Certification of Prepreg-Based Discontinuous Composite Materials: Stiffness and Strength Predictions
A stochastic finite-element modeling approach has been developed to predict the variability in stiffness and strength exhibited by prepreg-based discontinuous fiber composites (DFCs). The structure of interest is divided into regions called Random Laminate Volume Elements (RLVEs). A non-symmetric stacking sequence is generated randomly for each RLVE, and all finite elements present within a given RLVE are assigned the same non-symmetric stacking sequence. Consequently the local stiffness and strength of a component varies from one RLVE to the next, which affects the overall behavior of the DFC component. A simple damage accumulations approach is used to predict final fracture. Unit loads applied to the finite element model are increased until a ply is predicted to fail in an element somewhere in the structure. Stiffnesses of the failed ply are reduced and loading is increased until the next ply failure is predicted. Final fracture is declared when all plies within a single element have failed. A typical analysis predicts that damage will occur at many distributed regions within a DFC part prior to final fracture. Performing many analysis using random RLVE stacking sequences allows prediction of the variation in stiffness and strength expected for a DFC component.
Author: Mark Tuttle
Conference: SAMPE Seattle 2017