The scale effect in composites: An explanation physically based on the different mechanisms of damage involved in failure

The strength of a lamina of a laminate was considered from almost the very beginning of the application of composites as a value depending on the lamina thickness. This was generically called scale effect, the value of the stress at the appearance of first damage in a lamina being identified as the in situ strength. The ultra-thin plies have allowed this first damage, typically transverse cracks in the 90-degree laminas, to be delayed. This...