Cold Fussion wrote:I would think that you're going to have to define you're own custom material and the material properties you enter will be of the resin + fibre composite. In introductory material science classes a composite material is often defined a linear mix of both elements, which varies based on the load direction relative to the fibre direction, however this is probably too simplistic for your analysis. Material science was never a strong point for me so I can't help you beyond that.
I used a Software called Autodesk Simulation Composite Design 2014, i went into New Item/New Lamina from Micromechanics
and then i defined the materials and their percentage as follow: E-Glass, 50% and Polyester 50% and after i clicked Calculate so the software gave me all the properties that are shown in the solidworks Properties manager, so now i will be making Ud study for many patter and angles and will the see the best of it !
I would like to here your Opinions please about this ?
Ok here is my response to a lot of whats been mentioned in this thread but possibly not clear.
Stress-Strain diagrams are simply an X-Y chart with Stress on the Vertical (Y) axis and Strain on the Horizontal (X) axis. The strain is the amount the material is increased in length divided by the original length as a result of an applied load. The stress is the applied load divided by the cross sectional area of the material you are testing for the stress strain chart. So if you have a metal rod, and you pull from both ends, as you stretch (strain) the metal, the material faces an amount of stress that is directly related to the strain.
Now if you look at the stress strain curves for a linear material, you will see a region that has a constant slope (the elastic region). The elastic modulus is related directly to this slope, so obviously a material with a very high modulus will take much more stress without "stretching" (straining) as much. A material with a high modulus would be carbon fiber or a high strength steel, while a low modulus material would be a rubber. Even when just looking at metals, steels will have a higher modulus than brass alloys...and aluminum will have a lower modulus than both. Even if they all had the same tensile strength, the aluminum will stretch or deflect more under load than the other 2 types of metals, but it may not fail.
So how can we use this elastic modulus when designing? If you do not want a material to Stretch, strain or deflect much at all, you would want it to be of higher modulus. That is what happens when you add fibers to a resin thus making it a composite (among other things). OR, if you are designing a part that you want to deflect more under a particular loading, you can use a lower modulus material. An example of this would be a part that is designed to retain elastic energy under loading, a spring, a rubber band...etc.
Now that we understand that a linear material is a material that has a constant slope in the elastic region on a stress strain curve, we can talk about how a NON-linear material is different. A non linear material will not have a constant slope, so that means that as the load is increased, the amount the material stretches (strains) will not be the same throughout the stress range. This matters if you are measuring the deflection of the steering wheel handles as well as other factors. Composites and most plastics are not truly linear. Metals are typically analyzed as linear unless they are being used past the elastic point on the stress strain diagram (you can see this is where the constant slope changes shape). However, for your analysis you simply don't have the data to construct a non-linear stress strain diagram for the solver to use. So we have suggested that you use a linear solver and just make sure you have plenty of margin.
Now for isotropic vs non isotropic. If a material is isotropic it will behave the same when stressed from all directions. A piece of 17-4PH stainless steel for example will be treated isotropically because it doesn't matter if you stress it side to side or up and down...it will always have identical material properties in all directions. But a material that is not isotropic will be stronger in one direction than the other. Composites are not even close to isotropic in nearly all cases...especially layups. A Ud composite will be very strong when stressed in the direction of the axis of the fibers. But if you stress the Ud composite perpendicular to the fiber axis, it will be less than 1/10th of the strength in the other direction. Now if you layup the material, you are just gluing sheets on top of each other without any fibers in the long direction. So now you have almost no long fiber reinforcement in the transverse direction.
We haven't even started to touch on Shear yet. With Isotropic materials, it is the same in all directions again...but with non isotropic materials it is not. There is inter laminar shear that will try to cause the layers to delaminate since they are relying on the resin only for the bond. Obviously some layers will be force to STRAIN more than other layers when they encounter a bending moment...if the resin cannot support the shear forces induced by this strain differential, the composite will delaminate.
It's also worth noting that adding fibers to the composite will help to increase the modulus so you will not have the steering wheel handles deflecting so much under normal use.
