Elastoplastic properties of starch-based materials as revealed by microindentation measurements

The elastoplastic properties of injection-molded starch and starch-cement c omposites were investigated by load-displacement analysis from depth-sensin g experiments. The creep behavior under the indenter was studied. Hardness data from the depth-sensing and imaging methods were shown to be in good ag ree ment. 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 sta rch and of the starch-cement composites, processed under a water vapor atmo sphere, was investigated. Results reveal a hardening of the materials on th ermal treatment. This hardness increase is associated with an equilibrium w ater content decrease detected within the samples.