Correlation between compression strength and failure mechanism of carbon fiber composite with tailored modulus of amide acid/SiO2 synergistically stiffened epoxy matrix

Abstract

Epoxy matrix with high modulus was synergistically designed by organic amide acid (AA) and inorganic nano silica (SiO2) as well as stiffened interphase of carbon fiber composite, and the effects of matrix modulus on longitudinal compressive strength and failure mechanism of composites were investigated. The elastic and shear modulus of matrix was enhanced by increased chemical cross-linking cites of AA and mechanical restraint of SiO2, contributing to improved interfacial properties from the construction of modulus intermedia layer in carbon fiber composite. Using combination model of elastic-buckling and plastic-kinking models, compressive strength of composites was simulated and predicted, which showed a close agreement to measured results and positive relationship with matrix modulus. Schematic mechanism of compression failure in CFRP composites were proposed, and stiffened matrix and favorable interphase could restrict fiber-buckling and facilitate kink-band formation to avoid interface delamination during elastic-plastic process, resulting in increased ultimate compressive strength.