I am looking to test the FlexiForce sensor in measure force, however for accurate readings the load needs to be disturbed evenly over the sensing area. As such I am having "discs" made to cover the sensing area. For my application the thinner the material of the disc the better (1 mm or less in thickness). Which of the following materials will be most suitable to manufacture the disc for the stiffest/strongest possible part?

  1. Brass & Copper
  2. Aluminium
  3. Stainless Steel
  4. Mild/Carbon Steel

The disc will be 25.4 mm in diameter with a thickness of 1 mm.

Here's an illustration of what I mean:

  • $\begingroup$ The densities of the materials you list vary greatly. Are you sure that a 1mm disc of aluminum will meet your needs? I ask because 1mm seems to be your only limiting requirement. $\endgroup$
    – hazzey
    Dec 2, 2015 at 15:46
  • 1
    $\begingroup$ What is the maximum load you are looking to measure on this sensor? None of those should deform if you're looking at a 1 pound load or less, but that might change if you go up to 100lbs. A range of weights is necessary to determine which material is most suitable. $\endgroup$ Dec 2, 2015 at 16:20

2 Answers 2


Which of the following materials will be most suitable to manufacture the disc for the stiffest/strongest possible part.

It seems that you need a material that will transform a non-uniform load into a more-or-less uniform load by providing consistent bearing. As such, you're looking at something like a plate on an elastic foundation, albeit on a much smaller scale. This type of problem can be quite complex due to the interplay between the stiffness of the plate and the foundation and the loading on the plate.

The only variables you seem to have locked down are the 1 mm thickness and 25.4 mm diameter of the disc. Strength is not an issue here (assuming you have a ductile material); stiffness is the only real requirement.

If you are truly looking to get the stiffest material for your disc, the carbon steel you have listed is probably your winner, with stainless a possibility depending on the alloy. Assuming all the discs have the same thickness/diameter, the only thing that will then affect stiffness is the material's modulus of elasticity. The greater the modulus, the stiffer the disc.

Tungsten carbide might be worth looking into for your disc as well. It's incredibly stiff (twice that of steel) and not terribly expensive.

  • $\begingroup$ Thank you, very well answered. I shall go with the carbon steel. Unfortunately my go to manufacturer does not offer tungsten carbide. $\endgroup$ Dec 3, 2015 at 4:33

1) I've used several brands of FSRs, including FlexiForce and you're very unlikely to get results usable in trade; their responses to pressure vary with temperature (because, I suspect, the stiffness of the polymers in the sensor itself vary w/temp.)

2) The application guides I've read strongly suggest NOT using extremely stiff materials or sharp radii in direct contact with the sensor that can cause stress concentrations.

3) The stiffness and shape of both what's on top of the sensor and what's underneath both matter.

4) all of the materials you're considering are orders of magnitude stiffer than the sensor, so they'll likely give you equally wrong and expensive results.

5) I suggest you first try either thin disks or very-slightly rounded domes made with something like Nylon or HDPE (High-density polyethylene, AKA cutting-board plastic.) I suspect you can back those with disks of a more rigid material; steel would be fine.

6) The disk has to be same-size or slightly smaller than the sensor's active area, or else some of your load will bypass the active area, leading to systemic errors. And you'd better radius the edges, lest you create a stress concentration right there.


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