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Introduction, History, and Origin of Composite Materials
Published in Subhash Singh, Dinesh Kumar, Fabrication and Machining of Advanced Materials and Composites, 2023
Subhash Singh, Mohammad Uddin, Chander Prakash
The marine field was the largest composite material in the 1960s. The patent on carbon fibers was approved in the year 1961, but it took several years past that since it was been applied commercially. The carbon fiber composites enhanced the stiffness-weight ratios of the thermoset components. It was largely utilized in the fields related to consumer/sporting goods, automotive, and aerospace, which it boosted with its superior characteristics. The year 1966 was when Kevlar, an advanced, carbon fiber derived composite, was invented by Stephanie Kwolek, a chemical expert at DuPont [23,31]. Kevlar is a strong fiber that is para-aramid and is familiar for its application in stab as well as ballistic-resistant armor. This proved to be extremely beneficial for protection of police as well as the armed forces. The development of novel and enhanced resins greatly enhanced the requirements of composites, especially in the areas pertaining to corrosion and higher temperatures. Apart from this, there was also a predominant usage of metals like aluminium (Al) and steel used around this time, which has continued till the modern times. Composites comprising of the metals like Al and boron came into existence in the year 1970. Also around this time was the usage of rods of iron combined with concrete that were employed for structural applications. This resulted in the growth of steel-reinforced concretes.
Fibres
Published in Ashok R. Khare, Principles of Spinning, 2021
It is the reaction between amine group and halide group that leads to aramids. The polymer is dissolved in anhydrous sulfuric acid and is subsequently produced with the help of liquid chemical blend. The fibre shows strong resistance to abrasion, organic solvents, heat and flame. Even at 500°C, the fibre does not easily degrade. Owing to almost no moisture content, it easily builds up static. Also, the fibre shows sensitiveness to acids and ultra-violet radiations. Kevlar has very high strength, high Young’s modulus, high tenacity, low creep and low elongation at break. But its dyeing is difficult. Hence, solution dyeing is used.
Materials
Published in Sumit Sharma, Composite Materials, 2021
Kevlar is perhaps the most common polymer fiber. It was developed by the DuPont Co. in 1968 and is an aromatic polyamide called poly(paraphenylene terephthalamide). The aromatic rings make the fiber fairly rigid. Kevlar fibers are manufactured by the extrusion and spinning processes. A solution of the polymer and a solvent (hexamethylphosphoramide) is held at a low temperature, between −50°C and −80°C, before being extruded into a hot-walled cylinder at 200°C. The solvent then evaporates, and the fibers are wound onto a drum. The fibers at this stage have low strength and stiffness. The fibers are subsequently subjected to hot stretching to align the polymer chains along the axis of the fiber. Afterward, the aligned fibers show a significant increase in strength and stiffness. Figure 2.17 shows a schematic of its structure. The polymer molecules form rigid planar sheets, and the sheets are stacked on top of each other with only weak hydrogen bonding between them. These sheets are folded in the axial direction and are oriented radially, with the fold generally occurring along the hydrogen-bonding line.
Effect of TiO2 and nozzle geometry on diesel emissions fuelled with biodiesel blends
Published in International Journal of Ambient Energy, 2019
P. Gunasekar, S. Manigandan, N. Ilangovan, S. Nithya, J. Devipriya, W. S. R. Saravanan
A four-stoke water-cooled CI engine is used to calculate the combustion and emission characteristics of CIME biodiesel. The specifications are mentioned in Tables 1 and 2. The fuel is tested at different speeds and engine loads. The engine load is varied by means of a dynamometer. The eddy current dynamometer is connected to the closed-loop controller. The fuel consumption monitoring system is placed to measure the intake of fuel. Similarly, air consumption is also monitored. The exit of the exhaust nozzle is changed from a circular to elliptical one, since an elliptical jet has better mixing efficiency than a circular jet. The emission of exhaust gases such as HC, CO and NOx is measured using the AVL gas analyser. EGT (exhaust gas temperature) is measured using a thermocouple. The values such as cylinder pressure, crank angle and piston position are obtained using a data acquisition system. The exhaust pipe is made of Kevlar fibre and a thin-walled metallic inner layer. Kevlar fibre is used for its high strength and low weight. The geometry of the exhaust pipe nozzle is modified based on the literature (Gunasekar et al. 2016; Manigandan et al. 2016).
Fabrication and testing of hybrid fibre reinforced composite: a comprehensive review
Published in Australian Journal of Mechanical Engineering, 2022
Kapil K. Sharma, Jitendra Kushwaha, Kapil Kumar, Harshit Singh, Yogesh Shrivastava
On the other hand, Kevlar is a most commercial man-made synthetic and have low weight, excellent strength to weight ratio, high impact resistance and great flexibility (Bhudolia, Kam, and Joshi 2018) and is often used for making specific engineering materials where high impact resistance and flexibility is needed. The sheet or fabric of Kevlar fibre contains aromatic polyamide structure; Figure 6 shows the structure of Kevlar polymer. Also on hybridisation, a higher number of Kevlar layers increases the magnitude of peak load on hybrid composite. Kevlar fibres also resisted the bending effect due to high impact resistance (Bhudolia, Kam, and Joshi 2018).
Study on chest injury and bulletproof vest protection under the combined action of blast wave and fragments
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Zhihua Cai, Zhi Wang, Lijun Chang, Xingyuan Huang, Hui Zhao
As shown in Figure 1b, for the fragment material of the IED, the STEEL4340 model in Autodyn material library was adopted. Kevlar is an ideal material for bulletproof vest because of its impact resistance, high strength and low weight. In this paper, KEVLAR EPX model in Autodyn material library was used for bulletproof plate material, and Von Mises strength model was selected (Cai et al. 2016). Viscoelastic materials were used in muscle, heart and lung, and elastic materials were used in other organs. The material parameters of chest organs are shown in Table 3.