Researching Damage mechanic models

I spent a while looking at damage mechanic models only to discover everyone who has written a paper says they have a model for what ever it is they are looking at, which is annoying. So I eventually searched for review of damage mechanic models yielding slightly more information but not descriptive enough. I got an email from my supervisor saying to model a basic solder model and look at "Cohesive Zone" and "Fracture Mechanics Method (Paris Law, etc)". Now I want to know what is "Cohesive Zone" and "Fracture Mechanics Method (Paris Law, etc)"

Cohesive Zone modelling

I wanted a description of Cohesive Zone Modelling, one of the first papers I found was written by a PhD student (not sure if the paper was accepted or not) the report went in to some detail. It says it was invented by Dugdale(1960), Barenblatt (1962), Rice (1968) amongst others. From what I can gather it regards a fracture as an gradual process where separation takes place between two adjacent surfaces across am extended crack tip (cohesive zone) and is resisted by the presence of cohesive forces.
Cohesive forces: it is the force of attraction between the particles of the same substance
Unfortunately I got confused after this, so I came across this paper