Hi, Does anyone have any advice on how to fit the polynomial expression for laminate properties to data from carpet plots please?

I've seen recommendations to enter laminate allowables as polynomials. I have carpet plots for several laminate properties, but can't get a reasonable match using the polynomial form. I've been running Excel solver with various constraints, but didn't get anything close.

Alternatively, if I can't get a good match, is there a way to define individual curves for a number of different %0 laminates, rather in the one equation?