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Guided ultrasonic wavefield propagation imaging (GUPI) is useful for visualizing hidden flaws in aerospace thin-walled structures, but the need for subjective signal processing involving three-dimensional Fourier transformation to increase the visibility of subtle flaws hinders its wider acceptance. A high-resolution wavenumber bandpass filter capable of consolidating subtle flaw-relevant information from a wide frequency band using only two-dimensional Fourier transformation was proposed. The filter overturns the long-standing belief that modes must be separated based on narrow-band data acquisition or processing to achieve high flaw visibility. Its characteristics and advantages were experimentally demonstrated through enhanced visualization of hidden wall-thinning flaws of a plate specimen. Its strength was further demonstrated through the first GUPI visualization of a partially loosened bolt, with unprecedented clarity to discern bolt tightness levels. The results conclusively proved that the proposed filter significantly enhances the resolution of GUPI within a structured processing framework. [ABSTRACT FROM AUTHOR]

The emergence of high-strength graphene marks a new milestone in the material science field. With only a small percentage inclusion into the matrix system, this organic nanoparticle could tremendously improve the strength in vast arrays of composites. At the same time, there is a growing interest in using the low-cost, lightweight, and high early strength geopolymer as the new binder for concrete. Compared to the traditional Ordinary Portland Cement (OPC), geopolymer emits 80% less CO2 during its production while exerting similar strength. Thus, the geopolymer has the potential to commercialize as new and green concrete. Geopolymer is a mixture of aluminosilicate powders and alkaline solutions. When incorporated with nano-sized graphene, the material forms a composite known as Graphene Reinforced Geopolymer Nanocomposite (GRGN). The addition of graphene enhances the strength of geopolymer, which can further improve its competitiveness. However, this depends on several factors, including the types of graphene, the surface modification of graphene, and the concentration of alkaline solutions. Generally, the presence of graphene alters the porous structure of geopolymer into a substantially filled porous structure, thus increasing compressive strength and flexural strength. On the other hand, Graphene Oxide (GO) undergoes a chemical reduction in the alkaline solution, producing epoxy functional groups. The chemical treatment results in two conditions which are weak interaction between graphene and geopolymer matrix, and better graphene dispersibility in geopolymer matrix. This review also highlights the analytical modelling aspect of GRGN. The dissolution of Si(OH)4 and Al(OH)4- from the aluminosilicate source was consistent with experimental work and analytical modeling, while the dissolution of Si–OH on the surface-modified graphene indicated otherwise. Therefore, this paper will provide an insightful review of the GRGN mechanical properties.

Medical imaging phantoms are considered critical in mimicking the properties of human tissue for calibration, training, surgical planning, and simulation purposes. Hence, the stability and accuracy of the imaging phantom play a significant role in diagnostic imaging. This study aimed to evaluate the influence of hydrogen silicone (HS) and water (H2O) on the compression strength, radiation attenuation properties, and computed tomography (CT) number of the blended Polydimethylsiloxane (PDMS) samples, and to verify the best material to simulate kidney tissue. Four samples with different compositions were studied, including samples S1, S2, S3, and S4, which consisted of PDMS 100%, HS/PDMS 20:80, H2O/PDMS 20:80, and HS/H2O/PDMS 20:40:40, respectively. The stability of the samples was assessed using compression testing, and the attenuation properties of sample S2 were evaluated. The effective atomic number of S2 showed a similar pattern to the human kidney tissue at 1.50 × 10−1 to 1 MeV. With the use of a 120 kVp X-ray beam, the CT number quantified for S2, as well measured 40 HU, and had the highest contrast-to-noise ratio (CNR) value. Therefore, the S2 sample formulation exhibited the potential to mimic the human kidney, as it has a similar dynamic and is higher in terms of stability as a medical phantom.

This study aimed to introduce an alternative, inexpensive, and straightforward polymer with specific mechanical and dielectric properties suitable for the fabrication of a clinical-grade kidney phantom. Two polymer-based phantom materials, polydimethylsiloxane (PDMS) and silicone elastomer (SE), were investigated for their capability to meet the requirements. The concentration ratios of base to curing agent (B/C) were 9.5/1.5, 19/3, 10/1, 20/2, 10.5/0.5, and 21/1 for PDMS and 4.5/5.5, 10/12, 5/5, 11/11, 5.5/4.5, and 12/10 for SE. All samples were mixed, degassed, and poured into Petri dishes and small beakers. The polymer was cured under room temperature for 2 h and then demolded from the hard mold. The air bubbles produced were removed using a vacuum desiccator for 30 min. All samples underwent mechanical testing (tensile strength and elastic modulus), and their dielectric properties were measured using a dielectric probe kit equipped with 85071E materials measurement software. The radiation attenuation properties were also measured using PhyX-Zetra for PDMS phantoms with the chemical formula C2H6OSi. Small changes in base and cross-linker play an essential role in modifying the elastic modulus and tensile strength. The effective atomic number of PDMS showed a similar pattern with human kidney tissue at the intermediate energy level of 1.50 × 10−1 to 1 MeV. Therefore, PDMS can potentially be used to mimic the human kidney in terms of tensile strength, flexibility, the acceptable real part of the complex dielectric constant ε′r, and conductivity, which allows it to be used as a stable kidney phantom for medical imaging purposes.

