Thickness 1

[phk]

If I had a sheet metal plate 5"x5"x .023" thick what thickness would I be looking for to get the same strength in plastic ?? 30% more thickness 45% thicker ???
thanks, Phk

 

[ornerynorsk]

It depends on what grade of sheet the metal is, and what its physical properties are, and also on any criteria constraints as to what kind of plastic it will be replaced with. Also, flexibility and hardness come into play, as well as operating temperature and about a hundred other characteristics.

 

[insideman]

Please add information to your question. Are you loading the plate in tension or with a pressure against one side or what?

 

[patprimmer]

Much, much more info is needed to even begin to prepeare a recomendation

What is the application
What is the enviroment
What is the required life
How many parts are required
Is weight a factor
Is cost a factor Regards
pat

 

[Berserk]

Is it possible to add ribs on the new plastics?
This could help in lessening the thickness required on the plastics

 

[plasgears]

Both DuPont and Ticona give an analysis of plastic panels with ribs. Assuming that you are loading the panel spanwise, the plastic panel will typically have ribs thinner than the base. (When transforming from metal to plastic, the plastic part tends to look very different.) The ribs can extend bi-directionally (90 deg apart) in egg crate fashion.

The design criterion should be max deflection under load, whether you have a metal plate or a ribbed plastic plate. Of course, the stresses need to be manageable under both systems. Another variable is neat polymer or glass reinforced.

 

[Berserk]

Some former customers who make those new brakes for FORD (the one where you could adjust the height of the gas & break pedal) used to use metal sheets, then they change it to glass filled nylon (30%?) with LOTS of ribs.

 

[patprimmer]

In the early 80' Girlock in Australia designed a brake booster in GF PBT to replace the pressed steel parts, (and consequently ended up with a large export order for brake copmonents for the Corvette and some Pontiacs), but the material chioce was largely dependant on a large number of factors, including underbonnet temperatures and brake fluid resistance. From memory, the ribs were about 1" deep, whereas the sheetmetal was probably only about 18 or 20 gauge, but neither design was flat. So what?

Before any sensible comment can be made, details of critical properties and the environment of use need to be considered.

The temperature of the environment, and the load, and wether the load is constant or cyclic are most critical, as is the avaliable space for ribs. Does it need to be clear, or flame retardant? Is it in contact with any chemicals, including water? Which aspect of "STRENGTH" is being refered to, impact strength, tensile strength, flex modulus?

Regards
pat