A schematic view of the repeated drop weight apparatus is given in Fig.2. A number of variables can be investigated using the apparatus. Various masses, P, ranging from 1 to 4 kg together with various drop heights, H, ranging from 0.5 to 2m, have been studied. Suitable combinations of drop heights and masses can be used with this test apparatus - for example to provide the same impacting energy but covering a range of impacting velocities. In addition to the variables provided by the apparatus, the test specimens can also be varied - a range of Mode I and Mixed-Mode fracture test specimens have already been tested by means of this apparatus. In this particular study, the impacting mass, P, was dropped onto the free arm of the testing arrangement shown in Fig.l.