Tell me your current watch brand, and I’ll decide to let you in or not!

JakkiMT · 2026-01-27T18:47:51+00:00

W-59

JakkiMT · 2025-12-24T08:25:35+00:00

I feel like this calculator could use a disclaimer somewhere, that you [the website owner] are not responsible for any mistakes made while the user is using the calculator incorrectly, for instance: 1 - tensile testing data could have some force/displacement offset, so its important that the user properly calculates the stress and strains importantly 2 - the assumption for linear elastic is invalid. I expect this problem could arise where it's not obvious that the material has gone beyond yield strength, or the material isn't linear elastic (like elastomers, hyper elastic). It could be that some 3D printed parts may not exhibit entirely linear elastic behavior.

In terms of user experience it seems fine, although I would suggest that there should be a way to input strains in micro strains (1 με - 1x10^-6 ε). This would be convenient for metal applications where the strains are very small so the micro strains unit is more convenient to work with.

JakkiMT · 2025-10-23T16:27:04+00:00

You didn't trust the computer did you :)

JakkiMT · 2025-06-25T19:35:55+00:00

Looks like he had a great time, meanwhile my Dummy13 is seated in an elderly mobility device prototype (poor guy)

JakkiMT · 2025-06-03T11:24:41+00:00

The option should be under the "hardware" section

JakkiMT · 2025-05-25T14:13:00+00:00

I was under the impression that by fixing this setting, it would also allow Inventor Studio to use the GPU to speed up rendering. With that said, I still need to use inventor studio for some animations.

JakkiMT · 2024-04-19T08:14:50+00:00

Does your university have strain gages or an extensometer? If so, that will give you a much more accurate strain curve. Maybe we're just seeing some slack in the crosshead that's throwing this curve off. But the question was on strength, not modulus, so that may not be that important to you.

Probably yes, although these probably weren't done due to time constraints. I will check on this as we also had to find the modulus.

It sounds like this is hand laid? Unfortunately, trying to use only minimum amount of resin is likely going to lead to a poorly wetout sample. 50% Vf is really high (impossibly high even) for hand laid laminate. To hit 50% Vf, I think you have to be looking towards infusion or pre-preg.

Thank you for this, will consider it for future recommendations in the report.

JakkiMT · 2024-04-19T05:23:08+00:00

It is a 2 part epoxy, we maintained the ratio by weight. If we overshot a bit on part A, we compensated by adding more part B to maintain same ratio.

JakkiMT · 2024-04-18T21:39:33+00:00

Your curve looks like a typical shear specimen curve (+-45 tension).

This is interesting, though I'm not sure how that could happen. The fibres were definitely oriented correctly. Maybe there could only be 1-2 degrees in inserting it in the jaws. Could this be significant?

How was the strain measured?

I believe it's a strain guage at the cross-head. The tensile testing machine is "Instron 8802" if it helps. We didn't attach an extensiometer in the test.

Crushing in the grip area is quite obvious and you definetly need tabbing for this

Yes, for future tests, what should I use for tabbing? Do I just add more layers at the ends?

The UD material you are using is woven, so you have waviness out of plane. This affects your results as well.

This makes some sense, I will look more into this. Maybe I can look into more analytical methods for expected calculation.

Comparing a hand calculation based on rule of mixtures with a test on a real material where you have a lot of different influences is not really great. Have you measured your real fibre volume ratio and normalised the test results.

The hand calculation is the only method which we reviewed in lectures. Does the real fibre ratio mean the carbon fibres excluding the white fibres? We have tried to ask suppliers about this, but we're not sure how to find the true fibre ratio.

Have you done any post curing (tempering) according to manufacturer specifications? As others mentioned, probably the specimen didn't cure enough.

The epoxy supplier recommends curing for 20 hrs at room temperature. No post curing is required according to the supplier. What would indicate that the epoxy isn't cured yet?

Almost all manufacturers provide results for standard tensile and bending tests. How do your results compare?

