Fabrice Laurent

A new active composite

CETIM CERMAT and the LPMT have been developing a new kind of active structure over the past few years: CBCM (controlled behavior composite material). The CBCM process consists in generating an internal source of heating within the composite structure and then in using the thermomechanical properties of the various components in order to deform the material. Carbon yarns are used as the internal heating source: being connected to a power supply, they are conductive and provide heating by the Joule effect. In this work, various aspects of the CBCM are studied by means of model plates. First, the plates and their constitutive layers are described. Second, the bending properties of the CBCM are presented. Third, it is shown how the structure can become active. Finally, in order to illustrate the capacities of this new active composite, a prototype of an aerodynamic flap integrating CBCM is developed. Experimental and numerical results are compared.

Thermomechanical Modelization of a New Active Material

The controlled behavior of composite material (CBCM) is a thermomechanical active composite using Joule effect and heterogeneous thermal elongation properties as an actuator within composite structures. An ‘active layer’ made of carbon yarns is used as internal source of heat. To help the design of this composite a simple model based on thermomechanical and composite homogenization considerations is presented. A three-point bending test is used to compare the calculated results to experimental results. A good accordance between the relevant data (maximum of deflection and temperature on the plate) at stabilization being observed, the model is used to study the influence of some parameters. The position of the active layer, a design parameter of great importance, is particularly studied and an optimized solution is proposed. Then, the model is used for a sensitivity analysis of some design and working parameters. Finally, the results of a FEM model are compared to the previous.