A SIMPLIFIED DETERMINATION OF THE J-INTEGRAL FOR PAPER

A novel, simplified, method for evaluating the J-integral for paper sh eets has been developed. The inaccuracy of the single-specimen method (proposed by Rice et al. [8]), when applied to the fracture toughness testing of paper, was found to result from an erroneous assumption abo ut the relationship between the load and the displacement due to plast icity. A new method was developed theoretically; it is based on a modi fied assumption about this relationship. Using this method, the J-inte gral can be evaluated with a single load-displacement curve together w ith a new parameter that must be separately evaluated using at least o ne additional specimen. Although the new method requires a minimum of two notched specimens, it provides more flexibility than previous modi fications of the single-specimen method. The experimental study indica ted that the present method yields values of J(c) (the critical value of the J-integral) which agree very closely with those obtained using the cumbersome multiple-specimen method, and is therefore more suitabl e for paper testing than other methods presently available.