Problem about testing composites is, anything can change the results. Material, layup schedule, resin, processing conditions, pressure, sizing, etc. Tension was great, but compression was 1/3 off!
http://udel.edu/~roseman/tenCFPPS1.AVI
(link should work, it’s 39mb, I didn’t wait to test it while posting this 
So, depending on how long it takes to upload, the early readers might not see it yet)
Videos of testing can be just like running the test - slow and boring – until something happens! You take me back to my days in the lab at uni Some day I’ll tell about the time we spun a shape 3 “laps” round the low speed wind tunnel!
So, can you share some details?
Was that 2x2 Twill - or uni with wide stitching?
What was the fiber count? 12k - or less?
Was it an epoxy matrix?
How many lams? The cross sectional area too please?
What was the load at the first separation on the near side?
The load at burst – and termination (I guess)?
Anything you can share would be very nice - Are all your tests in association with a course at U-Del - or are you getting in some “after hours work?”
TIA and Cheers - Jim
haahaa! I don’t know how much info I CAN give, but it’s nothing overly new.
Fabric is 8 layers T700, I think 24oz carbon, Plain weave, possibly calendered.
Resin is PPS, I can’t not say more than equal # of layers of film compared to fabric. However, it might be resin starved due to horrible compression tests. (which is a boring video)
Stinks like a mother. Rings like a wind chime.
Failure of my samples ranged from 8000 to 11000lbs, depending on how much fiber movement there was (hot press consolidation)
Beginning fiber/matrix failure was near 5000 for the first DING.
Thickness was about 0.118", sample width ~1", height ~9"
I can’t mention strain, since I don’t understand it enough to give a number.
My testing is all about contracts. I am not a student, so everything I do is for outside contract research. I only do my own stuff “after hours”…do you know how much scrap I have laying around!!!
If your anything like Boeing, you have a lot of scrap.
I have Boeing material…does that count?
Haha, very true. I just came from a clients facility, and one cart alone had $1/2 million worth of rejected parts. Exactly why the employees are going through training!
riff42
Please take this as intellectual curiosity. I am not trying to offend - just real curious on strength of materials and the testing results.
I did a bit of “backing-in” the details - maybe you can let me know if I am even close. [All units in inches and pounds]
Things Known:
Lets check what the Ultimate Strength of the materials as tested is. Using the cross section area and the breaking strength:
Breaking Strength = (Ultimate Strength)X(Cross Sectional Area) So, 11,000 = Ultimate Strength X (0.118 insq)
Ultimate Strength = 11,000/(0.118) = 93,220 psi This is then the Ultimate Strength – not as T700 says it should be.
Well, that shows the Ultimate Strength of the Test Piece is a bit lower than 700,000 psi. :rolleyes:
Mind you, its a good ultimate strength to work with - just lower than I might have expected. That seems like a lot of difference to explain with layup, cure, etc.
If we use the 700,000 psi [4900Mpa] Ultimate Strength (Tensile)as listed for T700 - when should the sample fail? Looks like:
Breaking Strength = (700,000) x (0.118) = 82,600 pounds. A bit higher than 11,000 pounds.
SO A COUPLE OF QUICK QUESTIONS:
As I wrote - not flaming - or anything - just trying to understand the fraction that is Real/Ideal on CF Composites!
Cheers - Jim
He is not working with a piece composed of solid carbon tows with no airspace in between.
Im doing some side work with an ex-boeing employee. He mentioned a part that if you bridged the first layer, and/or, if the bag popped when it saw 100psi in the clave. You were fired on the spot. I believe the price tag was $500 g’s per part.
T700 would count…especially if you cut 10" off of a yard and then threw the rest away…Boeing sytle!
In reality though I think they have a monster ultra sonic cutter now. Way less waste going on.
Everyone has scrapes unfortunatly, for that reason…things can and will go wrong! My first infusion used at least 10yd of fabrics!
I remember interviewing at a company where they had stacks of composite tables, carbon and kevlar, waiting to be double checked before being tossed!!!
I know G! There is just limited amount of engineering data I can provide for various reasons.
I manufacture, and test. Results go to someone else. I only know what they say to me, and what I might understand. So I’m not always the best help for the science of it, but definatly on the way it was produced WHile I DO hold the raw data for load, and strain for all tests I do, I can’t give them out.
Also, the ideal ultimate strength might be for unidirectional samples. If you have a 0/90 weave, then you are losing half your strength fibers in the load direction. The 90’s don’t mean anything to the sample. That might be able to rework some of those numbers better?
