The adhesive fracture energy of structural adhesive joints may be readily ascertained from linear-elastic
fracture-mechanics (LEFM) methods, and indeed an ISO Test Method (ISO 25217: 2009)
now exists for the LEFM Mode I value, Gc, as a result of the efforts of the European Structural Integrity
Society (ESIS) ‘TC4 Committee’ [1,2]. These LEFM test methods involve the preparation
and testing of adhesively-bonded double-cantilever beam (DCB) and tapered double-cantilever beam
(TDCB) specimens [3,4]. Notwithstanding the sound and reproducible results that may be obtained
from such methods, the LEFM test specimens are relatively complex and expensive to make and test,
and many industries would far prefer to deduce the value of the adhesive fracture energy from the
very common and widely-used ‘peel test’. (In the present paper, for clarity, the adhesive fracture
energy is termed GA when deduced from a peel test.) Indeed, the peel test is an attractive test method
to assess the fracture performance of a wide range of structural adhesive joints and flexible laminates.
However, although it is a relatively simple test to undertake, it is often a complex test to analyse and
thus obtain a characteristic measure of the toughness of the adhesive joint, or laminate.