Elastoplastic Properties of Starch-Based Materials as Revealed by Microindentation Measurements

Abstract

The elastoplastic properties of injection-molded starch and starch-cement composites were investigated by load-displacement analysis from depth-sensing experiments. The creep behavior under the indenter was studied. Hardness data from the depth-sensing and imaging methods were shown to be in good agreement. The Young modulus values derived from the compliance method were studied; results are discussed in the light of the various materials used. Finally, the influence of annealing temperature on the microhardness of starch and of the starch-cement composites, processed under a water vapor atmosphere, was investigated. Results reveal a hardening of the materials on thermal treatment. This hardness increase is associated with an equilibrium water content decrease detected within the samples.

Keywords:

• Depth sensing
• Microhardness
• Starch
• Young modulus

ACKNOWLEDGMENT

Grateful acknowledgment is due to DGICYT (grant PB94-0049) for the support of this investigation. A. F. also thanks the Comunidad Autonoma de Madrid for the award of a postdoctoral grant.