As for the ideal compression strength, I am not sure. I think they were failing at 3000lbs on avg. Might be wrong there. I have to test another set today quick to see if more resin helps.
I’ll try to remember those numbers.
No, I saw everything large enough to make something, and borrow some VER or Epoxy later in the evening 
though, I need to start modeling so we can rapid, or cnc some molds…tried of making flat plates all the darn time! BORING!
yyyeah, i guess all the new employees are the cleanup crews then…they work their way up to cutting, then kitting, and THEN mold cleaning…maybe 10 years, laying up
riff42 did us all a big favor in sharing his testing results! and, riff42 - I understand you not being able to share the complete test info - thanks for what you have!
Like you and TET wrote, the loads I posted should be halved - because it was not uni = so the breaking strength and ultimate strength would be 1/2 of what I had shown in previous post. (I asked for help! - thanks – Keep checking my stuff – please. )
The Ultimate Strength derived from the sample test would be 46,610 psi - not over 90,000 as previous post.
Or, the calculated load the test piece should have held to 41,300 pounds. But didn’t - it failed at 11,000. A lot of possible things could explain that - hopefully today’s testing bears fruit!
This brings up an interesting point, what if E-Glass were used and not Carbon? Well, lets check the cross section in E-Glass and “guess” when it should break. [May not be germane for the customer riff42 is working - but useful analysis for the rest of us – maybe]
E-Glass Tensile Strength = 3450Mpa [500,380 psi] That would be uni - not woven, not crimped, high strength – not commercial grade
1 E-Glass 500,380 psi
2. Thickness t = 0.118", sample width ~1" Cross Sectional Area = 0.118 sq inches – [use values from test piece]
3. Breaking Strength = (Ultimate Strength)X(Cross Sectional Area)
So, with E-Glass:
Breaking Strength = 500,380 x (0.118) = 59,044 pounds
Now, if only 1/2 the fabric supports the load - then the Breaking Strength would be 29,522 pounds! Double the CF sample. Take out another 20 percent or so for crimping etc from the weave process - and its still at nearly 24,000 pound tensile breaking strength - in woven E-Glass.
Now if your product --what you are building" could “tolerate” being thicker - say 0.25 1/4 inch vs 0.118, then the answers would be 120,095 pounds [for uni] and 62545 pounds (less 20% near 50,000] respectively in E-Glass - not Carbon Fiber.
My purpose in this post is NOT to say E-Glass is the same as CF or is a replacement-- in all cases. BUT - if you know what the product is supposed to do - load wise, and it can tolerate a little reinforcement to get the stiffness, and the customer doesn’t mind a little extra weight – and they want it to just needs to look sexy then a lot of money can be saved using a Black Fiberglass - rather than Carbon Fiber. [I seem to recall the price of a fair representative of Carbon Fiber in Black Fiberglass is about 1/3 the price – not insignificant.] Mind you let them know what they’re getting for that discount though!
Again, good luck on today’s tests. I bet as TET offered; the extra resin might not improve results – unless the previous sample was starved - and not at a (more) optimum ratio glass/resin.
Anxiously awaiting some news - Cheers - Jim
PS - riff42: may I send you a PM regarding your testing facility, etc?
It’s all about properties and end needs. There has been work using CF/G/Kevlar prepreg fabrics, where they tried to combine all fabrics to balance out all numbers. Not sure if it ever worked.
The part is for an aircraft I think, so it has to be light as possible, and it is not a load bearing part. Well, other than, it better not fail no matter what!! One also has to worry about the CTE between materials. Glass -1 x 10-6 to 1 x 10-6 and carbon:6 x 10-6 to 8 x 10-6. So for something that will see a change in temps, like an aircraft, the bondline between the glass and carbon might fail. Many things to look into for a part.
As for looks, PPS resin is anything but pretty. It’s a brownish/gray color. Does not show the weave at all. The only reason why I would make something out of CF/PPS is for the sound of the part. (nice ringing sound)
Glass has it’s advantages. It elongates, and is cheaper. Carbon is more brittle, but stronger. Kevlar can stretch and hold the load, but not light, and not strong.
As for the compression, off a 1" x .450" gauge area, 0.150avg thickness, the last set had only a 2300lbs avg, this new set with more resin ended up 2800-3300lbs. Still below expected (i think he got 49kpsi, when it should be 60-80kpsi?), which can be the fiber sizing, or fabric weave. We don’t know yet.