2.3.4 Experimental laminas

Experimental laminas are not derived from other object’s properties, but rather they are basic objects like fiber and matrix. Here you have to enter all the properties, assuming you know them from experiments. Hint: If you don’t know all the properties, you can start the lamina as unidirectional, save it, then change its type to Experimental. CADEC will populate all the fields with predicted values, and then you can change only those for which you have data.

When you create \includegraphics[width=14pt]{./Images/New.png} or edit \includegraphics[width=14pt]{./Images/Edit.png} a lamina, you get a page like this:

The screenshot above is for a Unidirectional lamina, but you can easily change to Experimental, Fabric, or CSM by selecting the radio buttons.

Many engineers, mainly in the aircraft industry, work with experimental laminas. This is because they use mostly prepreg and they get the properties of the cured prepreg from the manufacturer. This means they cannot change the fiber, matrix, or volume fraction as they are fixed for the prepreg they are using. Since they have the properties of the lamina, they do not need to use Chapter Micromechanics.

However, before you rush to click the radio button for Experimental, consider that, for the most comprehensive analysis, the Experimental lamina requires 22 properties: 6 intrinsic properties (for which Cadec gives you default values), 5 moduli, 7 strengths, 2 coefficients of thermal expansion (CTE), and 2 coefficients of moisture expansion (CME). Good luck finding all those values!

Well... you can cut yourself some slack by first considering the lamina as unidirectional. Use a Fiber, a Matrix, and a fiber volume fraction Vf similar to the one used in your prepreg. Save the lamina. This will calculate all 22 properties using Micromechanics. Now click the button Experimental and you will see the calculated values. Next, overwrite the properties that you got from the manufacturer. The rest of the values are good approximations provided that you entered the correct fiber, matrix, and Vf.

You must give a Name to the new lamina, then select the Fiber and Matrix using the drop down boxes. As you can see, only the fibers and matrices that you previously entered in your database are now available for use. Therefore, it is a good idea to populate your database with the most common fibers and matrices that you expect to use in your work.