Overview of Composite Shells

Composites are a combination of two or more materials that have different properties macroscopically. The number of material phases are usually two and are not soluble in one another. One is the reinforcing phase (e.g. carbon or glass fiber, silica particles) and the other is the matrix phase (e.g. epoxy, vinyl ester) in which the reinforcing phase is dispersed. They can be classified into continuous fiber composites, short fiber composites, and particulate composites.

There are three types of composite options to define the arrangement of plies, thicknesses, material properties, and orientations.

  • An unsymmetric laminate has an unsymmetric arrangement of plies about the mid-surface. This is the most general composite option. A schematic of an unsymmetric laminate with five layers is shown. Different colors represent different material properties and orientations. The shell mesh is created at the mid-plane.

  • A symmetric laminate has a symmetric arrangement of plies (materials, ply orientations, and thicknesses) about the mid-surface. This implies symmetric ply thicknesses, material properties, and material orientations about the mid-plane.

  • The sandwich composite is a special case of the symmetric laminate with three layers. You can use such laminates when higher resistance to bending loads is required. The outer two plies are recommended to be stiffer, stronger, and thinner than the middle ply.

    The core is usually lighter to reduce the overall mass and has a high shear modulus of elasticity to resist sliding of skins.

You can use a composite shell for structural members in which you require weight savings. Composite shells also offer improved fatigue strength, corrosion resistance, and thermal conductivity.

You can process models with composite shells in the following ways:

Shell Definition Use the Shell Definition PropertyManager for defining a symmetric laminate, unsymmetric laminate or a sandwich composite. You can define 2-50 layers for a composite shell. The PropertyManager allows you to set different thicknesses, material orientations and same or different material properties for each ply.
Ply Stacking Sequence The program locates the plies from the bottom to the top shell face. So, the first ply is located at the bottom face of the shell and the last ply is located at the top face of the shell.
Flipping the mesh reverses the ply layup with first layer located at the bottom.
Ply Angle The ply orientations for each ply can be defined through the Angle column in the Composite shell plies table of Shell Definition PropertyManager. The material orientation of 0 degree ply angle for each ply is visually represented by stripes in the model workspace. In addition, you can also adjust the ply orientation options through the Composite Orientation options.
Results Apart from the results available for shells, you can show the following plots:
  • Maximum stress across all plies.
  • Stress on top or bottom face of each ply.
  • Stress along the ply orientation direction or in transverse direction to ply angle.
  • Interlaminar shear stress at the junction between two different plies.

See Stress Analysis for Composite Shells to interpret the results. See Stress Plot PropertyManager and Factor of Safety Plot PropertyManager.

Displacements and strains are continuous across plies and cannot be controlled at ply level. Stress across different plies are plotted for individual plies as they are generally not continuous (material properties and orientations vary through thickness).