Effective properties
Invert A and divide by the thickness to get engineering constants you can compare: Ex 73.8 / 54.7 / 23.4 GPa and Gxy 6.9 / 21.2 / 35.6 GPa for [0/90]2s, quasi-isotropic and [±45]2s; from AddPly's own A table, Ex = (A11² − A12²)/(A22·h) = 54.7 GPa and νxy = 0.286.
Predict · at 0:36 in the video
Which pulls stiffer along zero: zero, ninety, twice symmetric, or quasi-isotropic? And by how much?
Zero, ninety: about 74 gigapascals against 55. But in shear it's the reverse: 7 against 21, and plus and minus forty-five reaches 36. Poisson's ratio swings too: almost zero for zero, ninety, and 0.7 for plus and minus forty-five.
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.
