Crack Propagation Modes in Particulates: A Study Approaching Reality

Abstract

Cracked composite plates with spherical glass inclusions bonded inside a flexible matrix made of an epoxy polymer were subjected to impact. The effect of the inclusions on an edge crack propagating inside the plate was investigated, as well as the interaction of two skew-parallel edge cracks propagating in the same composite plates. It was found that generally the inclusions repel the cracks in both cases studied, and they are responsible for the bifurcations of the propagating cracks. A crack arrest phenomenon also appeared at the neighborhood of inclusions, which was followed by a subsequent emission backwards of Rayleigh waves. Moreover, the skew-parallel cracks always attracted each other, although the inclusions provoked the cracks to deviate from their initial paths. For the study of crack propagation inside these composite plates the optical method of caustics was used for the evaluation of the crack velocities, as well as the instantaneous values of the dyanmic stress-intensity factor K r (t) and K rr (t) at the crack tips. Interesting results were derived concerning the variation of the velocities and SIFs of the cracks inside particulatefilled plates.

Fracture Toughness of Polypropylene-Based Particulate Composites

“…The presence of a plastic zone affects not only the fracture initiation but also the propagation values (e.g. crack bifurcation, deviation [ 31 ]). Crack bifurcation in a filled system with coarser particles may generate a zig-zag path and thus enhances the tearing modulus.…”

Co-milling-assisted exfoliated graphite nanoplatelets filler introduction in polyethylene and alumina composites

“…The breaking stress and strain characteristics of the sets of samples tested are represented in Table 1. The results indicate that the addition of 0.25–0.75 wt% M ex GnP-8 filler, and addition of 0.25–0.75 wt% graphite exfoliated via a co-milling route, had effectively enhanced the strength via an established effect of filler disrupting the propagation of cracks induced by the tensile stress during the tensile test, 48,49 resulting in greater tensile stress to break. 50 Direct addition of 0.25–0.75 wt% graphite into polyethylene, however, was not able to attain the same enhancement in tensile strength like it did for the addition of 0.25–0.75 wt% M ex GnP-8 or addition of graphite exfoliated via co-milling.…”

Computational Approach to Modelling Fracture Behaviour of Polypropylene/Talc Composites

“…The fracture behavior/toughness of polymers is strongly affected by the addition of rigid particles [16][17][18]. Several features of the particles have a decisive influence on the values of the fracture toughness: shape and size, chemical nature, surface nature, concentration by volume, and orientation.…”