Impact resistant properties of Kagome truss reinforced composite panels

The application of fibre composites in the construction of protective structures for impact and blasts is an active area of research. Important mechanical properties like compressive strength, tensile strength, flexural toughness, acoustic impedance, mass density, ultrasonic pulse velocity, are required to determine the high velocity impact (HVI) resistance of the cementitious composite target panels. However, the above mechanical properties of steel fibre reinforced cementitious composites (SFRCC) for varying fibre volume fraction are difficult to find in existing literature. This paper presents results of an extensive experimental study, conducted to characterize the SFRCC for varied fiber volume fractions between 0 and 12 %. Hooked end steel fibres having an aspect ratio about 66 (fibre length 30 mm diameter 0.45 mm) are used in the preparation of control specimens. Important engineering properties like, compressive, tensile, and flexural strengths, toughness and acoustic impedances are determined through the laboratory tests. A total of 250 numbers standard cylinder, cube, prism and dog-bone specimens are prepared for the characterization of steel fibre reinforced cementitious composite. The significance of the present study in impact resistance applications is also demonstrated through the HVI tests on SFRCC panels. This study highlights various aspects related to judicious selection of materials in layered cementitious composite targets.

The objective of this work is to study the effect of impact and blast dynamic loading upon concrete plates reinforced with normal deformed steel bars as well as steel or glass fibers. In order to examine the effect of using different volume and weight fractions of s skeletal bars and steel or glass fiber reinforcements on the impact and blast resistance, 24 plates and 24 prisms were manufactured as test specimens. A set consisting 0f 8 plates were tested under high velocity impact using 14.7 caliber bullets with a shooting distance of 63 m. The specimens with 1.5 % steel fiber and two layers of steel mesh (8 mm at 75 mm) have shown resistance to full perforation of the bullet. Improvements to the resistance to spalling, scabbing and crack growth have also been observed. Field blast testing was carried out on a second set of 8 specimens by using a charge of 100 gm located at the center of each specimen. All the plates were 160 mm thick and with had minimum reinforced of 0.75% glass fiber and a single layer of steel mesh (8 mm at 75 mm). Have shown resistance to full perforation of waves and have restricted the number, the width and the growth of cracks. The last set of the remaining 8 plates was subjected to a low speed impact test performed by a falling steel ball. Test results clearly show the significant effect of using steel and glass fiber besides deformed bars to enhance the impact resistance by 400 % and 20 % by using 1.5 % steel fiber and 0.75 % glass fiber resistance .Energy absorption capacity and ductility were also increased by 100 % and 600 % by using 1.5 steel fiber. Chang in compressive strength of about ±6 % and ± (20 – 30 ) % were observed by using 1.5% steel fibers and 0.75% glass fibers respectively. The inclusion of 1.5% steel fibers and 0.75% glass fibers together with deformed steel bars have improved the tensile strength by 200% and 70% respectively.

Experimental investigation on the mechanical properties and microstructure of hybrid fiber reinforced recycled aggregate concrete

Response of UHPFRC and HDFRC under static and high-velocity projectile impact loads

Cement composites subjected to high-velocity projectile shows local failure and it can be suppressed by improvement of flexural toughness with reinforcement of fiber. Therefore, researches on impact resistance performance of cement composites are in progress and a number of types of fiber reinforcement are being developed. Since bonding properties of fiber with matrix, specific surface area and numbers of fiber are different by fiber reinforcement type, mechanical properties of fiber reinforced cement composites and improvement of impact resistance performance need to be considered. In this study, improvement of flexural toughness and failure reduction effect by impact of high-velocity projectile have been evaluated according to fiber type by mixing steel fiber, polyamide, nylon and polyethylene which are have different shape and mechanical properties. As results, flexural toughness was improved by redistribution of stress and crack prevention with bridge effect of reinforced fibers, and scabbing by high-velocity impact was suppressed. Since it is possible to decrease scabbing limit thickness from impact energy, thickness can be thinner when it is applied to protection. Scabbing of steel fiber reinforced cement composites was occurred and it was observed that desquamation of partial fragment was suppressed by adhesion between fiber and matrix. Scabbing by high-velocity impact of synthetic fiber reinforced cement composites was decreased by microcrack, impact wave neutralization and energy dispersion with a large number of fibers.

