A word of caution for those post-curing flying surfaces with blue foam
cores: stick to the upper temperature limit of 50C in the Europa Build
Manual quoted below. While the Gurit datasheets for Ampreg 20 and 21 to
-----Original Message-----
From: owner-europa-list-server@matronics.com
<owner-europa-list-server@matronics.com> On Behalf Of Kelvin Weston
Sent: 29 May 2020 15:35
Subject: Europa-List: Re: Post curing response
Gents
The Europa Build Manual calls for a post-cure, see Chapter 37, Page 2, whic
h
states:
"The first thing that you need to do with your flying surfaces is post-cure
them at a temperature between 40 - 50C.=C2- This will improve their stren
gth
and cook off any remaining volatiles and moisture within the epoxy system.
Make a simple oven with foam blocks, timber or sheets and an electric fan
heater and cure your flying surfaces for 8-10 hours.
Do take care not to get them too hot and make sure that they are fully
supported."
The Ampreg 20 and 21 datasheets from Gurit shows an initial cure at a
minimum of 18C (ideally 24hrs at 21C) followed by an elevated post-cure of
5
hours at 70 - 80C or 16 hours at 50C.
The datasheet also states:
=C3=A2=82=AC=C5=93The post-cure need not be carried out immediately afte
r laminating. It is
possible to assemble several composite components and post-cure the entire
assembly together. It is recommended, however, that elevated temperature
curing should be completed before any further painting / finishing
operations.
Furthermore, care should be taken to adequately support the laminate if it
is to be post-cured after demoulding, and the laminate must be allowed to
cool before the support is removed.
When post-curing it is recommended to use a ramp rate of 10 degC/hour when
heating from ambient to the post-cure temperature, to ensure that the
thermal performance of the laminate stays ahead of the oven temperature.
Higher ramp rates may result in the resin softening and distortion of the
part.=C3=A2=82=AC=EF=BD
The resulting specs with standard hardener for Ampreg 20, 21 and 30 are all
very similar and result in a Tg of around:
58C - Room temperature cure (28 days at 21C) 73C - Elevated post cure (16hr
s
at 50C)
The ultimate Tg for Ampreg 20 and 30 is stated as around 98C.=C2- Ampreg
21 was
slightly lower at 91C
--------
Regards
Kelv Weston
Kit 497
kelv@kdweston.biz
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496570#496570
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