Material Models for Damaged Composite Laminates

Abstract

In long fiber composites with unidirectional or multidirectional orientation of the reinforcement several damage modes develop during the service life. The most typical and first damage mode is related to intralaminar crack formation in off-axis layers of prepreg laminates or in off-axis bundles in case of Non-Crimp Fabric (NCF) or woven composites. Accumulation of individual fiber fractures in layers oriented parallel to the main loading direction is also typical. More unusual are breaks of fiber bundles oriented in the loading direction observed recently in NCF composites. Part of the bundle interface can be debonded from the rest of the composite. Some examples are given in Fig.1. Common for these damage entities is that each damage mode is usually localized in a certain phase (in a fiber, matrix, at the interface, inside a bundle of a given orientation, inside a layer) and is characterized by a distinct orientation and size. This simplifies the damage characterization and model development.