Co-authors​ :

 Jakov RATKOVIĆ (CROATIA), Darko IVANČEVIĆ (CROATIA) 

In this study, progressive intralaminar and interlaminar damage models suitable for simulation of impact phenomena in woven fibre reinforced plastic (FRP) composites are introduced. In order to reduce costs of development and production of structural components in aeronautical, space, military and automotive industry, development of high-fidelity numerical models suitable for capturing the mechanical behaviour of FRP composites in all loading regimes is inevitable. Moreover, in order to accurately predict the load bearing capabilities and to be able to design the structural elements correctly, taking the strain rate effects in consideration is also imperative, as concluded in a large number of researches. Thus, by implementation of this comprehensive mesoscale numerical model in the commercial finite element method (FEM) software package Abaqus/Explicit as a VUMAT user-defined material model subroutine, an effort is made in advancing the current state of available woven FRP material models.
Intralaminar failure initiation and damage evolution is based on the Continuum Damage Mechanics (CDM) approach, whereas the interlaminar damage is modelled based on the Fracture Mechanics (FM), i.e., the Cohesive Zone Model (CZM) in the form of the decoupled bilinear traction-separation law. Both failure initiation and damage propagation are considered to be strain rate dependent. Hence, empirical logarithmic functions are utilized to scale both intralaminar and interlaminar material strengths and fracture toughness values based on the reference strain rate value and experimentally obtained data in quasi-static loading conditions. The fitting parameters of the empirical strain rate effect curves were then fitted according to dynamic experimental results. Material degradation is captured by a total of five intralaminar damage variables, and a single interlaminar damage variable. Removal of both cohesive (representing interfaces) and solid (representing FRP plies) finite elements is utilized in order to simulate the complete failure of the material point. Characteristic finite element length is used in the CDM approach in order to overcome the mesh dependency of the solution. Inherent oscillations of numerically obtained values in explicit integration procedures are treated by a low-pass filter-like algorithm.
In order to verify and validate the developed model, impact simulations at various impact energies, i.e., initial velocities, were performed according to experimental and numerical investigations found in the available literature. The results obtained by utilization of developed material model demonstrate a good agreement with the referent ones.