Paper number 176

STIFFNESS LOSS DUE TO TRANSVERSE CRACKING AND SPLITTING IN CROSS-PLY LAMINATES UNDER BIAXIAL LOADING

Maria Kashtalyan and Costas Soutis

Department of Aeronautics, Imperial College of Science, Technology and Medicine
Prince Consort Road, London SW7 2BY, UK

Summary

In an effort to evaluate the stiffness degradation of composite cross-ply laminates due to matrix cracking both in the 90o and 0o plies, a new theoretical approach was developed. It employs the Equivalent Constraint Model (ECM) [1, 2] and subsequent an improved 2-D shear lag analysis to determine stress field in the damaged laminate. In-situ Damage Effective Functions (IDEFs), used to describe stiffness reduction of the cracked or split lamina, were found to depend explicitly upon the crack density in the damaged lamina and implicitly upon the crack density of the neighbouring lamina. Theoretical predictions for CFRP and GFRP laminates revealed significant reduction in the shear modulus and Poisson's ratio due to splitting. Comparison of the new approach with existing models has shown reasonable agreement.

Keywords

transverse cracking, splitting, cross-ply laminates, stiffness degradation, 2-D shear lag analysis, Equivalent Constraint Model