First-ply failure
In a [0/90]s laminate pulled along 0°, the 0° plies carry 94% of the load; the 90° plies still crack first, at about 500 MPa laminate stress, while the 0° plies are at 41% of their strength. With the cracked plies discounted the laminate loses 6% of its stiffness and carries on to about 1,150 MPa.
Predict · at 0:27 in the video
When the first ply cracks, does the laminate break?
Usually not. At about 500 megapascals across the laminate, the ninety plies reach their 60 and crack. The zero plies are at 936, well under half their strength.
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.
