homogenizing a composite

[andrearrd]

Hi, I have the following problem. I have a certain layup, composed of, for example, 10 plies stacked at different angles (ie a laminate). I have all properties including ply thicknesses. If I have for instance a block of this layup, is there any simple program available that will allow me to find the equivalent 3D properties of a homogeneous "resulting material"? In other words, an equivalent material with certain properties in the 3 directions that will behave like the lamiante stack. All I have found so far is laminate programs which give me the equivalent properties only in the stacking plane.

Thanks in advance,
Andrea

 

[edrush]

Andrea,

There are no homogenous (i.e. isotropic) materials with equivalent properties.

The laminated plate program should give you tensile and bending stiffness in directions 1 and 2 (in plane). If your angle pys are evenly distributed about 360 degrees then the properties will be the same or similar in both directions. Direction 3 (though-the-thickness) will be much weaker and softer. If you are trying to simulate a loading condition in one of the in-plane directions you could use the bending or tensile stiffness or thermal expansion properties in the applicable dirction from the laminated plate program for an approximate calculation.

You could use micromechanics to determine your missing properties. It works well for some things, not so well for others.

I don't know of a laminated plate program which calculates properties in all 3 directions or one that deals with transverse loading, but if there is such a program available please share the information (anyone).

 

[gwolf]

When I have had these things calculated for me (I am a stress engineer only partly experienced in composites) the method goes something like this:

Use a laminate program to get the in-plane stiffness and then make some common sense approximations to the through thickness values based on matrix and fiber properties and volume fraction. This is usually good enough. If you have significant transverse behaviour you probably shouldn't be using composite laminates anyway.