This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.

Resource Abstract

Due to their superior weight-specific mechanical properties, carbon fiber reinforced polymers (CFRP) are increasingly used in automotive industry. One of the main reasons is the compensation of the penalty weight caused by the components for the electrification of the passenger cars. However, the brittle failure behavior of CFRP limits its structural integrity and damage tolerance in case of impact and crash events. Furthermore, the electrical conductivity of CFRP structures is insufficient for certain applications.
Former research attempts tried to resolve the mechanical and electrical deficits of CFRP by modifying the resin system (e.g. by addition of conductive particles or toughening agents), but could not prove sufficient enhancements. A novel approach is the incorporation of highly conductive and ductile continuous metal fibers into the CFRP. The basic idea of this hybrid material concept is to address both the electrical and load-bearing capabilities of the integrated metal fibers to improve the electrical conductivity and the failure behavior of the composite.
To understand the complex interaction of carbon and metal fibers of a loaded hybrid composite, a micromechanical model of unidirectional and multiaxial laminates is build up using the structure generators of the software GeoDict. For each constituent material, separate user defined material models (UMAT) with individual failure criterions are developed and implemented to simulate the macroscopic material behavior. Through the modelling of the microscopic structure and damages the strength of the laminate could be determined using the GeoDict module ElastoDict. This module uses a solver called FeelMath which is developed at the Fraunhofer Institute for Industrial Mathematics. This fast and memory efficient solver is capable to handle the huge number of elements required for such accurate micromechanical simulations. Additionally, the electrical conductivity of the different laminates is simulated using the GeoDict module ConductoDict.
The numerical study is validated with experimental test results on unidirectional and multiaxial specimens with different steel-carbon-fiber-ratios. The simulation results are in a good accordance with the experimental data and give additionally a detailed insight in the micromechanics of this complex hybrid composite material.