Overview
MIFACRIT aimed at developing a failure criterion for fiber reinforced polymer (FRP) structures. This criterion allowed reliability and lifetime assessments of structural parts and systems made of several stack configurations. It shall be deduced from mechanical effects within the microstructure of the FRP structures in order to cover various mechanical loading situations. This ambitious goal was approached by a symbiotic combination of experimental test and analysis work with in-depth assessment and evaluation based on numerical simulation applying fracture / damage mechanics concepts. The material tests comprised visco-elastic characterisation and stress tests applying constant strain rate and cyclic loads, respectively. The tests were performed at different temperatures and frequencies. Most importantly, they included a variety of loading situations such as tensile and bending loads but also combinations of normal and shear components.
The analysis determined the visco-elastic material properties and the micro-structural effects responsible for damage and failure of the FRP structure in a comprehensive way. The in-depth analysis of the damage and failure effects by means of numerical simulation applied a two stage (global / local) sub-modelling strategy. The essential model parameters were calibrated by measured data and the simulation results were verified by the experimental findings. Combining experiment and simulation this way, the common link between the failure effects caused by the various loading situations were shown and explained by means of an objective mechanical criterion, which was identified and validated throughout the MIFRACRIT project. In addition, threshold quantities were determined for the criterion found to ultimately provide the means for precise lifetime predictions based on this physics of the failure approach.
Funding
Results
Executive Summary:
The MIFACRIT project aimed at developing a failure criterion for fiber reinforced plastics (FRP). This criterion shall enable reliability and durability assessments of structural parts and systems of multiple stack-up structures. It shall be deduced from mechanical effects within the microstructure of the fiber reinforced polymer structures in order to cover various mechanical loading conditions. This ambitious goal is achieved through a symbiotic combination of experimental testing and analysis work based on numerical simulation using fracture/damage mechanic concepts. The material tests consisted of visco-elastic characterization and stress tests applying constant strain rate and cyclic loads. Most importantly, they include a variety of loading situations such as tensile and bending loads and combinations of normal and shear components.
The analyses determined the visco-elastic material properties and the micro-structural effects, which are responsible for damage and failure of the FRP structure in a comprehensive way. The detailed analysis of the damage and failure effects by means of numerical simulation used a two-stage (global/local) sub-modeling strategy. The required model parameters are calibrated by measured data and the simulation results are confirmed by the experimental findings. Combining experiment and simulation in this way, the common link between the failure effects caused by different loading situations were shown and described within the help of an objective mechanical criterion, which is identified and validated during the project MIFACRIT.