Adjusting Part Dimensions for Bondline Control

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Adjusting Part Dimensions for Bondline Control

Author	Message
FLD	FLD posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 468, Visits: 2.7K	This sounds awesome, can you post up pics as you go? I'd love to see it.
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Jabus10	Jabus10 posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 2, Visits: 10	It's part of a project to break the altitude record for a UK amateur built rocket. The design is not dissimilar to this though it's only 3m long and has only a single stage. In order to obtain permission to launch this we need to submit a detailed report showing that it will stay within a given distance of the launch site and remain in one piece even in the worst case scenarios. The documentation requires going into all the details about how the adhesives will be used. This base part has mounting points so that once it's inserted and the epoxy has cured the whole thing can be mounted onto the bed of a milling machine via the T-slots and the next section ( also mounted on the mill bed ) can be slid in using the flatness of the bed to ensure alignment. It's just getting the alignment right with this first base part which is proving tricky.
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Hanaldo	Hanaldo posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	May I ask what the part does and why you are making it? Reason I'd like to know, is my answer would vary depending on whether the part is structural or, given it is a student project, you are performing any structural tests on it. Or does it need to meet certain parameters, ie. aerospace? If this one part is just part of a larger project, and does not need to conform to certain standards, then I would say simply apply the adhesive to both surfaces before pushing the CF tube onto the insert. The adhesive will sort itself out, and you will have more control over alignment. The 0.1mm bond gap can be used as an indication of what you should have. However I know that in an aerospace application, there is very precise control over these things and 'close enough' is not good enough. In which case you would likely need to be specific with achieving your 0.1mm bond gap, and you may need to construct some sort of jig to control your alignment.
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FLD	FLD posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 468, Visits: 2.7K	CF tube shouldn't stretch! If you force it you'll damage it. You should machine the insert for the tube and bonding thickness. When you bond it you will need to jig the tube so that you dont get sag or miss-alignment as you have rightly indentified.
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Jabus10	Jabus10 posted 11 Years Ago HOT Topic Details
Group: Forum Members Posts: 2, Visits: 10	Hi, For a student project I'm involved in we're bonding a large carbon fibre tube onto an aluminium insert. We've settled on using Hysol E-40HT due to its high temperature performance ( the assembly will encounter some quite high temperatures ) and it's quite easily available to us ( it also doesn't have the scary toxic fume warning that some of the Hysol datasheets have which is good as our student lab is in the basement of the engineering department and the ventilation is somewhat dismal). In order to get the bondline gap of 0.1mm suggested in the datasheet we're mixing the epoxy with 0.004" glass beads. Do we need to adjust the dimensions of the aluminium insert in order to account for the 0.1mm gap required? Or do you simply push the CF tube onto the insert and hope that it stretches over some of the glass beads as you slide it on? The ID of the CF tube is 182mm and the aluminium insert is meant to be machined to max 181.985mm min 181.956mm (it's an H7g6 fit). Apologies for what is probably a really simple question but none of us have any practical composite experience. I imagine we'll have to make the aluminium insert have a 179.8mm diameter but then that gives alignment issues as the whole structure is about 3m long and the insert is at the base so if they're not quite concentric it will be very noticeable at the top.
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