Environmental crack and craze growth phenomena in polymers

Abstract

The nature of slow crack and craze propagation in polymers and crack propagation in inorganic glass has been considered in terms of time dependent processes. By using a fracture mechanics analysis together with time dependent material parameters, equations have been derived to describe crack and craze propagation in both inert and active environments. Experimental data from a range of materials suggest that a crack opening displacement (c. o. d. ) criterion governs the crack propagation behaviour. Incorporation of a simple fluid flow model into the c. o. d. analysis has allowed the failure processes in liquid environments to be described. The data on organic polymers and inorganic glass suggest that when there are no problems of maintaining the environmental supply, the crack growth behaviour is controlled by relaxation processes in the material. At high crack speeds a transition from relaxation to fluid flow control occurs when the time scale is too short for the liquid flow to be maintained. The flow of an environment in long crazes can be shown to influence their behaviour in a similar manner, while under other conditions relaxation controlled craze growth can occur.

Experimental Investigation of Dynamic Fracture Initiation in PMMA Submerged in Water

“…It was discovered that there is an increase in the energy required for fracture to occur in the presence of liquids, such as water, oils and alcohols, thus, plasticizing the crack-tip and increasing the toughness of the material. These results complement the findings by Williams and Marshall [4]. Additionally, it was discovered that the effect of water on fracture toughness is rate sensitive, which means that the effect of water on crack propagation was dependent on the crack-tip speed.…”

“…One of the first studies on the effect of liquid environments on fracture was performed on PMMA and inorganic glass by Williams and Marshall [4]. A fracture mechanics approach was used in conjunction with time-dependent material parameters to describe crack propagation in both air and liquid environments.…”

Decohesion Kinetics in Polymer Organic Solar Cells

“…13,23,32,33 The sigmoidal shape of these curves is more pronounced at high P3HT M W and decreases with decreasing M W . Viscoelasticity at the decohesion tip would allow for significant plastic deformation, which helps to dissipate mechanical energy and to resist decohesion growth.…”

Effect of mixed mode I and II loading on the fracture surface of polymethyl methacrylate (PMMA)

“…Crack propagation occurs by breaking (or scission) of the fibrils. Crack initiation has been suggested to occur at a critical craze tip opening displacement [21]. At higher stiffness higher stress levels may be attained before reaching the critical opening displacement.…”