Engineering & Analysis Methods > Material Strength Composites: Laminate Approach

Carpet plots to polynomial


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?

Here is one suggestion (assuming the raw data used to generate the plot is unavailable):

First, extract data from the carpet plots. I like to use WebPlotDigitizer ( Extract at least 10 or so data points along each %45 curve. Each data point will have three associated values: allowable, %0, %45.

Next, use the extracted data in Excel to perform multivariate regression to get the terms A-H for the polynomial equation. The allowable will be the dependent variable and the terms of our polynomial will be the independent variables (%0, %0^2, %45, %45^2, etc).

Here's a helpful link for multivariate regression in Excel:



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