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Review Article

Appl. Mech. Rev. 2018;70(3):030801-030801-23. doi:10.1115/1.4040448.

Composite laminate has extensive usage in the aerospace and automotive industries. Thus delamination, one of its most prevalent and challenging failure modes, has attracted substantial research efforts, and lead to the rapid development of both simulation and experiment method. Although reviews exist about simulation and experiment methods, there are not many that cover the development in the last five years. This paper is targeted to fill that gap. We covered a broad range of topic in delamination, from the basic delamination onset and propagation theories to complex loading scenarios, like impact and fatigue loading. From a simulation point of view, virtual crack closure technique (VCCT) and cohesive zone model (CZM), the two most famous methods of delamination modeling, are compared and elaborated. Their implementation techniques are described, and their merits and drawbacks are discussed. We also covered the failure mode of combined delamination and matrix cracking, which is prevalent in impact loading scenarios. Simulation techniques, along with the failure mechanisms, are presented. From experiment point of view, the discussed topics range from delamination fracture toughness (DFT) tests under static, dynamic, or cyclic loading conditions, to impact tests that aim to obtain the impact resistance and residual strength after impact. Moreover, a collection of recent experiment data is provided.

Commentary by Dr. Valentin Fuster
Appl. Mech. Rev. 2018;70(3):030802-030802-12. doi:10.1115/1.4040402.

This paper aims at presenting a survey of the fractional derivative acoustic wave equations, which have been developed in recent decades to describe the observed frequency-dependent attenuation and scattering of acoustic wave propagating through complex media. The derivation of these models and their underlying elastoviscous constitutive relationships are reviewed, and the successful applications and numerical simulations are also highlighted. The different fractional derivative acoustic wave equations characterizing viscous dissipation are analyzed and compared with each other, along with the connections and differences between these models. These model equations are mainly classified into two categories: temporal and spatial fractional derivative models. The statistical interpretation for the range of power-law indices is presented with the help of Lévy stable distribution. In addition, the fractional derivative biharmonic wave equations governing scattering attenuation are introduced and can be viewed as a generalization of viscous dissipative attenuation models.

Commentary by Dr. Valentin Fuster

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