Appendix A.5 - Argument #5: Progressive Failure Analysis

The 5th argument activates or deactivates the progressive failure analysis feature. If the progressive failure feature is activated, Helius PFA will routinely evaluate the matrix and fiber failure criterion to determine if either constituent material has failed. Each constituent failure criterion is based on the corresponding constituent average stress state. If one or both of the constituents fail, the stiffness of the failed constituent(s) are appropriately reduced to minimal values. Helius PFA calculates the current composite average stiffness based on the current state (failed, or not failed) of each constituent material.

The value of the fifth argument has different implications depending on the microstructure of the material.

Unidirectional Microstructures: A value of 1 activates the progressive failure analysis feature, while a value of 0 deactivates the progressive failure analysis feature.

Woven Microstructures: A value of 0 deactivates the progressive failure feature. A value of 1 activates the progressive failure feature and uses the matrix and fiber degradation levels from the material data file to calculate the failed material properties. A value of 2 activates the progressive failure feature and uses the matrix and fiber degradation levels specified by the 14th and 15th arguments to calculate the failed material properties.

Selecting a value of 2 for weaves will add approximately 45-60 seconds to the pre-processing time per woven material. A value of 2 is only supported for satin weaves that use the Reduced Unit Cell microstructure, not the Full Unit Cell microstructure. Refer to Appendix E in the Material Manager User's Guide for more information on the available woven microstructures. A value of 1 will not add run-time during pre-processing because the failed material properties (at the matrix and fiber degradation levels specified during material creation in Composite Material Manager) are already stored in the material file.

The progressive failure analysis feature is the foundation component of Helius PFA's nonlinear multiscale constitutive relations. Pre-failure nonlinearity can be invoked (via the 6th argument) however, this additional form of nonlinearity cannot be activated unless the progressive failure analysis feature is also activated. The values of SVAR1 differ depending on the microstructure of the underlying composite and additional forms of material nonlinearity invoked. A comprehensive listing of the possible values for SVAR1 is provided in Appendix C. Additionally, a description of each discrete composite damage state is written in the MCT (*.mct) file during the preprocessing phase of the analysis.

The image below shows a [0°/ ±45°]s unidirectional composite plate that was analyzed using the progressive failure feature with both pre-failure and post-failure nonlinearity turned off. It shows a contour plot of the MCT state variable SVAR1, representing the composite damage state in the 0° plies. The blue areas represent composite material with unfailed constituents (SVAR1=1). The green areas represent composite material with a failed matrix constituent (SVAR1=2). The red areas represent composite material with matrix and fiber constituents that have failed (SVAR1=3).

For further information on the progressive failure analysis feature, refer to the Theory Manual.