Lifetime prediction of pmc's  

Posting by holger lutz on June 02, 2008 at 19:56:08.

I am looking for advanced computer codes or models that could allow me to make predictions of the service life or lifetime prediction of Polymer Matrix Composites (PMCs) under the combined action of environment (especially aqueous solutions with high pH) and mechanical loading. If you have, or are aware of the existence of, any model with such capabilities, I would appreciate if you could let me know.

Please note that I am also interested in models or computer codes that can only partially answer my needs such as:
- only environmental degradation of Fibre Reinforced Plastics (FRP) composites (no external mechanical initiated ageing / fatigue);
- only environmental degradation of polymers (no fiber reinforcement).

Should you require further information, please do not hesitate to contact me. Your guidance and help would be greatly appreciated.

With best regards,

Holger Lutz

          follow up posts
    On 15 Oct 2008 at 15:32:40 Rodney Bennet posts:
    We conducted a research on the effect of stress on diffusion of water in cast epoxy cylinders and found that the diffusion coefficient, using the free volume concept, is related to the stress as follows:

    Ds = D0 e ^[a * (S / G)]


    Ds = diffusion coefficient in stressed situation [m2/s]
    D0 = diffusion coefficient in initial unstressed situation [m2/s]
    a = ranges from 6 to 10 in our experiments [-]
    S = compressive / tensile stress [N/m2]
    G = SHEAR modulus [N/m2]

    In case of a bend bar, the alpha factor for the compression side (a is near to 6) is lower than for the tension side (a is near to 10). Note that this formula does not include effects of long term chemical and physical ageing phenomena (see WLF / Struik like models), hence it should only be applied for relative short times.

    [responses: 0]

    On June 09, 2008 at 23:26:50 albert posts:
    I have a similar question. My company is considering employing Fibre Reinforced Plastic (FRP) to repair pressurised vessels. My concern is that this repair is "designed" to last 15-20 years, and knowing the ageing problems of certain polymers, I fear this option will cost more in the long term if the composite wrap is meant to be replaced every 5 years (due to ageing and not delamination and such).
    FYI, the Fibre Reinforced Polymer element will be subjected to cyclic loads (comparable to thermal spiking), Ultra Violet light (UV), hydrocarbons (plastization) in a marine (water) environment.

    I am looking for a reassurance or confirmation on the subject by means of a appropriate epoxy composite service life prediction or integrated composite life time prediction methodology.


    [responses: 1]

      On 23 Sep 2008 at 21:41:18 Alex Anderson posts:
      Hi Albert,

      According to the book of Springer, Environmental Effects on Composite Materials, change in strength and in modulus depends upon a) the material, b) the temperature and c) the envirionment (relative humidity of air or type of liquid chemical involved). It states that the weight uptake and change in strength and modulus are related, whereas saturated salt water, antifreeze and indolene have the most influence. After drying of the exposed samples it appeared that the losses in strength and Young modulus did recover - but not to their original values. Unfortunately this was not modelled in the work. However it is very probably related to chemical degradation of polymer chains (salt water) and/or the viscoelastic properties (indolene, antifreeze) of the polymer system.

      Alex Anderson
      [responses: 0]

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