Stiffness isn't strength
Turn a carbon ply 5° off the load and it keeps 88% of its stiffness but only about a third of its strength (845 of 2,300 MPa by max stress); and unlike stiffness, strength differs in tension and compression (2,300 / 1,725 along, 60.2 / 275.8 across). Strength takes five numbers.
Predict · at 0:26 in the video
So how much of its strength does it keep?
About a third. Along the fibres, this ply takes 2,300 megapascals. Five degrees off, about 850, by the simplest criterion.
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.
