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This study deals with drop-impact effects of new hybrid concrete plates strengthened with an ultrahigh molecular weight polyethylene (UHMWPE). The proposed 3D-UHMWPE results in excellent mechanical properties such as high abrasion resistance, impact strength, and low coefficient of friction. These special properties allow the product to be used in...
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... [,2526] Helmets made with UHMWPE and used in ballistic applications have been studied by many authors because of their high capacity to absorb impact energy and their lightness. [27] In their study, Bitlisli and Yazici [28] performed ballistic performance experiments on several composites, where the highest result was observed with UHMWPE, which was up to level FB4 (all soft ballistic threats) according to the EN1522 standard. [29] ...
In the defense industry, UHMWPE is primarily used as ballistic material because of its light weight, superior mechanical properties, and particularly, its excellent strength-to-weight ratio compared to metal alloys. In this study, the influence of the AWJ process parameters on machining UHMWPE material is investigated. Several UHMWPE plates have been prepared for trimming, pocketing, and hole making experiments using AWJ to understand the process parameter effects on performance measures. The design of experiment method has been used for all experiments and results are analyzed by the analysis of variance and response surface methods. Furthermore, a novel evolutionary optimization method known as particle swarm optimization has been applied to determine trade-offs between the conflicting performance measures of surface roughness and dimensional error in AWJ. With the resulting Pareto optimal solution curve, three industrial scenarios have been developed using k-means clustering algorithm and verified.
... In addition, it is important to evaluate the safety of the structures under extreme condition (load, temperature, etc.) caused by natural factors such as typhoons, earthquakes, and human factors such as explosions and collisions. As the risk of concrete structures increases by being directly exposed to extreme external forces, FRCC has received a lot of attention as one of the methods to increase the impact resistance of concrete structures against high rapid loads such as typhoons, earthquakes, explosions, and collisions [16][17][18][19][20][21][22][23][24][25][26][27]. ...
This paper aims to evaluate the resistance performance of the vinyl acetate ethylene polymer cement (VAEPC) composite and the polyvinyl alcohol fiber-reinforced cement (PAFRC) composite against a low-velocity impact in varying temperature. Their impact resistance performances are analyzed and compared with plain mortar after 28 days of age. Low-velocity impact tests were carried out under the various room temperatures of −70°C, 70°C, and 140°C. Also, an INSTRON CEAST 9350 drop-tower system has been used to get the impact load, fracture energy, and displacement of the specimens while loading low-velocity impacts. From these tests, the failure pattern, shape, and strength of each test specimen were evaluated for the VAEPC, the PAFRC composite, and the plain mortar. Those test results showed that the flexural strength of both the VAEPC and the PAFRC composites has increased compared to that of the plain mortar. However, the compressive strength of the PAFRC composite decreased slightly after 28 days, while its flexural strength increased by 24.4% compared to that of the plain mortar. In addition, the drop test results show that PAFRC composite specimens have the highest impact fracture energy compared to other specimens at −70°C, 70°C, and 140°C, whereas plain mortar specimens have their lowest. This is because the PVA fiber included in the PAFRC acts as a bridge to suppress crack propagation and to improve energy absorption performance, which helps it resist relatively better against impact. It is also known that while the VAEPC composite and the plain mortar were destroyed in a form of being perforated, the specimens of PAFRC composite were observed to some extent to suppress the perforation failures. Therefore, under a load of low-velocity impact, the resistance performance of the VAEPC composite and the plain mortar was proven to show brittle fracture behavior, while the PAFRC showed ductile fracture behavior in virtue of PVA fiber reinforcement which improved its flexural performance. According to the SEM observation which followed the tests, the PAFRC composite as a fiber-reinforced material of the hydrophilic material was found to show the most excellent interfacial bond adhesion compared to the other composite and the plain mortar. The PAFRC composite manufactured in the study has been proven to be very useful as a reinforcement material in both high and low temperature environments.
