Gildas L'Hostis

Thermally Activated Composite with Two-Way and Multi-Shape Memory Effects

The use of shape memory polymer composites is growing rapidly in smart structure applications. In this work, an active asymmetric composite called “controlled behavior composite material (CBCM)” is used as shape memory polymer composite. The programming and the corresponding initial fixity of the composite structure is obtained during a bending test, by heating CBCM above thermal glass transition temperature of the used Epoxy polymer. The shape memory properties of these composites are investigated by a bending test. Three types of recoveries are conducted, two classical recovery tests: unconstrained recovery and constrained recovery, and a new test of partial recovery under load. During recovery, high recovery displacement and force are produced that enables the composite to perform strong two-way actuations along with multi-shape memory effect. The recovery force confirms full recovery with two-way actuation even under a high load. This unique property of CBCM is characterized by the recovered mechanical work.

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.

The thermo-optical behavior of turbid composite laminates under highly energetic laser irradiations

From their prior emergence in the military domain but also nowadays in the civilian area, unmanned air vehicles constitute a growing threat to the todays civilization. In this respect, novel laser weapons are considered to eradicate this menace and the vulnerability of typical aeronautic materials under 1.07μm-wavelength irradiations is also investigated. In this paper, Kubelka-Munk optical parameters of laminated glass fiber-reinforced plastic composites are first assessed to build up a basic analytical interaction model involving internal refraction and reflection as well as the scattering effect due to the presence of glass fibers. Moreover, a thermo-gravimetric analysis is carried out and the kinetic parameters of the decomposition reaction extracted from this test with the Friedman method are verified trough a comparison with experimental measurements.