Proceedings of the 27 th Risø International Symposium on Materials Science: Polymer Composite Materials for Wind Power Turbines Editors: H. Lilholt, B. Madsen, T.L. Andersen, L.P. Mikkelsen, A. Thygesen Risø National Laboratory, Roskilde, Denmark, 2006 QUANTIFICATION OF DAMAGE AND EVOLUTION MODELING IN MULTIDIRECTIONAL LAMINATES Janis Varna Luleå University of Technology, SE 97187 Luleå, Sweden ABSTRACT The evolution of intralaminar cracking in laminates is analyzed using fracture mechanics approach for steady-state crack propagation and calculating the energy release rate, G using the crack closure technique. The work to close the crack is related to normalized average crack opening and sliding displacements which have been analyzed in details previously in (Lundmark et al 2005, 2006) where the relationships were described by power laws. These analytical fitting functions of FEM results allow using simple closed form expressions for G for laminates with an arbitrary orientation of cracked plies, materials and stacking sequence. Crack density versus applied strain data for reference cross-ply laminate in monotonously increasing quasi-static loading are used to determine the statistical distribution of 90 o -layer fracture toughness in Mode I. Microcracking simulation in plies of laminates where Mode I crack growths is the dominating mechanism is performed. 1. INTRODUCTION Microdamage in plies of laminates is a result of complex combinations of mechanical and environmental loads. Intralaminar (transverse) cracking, caused by combined action of transverse tensile stress and shear stress in a ply, is the first mode of damage. The crack is usually well defined and the crack plane is transverse to the laminate middle-plane. They propagate in a ply parallel to fibers. Typical damage evolution data are presented in Fig.1 showing appearance of first cracks at about 0.6% strain. With increasing strain many new cracks appear and the rate of the crack density change increases, slowing dawn again at high crack density. 349
QUANTIFICATION OF DAMAGE AND EVOLUTION MODELING IN MULTIDIRECTIONAL LAMINATES
Jun 16, 2023
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