The effect of microstructure on mechanical properties of corn cob.

ABSTRACT

As a natural biomass resource, corn cob has excellent mechanical properties and a special layered structure. To investigate the relationship between the mechanical properties and microstructure of corn cob, the ultra-deep field 3D microscope was used to characterize the macro geometric parameters, and the scanning electron microscopy (SEM) was observe the microstructure of the corn cob. The Fourier transform infrared spectrometer was used to analyze the fiber composition, revealing the contribution of fiber composition to the mechanical properties. Axial compression, radial compression, and three-point bending tests were performed on corn cob using a universal testing machine. Moreover, an impact testing machine was used for impact tests. The results show that a corn cob is structurally divided into the pith, woody ring, and glume, mainly composed of cellulose, hemicellulose, and lignin in fiber composition, respectively. The pith is a porous sponge-like tissue that has a greater bearing capacity while maintaining a low density. It is also a progressively hardening material with good buffering properties under impact loads. The woody ring is the primary source of mechanical strength, whose microstructure is a hollow tubular structure composed of cellulose and bonded by lignin. The internal microstructure of the glume is also porous and spongy, but the mechanical properties are mainly manifested in its macrostructure. The results of this study may provide a reference for the subsequent processing and industrial application of corn cob, and the unique structure of corn cob is also an excellent bionic prototype for lightweight design.