Peel Behaviour of Aircraft Fuel Tank Sealants: the Effect of Peel Angle, Sealant Layer Thickness and Peel Rate

Abstract

The peel performance of two aircraft fuel tank sealants was comprehensively investigated by means of a modified peel specimen previously developed. Experiments were carried out at five different peel angles in the range from 90 to 180 • using seven sealant layer thicknesses in the range from 0.1 to 5 mm. The effect of the peel rate was also investigated at a fixed peel angle and sealant layer thickness. The results were analysed in terms of the peel energy. Both peel angle and sealant layer thickness were found to affect significantly the measured peel energy of the sealants in a coupled way. In particular, it was found that the peel energy increased linearly with the sealant layer thickness, for the range considered in this study, and the rate of this increase was also found to increase as the peel angle was varied from 90 to 180 • . For very small sealant layer thicknesses (0.1 mm) there was no effect of the peel angle on the measured peel energy. The results were explained in terms of the amount of energy these materials dissipated upon deformation up to fracture and a relationship for the prediction of the peel energy was proposed. The peel rate was found to affect only slightly the measured peel energy, in the range studied.

The development of a novel test method to assess the durability of asphalt road–pavement materials

“…This is because there will be energy dissipation in the volume of a viscoelastic material, as discussed by Igarashi [35], and hence the adhesive fracture energy will depend on the adhesive layer thickness. A linear relationship between peel energy and adhesive layer thickness was observed by Igarashi [35] for rubbers and Giannis et al [36] for sealants. This explains why the peel force in Figure 7(c) was, on average, lower than that of Figure 7(a).…”

Quasi‐Static Fracture Tests

“…In the international standards ASTM C903 and ISO 8510-2, it is recommended to evaluate the average peel force over a peel length of at least 100 mm, excluding the first 25 mm. More sophisticated analysis methods can be employed to analyze the peel force and extract the peel energy, excluding contributions from the adherends or the adhesive itself, as presented elsewhere (Section 3.15, [138,164]). These methods aim at evaluating the peel energy as a material characteristic, therefore excluding the amount of energy dissipated in bending (elastic as well as plastic) of the flexible adherend, if necessary.…”

“…In the case of elastomeric materials, it has been shown in Ref. [164] that the energy during the peeling process dissipated to deform the material accounts for a large portion of the overall peel energy and needs to be accounted for if the peel energy is to be used as a measure of the fracture (tearing) energy. Tests could be performed either at room temperature and humidity conditions or at elevated or subzero temperatures and variable humidity levels to simulate the in-service environment of the material.…”