Defects characterization and evaluation of their effects on compressive failure of composite components

Abstract

In the design and certification of composite structural components for aircrafts, compression and combined compression and shear loading cases have to be considered. Various forms of defects such as ply waviness, delamination and porosity can be generated during the fabrication and service life of composite structures. Compressive strength is very susceptible to the existence of these defects. To evaluate the effects of two major defects, ply waviness and delamination, experimental and numerical studies are performed. Compression test is designed for the unidirectional (UD) composite coupons with in-plane fiber misalignment. The fiber misalignment is introduced by tilting the fiber orientation with a small angle (from 1° to 5°). A continuum damage mechanics (CDM) model is adopted in the numerical analysis. The capability of the CDM model in predicting the effects of defects is first verified using compression test results of unnotched specimens and then it is used in predicting the effects of ply waviness and delamination on the compressive strength of open-hole (OH) specimens.