Title page for ETD etd-03312011-161421


Type of Document Dissertation
Author Gopinath, Gautam
Author's Email Address gopinag@vt.edu
URN etd-03312011-161421
Title Progressive damage and failure of unidirectional fiber reinforced laminates under impact loading with composite properties derived from a micro-mechanics approach
Degree PhD
Department Engineering Science and Mechanics
Advisory Committee
Advisor Name Title
Batra, Romesh C. Committee Chair
Bayandor, Javid Committee Member
Cramer, Mark S. Committee Member
Hendricks, Scott L. Committee Member
Stremler, Mark A. Committee Member
Keywords
  • impact analysis
  • damage
  • failure
  • uni-directional fiber reinforced laminates
  • Micro-mechanics
Date of Defense 2011-01-31
Availability restricted
Abstract
Micromechanics theories have been used to develop macro-level constitutive relations for infinitesimal elastoplastic deformations of unidirectional fiber reinforced laminates. The matrix is assumed to be isotropic and deform elasto-plastically and the fibers transversely isotropic and linear elastically. We have analyzed damage initiation, damage progression, and failure of 16-ply unidirectional fiber reinforced laminates impacted at normal incidence by a rigid sphere. The damage is assumed to initiate when at least one of Hashin’s failure criteria is satisfied with the evolving damage modeled by an exponential relation. Transient three dimensional impact problems have solved using the finite element method (FEM) by implementing the material damage model as a user defined subroutine in the FE software ABAQUS. From strains supplied by ABAQUS the subroutine uses the free shear traction technique and values of material parameters of the constituents to find average stresses in a FE, and checks for Hashin’s failure criteria. If the damage has initiated, the subroutine evaluates the damage developed, computes resulting stresses, and provides them to ABAQUS. The irreversibility of the damage is satisfied by requiring that the damage evolved does not decrease during unloading. The delamination failure mode is simulated by using the cohesive zone model and the degradation of material properties already available in ABAQUS. The computed time histories of the axial load acting on the impactor are found to agree well with the experimental ones available in the literature. The effect of stacking sequence in the laminate upon the impact load has been ascertained.
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