Bernard Lorrain

Thermo-mechanical behaviour of ceramic metal brazed assemblies

This study investigates the effects of residual stresses developed during brazing on the performance of brazed ceramic metal joints. The thermal expansion gradient between ceramic and metallic materials leads to the development of such stresses during the cooling phase of the brazing process, which consequently reduce the strength of these composite structures. Here, the objective is to compare the failure behaviour of various assemblies observed during experimental tests and obtained through numerical simulations. In order to get a representation consistent with the physical mechanisms involved, these simulations must account for the brazing phase giving rise to residual stresses before applying in use solicitations to brazed joints. This paper focuses on the tensile strength of ceramic metal joints, for which two brittle failure modes (within the ceramic or at the interface) are observed during the experimental tests.

The Effect of the Cure Temperature on the Thermomechanical Characteristics of an Adhesive

The origin of this work takes place in the framework of an industrial collaboration in order to study the behavior of a mechanical joint, used in the industry of railway structures. One problem in using the structural adhesive in the industry is hygrothermal ageing. In these papers; the effect of the adhesive cure temperature on the mechanical properties of a commercial bi-component epoxy bonding joint will be studied. Usually the bi-component epoxy is cured at room temperature. The industrial goal in this study is to increase the mechanical performances of adhesively bonded structures. To achieve this goal the curing process of the adhesive will be optimized.

Mixed method ESPI-CND for the 3D characterization of the composites

The characterisation of composite plates used in structural work in the field of aeronautics is approached by associating ultrasound and speckle interferometry measurements. The reduced thickness of the specimens does not allow for gauge instrumentation to measure out-of plane deformation. A system was therefore used which makes it possible to obtain the cartography of the deformations in and out of-plane. This paper describes an application of electronic speckle interferometry in the measurement through thickness deformation in composites.