Evaluation of size effect on mixed-mode fracture behavior of epoxy/silica nanocomposites

Abstract

The aim of this study was to examine the effect of size on the mixed-mode fracture toughness of quasi-brittle nanocomposites with the help of modified maximum tangential stress criterion. The literature reveals that the effect of size on mixed-mode fracture behavior of brittle nanocomposites has not been well investigated previously using modified maximum tangential stress criterion. The studied nanocomposites were made of epoxy resin reinforced with 7 wt%, 20-30 nm nanosilica. The accuracy of the method was assessed by taking into account the high-order terms of Williams series expansion along with finite element over-deterministic method. To investigate the effect of size on fracture toughness, a number of three-point semi-circular bending tests with different radii and four angles of edge-crack orientation were conducted and subjected to mixed-mode loading. The size of fracture process zone and apparent fracture toughness (K c) were also evaluated as a function of sample size. Experimental results showed that the proposed approach can accurately predict the fracture behavior of studied nanocomposites.

An insight into mode II fracture toughness testing using SCB specimen

“…12,13 A review of literature on the application of SCB specimen in the brittle fracture tests shows that the researchers have utilized various types of supports when conducting the SCB tests. For example, the support that has been used in previous studies [14][15][16][17][18][19][20][21][22] is completely fixed and cannot move in the horizontal direction. There are numerous other investigations that have used the roller-in-groove type of supports (see previous studies [23][24][25] ).…”