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Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Flex cracking involves complex strain geometries, with various parts of the specimen being deformed under different stress conditions; some parts are in tension, others in compression, shear, etc. The crack propagation mechanism may be similar to that of tear tests. The tensile strength and tear resistance, shown in Tables 6 and 7, decrease with increasing temperature. The crack growth resistance is therefore expected to become lower as the heat builds up in the Demattia bars owing to repeated flexing.
Stab Resistance of Flexible Protective Armor
Published in Magdi El Messiry, Protective Armor Engineering Design, 2019
Cutting and stab performance of the protective fabrics is the main quality to be evaluated for the lots of the industrial applications to shield against various mechanical threats, stabbing, punching, cutting, and needle piercing.20 Studies pursuit the capability to increase the stabbing energy absorption by the use of multilayer compositions and optimizing them for applying into suitable stabbing protective fabrics from natural or synthetic fibers and their blends.20,64 The stab resistance is often calculated by taking an average value between the cutting and tearing or tensile strength. Material tear resistance relies on fabric strength, elongation, and packing density. More loosely packed fabric can be an advantage for tear resistance, but it inadequately resists the stabbing. One of strongest natural fibers is silk, it was revealed that as protective fabric, silk multilayer woven fabrics have high penetration resistance and provide more comfort in use. Additional fabric layers contribute to the increment of anti-stabbing fabric with the areal density adequate to the degree of protection required. The stabbing force of silk fabric is linearly related to its weight/m2 (Fig. 4.37).
Patterned Electrospray Fiber Structures
Published in Ahmed Busnaina, Nanomanufacturing HANDBOOK, 2017
Phil Gibson, Heidi Schreuder-Gibson
We saw qualitative differences in the failure mode and strength of patterned versus unpatterned elastomeric electrospun membranes. Pattern grid size (i.e., coarse, medium, fine) appears to affect tear propagation; patterns resist tear propagation better than unpatterned membranes. The tear resistance is enhanced by the presence of thicker regions of fibers that tend to stop tears. Because there also seems to be some fiber alignment along the metal screen wires that create the grid pattern, the membrane strength may also be enhanced through fiber orientation.
Ogden model for characterising and simulation of PPHR Rubber under different strain rates
Published in Australian Journal of Mechanical Engineering, 2023
Q. H. Jebur, Muhsin J. Jweeg, Muhannad Al-Waily
Rubber is a crop from which a range of products can be produced that have vital applications to society in a variety of ways. Knowledge of the properties of rubber continues to expand. In time, additional manufactured goods will be produced by the rubber industry. In general, there are two kinds of rubber usually utilised in industry, natural rubber and synthetic rubber. The applications of natural rubber (NR) overall different productions are due to its mechanical properties such as high durability, low hysteresis, elasticity, and high toughness. In overall, NR is an unstructured material. However, when stretched NR can crystallise. This crystallisation gives characteristics such as abrasion resistance, tensile strength, and tear resistance to the mechanical properties of NR. The rubber combination is the main product of rubber commodity. Roughly speaking, all rubber compounds use Carbon black (CB) as a filler. Carbon black filler improves the physical properties of rubber, increasing strength, as well as strengthening vulcanisation. The results of the rubber compound can be useful in producing bearings, belts, tyres for cars.
Performance analysis of multilayer flame-retardant fabric ensembles for different exposure conditions using numerical modeling
Published in The Journal of The Textile Institute, 2022
Bhavna Rajput, Nandyala Mahesh, Rochak Rathour, Tathagata Das, Bahni Ray, Apurba Das, Prabal Talukdar
In the present work, a fire protective ensemble is considered consisting of Nomex IIIA fabric with a honeycomb weave structure as an outer layer, aramid batting quilted to Nomex as a moisture barrier, Teijin Conex as an inner layer, and cotton as a face fabric. Nomex honeycomb weave structure has very high flame and heat resistance, does not form char, also does not melt or drip, and undergo any dimensional change till 260 °C. Furthermore, this fabric has high tensile strength, elongation, durability, abrasion and tear resistance, and breathability, as well as good quality tear resistance. A PTFE film laminated on a Nomex non-woven fabric serves as the moisture barrier. It prevents water from penetrating the fabric, transports moisture vapour from the body to the atmosphere, and improves the comfort of the garment. Teijin Conex fabric, which was used as the thermal liner, has a low weight, high porosity, flame retardancy, and comfort. It prevents the fabric from melting, holing, or adhering to the skin. It can withstand temperatures of up to 400 °C. Cotton was chosen as the face fabric because of its comfort, breathability, absorbency, and excellent wicking properties. The fire protective ensemble considered in the present investigation is shown in Figure 1.
A review on recycled concrete aggregates (RCA) characteristics to promote RCA utilization in developing sustainable recycled aggregate concrete (RAC)
Published in European Journal of Environmental and Civil Engineering, 2022
Aamar Danish, Mohammad Ali Mosaberpanah
The properties of RAC are influenced by the mechanical properties (aggregate abrasion, impact, crushing value and Los Angeles coefficient (LAC)) of RCA. The aggregate abrasion value (AAV) indicates wear/tear resistance of aggregate. A greater loss of material gives higher AAV, which is detrimental to be used in concrete. Generally, the AAV of RCA is higher than NA. The aggregate impact value (AIV) of aggregates is the resistance of aggregates to impact force or dynamic load. Aggregates' strength and AIV are directly proportional to each other. Studies show that AIV of RCA is greater than NA. Aggregate crushing value (ACV) indicates the resistance of aggregates to crush under gradual compressive load. Like AIV, ACV is also directly proportional to aggregate strength. Finally, LAC or abrasion test is used to indicate the toughness and abrasion of aggregates (or determines the resistance of aggregates to fragmentation). Table 5 shows the ranges of AAV, AIV, ACV and LAC of RCA and NA.