The formation of micro-cracks and crack propagation is still an acute problem in polymer and polymer composites. These micro-cracks usually occur while the materials are manufactured or serviced. The development and coalescence of these cracks reduces the lifespan and brings about a catastrophic failure of the materials. Novel scientific research on polymeric self-healing is emphasised in a number of publications, which consist of contributions from many of the prominent researchers in this area. Progress in this field can eventually enable scientist to construct new flexible materials that both monitor the material’s integrity and repair the deformed material prior to the occurrence of any fatal failures. This report describes recent trends that have been used in material science and computational methods to mitigate the development of micro-cracks and crack propagation in polymer composites.

https://www.mdpi.com/2073-4360/9/10/535/pdf

Self-Healing Polymeric Composite Material Design, Failure Analysis and Future Outlook: A Review.

Experimental investigation of explosion-welded CP-Ti/Q345 bimetallic sheet filled with Cu/V based flux-cored wire

The main factors affecting the mechanical properties of the deposited metal in arc hardfacing are primarily the chemical composition and the cooling rate. The latter depends on the filler materials composition, hardfacing condition (mode), and hardfacing technology, determining the geometric parameters and parameters of the welded bead shape, the amount of deposited metal dilution with the base metal, and the amount of the introduced heat. The goal of this work is to analyze the effect of exothermic addition introduction to the core filler and the effect of welding condition on weld bead morphology, thermal indicators, and mechanical properties of the deposited metal. The deposited metal of the Fe-C-Cr-Cu-Ti-V-Al alloying system was used. The Taguchi technique was adopted as the experimental plan design, as follows: the orthogonal array L9 (3 ^ 4) and signal-to-noise ratio (S/N). The analysis of variance (ANOVA) was also applied for determination of the variables contribution to the dependent parameters. Application of the Taguchi method is simpler, more efficient, and quicker. It requires fewer experiments to determine the optimal values of the studied variables. Microstructural studies using an optical microscope were additionally performed for individual samples of the weld metal with the best mechanical properties, for each of the experimental flux-cored wires. We determined that introduction of CuO-Al exothermic addition of to the core filler had a significant effect on such indicators of the weld bead morphology as the weld reinforcement height and the weld reinforcement form factor (WRFF). Introduction of exothermic addition (CuO-Al) to the core filler had a significant effect on the welding current (I), heat input rate (HIR), and microhardness. The arc voltage (Р(Ua) = 45.8 %) had the greatest influence on the microhardness value, while the percentage of exothermic addition in the core filler (P (EM) = 26.9%) and the wire feed rate (P (WFS) = 21.5%) had a smaller effect. It was shown that it is important to take into account complex parameters, such as dilution variation and weld reinforcement form factor (WRFF) for the geometric characteristics of the weld bead and heat input rate (HIR) for heat indicators in order to optimize hardfacing conditions and composition of the core filler (introduction of exothermic addition). According to the results of the article, the value is the most correlated with the average values of microhardness.

Application of Taguchi method and ANOVA analysis for optimization of process parameters and exothermic addition (CuO-Al) introduction in the core filler during self-shielded flux-cored arc welding

In recent years, stringent environmental regulations for air pollution have led to increased demand for liquefied natural gas (LNG). Therefore, the demand for the design and construction of LNG-fueled vessels has also increased. One of the most important points for the design of LNG-fueled vessels is the structural integrity of the LNG fuel tank, particularly at cryogenic temperatures. Low temperature materials are used in the construction of LNG fuel tanks to ensure structural safety. Among the various low temperature materials, nickel steel is commonly employed for the design of LNG storage tanks. In addition, Shielded Metal Arc Welding (SMAW) and Submerged Arc Welding (SAW) are commonly applied to the construction of LNG storage tanks. On the other hand, the application of Flux Cored Arc Welding (FCAW) for nickel steel as an alternative to SMAW and SAW appears to be necessary, considering the high productivity. Nevertheless, there have been few studies of the fracture behavior of nickel steel with FACW compared to SMAW and SAW processes. This study examined the fracture characteristics of 9% nickel steel and weldments considering application for the LNG storage tanks. The fracture characteristics of FCAW was compared with SMAW at 25°C and − 163°C temperatures. As the result, the mechanical properties with FCAW were higher than those with SMAW at 25°C and − 163°C. In addition, SMAW is slightly better than FCAW in terms of the impact absorbed energy. Moreover, the crack tip opening displacement (CTOD) values of the weld metal and heat affected zone (HAZ) with FCAW were higher than those with SMAW.

Effects of the Welding Process and Consumables on the Fracture Behavior of 9 Wt.% Nickel Steel

Flux cored arc welding(FCAW) process is characterized with its high deposition rate and productivity. Control of the operating parameters in FCAW is essential to obtain high production rates and good quality welds. Bead on plate welds were carried out on mild steel plates to study the influence of welding current and arc voltage on weld bead geometry parameters. The weld bead coss-sections were metallographically investigated. The effects of these welding parameters were evaluated by measuring penetration depth, reinforcement height, bead width, wetting angle, electrod deposit area and plate fusion area. The bead crosssection area and the weld shape factor were calculated from the measured results. The effects of welding parameters on weld bead geometry have been presented by histograms.

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Izatul Aini Ibrahim

Papers

The Effect of Flux Core Arc Welding (FCAW) Processes On Different Parameters