Ultrasonic additive manufacturing of nanocrystalline laminated composites

Ultrasonic additive manufacturing has been used to fabricate laminated composites of commercially pure aluminum and a nanocrystalline nickel–cobalt (nc-NiCo) alloy. The nc-NiCo alloy would not weld to itself but readily welded to aluminum. Thus, by alternating between foils of nc-NiCo and Al, we achieved multi-material laminates with strong interlayer bonding. Electron microscopy showed that the nanoscale grain structure of the nc-NiCo was preserved during deposition and that the nc-NiCo/Al weld interface was decorated with comminuted surface oxides as well as Al–Ni–Co intermetallics. These findings are considered in light of process models of junction growth, interdiffusion, and grain growth, which together reveal how the different pressure- and temperature dependences of these phenomena give rise to a range of processing conditions that maximize bonding while minimizing coarsening and intermetallic formation. This analysis quantitatively demonstrates that using a soft, low melting point interlayer material decouples junction growth at the weld interface from grain growth in the nc-NiCo, expanding the range of optimal processing conditions. Graphical abstract

Treatise on Sustainable Infrastructure Construction: Green Composites, Cross Laminated/Mass Timber, Wood Truss Connectors, Nondestructive Technologies, Health Assessment and Monitoring: Utility Poles and Geofoam

The understanding of the engineering performance of green laminated composites is necessary to the design of load bearing components in building and infrastructure construction, and packaging applications. These components are made of outer thin laminae called skins or faces and a thick inner layer called core. The use of bonding is unavoidable in the assembling of these composite products. Like all materials, the bonding materials have finite mechanical properties, e.g. stiffness, but when used in the literature, they are assumed perfectly rigid. That is an unrealistic assumption. Our analytical solutions change this assumption by using the real properties of bonding. In general, the analytical formulations are based on the equilibrium equations of forces, the compatibility of interlaminar stresses and deformation, and the geometrical conditions of the panels. Once solutions are obtained, the next step is to evaluate them. The numerical evaluations proved that perfect rigid bonding in laminated composites greatly underestimates the true performance. At low values of adhesive stiffness, the serviceability is multiple orders of magnitude of that at high values. The logical question is thus: what constitutes perfect bonding? The answer to this question lies in the core-to-adhesive stiffness. The lower the ration is the higher the error in using the rigid-bond theories. It is worth noting that green-composites in this chapter refer to components made of traditional materials such as wood, in addition to newly developed bio-based and bio-degradable and bio-based composites, made of renewable resources. In addition, bonding and adhesive are used interchangeably.

Study of mode II interlaminar fracture toughness of laminated composites of glass and jute fibres in epoxy for structural applications

Composites are being used in the place of metals in many industries as they have a lower density and are cheaper than metals. In aerospace industries there is requirement for light weight together with strength, and reinforced fibre composites are superior in some critical properties compared with metals. In this study, laminated composites were fabricated with woven E-glass and jute fibres in an epoxy matrix by a hand layup method. The samples were prepared as per the relevant the America Society for Testing ad Materials (ASTM) standard and tested for mode II interlaminar fracture toughness to investigate delamination resistance. Mode II interlaminar fracture toughness was evaluated by an end-notched flexure test using three-point bending. The fracture toughness G IIC was calculated for a curing temperature range from 40 °C to 70 °C at intervals of 5 °C for different sets of laminated composites. The investigations revealed that when the curing temperature of laminated composites was increased from 40 °C to 70 °C, the interlaminar fracture toughness G IIC was increased in neat woven E-glass laminated composites, decreased in neat jute laminated composites, significantly increased in laminated composites with woven E-glass fibres in compression and jute fibres in tension and slightly increased when woven E-glass fibres were kept in tension and jute fibres in compression.