The effects of waste iron powder and steel fiber on the physical and mechanical properties of geopolymer mortars exposed to high temperatures

The challenge of identifying and monitoring multiple types of solar panels has not been studied. Solar panels can be single, double, or double with a water heater on top. Some are packed closely together. Due to installation requirements, additional solar panels may have any random orientation. When combined with the difficulties of detecting different types of panels, this arbitrary orientation negatively affects the effectiveness of deep learning algorithms by resulting to false positive and erroneous panel classifications. Furthermore, no research on the identification of various solar panel types has been done yet. In this study, we concentrate in on two key problems: first, the detection of different types of solar panels; and second, the arbitrary orientation of these panels. Our method does not use horizontal bounding box, rather it leverages horizontal bounding boxes and generates rotated bounding box during the train time. Using our method, we were able to precisely identify three various types of solar panels with various orientations. We show a comparison of their differences for the identification of three different types of solar panels, including water heater photovoltaic (WPV), farm type photovoltaic (FPV), and SPV, in terms of box loss, objectness loss, classification loss, precision, and recall (single photovoltaic).

The impact response of a Nomex® honeycomb core/E-glass/epoxy composite sandwich structure to increasing velocities: Experimental and numerical analysis

콘크리트는 재료적으로 인장에 취약하고 변형에 취성이 크다는 태생적 단점을 갖고 있다. 콘크리트 조직에 인장에 강한 작은 섬유를 혼합한 섬유보강콘크리트는 이러한 취약점을 보완할 수 있는 좋은 방법으로 간주되었으며, 많은 종류의 섬유재료와 방법들이 제안되었다. 그러나 이 섬유보강콘크리트에도 아직까지 해결하지 못한 문제로서 균질한 배합이 힘들고 높은 체적비를 갖는 섬유 혼입의 어려움 등이 있다. 최근에 새로운 개념의 규칙적 다공질 금속(periodic cellular metal)이 개발되어 기계 분야에 많이 적용되고 있는 철선으로 직조된 카고메 트러스가 있다. 이 논문은 기존 강섬유보강콘크리트의 현실적 문제점을 해결하기 위한 방법의 일환으로 카고메 트러스의 적용 가능성을 검토하기 위한 기초 실험 연구 결과를 정리한 것이다. 3종류의 카고메 트러스로 보강된 실험체와 동일한 제원의 수직스터럽으로 보강된 보 실험 결과와 비교하였다. 그 결과, 카고메 트러스 보강 실험체에서는 강도와 연성이 보통 스터럽 보강 보 보다 더 우수한 결과를 나타냈으며, 복부 보강재로서 우수한 기능을 할 수 있는 것으로 판명되었다. There is mounting recognition among concrete researchers that fiber reinforcement makes up for the inherent weakness in resisting tensile force of structural concrete. In practice of application of the fiber to concrete, however, several problems still remain to solve for assuring a uniform mix quality. The Kagome truss that is widely used in mechanical engineering field seems to be a good replacement for the steel fiber. This paper presents the test results of a pilot study for the concrete members reinforced by Kagome truss which is a periodic cellular metal of wire-woven. Three types of Kagome truss bulk were prefabricated and filled with normal concrete to make small-scaled test beams. The beams reinforced by a normal steel stirrups were also tested up to failure to compare the behavioral results. From the results obtained, it is appeared that comparing with beams reinforced by normal stirrups, the beams reinforced by Kagome truss showed better performance in load carrying capacity as well as ductility. Therefore, the Kagome truss is proved to be a good web shear reinforcing material.

