This contribution is a review of past and current research progress on dynamic response of composites sandwich structures subjected to low-velocity impact. To obtain a comprehensive overview of the current state-of-the-art published works, impact responses on sandwich structures are broadly classified into two main groups, high-velocity and low-velocity impacts, with the focus on low-velocity impact. A summary of some of the commonly used theoretical solutions for low-velocity impact is provided and described in some details. The response of low-velocity impact has been determined based on mass ratio, which is defined as the ratio of the impact mass to effective mass of the structural component. As a result, the response under low-velocity impact was further subdivided into three possible categories, namely, large, small, and medium mass impacts. For each category of impact, currently available suitable solutions are discussed in details. To classify the response of low-velocity impact and also to explore the energy-absorption characteristics as well, the impact duration is identified as the key parameter. The review concludes with detailed discussions on the damage mechanisms and failure criteria for sandwich structures subjected to impact loads.

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In this review, we summarize the recent advances in the area of catalytic dicarbofunctionalization of unsaturated π bonds by underpinning the catalytic domino transformations involving radical capture by nickel.

A visible-light-promoted photoredox/nickel protocol for the enantioselective three-component carboarylation of alkenes with tertiary and secondary alkyltrifluoroborates and aryl bromides is described. This redox-neutral protocol allows for facile and divergent access to a wide array of enantioenriched β-alkyl-α-arylated carbonyls, phosphonates, and sulfones in high yields and excellent enantioselectivities from readily available starting materials. We also report a modular and enantioselective synthesis of flurbiprofen analogs and piragliatin lead compound to demonstrate synthetic utility. Experimental and computational mechanistic studies were performed to gain insights into the mechanism and origin of chemo- and enantioselectivity.

A nickel-catalyzed, enantioselective, three-component fluoroalkylarylation of unactivated alkenes with aryl halides and perfluoroalkyl iodides has been described. This cross-electrophile coupling protocol utilizes a chiral nickel/BiOx system as well as a pendant chelating group to facilitate the challenging three-component, asymmetric difunctionalization of unactivated alkenes, providing direct access to valuable chiral β-fluoroalkyl arylalkanes with high efficiency and excellent enantioselectivity. The mild conditions allow for a broad substrate scope as well as good functional group toleration.

The development of catalytic carboacylation of simple olefins, which would enable the rapid construction of ketones with high levels of complexity and diversity, is very challenging. To date, the vast majority of alkene carboacylation reactions are typically restricted to single- and two-component methodologies. Here we describe a three-component carboacylation of alkenes via the merger of radical chemistry with nickel catalysis. This reaction manifold utilizes a radical relay strategy involving radical addition to an alkene followed by alkyl radical capture by an acyl-nickel complex to forge two vicinal C−C bonds under mild conditions. Excellent chemoselectivity and regioselectivity have been achieved by utilizing a pendant weakly chelating group. This versatile protocol allows for facile access to a wide range of important β-fluoroalkyl ketones from simple starting materials.

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Substituted alkenes are pivotal structural motifs found in pharmaceuticals and agrochemicals. Although numerous methods have been developed to construct substituted alkenes, a generally efficient, mild, catalytic platform for the conversion of alkynes to this highly functionalized scaffold via successive C–C bond forming steps remains in high demand. Here we describe an intermolecular, regio- and syn-stereoselective alkylarylation of terminal alkynes with tertiary alkyl oxalates via photoredox-Ni dual catalysis. This catalytic protocol, synergistically combining Ir/Ni-catalyzed alkyne difunctionalization with photoinduced alkene isomerization, affords trisubstituted alkenes with excellent efficiency and syn-stereoselectivity. The mild conditions tolerate many functional groups, allowing for a broad scope with respect to terminal alkynes, aryl bromides, and alkyl oxalates.