Progressive Failure Analysis of Composite Open-Hole Tension Tests Based on Schapery and Crack Band Theories Ö. Şener∗, A. Kayran 1 METUWIND Center for Wind Energy Research, Middle East Technical University, Ankara 06800, Turkey ∗ osener@metu.edu.tr Keywords: Schapery Theory, Progressive Failure Analysis, Composites Due to their high strength, stiffness, and low density, the use of fiber-reinforced composites (FRP) has accelerated tremendously during the last half-century. The formed FRP laminae are innately orthotropic and can theoretically be modified in an infinite variety of configurations. For such complex structures, progressive failure analysis (PFA) methodologies that can predict failure initiation and progression are required. The fundamental source of nonlinearity in the stress-strain response of many polymer matrix composites is matrix microdamage. The pre-peak softening phase that transpires due to matrix microdamaging is often neglected in PFA methods. Schapery theory (ST), a thermodynamically based work potential theory, was designed for simulating matrix microdamage in FRPs [1][2]. The ST manages the evolution of damage inside the material by diagnosing the correlations between transverse/shear response and the dissipated potential induced by matrix microdamage. In Enhanced Schapery Theory (EST), an extended version of ST, it is presumed that matrix microdamage confines into more pronounced damage modes and failure initiates in which the element domain is no more viewed as a continuum, and the embedded discontinuities are characterized using crack band. This work proposes a failure analysis tool modeled and employed in readily available explicit finite element analysis software ABAQUS as user-defined material model subroutine (VUMAT) which comprises nonlinear microdamage as well as mesh objective failure evolution. The developed tool uses mechanical properties of the composite obtained from the characterization tests. Nonlinearity of the transverse & shear moduli are taken into account with empirical polynomial functions acquired from tests of coupons with varying stacking sequences. Crack Band Theory (CBT), a nonlinear mesh objective failure evolution method, is used in the post-peak phase [3]. This study aims to compare failure predictions using the developed method with experimental results and ABAQUS built-in failure criteria. Experimental and numerical studies are conducted on unidirectional (UD) composite open-hole tension (OHT) specimens. Preliminary analyses indicated that the developed EST-integrated method outperforms the ABAQUS built-in failure model for plane stress problems. Moreover, as additional work to be conducted, strain contours of the specimens will be acquired using Digital Image Correlation (DIC) and compared with the numerical results. The validity of the user-defined material model subroutine will also be assessed. References 87
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