Polymer Sheet Manufacturing Studies and Testing Development

Project Description

Materials Laboratory needed for research studies to help determine the current stress on molded sheets and in annealed sheet polymer plastic products. The various manufacturing methods we utilize for producing a stock plastic shape ( Sheets / Rods) causes stress in the sheet. This stress manifests itself as warpage when our customers machine the sheet product. We use a few annealing methods to remove the stress but we need research to help us determine the current stress within our as-molded sheet and in our annealed sheet products. We are looking for help in developing a standardized test to help us to measure residual stress in the compression molded sheets we produce. We want to use the testing to help us determine:
1. Is there residual stress in our as-molded sheet?
2. Which annealing process provides the best results for stress relieving in our sheet products?
Attached are documents that seem to be a method that could help us to determine residual stress and to confirm which annealing process gives us the best results.
1. Shrinkage test. Primary for film, but could maybe be adapted for sheet products
a. https://www.astm.org/Standards/D2732.htm
2. Layer removal test layer - This Layer removal technique gives the most consistent results for through-thickness residual stress measurements.
a. Primary for sheet, but could be adapted for rod products
i. Mechanical Determination of Biaxial Residual Stress in Sheet - Attached
3. Additional References for determining residual stress
a. A. Turnbull, A.S. Maxwell, S. Pillai, J. White, Measurement Good Practice Guide - Residual Stress in Polymeric Mouldings, National Physical Laboratory, 1998.
b. M.W.A. Paterson, J.R. White, Layer removal analysis of residual stress, J. Mat. Sci. 24 (1989) 3521.
c. R.G. Treuting, W.T. Read, A mechanical determination of biaxial residual stress in sheet materials, J. Appl. Phys. 22 (1951) 130.
d. ASTM E 837-99, Determining Residual Stresses by the Hole-drilling Strain-Gage Method.
e. A. Turnbull, A.S. Maxwell, S.J. Pillai, Material Sci, Residual stress in polymers - evaluation of measurement techniques 34 (1999) 451. - Attached

I'd like help to determine if any of these tests can be adapted or which is/are the best to get us the data we need? Would you have or know of a better test to measure residual stress? ASTM?

Is this something that you can help us create and perform the testing?