Experimental methods have been developed so that in situ transmission electron microscope (TEM) tensile studies can be performed on bulk polymer sections, and failure processes observed; real time can be correlated with failure in bulk parts. Using specially designed support grids, polymer section geometry and in situ tensile procedures, the submicrometre failure response of polycarbonate-poly(ethylene terephthalate) phase morphology to crack propagation has been studied. This paper focuses on the design of the tensile grids, sections and procedures, which had to be devised for these studies. The techniques developed allow quantification of strain rates and crack velocities. TEM experiments performed showed that artefacts, such as vacuum or radiation damage, were not significant factors influencing the morphological response to crack propagation. A companion paper presents the failure processes found insitu and correlations with failure processes found in bulk tested parts.