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Hello All,

I would like to write a Wiki draft on the CheFEM App. The first draft is described below. For this draft, please use this forum to add your adjustments, corrections, independent technical sources. Thanks to all of you. Please contact me for any further question or ideas via stuart.j.green@outlook.com.

==CheFEM App==

CheFEM App is thermo-mechanical simulation software that enables users to plug environmental effects into applied mechanics of polymers and their composites [1]. In addition, the program computes chemical absorption, chemical permeation and chemical degradation characteristics of these polymer based materials. CheFEM App is developed by Composite Analytica for Oil and Gas, Aerospace, Electronics and Membrane applications. The program was officially released at the JEC World Conference in Paris on 11 March 2014[2].

==Purpose==

CheFEM uses enhanced Sanchez-Lacombe Equation of State (SL EOS) [3] and Free Volume Theories [4] to predict chemical mixing and reaction thermodynamics of an absorbed chemical in a polymer matrix. This thermodynamic algorithm is combined with (FEM) [[micromechanics]] (Classical Laminated Theory, Rule of Mixtures, Linear and Non-Linear Fracture Mechanics) [5]. CheFEM allows users to reduce/optimize chemical-mechanical laboratory experiments. Furthermore, the program is used to discriminate between chemical-physical material effects of each component in a chemical mixture and to quantify the membrane function of (nano) polymer based materials.

==Principles==

The Sanchez-Lacombe Equation of State is used to quantify the thermodynamic properties of the exposing chemical/mixture (Chemical EOS) and polymer matrix (Matrix EOS). The SL-EOS referenced foundation parameters, such as critical temperature, compressed density, related cohesive energy density, etc., are calibrated and hard-coded in the respective EOS databases. If the user sets the chemical name, temperature, pressure and chemical activity/fugacity, the Chemical EOS computes the thermodynamic properties of the determined state: liquid, vapour or (supercritical) gas. The Matrix SL EOS includes handling of matrix glass transition, related matrix free volume and effects of matrix crosslinks and crystallinity. As such, thermodynamic properties of below-Tg thermosets (e.g. [[Epoxy]], [[Polyurethane]]) and semi-crystalline thermoplastics (e.g. [[PEEK]], [[PPS]]) can be analysed. Mechanical constraints and interface behavior are included in these computations. On this basis, CheFEM determines the plasticized mechanics of the polymer matrix, residual chemical-thermal stresses in the matrix, chemical degradation kinetics. Upon combination with polymer and composite (FEM) micromechanics, CheFEM determines the "chemically exposed" tensile/compression stiffness and strength. CheFEM can be used in conjunction FEA software packages such as [[Abaqus]], [[Ansys]] and [[Solidworks]]. In these cases, CheFEM is used as a plug-in, supplying the exposed source material property data to the FEA package.

==References==

[1]Vineet, J., Dodds N., et al.[https://www.researchgate.net/publication/266663965_Flexible_Fiber-Reinforced_Pipe_for_10000-Foot_Water_Depths_Performance_Assessments_and_Future_Challenges "Flexible Fiber-Reinforced Pipe for 10000-Foot Water Depths"], ''[[Offshore Technology Conference]]'', May 2014. Retrieved on 12 November 2017.
[2] Tsai, S. et al. [http://www.cetim.fr/content/download/75103/2203674/version/3/file/Program_ICS_JE14.pdf "Composite Simulation & Design Conference"], March 2014. Retrieved on 5 January 2018.
[3]Sanchez, I.C., Lacombe, R.H. [http://pubs.acs.org/doi/abs/10.1021/ma60066a017?journalCode=mamobx "Statistical Thermodynamics of Polymer Solutions"], ''[[Macromolecules]]'', November 1978. Retrieved on 7 September 2017.
[4] Struik, L.C.E. [http://web.mit.edu/afs.new/athena/course/3/3.91/www/slides/Struik.pdf "Physical Aging in Plastics and Other Glassy Materials"], Polymer Engineering and Science, March 1977. Retrieved on 7 September 2017.
[5] Tsai, S.W., Melo, J.D.D. (2015). ''Composite Materials Design and Testing'', Stanford University, Stanford. {{ISBN|978-0-9860845-1-5}}.