A developmental process, independent of morphogenetic (shape) change, that is required for a platelet to attain its fully functional state. A platelet is a non-nucleated disk-shaped cell formed by extrusion from megakaryocytes, found in the blood of all mammals, and mainly involved in blood coagulation. [ GOC:vk http://purl.obolibrary.org/obo/CL_0000233 GOC:BHF ]