Ruixiang Bai

Interfacial mechanical behaviour of protein–mineral nanocomposites: A molecular dynamics investigation

Biological composite materials, such as bone, tooth and nacre, are comprised of a mixture of nano-sized hard components (e.g. mineral platelets) and soft components (e.g. protein molecules). Their mechanical behaviour greatly depends on the protein-mineral interfaces. This paper investigates the effects of mineral surface nanostructures on the interfacial interaction and mechanical behaviour of protein-mineral nanocomposites. Interfacial shear between osteopontin (OPN) and hydroxyapatite (HA) mineral layers with surface nanostructures is investigated using the atomistic molecular dynamics (MD) simulations. The results indicate that the OPN residues can be attached to HA surfaces but the surface nanostructures greatly affect the interfacial interaction and mechanical behaviour. The HA layers with a higher number of nano-sized grooves (defects) increase the surface roughness but reduce the pulling force and energy dissipation.

Study on Low-velocity Impact and Compression Failure of Composite Foam Sandwich Panel

In this paper, the surface deformation and energy absorption of the structure after low-velocity impact and the bearing capacity of the compression after-impact structure were numerically simulated and experimentally studied. Firstly, the finite element method was used to simulate the low velocity impact process of the composite foam sandwich panel. The damage of the laminated structure panel is judged by the Hashin criterion. The simulation results show that the tensile failure of matrix on the outer panel is the main failure mode during process of impact. In addition, the energy absorption behavior of both the panels and the foam were compared, which is founded that the foam absorbs a lot of energy, and the remaining energy is basically absorbed by the outer panel. Finally, the axial compression calculation was carried out using the model with impact damage and undamaged condition, demonstrating that the bearing capacity of the structure with impact damage is greatly reduced.

Study on 180o Peel Test of Interface Adhesive Honeycomb Sandwich Structure

180o Peel experiment was designed and performed to estimate the peel strength parameters and failure modes of the interface adhesive Honeycomb Sandwich Structure (HSS). The aluminum-lithium alloy honeycomb core and skin specimens were bonded with adhesive according to the adhesive bond strength test standards, and the honeycomb shape is hexagon. 180o peel test was conducted using the designed fixtures so as to compare the peel strength and failure form of the adhesive layer. The peel strength was calculated by recording the peel load-displacement curves and observing the destruction of the interface during the experiment. Simultaneously, local strain field, especially at the critical moment of the breakage point, was obtained by digital image correlation (DIC). The results show that failure mode of the HSS with interfacial adhesive is cohesion failure of the adhesive, and the results of numerical analysis are in good agreement with the experiments.

The strength and failure of silica optical fibers

The mechanical strength and failure behavior of conventional and microstructured silica optical fibers was investigated using a tensile test and fracture mechanics and numerical analyses. The effect of polymer coating on failure behavior was also studied. The results indicate that all these fibers fail in a brittle manner and failure normally starts from fiber surfaces. The failure loads observed in coated fibers are higher than those in bare fibers. The introduction of air holes reduces fiber strength and their geometrical arrangements have a remarkable effect on stress distribution in the longitudinal direction. These results are potentially useful for the design, fabrication and evaluation of optical fibers for a wide range of applications.

Fracture Behaviour of Microstructured Silica Optical Fibres

Abstract Microstructured optical fibres (with a periodic transverse microstructure) are of interest since they offer a simple alternative to controlling the index profile of optical waveguides. Although many types of optical fibres and cables have been developed to meet the needs of communications service providers for long-term performance and reliable operation, the brittle nature, aging and fatigue of these fibres remain as the key materials issues. The flaws on the surface of fibres caused by processing (drawing) or subsequent assembling make the situation more complex. In this work, experimental investigation and fracture mechanics analyses have been conducted to understand the fracture behaviour of these newly-developed optical fibres. The results are believed to be useful for design, fabrication and evaluation of optical fibres for a variety of applications.