Mixed mode I + II interlaminar fracture of carbon/epoxy laminates

• Published in: Composites. Part A, Applied science and manufacturing Applied science and manufacturing, 2008-02, Vol.39 (2), p.322-333
• Main Authors: Pereira, A.B., de Morais, A.B.
• Format: Article
• Language: English
• Subjects: A. Polymer–matrix composites (PMCs); Applied sciences; B. Delamination; B. Fracture toughness; C. Finite element analysis (FEA); Exact sciences and technology; Forms of application and semi-finished materials; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Laminates; Physics; Polymer industry, paints, wood; Solid mechanics; Structural and continuum mechanics; Technology of polymers
• ISSN: 1359-835X; 1878-5840
• DOI: 10.1016/j.compositesa.2007.10.013

This paper reports a study of the mixed mode I + II fracture of carbon/epoxy unidirectional and multidirectional specimens with symmetric, quasi-symmetric and markedly asymmetric legs. A beam model was developed for predicting the compliance and total strain energy release rate, G. Its predictions agreed well with three-dimensional finite element models and with experimental data of double cantilever beam, end-notched flexure and mixed-mode bending tests. The mode mix was determined from a virtual crack closure technique limit value analysis, in order to overcome ambiguity for delaminations between differently oriented plies. Initiation G c values versus mode II ratio G II/ G plots had practically identical shapes, showing a linear G c increase with G II/ G ⩾ 25%. Multidirectional specimens with quasi-symmetric and markedly asymmetric legs had similar G c values.