Hi Chris,

I use an inexpensive bar heater... it has two bars... each about 6-8"
long... I
only use one unless the box is very large. It doesn't have an overheat
protection, but I did have to disable an orientation interlock so it can
lie flat...
open face up..!... The kiln controller is highly recommended to keep the

temperature under control.. but not cheap..!..

Craig

At 20:47 02 January 2019, wrote:
On Wednesday, January 2, 2019 at 11:00:06 AM UTC-6, Craig Lowrie
wrote:
Hi Chris,

I build a cellotex box (building insulation material) and then use a
small bar heater placed low in the box. The Control is achieved using
a commercial Kiln controller which achieves the required temperature
from a thermocouple placed somewhere appropriate in the heat box,
and then controls the temperature to +/- about 1 degree by turning
the bar heater on and off. You can program the cure time and it cuts
it off at the end. I use a separate USB temperature monitor to get
the date to support the cure. Done about 25 cures with this system
now and no problems.... I have done most cures at temperatures of
55C but also done some specialist cures as high as 80C....

I think a fan approach might struggle into a sealed box....

Craig

At 20:45 31 December 2018, wrote:
I am looking for some advise regarding "Post Curing of Epoxy
Composites".=
=20

The sailplane composite repairs have been completed regarding my
salvaged
A=
SW-27. The tail boom has a new 3'long intermediate section that
has been
s=
carfed and glassed into position. The fuselage pod had some radial
cracks
=
and the seat pan had some fractures that were all scarfed and
glassed. All
=
of the composite repairs were done at room temperature using OEM
materials
=
and MGS epoxy.=20

What temperature is recommended and for what duration should I
be using
for=
post curing the repaired areas. Is there a temperature ramp up
and ramp
do=
wn time that I need to work with. I plan to build a foam insulation
box
ar=
ound the repair areas and use a fan with a number of light bulbs to
regulat=
e the temperature.=20

Any advise is greatly appreciated,
Thanks,
Chris


Craig,

Are you using an infrared bar heater or something different. What size
and
type has been working for you. Have you had any problems with the
overheat
cut off protection.

Thanks,
Chris

I've spent a lot of my career either heating things up or trying to cool them off. Go with a low watt density heater, not anything that glows red. Maybe a milk house heater on low, at 60C you will have to disable the internal thermostat. Temperature distribution is going to be an issue, small circulation fans will help with that, you need some air movement, you don't need a lot. separate the fan and the heating element on the milk house heater and you get both in one package. TC's are cheap if you just buy the wire and make them your self, put a few extras on the structure you are heating, you can then spot check your temperature differences there will be more than you think. Sort things out at 40C, take it up to 60C after you are comfortable with what you have, including an automatic high temperature cutoff tested at a lower temperature. Automation direct has some pretty good $100 temperature controllers. This is one of those cases when Mo' ain't better. A well sealed foam board box with a few blankets over it isn't going to take a lot.