Methods and Systems to Evaluate Structures to Account for R-Curve Effects

A method of determining propagation of a crack within a structure made of a bonded or layered material, the method comprising:

• performing experimental testing on one or more test coupons of the material;
• determining an R-curve and a Paris law curve of the material;
• performing computer simulations on a computer model of the structure;
• and
• applying results of computer simulations to the R-curve and the Paris law curve and determining a change in a crack in the structure.

A computing device configured to determine propagation of a crack within a structure made of a bonded or layered material, the computing device comprising:

• processing circuitry;
• and
• memory circuitry comprising a computer model of the structure and physical properties of the structure, the memory circuitry further comprising program instructions that, when executed by the processing circuitry, configures the computing device to:
• perform a computer simulation that applies a cycle of loads to the computer model;
• determine strain energy release rates and a crack length after each of the applied loads through the computer model;
• apply the strain energy release rates and crack lengths to an R-curve of the material and determine effective strain energy release rates for the applied loads;
• apply the effective strain energy release rates to a Paris law curve of the material and determine changes in the crack length for the load cycles;
• and
• advance a crack that is simulated in the computer model after the load cycles.