The elastic modulus for maize stems.

Background: Stalk lodging is a serious challenge in the production of maize and sorghum. A comprehensive understanding of lodging will likely require accurate characterizations of the mechanical properties of such plants. One of the most important mechanical properties for structural analysis of bending is the modulus of elasticity. The purpose of this study was to measure the modulus of elasticity of dry, mature maize rind tissues using three different loading modes ( bending , compression and tensile ), and to determine the accuracy and reliability of each test method.

Results: The three testing modes produced comparable elastic modulus values. For the sample in this study, modulus values ranged between 6 and 16 GPa. All three testing modes exhibited relatively favorable repeatability (i.e. test-to-test variation of < 5%). Modulus values of internodal specimens were significantly higher than specimens consisting of both nodal and internodal tissues, indicating spatial variation in the modulus of elasticity between the nodal and internodal regions.

Conclusions: Bending tests were found to be the least labor intensive method and also demonstrated the best test-to-test repeatability. This test provides a single aggregate stiffness value for an entire stalk. Compression tests were able to determine more localized (i.e., spatially dependent) modulus of elasticity values, but required additional sample preparation and test time. Finally, tensile tests provided the most focused measurements of the modulus of elasticity, but required the longest sample preparation time.