So you are in a difficult situation. Without having the exact non-linear properties, you cannot simulate this as non-linear accurately. And without the anisotropic (same as non isotropic) properties, you cannot simulate this as a non isotropic material. This is why we have said that for academic purposes, your best bet is to go with conservative material properties and run a linear isotropic simulation. The material properties you are using for e Glass are continuous fiber, but if you are using CSM then you need to go with a much lower tensile strength as I mentioned earlier.
firasf1dream wrote:Hello Guys,
I will be solving the problem this :
I used a Software called Autodesk Simulation Composite Design 2014, i went into New Item/New Lamina from Micromechanics
and then i defined the materials and their percentage as follow: E-Glass, 50% and Polyester 50% and after i clicked Calculate so the software gave me all the properties that are shown in the solidworks Properties manager, so now i will be making Ud study for many patter and angles and will the see the best of it !
I would like to here your Opinions please about this ?
thank you
If you are treating this as a continuous fiber material, your strength value will be much too high and your deflections much too low. CSM is just so much weaker than continuous as I have mentioned earlier.
Think if it this way...take several pieces of 30cm long string and pull them apart longways as if trying to break them. Now, chop them into many 1 cm pieces, arrange them in different directions, and glue them into a rod that is 30 cm long. They will no longer be nearly as strong because the glue dominates the load transfer instead of the fibers.
Can you see the table on page 73 of the book in the link below:
You wont get all the properties without actually testing. The strength referenced there is most likely in plane loading. but i would run this as a linear isotropic material and just make sure theres a high safety factor and never use it in a safety critical application.
sgth0mas wrote:You wont get all the properties without actually testing. The strength referenced there is most likely in plane loading. but i would run this as a linear isotropic material and just make sure theres a high safety factor and never use it in a safety critical application.
yes exactly i was thinking the same after i read the page 72 to 74, the say the Chopped strand mat is considered isotropic so from there i decided my last decision will be to use the properties from here and from the ones i calculated using the percentage method on Autodesk Simulation Composite Design and make a simulation for an Linear Isotropic material,
so you suggest that if a property is for example 100 MPa, i take it as 80Mpa for example to be on a safe side ?
Yes that would give you some margin. The other option is to just run it at 100 MPa and make sure you have even more safety factor at the end. Since you are running linear elastic, its really the modulus that will play a bigger role. Also, with it being linear you only need to run the analysis for each load case once and can scale for different load magnitudes of each case.
For example, if you ran the simulation at 100N, and you got a max stress of 25 MPa, but you decide that the load really may be double (200N), all you have to do is also double the 25MPa to get a new stress of 50 MPa. This is a property of a linear analysis.
sgth0mas wrote:Yes that would give you some margin. The other option is to just run it at 100 MPa and make sure you have even more safety factor at the end. Since you are running linear elastic, its really the modulus that will play a bigger role. Also, with it being linear you only need to run the analysis for each load case once and can scale for different load magnitudes of each case.
For example, if you ran the simulation at 100N, and you got a max stress of 25 MPa, but you decide that the load really may be double (200N), all you have to do is also double the 25MPa to get a new stress of 50 MPa. This is a property of a linear analysis.
ah ok great thank you so much for the help and thanks to all
sgth0mas wrote:How has the simulation worked out? Have you gotten the chance to start manufacturing?
hello sgthomas, hope you doing well
thanks for asking well now i am writing my report must finish because this week is my presentation and after will make some changes, the most part is around the weight distribution and forces static and dynamic on the chassis and suspensions
sgth0mas wrote:How has the simulation worked out? Have you gotten the chance to start manufacturing?
hello sgthomas, hope you doing well
thanks for asking well now i am writing my report must finish because this week is my presentation and after will make some changes, the most part is around the weight distribution and forces static and dynamic on the chassis and suspensions
Good luck! If you need someone to review it just PM me. Tomorrow i will only be doing housework and simple projects...but it seems as if youve got it:)
sgth0mas wrote:How has the simulation worked out? Have you gotten the chance to start manufacturing?
hello sgthomas, hope you doing well
thanks for asking well now i am writing my report must finish because this week is my presentation and after will make some changes, the most part is around the weight distribution and forces static and dynamic on the chassis and suspensions
Good luck! If you need someone to review it just PM me. Tomorrow i will only be doing housework and simple projects...but it seems as if youve got it:)
Thank you so much sgthomas i will show you the result when i finish but it's in french still didn't make the english version it's gonna go for later because might occur
still didn't make the english version it's gonna go for later because might occur