Modeling Interfaces Through an Extension of Continuum Mechanics to the Nanoscale with Application to Fracture and Debonding of Composites
Final rept. 1 Apr 2006-31 Dec 2007
TEXAS A AND M RESEARCH FOUNDATION COLLEGE STATION
Pagination or Media Count:
This report summarizes the progress made in developing the theoretical underpinnings for a new theory of brittle fracture based upon an extension of continuum mechanics to the nanoscale. In contrast to classical fracture theories, the new theory predicts bounded crack tip stresses and strains by including a novel boundary condition arising from the jump momentum balance enforced on fracture surfaces which are modeled as dividing surfaces with excess physical properties including surface free energy, surface tension and surface entropy. As a result of the bounded crack tip stresses and strains, it was necessary to introduce a new notion of crack tip Energy Release Rate ERR, a new fracture criterion based this new ERR and a method to estimate from first principles the corresponding Critical ERR cERR. Estimates of the cERR for diamond, silicon and silicon-carbide compared favorably with published NIST data with no adjustable parameters.