From ply to laminate
A laminate's stiffness is three 3×3 matrices built by adding up its plies through the thickness: A (stretching) weights every ply equally, D (bending) weights it by the cube of its distance from the mid-plane, so in eight plies the outer two give 58% of the bending stiffness; B couples the two.
Predict · at 1:04 in the video
So is a laminate's stiffness just the average of its plies?
For stretching, yes. A is the plies added up, all counted equally. For bending, no.
This course is our own. These books go deeper.
- Basic Mechanics of Laminated Composite Plates, A. T. Nettles, NASA Reference Publication 1351, 1994
- Mechanics of Composite Materials, R. M. Jones, Taylor & Francis, 2nd ed., 1999
- Engineering Mechanics of Composite Materials, I. M. Daniel & O. Ishai, Oxford University Press, 2nd ed., 2006
- Design and Analysis of Composite Structures, C. Kassapoglou, Wiley, 2nd ed., 2013
- Composite Materials Handbook (CMH-17), Volume 3, Rev. G, CMH-17, SAE International, 2012
The course designs in AddPly, our browser app for laminate design: regions, ply stacks with live stacking-rule checks, thickness, mass and the ply book. It does not do strength, failure or draping; where a lesson covers those, the simulation is our own.
Simulations in this lesson are our own. Ply data come from the datasheet or textbook named on screen; where a number rests on an assumption, the video says so.
