Three-dimensional stability calculation method for high and large composite slopes formed by mining stope and inner dump in adjacent open pits

The 2D limit equilibrium method is widely used for slope stability analysis.However,with the advancement of dump engineering,composite slopes often exhibit significant 3D mechanical effects.Consequently,it is of significant importance to develop an effective 3D stability calculation method for composite slopes to enhance the design and stability control of open-pit slope engineering.Using the composite slope formed by the mining stope and inner dump in Baiyinhua No.1 and No.2 open-pit coal mine as a case study,this research investigates the failure mode of composite slopes and establishes spatial shape equations for the sliding mass.By integrating the shear resistance and sliding force of each row of microstrip columns onto the bottom surface of the strip corresponding to the main sliding surface,a novel 2D equivalent physical and mechanical parameters analysis method for the strips on the main sliding surface of 3D sliding masses is proposed.Subsequently,a comprehensive 3D stability calculation method for composite slopes is developed,and the quantitative relationship between the coordinated development distance and its 3D stability coefficients is examined.The analysis reveals that the failure mode of the composite slope is characterized by cutting-bedding sliding,with the arc serving as the side interface and the weak layer as the bottom interface,while the destabilization mechanism primarily involves shear failure.The spatial form equation of the sliding mass comprises an ellipsoid and weak plane equation.The analysis revealed that when the coordinated development distance is 1500 m,the error rate between the 3D stability calculation result and the 2D stability calculation result of the composite slope is less than 8%,thereby verifying the proposed analytical method of equivalent physical and mechanical parameters and the 3D stability calculation method for composite slopes.Furthermore,the3D stability coefficient of the composite slope exhibits an exponential correlation with the coordinated development distance,with the coefficient gradually decreasing as the coordinated development distance increases.These findings provide a theoretical guideline for designing similar slope shape parameters and conducting stability analysis.

Ballistic impact response of flexible and rigid UHMWPE textile composites:Experiments and simulations

This study elaborates on the effects of matrix rigidity on the high-velocity impact behaviour of UHMWPE textile composites using experimental and numerical methods.Textile composite samples were manufactured of a plain-weave fabric(comprising Spectra?1000 fibres)and four different matrix materials.High-velocity impact tests were conducted by launching a spherical steel projectile to strike on the prepared samples via a gas gun.The experimental results showed that the textile composites gradually changed from a membrane stretching mode to a plate bending mode as the matrix rigidity and thickness increased.The composites deformed in the membrane stretching mode had higher impact resistance and energy absorption capacity,and it was found that the average energy absorption per ply was much higher in this mode,although the number of broken yarns was smaller in the perforated samples.Moreover,the flexible matrix composites always had higher perforation resistance but larger deformation than the rigid matrix counterparts in the tested thickness and velocity range.A novel numerical modelling approach with enhanced computational efficiency was proposed to simulate textile composites in mesoscale resolution.The simulation results revealed that stress and strain development in the more rigid matrix composite was localised in the vicinity of the impact location,leading to larger local deformation and inferior perforation resistance.

X-ray Computed Tomography Characterization of 3D Tufted Twill Textile Composite for Aerostructures

Damage assessments in three dimensional (3D) textile composites subjected to mechanical loading can be performed by non-destructive and destructive techniques.This paper applies the two techniques to investigate the fracture behavior of 3D tufted textile composites.X-ray computed tomography as a non-destructive evaluation method is appropriate to detect damage locations and identify their progression in 3D textile composites.Destructive methods such as sectioning toward observing damage provide valuable information about damage patterns.The results of this research could be utilized to evaluate the initial cause of rupture in 3D tufted composites used in aerospace structures and analyze fracture modes and damage progression.

Simulating Resin Infusion through Textile Reinforcement Materials for the Manufacture of Complex Composite Structures

