Flexural and fracture behaviors of functionally graded long fibrous polymeric composite beam-like specimens

Abstract

From the early seventies of the twenty-centenary until now, polymeric composite materials (PCMs) have been a tremendous development in structural engineering applications such as decks and beams of bridges. However, most of the specifications still used only plate-like specimens (breadth ≫ depth) rather than beam-like specimens (depth ≫ breadth). The present work has studied the flexural and fracture behaviors of beam-like specimens made of conventional and functionally graded (FG) PCMs. The three patterns: linear, non-linear, and stepwise/layered FG-PCMs, resulting from the distribution of fiber through the depth, were manufactured from long glass fibers reinforced epoxy. A three-dimensional finite element method was employed to demonstrate the progressive damage process of smooth and matrix-cracked specimens. The present results showed that the FG-PCM beams have higher flexural strength and fracture toughness values for the same fiber volume fraction than those of the conventional beams. In the case of long fiber PCMs, the matrix cracked specimens withstand a higher applied load than the through-thickness (common) cracked specimens confirming that the fracture toughness measured from the common cracked specimens is not applicable. The fracture toughness of PCMs depends on the type of test and the specimen geometry. Numerical predictions showed good agreement with the experimental results.