1. Introduction
There are many natural disasters and extreme cold and heat weather around the world, all caused by unexpected climate change. Also, the risk of explosion and impact due to terrorism or collision of vehicles, ships, aircrafts, etc. is gradually increasing, and there is always a possibility of accidents anytime. This causes many concrete structures to deteriorate. Therefore, all buildings and civil infrastructure facilities require high performance in order to resist against hostile environment. In particular, concrete structures should be designed to endure the unexpected impacts of climate change or careless accidents such as typhoons, earthquakes, explosions, and collisions, with high safety requirements [1, 2]. Accordingly, the fiber-reinforced cement composites (FRCC) have been widely applied in many buildings and civil infrastructure facilities for decades to ensure their safety against external impacts [3–9].
Cement composite materials have excellent compressive strength, so they are most widely used in the construction of building and civil infrastructure facilities, but their tensile strength, flexural toughness, and ductility are relatively low [10, 11]. Cement composites have been developed to improve the strength properties of concrete using VAE polymer or PVA in plain mortar, in order to increase the resistance to flexural performance and to improve brittle properties [12–15].
In addition, it is important to evaluate the safety of the structures under extreme condition (load, temperature, etc.) caused by natural factors such as typhoons, earthquakes, and human factors such as explosions and collisions. As the risk of concrete structures increases by being directly exposed to extreme external forces, FRCC has received a lot of attention as one of the methods to increase the impact resistance of concrete structures against high rapid loads such as typhoons, earthquakes, explosions, and collisions [16–27].
Currently, many researchers have performed intensive research on high-performance cement composites as one of the most effective ways to improve the properties of cement composite materials in order to effectively manage the brittle properties of cement composite materials and the existing structures [28–31]. Among these cement composites, high-performance fiber-reinforced cement composites have been developed. They exhibit high flexural toughness and energy absorption capacity by incorporating PVA fiber into plain mortar [32–34]. Accordingly, FRCC is expected to be used for various applications such as for repair and reinforcement materials and impact and energy absorption materials. Also, the VAEPC composites based on polymer composite materials have been reported to have superior effects on improving tensile strength, flexural strength, adhesiveness, permeability, abrasion resistance, and chemical resistance compared to plain mortar [35–38].
As mentioned above, although many researchers have confirmed that VAEPC and PAFRC composites increase the flexural performance and water-tightness as well as the impact resistance, researches on the impact fracture behavior under different temperatures of cement composites in extreme environments are rare. Information is needed on the impact resistance when exposed to such extreme environments. It is very important to evaluate the impact resistance of cement composites in extreme environments where high and low temperatures occur repeatedly. Therefore Banthia et al. examined the impact resistance of fiber-reinforced concrete under abnormal temperature conditions [39]. Also, Liu et al. [40] investigated the energy absorption and fracture characteristics through impact tests of AR-glass textile reinforced mortars (TRMs) at −25°C∼100°C. The experimental results showed that the variation of temperature did not affect the impact performance compared to other conditions. In addition, the flexural strength test results of high-performance slurry-filled steel fiber-reinforced cement composites, with respect to exposure to high temperatures, have been reported to decrease the flexural strength with increasing exposure temperature [41].
Recently, demand for construction in extreme heat regions such as Saudi Arabia, Kuwait, and Qatar (hottest in the world) has increased, and Antarctic bases has secured resource ownership in extreme regions such as Antarctica (the coldest in the world). As the interest in extreme heat and cold regions increases with base construction competition, so does the necessity of construction technology as well as the design of the related regions. The temperature control range of these regions is −65°C to 75°C. Based on the performance of existing facilities, it is necessary to simulate the temperature of the deserts in extreme heat and the south poles and north pole in extremes cold. The behavior properties and performance of existing structures should be evaluated by simulating the extreme loads (explosion, impact, temperature, etc.) caused in buildings and civil infrastructure facilities due to human and natural factors. Furthermore, material and structural performance needs to be verified with different temperatures using environmental chamber that can simulate the current environment. Until now, researches have been mainly conducted to evaluate the impact resistance of cement composites. There is not much about the evaluation of impact resistance performance in consideration of environmental factors such as temperature variations [42, 43]. In particular, it is necessary to review fully the impact resistance performance with different temperatures of structures under extreme environments such as typhoons, earthquakes, explosions, and collisions. However, the aim of the paper is to evaluate the impact resistance performance with different temperature using environment chamber of VAEPC and PAFRC composites under low-velocity impact loading.
