Disbondment zone

FIGURE 4. Disbondment zone of a pressure-sensitive tape Kaelble s Schematic. . . peel profile and experimental boundary distribution of normal stresses. (From Reference 14.)... 

Figure 16.36 shows the applicafion of EMIS for the detection of 20 mm long delamination on a 2 mm thick L-section bonded stiffener [82] PWAS a2, which is placed in a zone proximal to the delamination, displays new resonances associated with disbond vibration at 350 and 510 kHz. In the same time, these new resonances are not present in the spectmm measured by the witness PWAS transducers al and a3, which were placed on the same stiffener but some 70 mm away on either side of the disbond. The fact that the al and a3 spectra are almost identical confirms the consistency of the EMIS method. 

We have mentioned, earlier, the fact that a local, transient temperature rise has been observed in the peeling of pressure-sensitive tapes.0 3) peak temperature rise of 12.5 °C has been measured, in peeling at 1(X) cm/min (Figure 12). The temperature rise ATj appears to be associated with dissipative processes occurring in the filaments that are drawn, in the disbond-ment zone, when a pressure-sensitive tape is peeled off a solid. In fracturing a brittle polymer, the work (per unit area) done is converted into heat, and most of this heat is released in the craze filaments.2) A transient temperature rise, above 500 °C, has been reported with PMMA, and above 400 °C for polystyrene O) (see below). 

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