Nonlinear Characterizing of the Crack Growth Behavior in a Filled Elastomer

In this study, the crack growth behavior in a filled elastomer, containing hard particles embedded in a rubbery matrix, was investigated. The specimen was tested at a constant strain rate of 0.067 cm/cm/min at room temperature. Two initial crack lengths, 2.54 mm and 12.7 mm, were considered. A hybrid experimental-numerical method was used to calculate the Jintegral value. They also revealed that the initial crack length had a significant effect on the critical J-integral value for the onset of crack growth but had no significant effect on the subsequent crack growth behavior. It also revealed that a power law relationship existed between the crack growth rate and the J-integral. Introduction: An important engineering problem in structural design is the evaluation of structural integrity and reliability. There are two well-known structural design philosophies; namely, safe-life and damage-tolerance. According to the safe-life design philosophy, no crack will initiate in the structure during its design service life. In other words, the service life of a structure is terminated once a crack is predicted or detected. On the other hand, the damagetolerance design philosophy assumes the existence of cracks or defects in the structures and guards against their unstable growth. Meaning that the damage-tolerance design approach seeks to avoid the growth of the existing crack to a critical crack size. Therefore, in order to determine the ultimate service of a structure or the critical crack size, a crack growth model needs to be developed. . In recent years, a considerable amount of work has been done studying crack growth behavior in particulate composite materials under different loading conditions (1-6). Experimental findings indicate that power law relationships exist between the crack growth rate, da/dt, and the Mode I stress intensity factor, KI. These experimental findings support the theory developed by Knauss (7) and Schapery (8) in their studies of crack growth behavior in linear viscoelastic materials. Classical fracture mechanics principles, especially linear elastic fracture mechanics, are well established for single-phase materials. Experimental data indicate that linear fracture mechanics theories are applied to the particulate composite materials with varying degree of success. However, there has been relatively little effort in characterizing the crack growth behavior in highly filled elastomers based on nonlinear fracture mechanics. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 27 MAY 2004 2. REPORT TYPE 3. DATES COVERED 4. TITLE AND SUBTITLE Nonlinear Characterizing the Crack Growth Behavior in a Filled Elastomer 5a. CONTRACT NUMBER