商用飞机对减轻机身重量和提高燃料效率的需求日益增强,这一需求促进了复合材料在商用飞机结构中的应用。当飞机的复合材料结构变得更庞大、更复杂时,传统的热压罐生产方法就会变得相当昂贵,这一现象引起了研究者对非热压罐成型技术的关注。在此技术中,树脂被注入强化预浸料层。然而,树脂灌注工艺与操作人员的技术和经验息息相关,特别是在开发复杂部件的生产策略时。作为一种用于预测的计算工具,流程建模旨在解决可靠性问题以及传统反复试验法所导致的浪费问题。大多数传统建模仍应用于工业,主要针对各向同性多孔强化材料的流体流动模拟。然而,最近的一些研究开始将编织材料的多尺度和多学科的复杂性纳入考虑范畴,其模拟方法可以提供更高的保真度。尤其考虑到具有渗透性和多孔性的强化材料导致的织物变形效应,新的多物理场流程模拟能够通过织物更好地预测树脂的灌注行为。除了综述与流程模拟相关的前人研究和工艺现状,本文还重点论述了最近关于复杂双圆顶组件的多物理场流程模拟与实验灌注的对比验证。通过考虑变形依赖的流动行为,多物理场流程模拟能够预测实际的流动行为,证明其与基础的各向同性渗透模型相比有很大程度的改进。

Preparation of Composite Phase Change Material Based on Sol-Gel Method and Its Temperature-Adjustable Textile

In this study,the sol-gel method was introduced to prepare the composite phase change material (CPCM). The CPCM was added to fabric with coating techniques and the thermal activity of modified fabric was studied. In addition,the thermal property and the microstructure of CPCM were also discussed in detail by means of polarization microscope and differential scanning calorimeter,respectively. According to the analysis of main influencial factors of the property of CPCM,the optimal preparing technique was determined. It was proved that CPCM could exhibit a good thermal property while phase transformation process took place,and a better appearance of the fabric modified with CPCM could be obtained due to the fact that in a warm circumstance,the liquid-state phase change material could be firmly enwrapped and embedded in the three-dimensional network all the time during the phase transformation. Besides,the fabric treated with CPCM had a high phase-transition enthalpy and an appropriate phase-transition temperature. As a result,a desirable temperature-adjustable function appeared.

The Study for the Reinforced Composites of Textile Gradient Structure

Based on references, this paper further develops the composites of textile gradient structure, tests and analyses the mechanical properties of composites of gradient struture, moreover, makes a comparison between composites of gradient structure and common laminated composites.

Development of Composite Textile Structures for Wound Dressing Applications

The main objective of this research work was the development of novel and responsive nonwoven composite structures containing gelling materials for wound management. The development of novel all inclusive collagen booster(CB) therapeutic nonwoven wound dressings was mainly focused on. It provides essential functional properties such as high absorption,vertical and lateral wicking,and antibacterial and acidic pH properties. The developed composite wound dressing consisted of carboxymethylcellulose(CMC) fibre and also it was reinforced with polylactic acid( PLA) fibre. The produced composite wound dressings were treated with two different CBs at 4% by using the spray method. The details of the CBs have not been disclosed in this paper due to the Intellectual Property Rights( IPR) issues. The important benefit of using CB treatment is that it allows the maintenance of an acidic pH environment at the wound area. It is well known that acidic pH reduces the wound healing time and enhances the wound healing process. Furthermore,one of the CBs not only promotes the proliferation of the epithelial cells in wounds but also can provide antibacterial action. The PLA fibre reinforced CMC composite dressing has enhanced wicking properties which help to minimise the pooling of exudate on the wound bed and as a result maceration is prevented. The CBs treated dressings maintain the wound bed in an acidic pH condition which also improves the wound healing process. In addition to the above-mentioned properties,the CB treatment imparts antimicrobial activity against Gram-positive and Gram-negative bacteria,thus resulting in the reduction in the propensity for wound infection. Ultimately,the research has proved that the 4% CB treatment enhances the antimicrobial activity and the acidic pH characteristics of the developed CMC /PLA composite wound dressings.

Textile-Based Sensors for Inspection of Composite Materials

The monitoring of mechanical deformation and damage of composite materials is normally performed by established analytical methods,such as strain gauges and optical and piezoelectric sensors.However,large areas outside of the measuring cell remain unconsidered.A large-area sensitive sensor for composites is presented,which is simply generated by printing a carbon layer on the reinforcing glass fiber fabrics or on any composite itself.Such printed sensors enable to determine mechanical deformations and damages of the entire component and it responds with a measurable electrical resistance to external tension or pressure without any hysteresis.The strongest influence on sensor signal was identified with low carbon concentration and thin layers.The sensors signal linearly correlates with the degree of deformation and bending velocity whereas bending direction can be identified through signal change under residual tensile stress or compressive stress.

