FRACTURE TOUGHNESS CHARACTERIZATION OF FIBER-REINFORCED COMPOSITES

CONCEPT ANALYSIS CORPORATION (CAC) PROPOSES TO DEVELOP A NEW ANALYTICAL APPROACH FOR THE FRACTURE CHARACTERIZATION OF FIBERREINFORCED COMPOSITES. THE BASIC PHYSICAL FAILURE MODES IN THE FORM OF; FIBER BREAKAGE, MATRIX CRACKS, FIBER-MATRIX INTERFACE DEBOND, FIBER PULLOUT, AND MATRIX YIELDING (WHICH ARE CHARACTERISTICS OF THESEHETEROGENEOUS MATERIALS) WILL BE TAKEN INTO ACCOUNT BY PERFORMING A MICROMECHANICS ANALYSIS OF THE FIBER-REINFORCED COMPOSITE. A 3DIMENSIONAL ELASTOPLATIC, GENERAL ORTHOTROPIC FINITE ELEMENT CODE WITH CRACK INITIATION AND PROPAGATION CAPABILITY (WHICH IS AVAILABLE ON CAC'S VOX AND CELERITY COMPUTERS) WILL BE EMPLOYED FOR THE ANALYSIS. THE CRACK PROPAGATION CAPABILITY DEVELOPED BY THE PRINCIPAL INVESTIGATOR IS BASED ON THE VIRTUAL CRACK EXTENSION METHOD. THE MICROMECHANICS ANALYSIS WILL PREDICT THE FRACTURE TOUGHNESS OF THE UNI-DIRECTIONAL LAMINA AS A FUNCTION OF THE ENERGY RELEASE RATE CORRESPONDING TO THE ONSET OF UNSTABLE CRACK GROWTH FROM MICROSCOPIC FLAWS. A RELATION BETWEEN SIZE AND DENSITY OF MICROSCOPIC FLAWS IN THE FORM OF BROKEN FIBERS, MATRIX-CRACKS, FIBER-MATRIX INTERFACE DEBOND, AND THE FRACTURE TOUGHNESS OF THE FIBER-REINFORCED COMPOSITE WILL BE ESTABLISHED. THE INFLUENCE OF THE MATRIX MATERIAL DUCTILITY AND THE THERMAL RESIDUAL STRESSES DUE TO THE MANUFACTURING PROCESS ON THE FRACTURE TOUGHNESS OF THE COMPOSITE WILL BE STUDIED.