Short fiber composites consist of short (chopped) fibers arranged randomly in a matrix material. The directions of the fibers are random, while seeking to attain a certain orientation tensor. This allows you to create models where the fiber directions are uniformly at random, as well as models where certain fiber directions are more likely than others. In particular, you can create models where the fibers are oriented in a plane.
FE-Based Homogenization
The following options can be defined for Short Fiber using Finite Element Based Homogenization:
Specify Volume Fraction/Weight Fraction: Choose whether to define the RVE by specifying the fiber volume or the weight fraction.
Fiber Volume Fraction: (This option appears when you select Volume fraction for Specify.) The fraction of space within the RVE that the fiber material occupies.
Fiber Weight Fraction: (This option appears when you select Weight fraction for Specify.) The ratio between the weight of the fibers and the total weight of the composite.
Seed: The seed number against which the random fiber directions are generated.
Orientation Tensor: Specify the eigenvalues a11 and a22 of the target orientation tensor. See also Orientation Tensor.
Aspect Ratio: The ratio of the length to the diameter of the fibers.
Fiber Diameter: The diameter of the individual fibers in the active unit system.
Repeat Count: The higher this value, the larger the number of fibers in the RVE.
Algorithm: The algorithm used to generate the RVE geometry.
Sequential Addition: Fibers are added one after another.
Sequential Addition with Orientation Optimization: Fiber orientations are adjusted using a gradient descent method in order to better match the specified orientation tensor, similar to [Schneider (2017)].
Note: The fiber volume fraction and the orientation tensor are only reached approximately. See the status history after the generation of the RVE geometry for the actual values. In particular, high fiber volume fractions might not be reached when the target value is close to or exceeds the jamming limit.
Analytical Homogenization
The following options can be defined for Short Fiber Analytical Homogenization:
Specify Volume Fraction/Weight Fraction: Choose whether to define the composite by specifying the fiber volume or the weight fraction.
Fiber Volume Fraction: (This option appears when you select Volume fraction for Specify.) The fraction of space within the RVE that the fiber material occupies.
Fiber Weight Fraction: (This option appears when you select Weight fraction for Specify.) The ratio between the weight of the fibers and the total weight of the composite.
Fiber Volume Fraction: The fraction of space within the composite material that the fiber material occupies.
Orientation Tensor: Specify the eigenvalues a11 and a22 of the target orientation tensor. See also Orientation Tensor.
Aspect Ratio: The ratio of the length to the diameter of the fibers.
Note: When you specify the Weight Fraction, you must also define the density for the matrix and the fiber materials. Furthermore, the density must be constant and must not depend on field variables like temperature.