Thickness of material to support a heavy load

[malek340]

My situation is i have a 10kg battery that is mounted on top of a plastic material. How would i exactly calculate the right thickness for the plastic to support the 10kg battery?

 

[huntoon]

first you need to know what the other two dimensions are. the third dimension - it's thickness- will be dependent on them.

second, you need to describe the exact type of plastic.

 

[malek340]

Other two dimensions?

 

[Travis_King]

The length and width of your piece of plastic (along with the locations of any supports) will dictate the thickness required to support the load.

The type of plastic, as well, will be a required known.

 

[Studiot]

Personally I'd go for some glass fibre reinforced plastic or perhaps steel mesh reinforced.

A sheet up to 400mm x 400mm x 5 mm thick would readily take a 10Kg point load if supported on two or four edges.

Is this for a boat or car?

 

[malek340]

What if i were to use syntactic foam for the base to support the load?...Give me your thoughts anyone..

 

[huntoon]

What if i were to use syntactic foam for the base to support the load?...Give me your thoughts anyone..

dude, it really depends. how accurate do you need to be? how important is that accuracy?

you need an exact material spec to start. then you need to model the 3 dimensional structure.

the basic strength analysis would be to determine thickness by strength necessary for a given cross section.


i mean who knows about this foam? it could be super strong in tensile but super weak in yield or compression.


you could always run tests of varying thickness foam. it would super awesome if you documented the process and and posted links or info here.

 

[Studiot]

What if i were to use syntactic foam for the base to support the load?...

What if you did?
What would you then support that on?

 

[Travis_King]

Or you could just by a piece of really thick plastic. It's not that expensive. There's no sense modelling it, jut build it bigger than it needs to be.

 

[malek340]

Do u have any formula to calculate the thickness needed?

 

[zero_delta]

google "strength of materials + bending stress" and youll see equations like:

E = (P*L^3)/(4*w*y*t^3)

For E you can use modulus of elasticity. P is the load, L is the length, w is the width, t is the thickness and y is the deflection or bending. Look up E, solve for t.

 

[malek340]

By p/load, you meant the force or the weight of the load and the length and with is of what?

 

[zero_delta]

For P use weight. I prefer SI units and in this case it would be 10kg * 9.8 m/S^2 or 98 N.

The dimensions (L, w, t) are for the plastic or whatever supporting material you wish to use.

 

[malek340]

Thank you very much!

 

[malek340]

Hey bro, but by Y, what does it mean by deflection at load point?? Sorry, i need to know this

 

[zero_delta]

While considering the center of mass of the battery to be the load point, and the battery would be on the center of the supporting material, y is the maximum amount of bending from a neutral flat position.

These types of equations are great, but this is just about as simple as they get. The expression I gave is for a highly idealized and restricted situation.

 

[Studiot]

Bear in mind, zero delta, that the OP has already been asked about the available supports without response.

 

[malek340]

So if i do not want it to bend, meaning i will calculate y as zero. I do not have the material with me and most importantly do not want it to bend while supporting the load.

 

[afreiden]

Everything bends, even if you can't see it with the naked eye.

 

[rcremont]

If you have a Mechanics of Solids/Mechanics of Materials book I would refer to them. The type of chapters in those books you are looking for is "Bending of Straight Beams" and "Bending of Flat Plates" or just general beam deflection/thickness theory. But from intuition alone, you are working with a 10 kg load = 22 lbs, considering a common plastic = PVC, I would say that a thickness of 5-8 mm thick depending on the other two dimensions because bending would have to be considered. Any more than 8mm would be excessive.

 

[Travis_King]

Any more than 8mm would be excessive.

So? PVC is generally not a cost prohibitive material...A nice thick sheet of PVC will not cost too much more than a relatively thin sheet, and you will get the benefits of both rigidity and strength.

 

[rcremont]

@ Travis King

I wasn't considering cost because I understand that PVC is very inexpensive compared to other materials. Anything greater than 8 mm that would be not necessary. The OP wanted an exact number or range to go and purchase otherwise he/she wouldn't have posted and would have just went out and purchased a sheet themselves. Also I am assuming this is for a car or some other environment where size does matter.