### 5.4.1. Overview

Classical Laminate Theory provides useful information about the mechanical behavior of a composite structure. The in-plane and flexural laminate stiffness represent characteristic values which can be compared with other laminates. These information can be quite useful since no external loads and boundary conditions are necessary to evaluate these values.

Classical Laminate Theory is described in many text books ([ 34 ] and [ 35 ]). The basic assumptions are:

- Layers are perfectly bonded together.

- The material properties of each layer are constant through the thickness.

- Linear-elastic strain-stress behavior.

- Lines originally straight and normal to the mid-plane remain straight and normal in extension and bending.

- Plane stress state.

- In-plane strains and curvature are small compared to all other dimensions.

This requirements are fulfilled in a relatively thin or moderate thick laminate where the thickness is small compared to the in-plane extensions (length and width).

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