Panel structures which are mainly used as insulation materials should possess high fire resistance characteristic. In addition, their mechanical requisites for walls and doors such as compressive strength must not be unduly compromised. Rice husk ash (RHA) was used as an aluminosilicate source and two factors namely RHA/AA ratio and NaOH concentration were analyzed using statistical tool to study the effect of both factors on the compressive strength. Surface morphology and fire resistant behavior of four selected samples based on their compressive strength (brittle, semi-brittle, ductile, and semi-ductile samples) were studied to determine the correlation between compressive strength and fire resistant performance of those selected samples. Results showed that RHA-based geopolymer sample recorded high compressive strength above 28 MPa when its RHA/AA ratio and NaOH concentration were high ranging from 0.7 to 0.8 and 12M to 14M, respectively. Brittle geopolymer sample (GS) with low Si/Al ratio shows high compressive strength together with high degree of geopolymerization. Ductile GS in comparison, shows low compressive strength irrespective of its degree of geopolymerization. Semi-ductile GS showed the best fire resistant properties with a maximum non-exposed surface temperature of only 50°C after 50 minutes (after it was exposed to a direct fire with temperature of 900°C) followed by semi-brittle and brittle GS.

The engineering properties of porous alumina ceramic composites such as sintering linear shrinkage, density, porosity, hardness, tensile strength and microstructure analysis were studied. Different sintering temperature of 1250°C, 1350°C, 1450°C, 1550°C was used. The alumina, rice husk ash, aluminium and sucrose solution binder were mixed and pressed through powder compaction technique. The porous structure and elemental analysis of the mixed powder have been characterised using field emission scanning electron microscopy (FESEM/EDX). For the phase identification, x-ray diffractiona nalysis has been performed. Results depicted that there is no contamination of the mixed powders. The pores structure reduced as the sintering temperature increased to 1550°C. The mechanical analysis revealed that the properties of the porous alumina ceramic composites sintered at 1550°C showed the best performances. Sintering linear shrinkage increased with increasing sintering temperature, resulting in higher volumetric changes. Thus, this effect increases densification and reduces total porosity while improving the tensile strength of the porous alumina ceramic composites. [ABSTRACT FROM AUTHOR]

This research studies the thermogravimetric and dynamic mechanical analysis of woven glass/kenaf/epoxy hybrid nanocomposites filled with clay. Epoxy resin modified with 1.0 wt% silicon is sonicated with varying clay loading of 1.0, 3.0 and 5.0 wt%. The resin is then spread onto alternating woven glass and NaOH-treated woven kenaf. Thermogravimetric analysis (TGA) reveals the benefits of dispersing clay onto the thermal properties of nanocomposite. Higher residue and higher temperature at 10 wt% mass loss is observed in clay nanocomposite. In addition to that, kenaf treatment, woven glass reinforcement and epoxy modification also help in improving the thermal stability of composites. Dynamic mechanical analysis (DMA) reveals that TKG1% composite possessed the highest storage modulus at room temperature with 136.74% higher than UKG1% composite due to the polymer chain diffusion between well dispersed clay structures. TKG1% also achieved the highest loss modulus which indicates strongest internal friction among other composites. Despite that, TKG1% composite exhibited the lowest Tg which is 72°C. This could be reasoned with the elimination of hemicellulose due to fibre treatment that is responsible for stiffness in natural fibre. Elimination of hemicellulose is proven through Fourier-transform Infrared Spectroscopy (FTIR) analysis conducted on treated kenaf fibre at wavenumber 1514, 1696 and 1726 cm−1. [ABSTRACT FROM AUTHOR]

Adding carbon nanotubes (CNTs) into epoxy resin of the composite plate can improve the mechanical properties like the tensile strength. In particular, carbon-Kevlar® hybrid fabrics epoxy resin, which reinforced with CNT obtained from noble fibres instead of the conventional fiberglass. Current research investigates the tensile properties of epoxy matrix composite systems that were incorporated with prior to 1.0% of CNT. The results obtained have shown a significant increase in stiffness (Young's modulus) and tensile strength with inclusion of the CNT at 0.3%. The increase in total fracture was revealed for more or less than 0.3 vol% of CNT incorporation. Therefore, fracture was restricted like the module and tensile strengths will improve. The scanning electron microscopy (SEM) analysis has observed a mechanism of crack capture by the fibres and proper ingrained in the composite matrices. [ABSTRACT FROM AUTHOR]