Life Prediction of Polymer Components

Many service components have specified overhaul/change-out/maintenance intervals irrespective of their condition, but which are based on time in service, flight, mileage, cycles etc.

In many instances the effect of the service environment (i.e. load, chemical degradation, ageing, etc.) has not been assessed and service parts may be able to be left in service for extended intervals.

MERL mechanical testing laboratories along with numerical analysis can perform independent condition and life assessments of a variety of components.

There are often two major considerations:

• Chemical durability, or resistance to ageing
• Mechanical durability

Assessment of chemical ageing - the chemical and physical characteristics of parts removed from service are compared with those of new parts that have not seen service - ageing studies are then performed on the material - using Arrhenius methods - to extrapolate this deterioration to a longer service life, to give guidance on whether, for example, the parts will still be suitable for extended service.

Assessment of mechanical performance - changes in mechanical performance that have occurred and that would prevent the components from fulfilling their required function are assessed - components are quasi-statically tested to determine whether the stiffness of the parts has changed significantly over the service life - preferably tests are performed on components that have seen various lengths of service, so that the change in a property (such as the stiffness of the part) can be tracked.

Test programs can be defined that are tailored to individual applications.