QinetiQ Ltd
The influence of non-visible damage on the performance of aircrew
helmets.
Charlotte B Meeks*, Sarah E Day** and Andrew D
Foreman*
*Materials and Energy Centre, **Air Division, QinetiQ
Ltd.
All helmets are susceptible to damage during normal use.
However, this is particularly true of aircrew helmets which have to
endure
particularly severe in-service conditions, such as canopy strike
during agile combat or 'buffeting' in the rear of helicopters or
transport aircraft.
Due to the design features of helmets i.e. an outer composite
shell with internal foam liner, potentially strength reducing
damage is not always visible externally. The extent of the problem
caused by non-visible damage is not known for current UK aircrew
helmets. A study has therefore been completed within the Military
Aircrew Helmet Impact Standard (MAHIS) working group [1], to
determine how much energy a helmet can absorb without visible
damage, and subsequently to determine what affect non-visible
damage may have
on helmet performance.
To determine the extent of non-visible damage, a range of non-destructive evaluation (NDE) techniques have been used to inspect helmets, prior to residual performance testing. All of the NDE techniques investigated provided some useful data to help identify non-visible damage. However, two of the techniques, thermography and CT scanning, appeared to offer the best solution for damage detection in helmets.
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