The „Platform Material Digital“ (www.materialdigital.de) advances digital twins within material science, based on a semantic description using ontologies. The aim is to digitally represent (new) materials, their properties and crucial processing steps. We are actively involved in this endeavour by digitalizing graphene-based conductor materials. An ontology is created and enriched with simulation data and experimental data, covering various aspects such as model parameters, preparation processes, and measurement processes. We create the following demonstrator use cases with a semantic data description: (1) the integration of our simulation methods as workflows within the „Platform Material Digital“, (2) an App to store, filter, and post-process our production and measurement processes and material properties of the graphene-based conductor materials.