Designing Composite Structures

Increased Complexity for Increased Accuracy of FEA models for Composite Structures

Reducing weight while improving structural performance and design aesthetics is a challenge every engineer faces. Composites are a great material alternative to drastically reduce weight in structural products. However, these materials are difficult to model because of their non-homogeneous material properties and their exceptional dependence on the manufacturing process to deliver maximum performance.

Complex shapes and degradation of material properties due to manufacturing add complexity to the modeling of composite parts, but they need to be captured to improve the accuracy of simulation models.

The video below explains why and how degradation of material should be included in a simulation model.

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It is important to take into account the effects of temperature, shear due to ply-draping, and material degradation due to manufacturing or other artifacts on your material’s elastic and strength properties. Typical controllable material properties include isotropic and orthotropic elasticity, orthotropic strain and stress limits, and Puck constants. Our example of a blade clearly shows this: A model that does not include any effects caused by imperfections would be considered safe, while the inclusion of all effects reveals critical areas that require design modifications.

Effect of including imperfections in the composites model:

Composites No Imperfection arrow Model without imperfections showing a safe design
Draping effect indicates potential issue in the bottom right had cornerarrow Composite Draping Effects
Composites Temperature arrowTemperature effect shows critical areas in the root and notch regions
Degraded material properties, in which the critical regions extend clearly (red areas)arrow Composite Tmat Properties

The blade model shown in the video also exhibits geometric complexity. This compressor blade is a thick structure with geometric singularities. To model this, it is necessary to use extrusion tools as well as cut-offs that are defined from CAD models. ANSYS tools perform these operations in an easy manner, while preserving the complexity of the shapes and applying proper cut-off rules to the layers in the composite model.