Modeling of fracture processes in laminate composite plates with embedded delamination
Mikhail A. Tashkinov
Perm National Research Polytechnic University, Russia
ABSTRACT. This work is devoted to research and development of models for
the processes of nucleation and growth of delamination in laminated
composite materials. Possibilities of fracture mechanics approaches using
virtual crack closure technique as well as progressive failure analysis based on
the failure criteria are demonstrated. Influence of the initial delamination size
on the rate of growth of the defect is studied. A comparative analysis of the
applicability of fracture criteria to modeling of samples with delamination
were performed, including implementation of element deletion algorithm.
The numerical results obtained with the studied methods were compared.
KEYWORDS. Composite laminates; Delamination; VCCT; Progressive failure analysis; Fracture criteria; Element deletion.
Several methods of simulation of the delamination in composite materials samples have been investigated. The effect
of defect size on the parameters of deformation and failure of the sample was established. Computational
experiments were performed to explore the possibility of the delamination simulation using progressive failure
models, applying various criteria.
It can be stated that a defect in the form of delamination has a significant influence on the strength of the samples and its
presence can be modeled using both methods of fracture mechanics and methods based on failure criteria. The energy
approaches for modeling the growth of the delamination seem more promising, however, because the methods using the
values of stress fields in the failure criteria, in general, impose additional conditions on the model’s geometrical properties.
Thus, the appearance of a singularity due to distortion of the geometry or features of the finite-element mesh, can prevent
achieving reliable results.
At the same time, disadvantage of the energy techniques is that they require a predetermine position of the delamination
in the structure. Thus, currently the combined methods are being developed, which utilize failure criteria for locating the
start of delamination and the fracture mechanics methods to modeling its subsequent growth .
The initial information about the presence of the delamination can be also obtained by experimental approaches. Among
them are the non-destructive testing methods such as acoustic emission, ultrasonic examination and others [30-33].
Another promising direction is embedding of the sensor elements, such as piezoelectric sensors and sensors, based on
optical fibers [34-36]. Indications of such sensors may be also used for verification of failure models as well as predictions
of durability of structures based on them.
Another approach to improve the models of delamination in composites is account of a different nature of defects. Thus,
in the case of manufacturing-induced defects, the occurrence of delamination is often accompanied by the presence of socalled “resin pockets”. In this case, a more accurate model is required, that considers resin as a separate component with
isotropic properties. Also, the temperature factors can affect the rate of growth, the effect of which may be incorporated
in the models with the appropriate constitutive relations.
Thus, based on the basic principles, including those reflected in this paper, for each specific case of the composite
structure the model that most closely simulates the formation and development of the defects can be created.
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