Re: Milli a new composite mill kit
Hi Thomas - I only have had poor results on this particular long thin test piece. All my other casts have been very good. The dry pack approach is to sidestep the issue of entraining air in the mix. My preferred process is infusion this gives excellent results. I think trying to wet mix stack a 6mm thick mould then get a bag on it is more trouble then a dry pack approach. The current mould suffered a few design issues. 1) the side strips stood a bit proud and stopped the top mould from coming down fully 2) not enough screws in the top mould. To remedy that a dry pack, vacuum bag approach and vacuum fill will sort it and use plastic mould edges vs the timber..... Peter
and to clarify the casting issue a little further. Its easy to cast any object and get an apparent 99% good cast (wet or dry approach). The aim of this cast is to make a representative object for a stiffness test, which is a bit more challenging then production of a generic part. I would say most people don't publish their trials and tribulations only their successes but here they are...
Last edited by peteeng; 04-07-2021 at 06:28 AM.
Re: Milli a new composite mill kit
When measuring deflection on such a thin test piece are you getting a less than optimal result because of the extra resin on the surfaces ? An accurate test would require you to cut the piece to size, to allow aggregate to be evenly distributed right through, but this would weaken the material too.
Re: Milli a new composite mill kit
Hi Zorbit - On this piece (no1) the top surface is very poor (the bottom surface is excellent) and the geometry is poor. Next one will be better. Cutting alox is a bit difficult. Its effectively a grinding wheel. I will get some finer alox and make a two size mix down the track. I have done this with alox/aluminium see prior. The surface is a bit less dense but for now its as good as can be expected. I may build a thicker No2. But my aim was to show a sample side by side with the aluminium extrusion... I think the material is very well distributed and my target of 70GPa is well below theoretical so averages should be OK for now.... Making large samples is easier but doesn't achieve what I wanted....Peter
Re: Milli a new composite mill kit
Evening all - I have been thinking about this cast material and the next mould. For the mould I shall get some 25x6 aluminium flat bar for the mould surround. This will be better then plastic and will be better for the CSA grout coupon to follow. I have played with the piece I have and I feel even the next piece maybe "soft". In another thread a person has had EG samples made and lab tested and found the modulus to be down in bending. All the main figures published are from compression tests and these test high.... We shall see soon I imagine... This skepticism made me create a decision table for some materials and steel wins out. I played with some of the numbers and St still won so maybe that's the best direction if I can't get 70GPa out of CSA or ALOX... The main characteristics for the table I selected are stiffness first, then cost then dampness then density. These are then given weights and normalised as averages, then added to create the biggest number wins scenario... Steel is cheap and stiff is the driver here and scores 2.11 then UHPC 2.10 then alox/EP then Al.... To make steel damp I can laminate it, but I think I'd go with laminated aluminium so it can be machined on a router....
I also came across Uni of Pennsylvania doing interesting structural optimisation work... I downloaded their software and will have a play...
https://psl.design.upenn.edu/
Keep making Peter
Re: Milli a new composite mill kit
Morning all - I've been tidying up a bunch of small jobs that are growing moss. So my lists and headspace are now more manageable. Came across this blooper video. So many dial gauges broken!!
Peter
Re: Milli a new composite mill kit
That's what you get when the users are not machinist's, this main guy was just a hobbyist to start with and started doing lots of video's, then got sponsors to give him free stuff, they have got quit good by trial and error and do make some good video's and projects, and have improved there machine operating skill levelOriginally Posted by peteeng
Mactec54
Re: Milli a new composite mill kit
Getting free machining stuff sounds good...if only I had a personality...
Re: Milli a new composite mill kit
Sorry, now back to the topic
Last edited by catahoula; 04-11-2021 at 01:54 PM.
Re: Milli a new composite mill kit
Morning All & Ragtag out there - I have been playing with the alox/ep chunk I have and I have doubts about getting good flexural stiffness out of it. In another thread another poster has had EG samples commercially flexural tested and the results were 1/3 the published values for that commercial mix. Since most of the stiffness values for EG are derived from compression tests I think this maybe a biased number. But I shall make a new sample and we shall see how that goes. I have found the 25x6 al extrusions local and shall pick those up this week.... But I want to get Millis design moving again.
Then there's the issue of machining so I think infused fibreglass is the go. So I think I have to fall back to ~30-33GPa as I have reliable test data on this material. This is similar to G10 material but since I can design the laminate & I can optimise in some ways... Carbon fibre is the best but too many $$$ Here's some thick laminates I made many years ago for an insulated crane boom structure. They are cut outs for cable holes etc. So I'm thinking infused FG thick skins, and if needed filled with CSA grout. I can also embed metal in the skins if needed... But a mono material structure is best I think... Peter
Re: Milli a new composite mill kit
Hi All- Germans are so thorough - Peter
https://www.sciencedirect.com/scienc...07850615001444
Re: Milli a new composite mill kit
If you or anyone actually need to read that, its available on libgen.
Re: Milli a new composite mill kit
Morning all - A USA based watcher has been in touch about CSA grout. So all of yoz in USA can use this sort of thing Rapidset ultraflow 4000/8 CTS Cement have all sorts of levelling, primers and additives for this sort of material. Including adhesives for anchors... Their engineers may even be able to help with a high modulus mix... Peter
Re: Milli a new composite mill kit
Afternoon all - I put a request into CTS USA about the modulus of their ultraflow this morning. About 30mins later I get a call from a local cement distributor. He's the local Rapidset guy! They don't stock it here but they can get it into OZ but they have a similar product in stock here. He's sending through its datasheet soon... Small planet. Peter
Re: Milli a new composite mill kit
Evening all - came across some interesting videos on high modulus concrete testing and use in buildings. Structural Engs are a bit compressive modulus centric for tall buildings. But I think the tensile modulus Et will be down on Ec....
Peter
Re: Milli a new composite mill kit
Morning All - Been involved in an intense commercial project over the last 3 weeks that has soaked up all of my time. I think we're over the hump now so can get back to a more normal routine. I shall review Milli and get it moving again.... Peter
Re: Milli a new composite mill kit
Hey Peter,
Don't know if you read this before, lots of composite info.
https://publik.tuwien.ac.at/files/PubDat_245068.pdf
Re: Milli a new composite mill kit
Thks Ard - Yes its the German are thorough doc... Peter
Re: Milli a new composite mill kit
Hi All - Local CTS rep got back to me and here's the tech sheet. Its for Cement All. MOE is 38GPa at 28 days. This will be the Ec... Peter
Re: Milli a new composite mill kit
That's a long but interesting read. I'll be enjoying that.
A quick look through it, and this caught my attention:
"Lee achieved 5 times larger depth of cut with a graphite epoxy composite boring bar compared to a steel bar before the onset of chatter"
That has immense potential.
Re: Milli a new composite mill kit
Yea... that's actually short, german papers are more like this.
https://publications.rwth-aachen.de/...les/731208.pdf
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