Special Classes of Laminates — Lesson 1

This lesson covers the different types of laminate stiffnesses, including symmetric, anti-symmetric, and quasi-isotropic laminates. It explains how the characteristics of these laminates are determined by the geometrical and mechanical properties of the constituent lamina. For instance, the lesson highlights how the stacking sequence and mechanical properties of the lamina can influence the value of each element in the ABBD matrix, which defines the characteristics of a laminate. The lesson also discusses the role of each sub-matrix in the ABBD matrix, such as the A matrix representing extensional stiffness and the D matrix representing bending stiffness. The lesson further delves into special cases of laminate stiffness, including symmetric and anti-symmetric laminates, and how their characteristics can be manipulated to eliminate undesirable responses.

Video Highlights

04:37 - Introduction to special cases of laminate stiffness
05:36 - Symmetric laminates
14:15 - Symmetric cross ply laminate
22:27 - Balanced Laminate
29:28 - Anti-symmetric laminates
37:31 - Quasi-isotropic laminates

Key Takeaways

- The characteristics of a laminate are defined by the ABBD matrix, which is influenced by the geometrical and mechanical properties of the constituent lamina.
- Symmetric laminates have no bending-extension coupling, simplifying their analysis and preventing warpage during fabrication.
- Anti-symmetric laminates, while having bending-extension coupling, eliminate in-plane shear-extension coupling and bending-twisting coupling.
- Quasi-isotropic laminates behave isotropically under in-plane loading, providing both longitudinal, transverse, and shear stiffness.