Papers by Author: Da Zhi Jiang

Abstract: The effects of CNR diameter and CNR number on tensile properties of the CNR-graphene hybrid structure (CGHS) were studied by molecular dynamics simulation in this paper. Results show that interactions between adjacent graphene sheets are significantly strengthened by the cross-linked CNRs. For CGHSs, the maximum strength is ~64.0 GPa and the maximum Young’s modulus strength is ~763 GPa. When the diameter of CNRs is large or the CNR linkers are dense, the tensile strength of CGHSs reached the maximum and the fracture mechanism of CGHSs changed from CNR-graphene junction fracture to graphene sheet fracture. Present work should serve as guide to experiments concerning physical properties of this novel material.

Abstract: In this work, a kind of conductive polymer-silver paste was used to fabricate carbon fabric composite frequency selective surfaces (FSS) with four-legged slot elements. Screen printing and 3D engraving process were carried out to coat the conductive polymer-silver paste onto the carbon fabric preform and sculpt composite panels into composite FSSs, respectively. Free space and finite element methods were carried out to measure and calculate the electromagnetic transmission characteristics of the composite FSS, respectively. The calculated results are in good agreement with the experimental data. The cascaded effect in double-layered FSS were investigated by finite element method and design of experiment technique (DOE).

Abstract: Dynamic response and damage mechanism of two-core sandwich panels with foam and honeycomb cores and glass fiber/epoxy composite sheets under low-velocity transverse impact are investigated. The emphasis is focused on the contact force response and crash mechanism of the two-core sandwich panels. Effects of configurations, impact energy levels and types of the cores on the dynamic response are investigated. A modified drop-test experiment is carried out to obtain contact force history of the two-core sandwich structures under different impact energies. The experimental results show that the 10:10 configurations for both honeycomb and foam core sandwich structures under lower impact energy absorb more impact energy than the other two structures. However, under higher impact energy, the honeycomb core sandwich structures of 15:5 configuration absorbs a little more impact energy than the other two, while for the foam core sandwich structures the 5:15 configuration shows a little better impact resistance. Results also show that when impact energy is low foam core sandwich structures do better in absorbing impact energy than the honeycomb ones.

Abstract: In this work, the hybrid fabrics of carbon and quartz fibers as filters were adopted in PMI core sandwich structures for low-observable radomes. The advantages of fabric composite frequency selective surfaces (FCFSSs) are easily fabricated by braiding and shaped into curved surfaces. This paper mainly studied the electromagnetic (EM) transmission characteristics of the low-observable radome wall with composite FSS by 3-dimensional electromagnetic analysis software. First of all, the accuracy of the simulation model composed of up and down composite face sheets, a layer of composite FSS and PMI core was validated by comparing with experimental results. Then, the studies on electromagnetic transmission characteristics of the sandwich structure with composite FSS and the sensitivity analysis about the thickness and permittivity of face sheets and PMI core were carried out. The results show that the sandwich structure with single layer composite FSS can realize the function of frequency selection, limit the reflection at the resonance frequency and decrease the sensitivity of EM transmission loss about the thickness of sandwich structures.

Abstract: Hybrid composites are increasingly concerned by the investigators and widely used in many areas, especially aerospace industry, for its multi-functional properties. In the present study, the mechanical properties and thermal properties of a structural component manufactured by a new hybrid composite consisting of quartz fiber, carbon fiber and cyanate ester resin has been investigated by finite element numerical simulation. The results show that the mechanical properties of the structural component are very good. And the temperature of inside face is 43.8 °C. The thermal strain is lower than 0.15%.

Abstract: Traditional sandwich structure consists of two face sheets and a core. With an internal sheet inserted into the core, a two-core sandwich structure is then formed. Two-core sandwich structures with composite laminated face sheets and a thin internal sheet subjected to low velocity impact are studied in this paper. Local displacement of the core under the point of impact is investigated. Simulated results show that the local displacement of the core along the direction of the impact has been decreased significantly by introducing the internal sheet into a traditional single sandwich structure and by reducing the space between the internal sheet and the impacted face sheet. Shear deformation in the cores of a two-core sandwich structure is also investigated and attention is focused on shear strains on interfaces between face/internal sheets and the cores. Results further show that strain levels in selected elements at the interested interfaces depend upon locations of the selected elements and arrangements of the internal sheet.