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Trace based simplified composite analysis. Opinions?

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stanislavz

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One more shot, on manufacturing side - can you make whole skin in one piece, and put ribs and longeron after. For non sandwtich - definetly yes, this is 2 layers of 300 gsm biax + 2 300gsm ud inside.

1598604648309.png
 
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stanislavz

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And with 5mm foam core (0.1N/mm = 10 kg per 1 metre of wing span. ) :

1598605126285.png
 

stanislavz

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Next batch, specially for me, skyranger to nynja like (175 km/h cruise, 195km/h vne), but with load bearing rear fuselage section. Is it viable ?

1599563013003.png

Weight of original structure, made from 40x1.5 tubes as main longerons plus 22x1.5 for little bracing in the middle . And some 3mm ss cables. Weight of 9.5 kg is without skin. Load of tail is per Orion rule of thumb - 1.5 mtow - 712.5 kg. Or per glider basic criteria at 200 kmh/ 130 mph is 25 psf or 250 kg for 2m^2 tail surface. I will Stick to Orion number.

1599562982048.png

And we are where yet :
1599563661187.png
But - more due to methodology. In fact, 3mm cable wire will hold till ~ 600kg, And we got on bracing a little less than half of it.

1599563729319.png
And deflections are :

1599563992765.png

So that flimsy tubes are more, than they looked from start.

More to come..
 
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stanislavz

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First alternative, skin divided into pieces, all piece is joined using some 20mm tube (to be done using Boku trick with PE stripe). First skin section and last - 300gs biax + 450 gsm biax, middle skins - 2 x 300 gsm biax. An we are perfect on deflection/safety and weight.

1599568818057.png
 

stanislavz

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Some optimisation :

1599569553845.png

+- its is in 10 kg range with solid skin.
 

stanislavz

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Ribs removed, only skin left as was 2x300gsm biax in wrong direction

1599569871325.png
 

stanislavz

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Added One ud 300 gsm in proper orientation :

1599570150113.png

And close on deflection side:

1599570393314.png

Last remark - i do omitted big and fat reinforcements on connection points.
 
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stanislavz

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Your local guy is using it for workout in a hangar ~ 50 kg point load, for skins only

1599574785823.png
 

stanislavz

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Will think next, how to model this kind of wing :

1599583136806.png

From caro glider, foamless :

 
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Vigilant1

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I am. But, since I'm not playing with the software, too, much of it is going right over my head.
A bit like Calculus 2. I'd watch the teacher do the work on the board, understand about 10% of it, then go home and grind through the work using my textbook, time, and my very meager talent.
FWIW, your posts are a lot more colorful and; interesting than my teacher's equations on the board.
 

Fireflyer228

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Ran across this recently and it looks like it might help those of us that are weak in the math needed for traditional composite analysis. Being one of those souls afflicted with apprehension at the mention of tensors and such this obviously interested me.

Would any of those HBA members that have real world experience with composite design care to look over this subject and comment on it's validity or usefulness?

CompoSIDE and Prof. Stephen Tsai collaborate to demonstrate new composites theory | JEC Group

www.sciencedirect.com/science/article/pii/S0266353814002188/pdfft?md5=b9f45ef859874bec2abbcab227dd6c00&pid=1-s2.0-S0266353814002188-main.pdf

I do PAUT (Phased array ultrasonic inspection) on carbon fiber parts for a small aircraft manufacturer. I’m very interested in what he has to say. I should be able to check it out tomorrow and get back to you.

Kenneth
 

stanislavz

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I don't think you're getting accurate results from your support positions. You're getting all corner strain.
Explain. Or it is showing where it will fail mostly at support positions ? It is ok and it is understandable. Composites hate point load. But - i see area, which i have to reinforce to achieve uniform reserve factor.
 

Hot Wings

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Any one reading this monologue ?
I take a look, but time is limited right now and like Vigilant1 I don't have the program. I can't ;justify the cost of the software and really hate downloading trial software knowing that time limits will expire before I have time to devote to proper study.

When I, and probably others, do find time to devote to the software I'm sure you posts will mean more and have much more value.
 

Fireflyer228

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I do PAUT (Phased array ultrasonic inspection) on carbon fiber parts for a small aircraft manufacturer. I’m very interested in what he has to say. I should be able to check it out tomorrow and get back to you.

Kenneth
Just my .02
I don’t think there data holds water. Let me explain. We have the most robust out of autoclave process for destructive and non-destructive analysis carbon fiber layups according to the folks we’ve been working with the FAA. Even the same tech at the same temperature and humidity laying up the same part can have variations in the quality and consistency of each layup.
Unless you all have access to an autoclave and even then we will be able to find variations in parts with ultrasonic inspection. Ultrasonic inspection is kind of a fancy ‘tap test’ (which is still used quite a bit). By sending sound into a part we either see the back wall of the part or we see the voids left my gasses that did not escape during bake or we see reflections in resin pockets also returning a shortened signal. In either situation the plys will not exhibit full strength as we have tested to failure.
I might be able to share some microscopy cross sections that supports this in carbon fiber layups. PM me if you need more details.
So, their presentation including “a circle is a perfect and simple shape”, while not incorrect, was misleading and left out a lot of data. They would need to correlate, through hundreds of build-ups with different people over time for each epoxy type they are comparing. Leading to a bell curve for each example, to determine a mean. Hope that helps.
Kenneth
 

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