Digital Mock-up (DMU) is a widely introduced technology to virtually investigate geometrical and mechanical product properties. Functional Digital Mock-up (FunctionalDMU) is a combination of traditional DMU with behavioral simulation in mechatronics. Enhancing DMU with functional aspects, considerably more insight in product properties can be gained. To enable FunctionalDMU two main tasks have to be solved: a) simulators in the areas of mechanics, electronics, and software simulation have to talk to each other (coupling) and b) the simulation results have to be visualized in an interactive DMU environment. In this paper we present an independent and open approach to a FunctionalDMU framework including co-simulation. Starting with proprietary and natively given behavior and geometric models (in formats like JT), we wrap the behavior models into SysML to enable data exchange on an agreed and standardized format. The native behavior models still are executed in the corresponding simulators. The simulators are linked to the FunctionalDMU framework using a wrapping approach. Currently we support simulators such as Matlab/Simulink, Dymola, Saber, Rhapsody, SimPack, ANSYS with our framework. During simulation a simulator coupling algorithm controls the simulation processes. A dedicated visualization environment enables the user to interact with the simulation, i.e., to send simulation stimuli, change parameters, observe the simulation run etc. This paper introduces the components of the FunctionalDMU framework and illustrates the approach with an application example.