The conventional approach to through-life-support for aircraft
structures can be divided into the following phases: (i) detection of
defects, (ii) diagnosis of their nature and significance, (iii)
forecasting future behaviour-prognosis, and (iv) pre- scription and
implementation of remedial measures including repairs. Considerable
scientific effort has been devoted to developing the science and
technology base for the first three phases. Of particular note is the
development of fracture mechanics as a major analytical tool for metals,
for predicting residual strength in the presence of cracks ( damage
tolerance) and rate of crack propagation under service loading.
Intensive effort is currently being devoted to developing similar
approaches for fibre composite structures, particularly to assess damage
tolerance and durability in the presence of delamination damage. Until
recently there has been no major attempt to develop a science and tech-
nology base for the last phase, particularly with respect to the
development of repairs. Approaches are required which will allow
assessment of the type and magnitude of defects amenable to repair and
the influence of the repair on the stress intensity factor (or some
related parameter). Approaches are also required for the development and
design of optimum repairs and for assessment of their durability.