Therefore, the paper was written with the basic strength (compression, flexural) test of the cement composites using VAE polymer and PVA fiber. In order to examine the impact resistance with different temperatures, the impact failure behaviors of VAEPC and PAFRC composite specimens under low-velocity impact loads at the selected temperature conditions of −70°C, 70°C, and 140°C were measured and compared. After the low-velocity impact tests, failure pattern and grade of specimens were evaluated. In addition, the interfacial bonding state (IBS) was observed through a scanning electron microscope (SEM) images to investigate the surface shape of the fractured specimen after the strength test.
2. Experimental Program
2.1. Experimental Plans
As the mix design conditions and experimental contents of this study are shown in Table 1, the W/C of VAEPC composites and plain mortar were at 40.0% and that of PAFRC composites was at 44.0% to obtain good enough workability for this special experimental test. The target average compressive strength was about 40 MPa at 28 days of age. Compressive strength and flexural strength were planned to be measured to show test results. In addition, the low-velocity impact tests are also conducted to evaluate the impact resistance performance of VAEPC, PAFRC composites, and plain mortar at selected temperature conditions of −70°C, 70°C, and 140°C.
Section
Factors
Levels
Mix design conditions
PAFRC
Fiber dosage (%)
0, 1.0
Fiber content (kg/m³)
0, 13
VAEPC
Displacement ratio (%)
0, 10
Displacement content (kg/m³)
0, 61
W/C (%)
Plain mortar (PM), VAEPC: 40.0; PAFRC: 44.0
C : S
1 : 2
P/C: polymer-cement ratio (%)
10
Target average compressive strengths at 28 age (MPa)
40
Experiment contents
Hardened state
Compressive and flexural strength (MPa): 28 days
Low-velocity impact tests
Temperature conditions: −70, 70, and 140°C
... SangYoul Lee et al. studied the drop-impact effects of composite concrete plates reinforced by the various pattern of UHMWPE fabric. They suggested 3D-UHMWPE fabric reduces the brittle fracture of concretes [11]. ...
A study of high-velocity impact behavior of multi-layer nanopolymer composites has been one of the most exciting research topics in materials science and engineering. The material researchers and designers developed and investigated the behavior of advanced materials suitable for impact resistance. Background information and current research activity in the field of fiber-reinforced hybrid nanopolymer composites are briefly reviewed. The factors influencing the performance of the polymer composites and failure mechanisms when subjected to high-velocity impact are presented. The ballistic properties of some representative composite materials containing Carbon, Glass, Kevlar, and hybrid fabric reinforced with suitable nanophase are briefly discussed. The material characterization methods and test standards are highlighted. A systematic approach that facilitates the formulation and fabrication of application-specific, ballistic properties-centered, and tailor-made design of polymer nanocomposites helps the scientific community achieve the desired material sufficiency. Such information can have important implications in the design of more sophisticated systems for a wide range of applications.
This study analyzed high-energy impact behaviors of concrete structures strengthened with multi-walled carbon nanotube (MWCNT) composites. The proposed multi-walled carbon nanotubes demonstrated excellent mechanical properties such as high stiffness, high strength, and improved elongation. These distinctive properties allow the use of the product in several high-performance applications. Using a multi-scale analysis, we investigated the impact mechanism of an MWCNT-reinforced concrete structure using various parameters. The parametric studies focused on the various impact effects on structural performance. In addition, a three-dimensional simulation was carried out for the verification of our experimental results.
