Quasi-isotropic
Equal numbers of plies at equally spaced angles (0, ±45, 90, or 0, ±60) give the same in-plane stiffness in every direction (54.7 GPa for this ply), but not the same bending stiffness: an 8-ply [0/±45/90]s bends about four times stiffer along 0° than along 90°.
Predict · at 0:48 in the video
So rotate a quasi-isotropic laminate by fifteen degrees. Does its stretching stiffness change? And its bending stiffness?
Stretching: no. It's 55 in every direction. Bending: yes.
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.
