An introduction to composites terminology and modeling methods.


Composite modeling terminology.

An individual composite part constitutes one laminate:
  • Laminates are made by stacking plies in a given sequence
  • Plies are made up of two or more constituents (typically fiber/matrix)
  • Laminate zones are areas of constant thickness within a laminate
  • Reference orientation defines the common orientation fiber directions are rotated from

Figure 1.

Modeling Methods

Composite modeling methods.

Shell-based modeling methods for composites include Ply-Based Shell Modeling and Zone-Based Shell Modeling.

Ply-Based Shell Modeling

Ply-based modeling.

Ply-based modeling provides an FEA methodology which is consistent with the composite manufacturing process. The ply-based modeling entities replace, and can generate, typical solver zone-based composite properties.

A valid ply-based model contains the following entities:
Typically, one laminate per physical part is defined. Primarily, laminates contain the stack of plies. Additionally, laminates specify symmetry and repeats of plies within a laminate, along with information that can manipulate the ABD matrices.
Plies define the material, thickness, orientation (from reference on element/property material direction), shape (Elements, or element sets if FEA-based. Lines, surfaces or solids if geometry-based), and ply type (the material product of the ply).
Template Property
If user profile is OptiStruct, a PCOMPP is used. If another user profile is selected, a standard zone-based composite shell property is used. The property defines typical solver specific attributes like offset and non-structural mass. Layer information does not need to be entered. It is automatically populated from the defined plies and laminate.
Consider the following composite part which is made up of 1 laminate, 7 plies and 1 template property:

Figure 2.

Ply-based models can optionally be used to generate zone-based shell models, continuum shell, and solid models.

Zone-Based Shell Modeling

Zone-based modeling.

Zone-based models define a table of layer properties at each zone of constant thickness. The layers on each property contain similar information to the HyperMesh ply, but do not explicitly convey information about the shape of the as manufactured ply. Some solvers do provide the ability to define a “global” id/name, which specifies how layers connect from zone to zone.

Figure 3.