The honeycomb (HC) core of sandwich structures undergoes flexural loading and carries the normal compression and shear. The mechanical properties and deformation response of the core need to be established for the design requirements. In this respect, this article describes the development of the smallest possible representative cell (RC) models for quantifying the deformation and failure process of the Nomex polymer-based hexagonal HC core structure under the out-of-plane quasi-static loadings. While the hexagonal single and multi-cell models are suitable for the tension and compression, a six-cell model is the simplest RC model developed for shear in the transverse and ribbon direction. Hashin’s matrix and fiber damage equations are employed in simulating the failure process of the orthotropic cell walls, using the finite element (FE) analysis. The FE-calculated load–displacement curves are validated with the comparable measured responses throughout the loading to failure. The location of the fracture plane of the critical cell wall in the out-of-plane tension case is well predicted. The wrinkling of the cell walls, leading to the structural buckling of the HC core specimen in the compression test, compares well with the observed failure mechanisms. In addition, the observed localized buckling of the cell wall by the induced compressive stress during the out-of-plane shear in both the transverse and ribbon direction is explained. The mesoscale RC models of the polymer hexagonal HC core structure have adequately demonstrated the ability to predict the mechanics of deformation and the mechanisms of failure.

Wastewater containing heavy metals, such as nickel ions (Ni2+), discharged from industry to water streams poses a serious threat because even at low concentrations, it does not naturally degrade and is toxic to human and aquatic life. This article reviews a novel technique for wastewater treatment using a Sayong ball clay (SBC) membrane to remove nickel from industrial wastewater. SBC powder was achieved through milling using a planetary ball mill (milling time; 10, 20 and 30Â h), further labelled as SBC 10, SBC 20 and SBC 30, with a ball-to-powder of ratio 7:1 and rotation speed of 300Â rpm. The physical characteristics of the apparent porosities, bulk density and shrinkage were investigated. XRD was used to study the phase, while FESEM was used to analyse the microstructure of the fired membrane. The FESEM microstructure indicates a decreased particle size (SB30). Filtration was conducted using a dead-end filtration system. The fabricated SBC 10, 20 and 30 membranes showed significant removal of nickel from industrial wastewaterâ88.87%, 82.96% and 85.13%, respectively. This study revealed that the SBC membrane is a promising membrane to remove nickel from industrial wastewater. The results also indicate the possibility of highlighting the introduced technique as a new technique for the treatment of industrial wastewater. As a new trend for waste management, pollution prevention could be applied in Malaysia as one of the advanced biotechnologies to solve various environmental problems. Keywords: environmental management, wastewater treatment, waste processing, heavy metal

This paper presents a comprehensive survey on the importance of free space optics (FSO) systems used as last mile for communication systems and their integration with optical fibers. Optical fiber is already being used in the backbone networks due to its high speed and high bandwidth qualities but the last mile has always been a problem. Last mile is the last physical connection between access network and the end user. FSO systems provide an innovative solution to this problem. The surveyed integration techniques are explained with their working principles. All the nodes used to make this integration possible are also thoroughly explained. The advantages and disadvantages of FSO systems are also listed and discussed. The paper also discusses current challenges and directions for future research.

The extensive applications of honeycomb (HC) core in sandwich structures necessitates the influence of the cellular geometry and cell wall base material on the mechanical response to be quantified. In this respect, this paper establishes the mechanics of the deformation and the failure processes of the HC core under the out-of-plane compressive, tensile, and shear loading. The corresponding mechanical properties are determined and the mechanisms of failure of the HC core structure are identified. The influence of the relative density (ρ*/ρ _s ) and the cell aspect ratio (H/c) of the hexagonal HC core on the compressive deformation response, the out-of-plane properties and the characteristic dissipation energy density (DED) of the structure is established. Results show that the compressive strength increases exponentially from 1.5 to 10.6 MPa over the relative density range of 0.028 ≤ (ρ*/ρ _s ) ≤ 0.125. The out-of-plane shear modulus, G ₁₃ and G ₂₃ are 33.9 and 58.2 MPa, while the shear strength, τ ₁₃ and τ ₂₃ are 1.07 and 2.03 MPa, respectively. The HC core with a low aspect ratio (H/c < 2.64) failed due to the early debonding of the double-wall hexagonal cells, while at H/c ≥ 2.64, by elastic buckling of the cells. A phenomenological model is formulated to highlight the combined effects of both parameters on the compressive strength (σ _c ) of the HC cores, covering the range of 0.028 ≤ (ρ*/ρ _s ) ≤ 0.056 and 2.5 ≤ (H/c) ≤ 5.62. Furthermore, the characteristic dissipation energy density (DED) under the out-of-plane compression varies linearly within the range of 2.5 < (H/c) < 5.62 for the HC core with ρ*/ρ _s = 0.056. The HC core with H/c = 3.96, but with twice higher ρ*/ρ _s exhibits about twice larger DED. These resulting properties and failure mechanisms of the anisotropic paper-based HC core are useful for the validation of the predictive computational models.