No abstract

Water leakage is one of the important agendas across the globe thus several effectual systems for leakage detection had been developed with the aim to improve sustainable use of water. Among the methods, acoustic leak detection technique had been proven as a promising approach to detect and localize leaks in water or gas pipeline. However, existence of noise in acoustic signals complicated the leak detection practices. Traditional de-noising methods like filtering and wavelet de-noising are not suitable for non-stationary and broadband acoustic signals. Therefore, Dual Tree Complex Wavelet Transform (DTCWT) is applied in this paper to reduce acoustic noise and decompose signals into several frequency bands. DTCWT decomposition is intended to resolve the problem encountered by the typical correlation-based leak localization method. Due to dispersive and frequency-dependent nature of wave propagation, correlation-based method normally assumes constant wave velocity which results in inaccurate leak source localization. In this paper, signal will be de-noised and decomposed by employing DTCWT. Wave velocity is evaluated based on the dominant frequency and dispersion curve. Then, time delay can be estimated via comparison study among cross correlation, CWT localization and convolution. CWT localization and convolution are proposed as new time-delay estimation method attributable to enhance localization accuracy. Experimental results validated that the proposed method, DTCWT-correlation outperforms other methods with a localization error of 4.67 %. Both CWT localization and convolution are also capable to pinpoint the location of leaks. Besides, leaking and non-leaking condition can be differentiated after multilevel decomposition of DTCWT.

The present work analyzed the fire protection performances, char formation and heat release characteristics of the thin film intumescent fire protective coatings that incorporate the eggshell (ES) waste as a renewable flame retardant nano bio-based filler. The fire performances of the coatings were evaluated using Bunsen burner and cone calorimeter. The fire behaviors of the samples in the condensed phase were conducted in accordance with the ISO 5660-1 standard. On exposure, the samples B and D reinforced with 3.30 wt.% and 2.75 wt.% of ES nano bio-filler, respectively showed a significant reduction in total heat rate, promoting thicker and more uniform char layer in protecting the steel structural. As a result, ES nano bio-filler composition has shown to be efficient in fire protective performance of the intumescent coatings.

The major drawbacks of 3D printed thermoplastic using fused deposition method (FDM) are exhibit weak mechanical properties. This reduces the usability of the printed part as the functional structure for part replacement in a real-world application. Therefore, in this study a co-extrusion of a continuous fibre of twisted Kevlar using FDM is conducted to examine the improvement of mechanical strength of the 3D printed part with reinforcement of continuous fibre. The coextruded reinforced plastic (CRP) parts consisting of polylactic acid (PLA) as matrix and twisted Kevlar as core fibre. The mechanical performance of printed parts was evaluated in a tensile test under ASTM D638 standard. The results of both CRPs were compared against unreinforced PLA which. It has been demonstrated that CRPs with twisted Kevlar was able to achieve significant increment in Ultimate tensile strength (+179.7%, 104.64MPa), maximum tensile strain (+257%, 5.384%) and relative similar Young’s modules (3.29GPa) compared to unreinforced PLA. As a result, this study created a unique material print which CRP with twisted Kevlar which offer high stiffness and high strength structure.

Polylactic acid (PLA) bioplastic is a common material used in Fused Deposition Modeling (FDM) 3D printing. It is biodegradable and environmentally friendly biopolymer which made out of corn. However, it exhibits weak mechanical properties which reduced its usability as a functional prototype in a real-world application. In the present study, two PLA composites are created through coextruded with 3K carbon fibres and twisted Kevlar string (as core fibre) to form a fibre reinforced parts (FRP). The mechanical strength of printed parts was examined using ASTM D638 standard with a strain rate of 1 mm/min. It has been demonstrated that the FRPs coextruded with 3K carbon fibres had achieved significant improvement in Young's modulus (+180.6%, 9.205 GPa), ultimate tensile strength (+175.3%, 103 MPa) and maximum tensile strain (+21.6%, 1.833%). Although the Young's modulus of Kevlar FRP was found to be similar to as compared to unreinforced PLA (~3.29 GPa), it has gained significant increment in terms of maximum tensile strain (+179.7%, 104.64 MPa), and maximum tensile strain (+257%, 5.384%). Thus, this study revealed two unique composite materials, in which the 3K carbon FRP can offer stiff and high strength structure while Kevlar FRP offers similar strength but at a higher elasticity.