Time-temperature analysis of damage initiation and growth in composite laminates
Polymer-based composites are used in aerospace structures due to their high strength to weight ratio. However polymers also exhibit time-dependent behavior and this behavior may in turn be affected by high temperature and humid environments. Long-term effects manifest themselves in the form of loss of stiffness and/or strength. And, in this regard, the contributing factors could stem from the time-dependent material behavior as well as the accumulation of damages in time. Clearly, generic methodology is needed which addresses the fundamental issues caused by both of the contributing factors. The objective of the present study is to investigate the time-dependent damage initiation and growth behavior associated with the various sublaminate damage modes in polymer-based composites. A quasi-three dimensional finite element procedure is first developed based on the linear theory of viscoelasticity for simulating sublaminate damages in composite laminates. Specifically the unidirectional plies of the laminate are represented by a set of linear anisotropic, viscoelastic constitutive relations. Damage modes in the forms of transverse cracks, delamination of fiber-wise splitting are incorporated in the analysis by means of appropriately evolving local boundary conditions. Calculation of the stress fields and fracture parameters such as the strain energy release rates (G) and the stress intensity factors (K) associated with the different modes of damage and a different stages of evolution are also made a part of the routine. Numerical solutions are obtained by a convolution as well as a quasi-elastic technique. To illustrate the applicability of the numerical routine, the problem of fiber-wise splitting is chosen. Since fiber-wise splitting is a mixed-mode type of failure, an appropriate mixed-mode fracture criterion is needed for predicting its onset and growth.
- Research Organization:
- Drexel Univ., Philadelphia, PA (United States)
- OSTI ID:
- 7020323
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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