User:Kate P Stuart/CheFEM

CheFEM stands for Chemical driven FEM simulation of polymer based materials.

CheFEM is used for analyzing diffusion, chemical resistance and forthcoming mechanical retention of nano, micro and macro materials.As such, CheFEM enables lifetime prediction of these materials during exposure to UV light and to chemicals (including mixtures) in any state: liquid, gas or supercritical. CheFEM simulation output intrinsically includes chemical permeation (emission) rates and failure (material fracture) analysis. CheFEM can be used in addition to existing FEM packages for material simulation, like Abaqus, Nastran, Ansys and SolidWorks Premium.

3 Key Modules
CheFEM consists of the following three modules:

101 Lattice Based Thermodynamics & Diffusion Module

Besides diffusion, permeation and time lag considerations, this module also predicts plasticizing and swelling due to dissolving and temperature gradients. Note that swelling gives rise to interfacial shears, and causes several intrinsic - dimension dependent - tension and compression stresses in the material. Effects of fatigue and ageing are included.

102 Surface & Chemical Activity Driven Corrosion Module

Although polymers can exhibit excellent corrosion resistance, chemical reactivity of the internal interfaces or the reinforcement materials themselves, could drive loss of interfacial strength, causing material failure and / or reduction of material service life performance. Routines are based on (experimental) library data on corrosion rates and 3D chemical activity (chemistry) determination.

103 Mechanical Restraint / Fracture Module

This module is based on Gibbs Free - Mechanical Fracture analysis. It is used to determine the swelling and expansion restraint due to - and within - different components of the composite, under hydrostatic pressure and swelling driven by temperature and mass solubility. Effects of fatigue and ageing of material components are included.

Mathematics
The solving of the partial differential equations of mechanically oriented problems in complex shapes or multiple (more than three) layers is solved using finite element methodology. For basic shapes and for sequencing nano / micro material sections, the simulator uses the finite difference method,.

Industrial Applications
Industrial examples of the CheFEM application are:

- Service life / failure assessment of Epoxy and Vinyl Ester Resins reinforced with Functionalized Graphene Sheets (FGS) in new high performance applications. - Service life prediction of composite (reinforced) bridge decks.

- Lifetime analysis of oil & gas pipelines and devices, in severe temperature and pressure conditions (such as Supercritical carbon dioxides - CO2).

- Integrated ageing & fatigue simulation and analysis of windmill rotor blades operated at sea (brine environment).

- Long term behavior of thin film flexible solar cells (mechanical stress, water, oxygen and nitrogen diffusion).

Development
CheFEM is developed by an independent firm, Composite Agency (The Netherlands). CheFEM is written in the programming language Java. A production version of CheFEM was demonstrated on JEC Composites 2008. Currently, the development of the program is ongoing.