Structural behavior of precast concrete sandwich panels under low‐velocity drop weight impact is presented in this paper. Three types of concrete panels are considered namely, solid concrete panel (SCP), concrete sandwich panels containing recycled tire crumb rubber as core (CRSP), and expanded polystyrene foam as core (FSP). The panels are reinforced with steel mesh or steel fibers. A total of 12 panels are cast in this study. Six panels are reinforced using steel mesh, and the other six panels are reinforced using steel fibers. The impact test is carried out by dropping a weight from a varying height to input impact energy, which can cause various levels of damage for all specimens. The structural performance is discussed in detail, including failure modes, impact force, deflection, and strain. It is found that the core material greatly affects the structural response of the precast concrete panels. The sandwich panel containing recycled tire crumb rubber performed well in terms of rebounding force, permanent deflections, and damage behavior by partially absorbing the impact energy in both types of reinforced concrete panels. In CRSP and FSP, the maximum deflection to permanent deflection ratio rose from 1.19 in SCP to 2.67 and 2.01, respectively. A decrease of 70% in strain value from the first impact to permanent strain was recorded in CRSP when reinforced using conventional steel mesh. In comparison to its counterpart FSP, the CRSP exhibited a significantly smaller fracture width on the tension face as a result of the core's ability to dissipate impact energy, resulting in lower deflections and less damage to the panel. The CRSP reinforced with steel fibers demonstrated comparable performance to the counterpart FSP in terms of energy absorption and deflection reduction; however, it performed noticeably better than the SCP reinforced with steel fibers by reducing residual deflection by 51.8 mm. Consequently, recycled tire crumb rubber can be used as a sustainable alternative to traditional core materials in precast concrete panels.

Environmental performance and durability of concrete incorporating waste tire rubber and steel fiber subjected to acid attack

The exposure of recycled concrete (RCA) to a sulphate environment in cold regions makes it crucial to overcome the freeze–thaw cycling effects of recycled concrete. Based on steel and basalt fiber reinforced recycled concrete, the freeze–thaw cycle resistance of recycled concrete was studied by exposure to a sulphate environment. The mass loss, dynamic elastic modulus loss and compressive strength loss of the specimens were studied through freeze–thaw cycle experiments. SEM techniques were used to explore the effect of fiber distribution on the freeze–thaw resistance of recycled concrete. The freeze–thaw mechanism of the basalt fiber and steel fiber recycled concrete exposed to a sulphate environment has also been summarized. The results show that, based on the sulphate environment, the composite fiber recycled concrete has a higher stability in terms of mass loss and relative dynamic modulus of elasticity than single fiber concrete. The compressive strength of S0.9RC (recycled concrete with 0.9% steel fibers) and BF5.5RC (recycled concrete containing 5.5 kg/m3 basalt fibers) increased by 8.62% and 13.62%, respectively, compared to normal recycled concrete after 28 days of maintenance; and after 150 freeze–thaw cycles, the compressive strength increased by 41.39% and 47.54%, respectively; compared to ordinary natural aggregate concrete, the compressive strength of S0.9RC and BF5.5RC increased by 32.90% and 27.36%, respectively. The compressive strength of the S1.5BF7.5RC (recycled concrete with 1.5% steel fibers and 7.5 kg/m3 basalt fibers) composite basalt fiber–steel fiber concrete also increased by 42.82%. SEM techniques indicated that the basalt fiber in the recycled concrete exhibited fracture damage, which inhibited the development of microcracks within the concrete. When the recycled concrete is subjected to coupled sulphate and freeze–thaw cycles, freezing occurs from the outside in, with ice crystals extending along the cracks into the matrix. Prior to freezing, a negative pressure is created by the compression of the air and the contraction of the salt solution, which pulls the external solution inwards. The brine is in a state where ice and water coexist during the continuous cooling process. The salt solution migrates from the inside to the outside during heating and melting.

Characterization and optimization of hardened properties of self-consolidating concrete incorporating recycled steel, industrial steel, polypropylene and hybrid fibers

Resistance of hybrid layered composite panels composed of fiber-reinforced cementitious composites against high-velocity projectile impact

7 - Damage analysis of glass fiber reinforced composites