Weibull statistics of the lap-shear strength of a symmetric interface of amorphous poly(ethylene terephthalate)

Abstract

For the first time, the distribution of the lap-shear strength (σ) developed upon the contact of two amorphous bulk samples of poly(ethylene terephthalate) (PET) in the surroundings of the PET bulk glass transition temperature has been analysed as a function of healing temperature and healing time by using a Weibull statistical model. The Weibull parameters, Weibull modulus (m) and scale factor (σ0) of partially self-healed symmetric amorphous PET–PET interface have been estimated by analysing some tens of the lap-shear strength experimental data sets. It has been found that the σ0 values are very close to the corresponding mean σ values averaged for each test series, meaning that the Weibull analysis gives physically meaningful results. It has been shown that the majority of the σ experimental data sets can be described properly with the standard Weibull distribution function proposed for brittle solids. The m values for the PET–PET interface have been compared with those reported recently for the polymer–polymer interfaces of non-crystallizable amorphous polymers. The impact of the potential ability of an amorphous polymer to crystallize on the scatter in the measured interface lap-shear strength has been discussed.