Influence of fiber orientation on global mechanical behavior and mesoscale strain localization in a short glass-fiber-reinforced epoxy polymer composite during tensile deformation investigated using digital image correlation

Advanced polymer composites are used in various fields such as light-weight automobile, aerospace and bio-implant engineering owing to their extraordinary mechanical properties. The various fields of application and the complex microstructures of such materials require better understanding of their micromechanical behavior under external loads. In this work, the tensile testing is coupled with the novel technique of surface displacement mapping via digital image correlation (DIC) is utilized for resolving the mechanical behavior and spatial distribution of the plastic microstrains in an epoxy resin reinforced with 35 wt% short borosilicate glass fibers. The DIC method works by correlating the digital images of surface patterns before and after straining. The material exhibited a pronounced mechanical anisotropy at both macro and mesoscale, which depends on the alignment of the fibers relative to the external load. The underlying microstructure of the material explained formation of strain gradients during evolution of full-field strain fields. The levels of localized strain are higher than the global failure strain of the material. Also, scanning electron microscopy (SEM) on the fracture surfaces revealed the multiple failure mechanisms of the material as a function of the fiber orientation.