Multiscale Analysis of Interlaminar Stresses Near a Free-Edge in a [±45/0/90]s Laminate
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© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. A multiscale model for a [±45/0/90]s laminate under uniaxial extension was used to investigate the effect of modeling the heterogeneous microstructure of unidirectional laminae near a free-edge. A random fiber arrangement was used for the entire 00 and 900 plies, and the predicted interlaminar normal stress was compared to the prediction using a classical homogeneous model, where all laminae are treated as homogeneous, orthotropic plies. The displacements along the boundaries of the models matched well, but the interlaminar normal stress near the free-edge differed significantly between the two models. When fibers and matrix were modeled discretely, the interaction of neighboring fibers created a complex stress pattern along the ply interfaces, especially the 0-90 ply interface. The interlaminar normal stress for two paths parallel to the y-axis along the 0-90 ply interface showed that the peak stress occurred at the free-edge for a path near a 900 fiber and occurred about two fiber diameters from the free-edge for a path near a matrix rich region of the 900 ply. After the classical homogeneous model was compared to the case where the entire 00 and 900 plies were modeled as discrete fibers and matrix, the effect of reducing the size of region modeled at the microscale was investigated, since this would significantly reduce the computational effort. For two cases, the region modeled at the microscale was reduced in the direction normal to the ply interface in the 00 and 900 plies to a size that was 25% and 10% of the ply-thickness. For any point with a significant stress, the two models introduced a maximum of 38% and 20% error respectively, but the peak stresses only changed by 1% and 6% respectively. Next, reducing the microscale region in the direction normal to the free-edge to be one and two ply-thicknesses in size did not have a significant effect on the predicted interlaminar normal stress at points within 75% of a ply-thickness of the free-edge.
author list (cited authors)
Ballard, K., & Whitcomb, J. D.