# Equivalent Single Layer (ESL) Theories

Reddy (2004) [reddy2004] defines two main group of models used to simulated laminated composite materials, the 3-D models and the 2-D models where the real three-dimensional structure is treated as a two-dimensional shell that translates and rotates.

The ESL theories are those using the 2-D kinematic assumption and many models are derived, depending how the in-plane strains are changing along the shell thickness.

Among the ESL models, the Classical Laminated Plate Theory (CLPT) and the First-order Shear Deformation Theory (FSDT) will be further detailed in the sections below.

- CLPT - Classical Laminated Plate Theory
  - Description
  - Models
- FSDT - First-order Shear Deformation Theory
  - Description
  - Models