The orientation of the fibers within each ply of a composite layup
plays an important role in determining the physical qualities of your model;
however, defining this orientation in a model based on a real-world application
is not straightforward.
Composite layups in
Abaqus/CAE
make the process more manageable by deriving the orientation of the fibers from
three parameters that are relative to each other—the layup orientation, the ply
orientation, and an additional rotation—as shown in
Figure 1.
Figure 1. Determining the ply orientation.
Layup orientation
The layup orientation defines the base or reference orientation of all the
plies in the layup. In conventional and continuum shell layups,
Abaqus
projects the specified orientation onto the surface of the shell, aligning the
direction of the layup orientation that you choose with the shell normal. In
solid composite layups the orientation is not projected.
Abaqus/CAE
provides several options for defining the layup orientation:
Part global: By default, the layup orientation is
the same as the orientation of the part.
Coordinate system: You can create and select a
datum coordinate system that defines the orientation.
Discrete orientation: You can create a discrete
orientation that provides an orientation value for each mesh element to define
the orientation.
Discrete field: You can create and select an
orientation discrete field that defines a spatially varying orientation.
User-defined: You can define the orientation in
user subroutine
ORIENT. This option is valid only for
Abaqus/Standard
analyses.
Normal direction: For all options except
User-defined, you can choose which axis defines the
approximate normal direction of the composite layup.
Additional rotation: If you choose a
Coordinate system, Discrete
orientation, or Discrete field to define the
layup orientation, you can specify an angle (in degrees) that defines an
additional rotation about the specified normal direction for the entire layup.
You can use a scalar discrete field to specify a spatially varying additional
rotation angle.
Ply
orientation
The ply orientation defines the relative orientation of each ply. In
conventional and continuum shell layups
Abaqus
projects the specified ply orientation onto the surface of the shell so that
the ply normal direction is aligned with the shell normal and the layup
stacking direction. In solid composite layups the plies are created with
respect to the layup stacking direction, and the unprojected ply orientation
defines the material orientation within a ply (see
Figure 2).
Figure 2. Plies and ply orientations for shell and solid composite
layups.
Abaqus/CAE
calculates the ply orientation from a combination of two variables that you can
specify—the coordinate system (CSYS) and a
rotation angle about the normal direction.
In cases where
Abaqus/CAE
attempts to draw coordinate systems for ply orientations in composite layups at
singularity points of the system (i.e., points for which the user-selected
coordinate system and the geometric normal from either geometry or elements
cannot be resolved into a valid orientation for display purposes in
Abaqus/CAE),
the coordinate system will be drawn collapsed.
If the layup orientation is specified using a discrete field, no display is
available for either the layup or ply orientation. For continuum shell
elements,
Abaqus/CAE
does not project the displayed orientations onto the midplane surface. In both
of these cases, you can perform a data check and view the output database in
the Visualization module
to verify the orientations. For more information, see
Performing a data check on a model.
Coordinate system
Abaqus/CAE
provides the following options for defining the coordinate system of the ply:
Layup: By default, the coordinate system of the ply
is the same as the coordinate system of the layup.
CSYS: You can create and select a datum coordinate
system that defines the coordinate system of the ply. If you choose to use a
coordinate system for a ply, it overrides the layup orientation for that ply.
You can also select the axis of the coordinate system that defines the
normal direction of the ply. The axis that you choose appears as the last digit
in the CSYS column in the layup table. For example,
Datum csys1.3 indicates that you chose
Datum csys-1 to define the coordinate system of
the ply, and you chose the 3-axis to define the
normal.
Rotation
angle
The rotation angle defines the orientation of the fibers within each ply
relative to the ply's coordinate system. For example, in a typical composite
the fibers might be oriented at −45° or +90° relative to the coordinate system.
You can also use a scalar discrete field to specify a fiber orientation that
varies spatially across the ply. If you specify a rotation angle, the ply is
rotated counterclockwise about the coordinate system normal, and the angle is
measured relative to the 1-axis.
Figure 3
shows the orientation of four plies in a composite layup and the corresponding
entries in the layup table.
Figure 3. Determining the orientation of each ply.
Abaqus/CAE
determines the ply orientation as follows:
You selected the layup orientation to define the coordinate system of
VerticalTape-1 and entered a rotation angle of 0°. The
resulting ply orientation is along the 1-axis of the layup orientation.
You selected the layup orientation to define the coordinate system of
VerticalTape-2 and entered a rotation angle of 90°. The
resulting ply orientation is a rotation of 90° counterclockwise about the
3-axis (the normal direction) of the layup orientation. The rotation angle is
measured relative to the 1-axis.
You selected Datum csys-1 to define the coordinate
system of DiagonalTape-1 and entered a rotation angle of
0°. The resulting ply orientation is along the 1-axis of Datum
csys-1.
You selected Datum csys-1 to define the coordinate
system of DiagonalTape-2 and entered a rotation angle of
90°. The resulting ply orientation is a rotation of 90° counterclockwise about
the 3-axis (the normal direction) of the datum coordinate system. The angle is
measured relative to the 1-axis.