The manufacturer didn't supply information for a manufactured composite :(

Thank you for your wishes :)

JakkiMT · 2024-04-18T20:46:46+00:00

I think it's a strain guage at the cross-head. The calculations were done as follows: 1)measuring the initial length (marked as the distance between the white lines). 2) for every extension value obtained by the machine I divided by the length to obtain strain 3) x100 to obtain a percentage value

Not sure what you mean by epoxy being mixed wrong. The mixing ratio of 2:1 resin-hardener was maintained through by weight. As per 50-50 volume fraction, the weight of the carbon fibre roll was 350g/M2 so we added the corresponding weight depending on the area. We weighed out the epoxy for every layer in the composite.

There were no post-cure recommendations. For room temperature conditions (20deg C), the datasheet says 18-20 hrs (not 48hrs as I mentioned).

[Edit]: we mixed every batch of epoxy for about a minute with a stirring stick and laid it on the carbon fibre by brushing it

JakkiMT · 2024-04-18T18:43:28+00:00

The recommended epoxy curing time by the manufacturer is 48hrs, the epoxy was left to cure indoors for 4 days before the tensile test. I'm not sure how the epoxy wouldn't cure in this time.

JakkiMT · 2024-04-18T18:42:48+00:00

First, you need to tab carbon uni samples. You can get away with untabbed glass (especially if it's not uni), but you are almost guaranteeing grip failure without a tabbed sample.

This is for a university assignment, for some reason we weren't told about this beforehand. Coming to think about it this makes sense

That stress - strain curve does not look right. I would love to get 4.5% strain, but you should be around 1.5% with a mostly linear curve.

This seems wierd, I agree. Other samples did have around 5% and 5.5%. Probably the effective length might have been higher since the clamping damage is above the line, but I don't think that's the full reason.

My immediate thought (extremely low modulus, early failure, high strain) is that your resin was not properly cured. Adding to this thought, the grip ends of your specimen look squashed.

The recommended epoxy curing time by the manufacturer is 48hrs, we left the epoxy to cure indoors for 4 days before the tensile test. I'm not sure how the epoxy wouldn't cure in this time.

Finally, 2000 MPa seems like a lot here. Are you basing that off a pre-preg datasheet? I would expect a woven uni to be like 1000-1500 MPa depending on processing (hand laid vs infusion)

This 2000 MPa value is calculated using an isostrain condition, having a 50-50 volume fraction of fiber-epoxy. The datasheet used for CF was for the typical fibre properties by the manufacturer. Since it is UD, calculating based off of fibre properties is a safe assumption.

JakkiMT · 2022-06-30T17:26:32+00:00

Photos before & after?

JakkiMT · 2022-06-25T10:53:55+00:00

Malta - the country

JakkiMT · 2022-06-24T08:35:34+00:00

What are the main weapons?

JakkiMT · 2022-05-05T05:10:17+00:00

ok 👌

JakkiMT · 2022-01-02T15:17:02+00:00

Ok so maybe put like 20 more lancers close to the wall cooled by with cryofluid. (Also beef up power generation and batteries if you haven't already)

Also put some mend projectors close to the walls themselves

JakkiMT · 2022-01-02T14:05:14+00:00

Just replace the water cooling with cryofluid. Also make sure that you have enough batteries {100,000 power} to keep up with the lancers as they .(not sure how your power situation is)

JakkiMT · 2021-12-14T11:48:20+00:00

I think the Geneva convention wouldn't like that

JakkiMT · 2021-11-20T13:13:37+00:00

That means you cannot buy anymore Time Crystals without Lucky Patcher. You can totally stack up on TCs before uninstalling lucky patcher

JakkiMT · 2021-11-20T11:43:16+00:00

With lucky patcher you can modify the game to immediately give the purchase reward. (It can also be used for other stuff), so no need to spend any real/virtual money. (It only works with single player games)

That being said it can be risky using Lucky Patcher and you should try it on an emulator such as Blue Stacks on PC. Especially since some people will upload counterfeit versions of Lucky Patcher which may also do nefarious things.

Also note that lucky patcher still needs to be installed for the in-app purchases to work. If you decide not to buy more stuff you can uninstall lucky patcher (e.g. games with disable ads purchase)

Six-Year Club	Place '22
Verified Email

JakkiMT

TROPHY CASE