Finite element model and experimental analysis of crack–inclusion interaction

Abstract

Illinois 60680, and 'The Dow Chemical Company, 2301 N. Brazosport Blvd., Freeport, Texas 77541 SYNOPSISOne of the key requirements for developing tough multiphase blend systems, for example, selecting the type of discrete phases (hard or soft) in a polymer matrix, is the ability to predict the fracture path. Most of these selections rely heavily on prior experience or on intuitive rationale. There are few mathematical guidelines for the materials scientists who are designing new multiphase systems. This article is designed mainly to provide such insight through the development of a theoretical model and through experimental observation. A finite element model has been used to predict the crack velocity and the crack path for a crack that approaches and penetrates a hard or a soft inclusion. A novel experimental approach is then utilized to verify these predictions by introducing hard and soft circular domains in poly (ethylene-co-carbon monoxide ) specimens by selective photodegradation. 0

Mechanical and fracture behavior of an artificially ultraviolet‐irradiated poly(ethylene‐carbon monoxide) copolymer

“…The biggest scatter bands are on the failure strain for lower irradiation times because this is the time of greatest sensitivity to UV irradiation. From Figure 5(a,b), it is clear that overall UV‐light exposure drastically affects the mechanical response of ECO, as reported in previous investigations 1, 8, 9–13. The elastic modulus increases with the irradiation time and after 130 h of irradiation attains a value about 2.15 times larger than that of the unirradiated one.…”

“…The initially very ductile ECO becomes increasingly more brittle with the UV‐irradiation time: the failure strain decreases, mostly during early irradiation times,1, 8 and the elastic modulus increases, with shorter wavelengths (<328 nm) being primarily responsible for this photodegradation 9. Exploiting this behavior, and motivated by the work of Li et al,10 Lambros et al11 developed a simple and inexpensive technique for the fabrication of laboratory‐scale graded materials by gradually altering the mechanical properties of ECO through selective UV irradiation. Figure 1 shows uniaxial stress–strain curves obtained by Lambros et al11 for ECO irradiated at different times.…”

Crack Path Selection in Microstructurally Tailored Inhomogeneous Polymers

“…From Figures 3.1-3.4, it is apparent that UV light exposure alters the mechanical response of ECO in a fashion very similar to that seen in previous works (Andrady, 1990;Andrady et. al., 1993;Li et. al., 1993;Ivanova et.…”

A discrete crack dynamics model of toughening in brittle polycrystalline material by crack deflection

“…Consequently, the energy release rate inside the soft inclusion was not computed. However, Li et al (49) found both numerically and experimentally that the energy release rate decreases as the crack propagates through the soft inclusion, as one would expect. As the crack exits the inclusion the energy release rate quickly reaches that of a crack at a grain boundary in the absence of a soft inclusion or a void.…”