---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Tue 06/02/20: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:03 AM - Re: Post curing response (John Wighton) 2. 01:29 AM - Re: Re: Post curing response (Brian Davies) 3. 03:36 AM - Re: Post curing response (John Wighton) ________________________________ Message 1 _____________________________________ Time: 01:03:54 AM PST US Subject: Europa-List: Re: Post curing response From: "John Wighton" Post-curing is essential to achieve optimal bond strength. This applies to laminated parts and also part to part glued joints. The regime for the post-curing depends on the system used. Some systems achieve full strength when exposed to RT (ambient 20 deg C) other require higher temperatures. Generally higher temperatures result in full post-cure properties being achieved in a shorter time. Ideally, Europa (composite airframes in general) should be post-cured in their entirety - achieved in an oven with a controlled environment. A Paintshop facility can provide these conditions. It should be noted that the Achilles heel of composite aircraft (at least those approved via the LAA) has been the requirement to use a 'Composites Super-Factor' (see LAA TL 1.17). This takes into account the significant variability in composite strength, stiffness, etc at non-RT conditions. It also includes a variability factor that accounts for variations in the processes of laminating, jointing, etc. This CSF can be as high as 1.50. A reduction in CSF may be negotiated, this is more likely if documented processes and post-cure is followed. Recent discussions with LAA Engineering indicate that CSF of 1.20 may be possible in some circumstances. This can have a significant influence on RFs (margins of safety) calculations and even MAUW determination. My advice to Europa builders is to post-cure their entire airframe. Survey the airframe to ensure no items are present that will degrade at the chosen post-cure temperature. A typical post-cure process will look something like the following (BUT adhere to the supplier instructions and limitations): 1. RT to 80C, ramped up at 1-2C per minute. 2. Hold (dwell) for 120 mins (typically 80C). 3. Ramp down at 1-2C/min. The structure should be free (no clamping or holding things down), I would assemble the airframe but this is rarely possible. -------- John Wighton Europa XS trigear G-IPOD Read this topic online here: http://forums.matronics.com/viewtopic.php?p=496600#496600 ________________________________ Message 2 _____________________________________ Time: 01:29:47 AM PST US From: "Brian Davies" Subject: RE: Europa-List: Re: Post curing response Hi John, I recognise your superior knowledge on this subject but is it wise to recommend that Europa builders in particular post cure their entire fuselage? There is now considerable in service experience with Europas that have not been subject to this treatment and I am not aware of any safety issues resulting from lack of post cure of the fuselage. I would also apply the same logic to the XS wings that use factory moulded parts. Regards Brian Davies -----Original Message----- From: owner-europa-list-server@matronics.com On Behalf Of John Wighton Sent: 02 June 2020 09:03 Subject: Europa-List: Re: Post curing response Post-curing is essential to achieve optimal bond strength. This applies to laminated parts and also part to part glued joints. The regime for the post-curing depends on the system used. Some systems achieve full strength when exposed to RT (ambient 20 deg C) other require higher temperatures. Generally higher temperatures result in full post-cure properties being achieved in a shorter time. Ideally, Europa (composite airframes in general) should be post-cured in their entirety - achieved in an oven with a controlled environment. A Paintshop facility can provide these conditions. It should be noted that the Achilles heel of composite aircraft (at least those approved via the LAA) has been the requirement to use a 'Composites Super-Factor' (see LAA TL 1.17). This takes into account the significant variability in composite strength, stiffness, etc at non-RT conditions. It also includes a variability factor that accounts for variations in the processes of laminating, jointing, etc. This CSF can be as high as 1.50. A reduction in CSF may be negotiated, this is more likely if documented processes and post-cure is followed. Recent discussions with LAA Engineering indicate that CSF of 1.20 may be possible in some circumstances. This can have a significant influence on RFs (margins of safety) calculations and even MAUW determination. My advice to Europa builders is to post-cure their entire airframe. Survey the airframe to ensure no items are present that will degrade at the chosen post-cure temperature. A typical post-cure process will look something like the following (BUT adhere to the supplier instructions and limitations): 1. RT to 80C, ramped up at 1-2C per minute. 2. Hold (dwell) for 120 mins (typically 80C). 3. Ramp down at 1-2C/min. The structure should be free (no clamping or holding things down), I would assemble the airframe but this is rarely possible. -------- John Wighton Europa XS trigear G-IPOD Read this topic online here: http://forums.matronics.com/viewtopic.php?p=496600#496600 -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 3 _____________________________________ Time: 03:36:00 AM PST US Subject: Europa-List: Re: Post curing response From: "John Wighton" Brian, thanks for your comment. I am not aware of any negative influence that a fully cured structure can provide. Post-curing of most Europa builds will occur in-service, hot days and heat soak can reach surface temperatures easily exceeding 55C. Prolonged exposure would compensate for the lack of higher temperatures, eventually. Hence most Europa will achieve something close to full strength over time. But that is hardly a controlled process. Due to the adoption of generous CSF our Europa aircraft are designed to load levels rarely, if ever, encountered in service. Crashworthiness aside, the Europa is somewhat over-engineered. Given that temperature exposure up to and beyond the Tg is not desireable, as chemical changes occur. Core temperature range is often cited as a limitation. However, aircraft materials should have the ability to work from -30C to +80C without degradation. Otherwise operational limitations will apply. It's a bit like having a car paint job and driving off before the paint has fully cured. Why would you? Sure, the paint will cure eventually, but in the meantime it is soft and will incur scratches and other damages. Maybe an imperfect comparison but hopefully you see what l am talking about. The tub to lower shell joint, top to bottle shells and wing pin reaction locations all need to achieve full strength. Post-curing to the manufacturer's process instructions is therefore my recommendation. -------- John Wighton Europa XS trigear G-IPOD Read this topic online here: http://forums.matronics.com/viewtopic.php?p=496602#496602 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.