PSI - Issue 2_B

Andreas J. Brunner et al. / Procedia Structural Integrity 2 (2016) 088–095 Author name / Structural Integrity Procedia 00 (2016) 000–000

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4. Summary

A procedure for fitting Mode I fracture fatigue data of CFRP composites with a modified Hartman-Schijve equation is investigated with respect to scatter in G thr caused by the scatter in the data and in the other fitting parameters. This consists of fitting the full, the lower and upper range of the data points in the double-logarithmic Hartman-Schijve graph with a power law for determining prefactor D and the exponent  . A can be selected as the average critical energy release rate from quasistatic-tests on the same type of CFRP. Finally, G thr is selected for each set of values of A,  and D such that a visually judged “best” fit between predicted and measured values is achieved. This will give an indication of the average value and of the scatter in G thr . This procedure can be extended by including more values of A,  and D in the fitting for G thr and calculating average and standard deviation from that. Acknowledgements G.B. Murri (NASA Langley) provided the raw fatigue data for the analysis, and discussions with A.J. Kinloch, J.G. Williams (Imperial College) and M. Hojo (Kyoto University) are gratefully acknowledged. References ASTM D5528 Standard test method for Mode I interlaminar fracture toughness of unidirectional fiber-reinforced polymer matrix composites, 2013, American Society for Testing and Materials International. ASTM D5229 / D5229M Test method for moisture absorption properties and equilibrium conditioning of polymer matrix composite materials, 2014, American Society for Testing and Materials International. ASTM E647 Standard test method for measurement of fatigue crack growth rates, 2015, American Society for Testing and Materials International. ASTM D6115 Standard test method for mode I fatigue delamination growth onset of unidirectional fiber-reinforced polymer matrix composites, 1997, American Society for Testing and Materials International. Brunner A.J., Murphy N., Pinter G. 2009, Development of a standardized procedure for the characterization of interlaminar delamination propagation in advanced composites under fatigue mode I loading conditions, Engineering Fracture Mechanics, 76, 2678–2689. Jones R., Pitt S., Brunner A.J., Hui D., 2012, Application of the Hartman-Schijve equation to representing mode I and mode II fatigue delamination growth in composites, Composites Structures, 94(4), 1343-1351. Jones R., Stelzer S., Brunner A.J., 2014, Mode I, II and Mixed Mode I/II delamination growth in composites, Composite Structures, 110, 317– 324. Murri G.B., 2013, Evaluation of Delamination Onset and Growth Characterization Methods under Mode I Fatigue Loading, Langley Research Center, Hampton, Virginia, NASA Technical Memorandum TM-2013-217966. Hartman A, Schijve J., 1970, The effects of environment and load frequency on the crack propagation law for macro fatigue crack growth in aluminium alloys, Engineering Fracture Mechanics, 1(4), 615–631. Hojo M., Tanaka K., Gustafson C.G., Hayashi R., 1987, Effect of Stress Ratio on Near-threshold Propagation of Delamination Fatigue Cracks in Unidirectional CFRP, Composites Science and Technology, 29, 273-292. Paris P, Erdogan F., 1963, Discussion on: Liu HW, Fatigue crack propagation and applied stress range, ASME Transactions, Journal of Basic Engineering, 85D(1), 116–120. Pascoe J.A., Alderliesten R.C., Benedictus R., 2013a, Methods for the prediction of fatigue delamination growth in composites and adhesive bonds – A critical review, Engineering Fracture Mechanics 112-113, 72–96. Pascoe J.A., Rans C.D:, Benedictus R., 2013b, Characterizing fatigue delamination growth behaviour using specimens with multiple delaminations: The effect of unequal delamination lengths, Engineering Fracture Mechanics, 109, 150–160. Pascoe J.A., Alderliesten R.C., Benedictus R., 2015, On the relationship between disbond growth and the release of strain energy, Engineering Fracture Mechanics, 133, 1–13. Smith R.A., 1977, On the short cracks limitations of fracture mechanics, International Journal of Fracture, 13(5), 717-720. Stelzer S., Brunner A.J., Argüelles A., Murphy N., Pinter G., 2012, Mode I delamination fatigue crack growth in unidirectional fiber reinforced composites: Development of a standardized test procedure, Composites Science and Technology, 72, 1102–1107. Stelzer S., Brunner A.J., Argüelles A., Murphy N., Cano G.M., Pinter G., 2014, Mode I delamination fatigue crack growth in unidirectional fiber reinforced composites: Results from ESIS TC4 round-robins, Engineering Fracture Mechanics, 116, 92–107. Yao L.J., Alderliesten R.C., Zhao M.Y., Benedictus R., Discussion on the use of the strain energy release rate for fatigue delamination characterization, 2014, Composites: Part A, 66, 65–72. Yao L.J., Alderliesten R.C., Benedictus R., The effect of fibre bridging on the Paris relation for mode I fatigue delamination growth in composites, 2016, Composite Structures, 140, 125–135.