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L Pauchard

Publications and source records attributed to L Pauchard.

6 recordsLinked to original sources
PubMed2006

Imbibition, desiccation and mechanical deformations of zein pills in relation to their porosity.

This paper deals with the interaction between zein (the main protein component of corn grain) and water. It induces macroscopic properties changes and may allow for the understanding of the basis of zein endosperm structure: vitreous endosperm is compact and floury endosperm is porous, giving the endosperm its hard and soft textures, respectively. In that aim porous pills made by compaction of zein powder submitted to different hydration/dehydration processes have been prepared and studied. In particular, imbibition measurements of a pure-water drop deposited onto a zein pill were performed. Also, desiccation of a zein pill previously imbibed induces strong mechanical stresses leading to crack formation and/or large deformations.

Mechanics↗
PubMed2005

Hierarchical crack pattern as formed by successive domain divisions. I. Temporal and geometrical hierarchy.

Crack patterns, as they can be observed in the glaze of ceramics or in desiccated mud layers, are formed by successive fractures and divide the two-dimensional plane into distinct domains. On the basis of experimental observation, we develop a description of the geometrical structure of these hierarchical networks. In particular, we show that the essential feature of such a structure can be represented by a genealogical tree of successive domain divisions. This approach allows for a detailed discussion of the relationship between the formation process and the geometric result. We show that--with some restraints--it is possible to reconstruct the history of the system from the geometry of the final pattern.

Journal Article↗
PubMed2003

Stable and unstable surface evolution during the drying of a polymer solution drop.

Drying of a sessile drop of a complex liquid can lead to intriguing complex shapes. We report here a study dealing with a model system, made of a hydrosoluble polymer that is glassy when pure. Under solvent evaporation, polymers accumulate near the vapor/drop interface and may form a glassy skin, which bends as the volume of liquid it encloses decreases. The conditions for the occurrence of this buckling instability have been investigated; the experimental results are well explained by a model that compares the characteristic times for drying and for the formation of a glassy skin. Depending on the experimental conditions, different types of shape distortion take place; secondary instabilities that break the axisymmetry are also observed.

Journal Article↗
PubMed2003

Morphologies resulting from the directional propagation of fractures.

When growing in a stress gradient, cracks have a directional growth. We investigate here this type of instability in the case of a colloidal gel deposited on a substrate and left to dry. The use of various materials reveals the existence of two distinct types of dynamics. When the crack nucleation is easy a well known situation is reached: an array of periodic fractures forms, which grow parallel to each other and move quasistatically with the stressed region. In contrast, in materials where the crack nucleation is difficult, a subcritical process is observed with the retarded formation of isolated cracks which move faster and which display an arch shaped trajectory. This type of process appears to be generic in all cases where there is delayed nucleation. This is confirmed by experiments on the directional propagation of cracks in thermally stressed glass.

Journal Article↗