Heat deflection temperature - polymer ageing  


Posting by lisa on April 17, 2008 at 15:19:52.

We have carried out a composite Heat Deflection Temperature under Load (DTUL) experiment on a bar of metal fibre resin laminate (FML) by placing it in an oil bath with a three-point bend fixture, and subsequently applying the mechanical load. Then, the bath was heated at a speed of 120 Kelvin per hour.

Besides, the difference in processing conditions of a sample (such as injection / compression molding, the conditions and temperature of postcure), is Heat Deflection Temperature (HDT) a good measure for the long term performance at elevated temperature?

And related: what is the influence of inorganic fillers and stabilizers on the HDT and use at high environmental processing temperatures?

Thanks

Lisa


          follow up posts
    On 04/17/2008 composite agency posts: Lisa,

    Further to the subsequent posting, here it goes:

    First of all, the sort of aluminium is of interest: this will determine the stiffness of the fibre metal laminate composite and fatigue properties of the composite to an important extent.

    The following background information gives an idea of the developments and considerations concerning this ultra modern composite material originally developed by Akzo Nobel.

    Fibre Metal Laminates (FML) consist of thin metal layers and glass reinforced epoxy resin. Fibre Metal Laminates have a low weight and have a very good ageing/fatigue properties. Their diffusion characteristics, especially for water vapours and gases, are still subject of laboratory research and mechanical-diffuson-corrosion simulations.

    A modern example of a Fibre Metal Laminate is Glare. This material is applied in the Airbus A360. A successor material of Glare, named Central, is most probably applied in the Joint Strike Fighter. Both materials have an excellent fatigue and impact resistance, but Glare is less suited at higher temperatures, to which parts of the Joint Strike Figher (JSF) are exposed.

    The original Glare contains the following materials: Aluminium 12024 - T3, S2-glass fibre and a 120 degrees Celsius curing epoxy resin. The subsequent version contains: Aluminium 2024 - T81, S2-glass fibre and a modified 177 degrees Celsius curing epoxy resin. This new material can be applied in application conditions of a temperature of 150 degrees Celsius.

    This second material has a stifness which is approximately 25% higher. On the other hand the energy of fracture is around 40% lower. So, even new high tech composite materials have its limitations.

    Improved materials can be developed using combinations of Titanium (Titanium-6Al-4V), with carbon fibres(IM600) and thermoplastic materials like Polyether etherketone, Polyimide, Polphenylene Sulfide will probably have better mechanical, corrosion and permeation properties than the materials discussed. This is because of their Titanium stiffness and fracture energy capability of thermoplastic materials, like PEEK and PI.

    Realize that dynamic and static tests always must be combined with advanced diffusion, permeability measurements (think of Electrical Impedance Spectroscopy - EIS - and Positron Lifetime Spectroscopy PALS) to give a good indication of real life performance.

    Please contact us for more quantitative information, such as ageing and fatigue properties in humid enviroments (yet only simulations available, were still waiting for experimental validations...)

    Composite Agency
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