Tamrakar et al. conducted strain rate-dependent experiments in which a microdroplet of epoxy resin was bonded to a single glass fiber and then that bond was broken by mode II shear loading [1]. With that data, Tamrakar et al. used finite element modeling to compute rate-dependent mode II traction-separation laws (TSLs) for the fiber-matrix interface. Based on microscale experiments, these TSLs have peak tractions of about 60-120 MPa. Later, Chowdhury and Gillespie used molecular dynamics (MD) simulations to predict related fiber-matrix interphase TSLs [2]. However, since the MD TSL predictions are derived from an atomic scale, defect-free interface, peak tractions are about 1-3 GPa, more than an order of magnitude greater than the experiment-based TSLs.
The present work develops a finite element model of a single-fiber microdroplet pull-out test, and introduces defects to the interface to better simulate the real fiber-matrix interface. The model uses as input the fiber-matrix interphase TSLs derived from Chowdhury’s MD simulations. Defects are introduced to the fiber-matrix interface by dividing it into 64 areas, each of which can have its governing TSL parametrically scaled. A mode II TSL is derived from this model, which is compared with Tamrakar’s experimentally-derived TSLs.
[1] S. Tamrakar, R. Ganesh, S. Sockalingam, J. W. Gillespie, Jr., Rate dependent mode II traction separation law for S-2 glass/epoxy interface using a microdroplet test method, Composites Part A, 2019.
[2] S. C. Chowdhury and J. W. Gillespie, Jr., Strain-rate dependent mixed-mode traction laws for glass fiber-epoxy interphase using molecular dynamics simulations, Composites Part B, 2024.
