Appendix A.13 - User Material Constant #14: Fiber Degradation Energy

The 14th user material constant is used to define the response of the composite after a fiber failure when energy-based degradation is used. Specifically, this value represents the total energy dissipated by the composite before and after a fiber failure.

If you request Energy-Based Degradation, this value represents the total energy of the composite before and after a fiber failure event. After a fiber failure event occurs, , , and are degraded linearly according to Appendix A.5 for post-fiber failure. As the composite strain increases beyond that at initial fiber failure, the composite properties are reduced according to the input fiber degradation energy, the composite strain at failure, the composite stress at failure, and the element volume. For more information on the fiber degradation energy, refer to the Theory Manual.

Note: After fiber failure, the matrix is assumed to have failed (whether it has or not), and the properties of the constituents are no longer needed to compute failure. Therefore, the properties of the constituents are not updated after a fiber failure.

Note: If the matrix constituent has failed prior to fiber failure, , , and are degraded according to the matrix degradation energy, otherwise , , and are degraded according to the fiber degradation energy.

Note: If the fiber degradation energy is specified as too low, the properties of the composite will be instantaneously reduced (instead of gradually) to near zero when the fiber failure criterion exceeds 1.0. Refer to Appendix A.5 and the Theory Manual for more information.