13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- Figure 6. Force displacement response of DCB specimen from experiment and simulation It is found that the value of bridging stress significantly affects the response of the specimen. Fig. 6 also implies that the linear law of σb-δ response doesn’t fit the experiments very well. By making GA = GB in Fig. 4, the determined σb distribution degrade the cohesive element too fast such as σb = 2.5 MPa in Fig. 6, or too slow as σb = 0.5 MPa in the figure. 4. Conclusion The delamination growth behavior of composite laminates with fiber bridging is experimentally and numerically studied. A normalized fatigue crack growth rates law and thresholds model is presented to introduce the R-curve effect caused by fiber bridging. The cohesive element approach is also extended from bilinear constitutive response to a tri-linear response to simulate the delamination both in fracture and bridging zone. The normalized fatigue law is found in accordance with experiments in high degree. The numerical model, however, degrades the cohesive element too fast or too slow due to the linear bridging stress law adopted. A nonlinear bridging law should be developed to fit the experiment better and a numerical verification for fatigue delamination growth will be conducted based on the new bridging law. Acknowledgement Financial support provided by the National High Technology Research and Development Program of China (863 Program) through grant number 2012AA040209, and by the National Natural Science Foundation of China through grant number 11202243 is gratefully acknowledged.
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