PSI - Issue 2_A

Michal K. Budzik et al. / Procedia Structural Integrity 2 (2016) 277–284 Budzik et al./ Structural Integrity Procedia 00 (2016) 000–000

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From the brief introduction given before, a sudden jump of the crack, viz . da/d Δ (in the present case ≡ da/dt → ∞) should be expected at the values of w λ = 1, and thus around w = 20 mm. The results suggest that this is, indeed, the case confirming that the process zone length could be used in the damage tolerant design or in deciding on acceptable sizes of the flaws inside the joints. 4. Conclusions We have studied in an experimental manner, crack propagation along heterogeneous interfaces with sharp transitions between weak and strong adhesion zones (or bonds and voids) perpendicular to the crack propagation direction. We found the raw experimental force vs . displacement curves are sensitive to the void sizes. The behavior is mainly affected by two length scales – the size of the void, w , and the process zone length, λ -1 , which could be gathered to a single non-dimensional parameter, w λ . In the present case, the voids resulting in w λ = 0.04 could be easily detected from the raw experimental curves. This, we believe, is an interesting and important finding showing good sensitivity of the experiment to the heterogeneities. We showed that the kinetics of the crack propagation is also affected by the aforementioned parameter. As expected, at the values of w λ close to 1, the crack becomes unstable, and as such it may be chosen as an additional design parameter following damage tolerance philosophy. Bresson, G., Jumel, J., Shanahan, M.E.R., Serin, P., 2013. Statistical aspects of the mechanical behaviour a paste adhesive. International Journal of Adhesion and Adhesives 40, 70-79. Brotherhood, C.J., Drinkwater, B.W., Dixon, S., 2003. The detectability of kissing bonds in adhesive joints using ultrasonic techniques. Ultrasonics 41(7), 521-529. Cuminatto, C., Parry, G., Braccini, M., 2015. A model for patterned interfaces debonding – Application to adhesion tests. International Journal of Solids and Structures 75-76, 122-133. Dundurs, J., 1969. Edge-bonded dissimilar orthogonal elastic wedges under normal and shear loading. Transactions of the ASME Journal of Applied Mechanics 36, 650-652. Gao, H., Rice, J.R., 1989. A first order perturbation analysis of crack trapping by arrays of obstacles. Transactions of the ASME Journal of Applied Mechanics 56, 826-836. Kanninen, M.F., 1973. An augmented double cantilever beam model for studying crack propagation and arrest. International Journal of Fracture 9, 83-92. Patinet, S.,Alzate, L., Barthel, E., Dalmas, D., Vandembroucq, D., Lazarus,V., 2013. Finite size effects on crack front pinning at heterogeneous planar interfaces: experimental, finite elements and perturbation approaches. Journal of the Mechanics and Physics of Solids 61(2), 311-324. Penado, F.E., 1993. A closed form solution for the energy release rate of the double cantilever beam specimen with an adhesive layer. Journal of Composite Materials 27, 383-407. Tadepalli, R., Turner, K.T., Thompson, C.V., 2008. Effects of patterning on the interface toughness of wafer-level Cu-Cu bonds. Acta Materialia, 56, 438-447. Willis, J.R., 2012. Crack front perturbations revisited. International Journal of Fracture 184(1), 17-24. References