Effects of Fiber Volume on Modal Response of Through-Thickness Angle Interlock Textile Composites

Prior static studies of three-dimensionally woven carbon/epoxy textile composites show that large interlaminar normal and shear strains occur as a result of layer waviness under static compression loading. This study addresses the dynamic response of 3D through-thickness angle interlock textile composites, and how interaction between different layer waviness influences the modal frequencies. The samples have common as-woven textile architecture, but they are cured at varying compaction pressures to achieve varying levels of fiber volume and fiber architecture distortion. Samples produced have varying final cured laminate thickness, which allows observations on the influence of increased fiber volume (generally believed to improve mechanical performance) weighed against the increased fiber distortion (generally believed to decrease mechanical performance). The results obtained from this study show that no added damping was developed in the as-woven identical panels. Furthermore, a linear relation exists between modal frequency and thickness (fiber volume).

Property of three-dimensional silica composites

Silica fibers-reinforced, fused silica composites were fabricated with repeated vacuum-assisted liquid-phase infiltration. The mechanical properties, thermal properties, and ablative properties of the samples were evaluated. The effect of the silica fiber content and treatment temperature on the flexural strength of the three-dimensional SiO2 （3-D SiO2） composites also was investigated. The SiO2 composites show good mechanical properties and excellent ablative performance. The flexural strength increases with an increase in silica fiber content, and decreases with an increase in treatment temperature. When the volume fraction of the silica fiber is 50vo1% and the treatment temperature is 700℃ the flexural strength of the composites reaches a maximum value of 78 MPa. By adding cyclohexanone surfactant, the infiltration property can be largely improved, resulting in the density of SiO2 composites increasing up to 1.65 g/cm^3. The fracture surfaces of the flexural specimens observed using SEM, show that the pseudoplasticity and the toughening mechanisms of the composites are caused by absorption of a lot of energy by interface debonding and fiber pulling out.

Microstructure-based three-dimensional characterization of chip formation and surface generation in the machining of particulate-reinforced metal matrix composites

Particulate-reinforced metal matrix composites(PRMMCs)are difficult to machine due to the inclusion of hard,brittle reinforcing particles.Existing experimental investigations rarely reveal the complex material removal mechanisms(MRMs)involved in the machining of PRMMCs.This paper develops a three-dimensional(3D)microstructure-based model for investigating the MRM and surface integrity of machined PRMMCs.To accurately mimic the actual microstructure of a PRMMC,polyhedrons were randomly distributed inside the matrix to represent irregular SiC particles.Particle fracture and matrix deformation and failure were taken into account.For the model’s capability comparison,a two-dimensional(2D)analysis was also conducted.Relevant cutting experiments showed that the established 3D model accurately predicted the material removal,chip morphology,machined surface finish,and cutting forces.It was found that the matrix-particle-tool interactions led to particle fractures,mainly in the primary shear and secondary deformation zones along the cutting path and beneath the machined surface.Particle fracture and dilodegment greatly influences the quality of a machined surface.It was also found that although a 2D model can reflect certain material removal features,its ability to predict microstructural variation is limited.

Mechanical Properties of Three-Dimensional Fabric Sandwich Composites

Three-dimensional( 3 D) fabric composite is a newly developed sandwich structure,consisting of two identical parallel fabric decks woven integrally and mechanically together by means of vertical woven fabrics. In this paper,six types of 3 D fabric sandwich composites were developed in terms of compressive and flexural properties as a function of pile height( 10, 20 and30 mm) and pile distance( 16, 24 and 32 mm) in pile structures. The mechanical characteristics and the damage modes of the 3 D fabric sandwich composites under compressive and flexural load conditions were investigated. Besides,the influence of pile height and pile distance on the 3 D fabric sandwich composites mechanical properties was analyzed. The results showed that the compressive properties decreased with the increase of the pile height and the pile distance. Flexural properties increased with the increase of pile height, while decreased with the increase of pile distance.

Effects of Fiber Volume Fraction on Damping Properties of Three-Dimensional and Five-Directional Braided Composites

The effects of fiber volume fraction on damping properties of carbon fiber three-dimensional and five-directional( 3D-5Dir)braided carbon fiber / epoxyres in composite cantilever beams were studied by experimental modal analysis method. Meanwhile,carbon fiber plain woven laminated / epoxy resin composites with different fiber volume fraction were concerned for comparison. The experimental result of braided specimens shows that the first three orders of natural frequency increase and the first three orders of the damping ratios of specimens decrease, when the fiber volume fraction increases. Furthermore,larger fiber volume fraction will be valuable for the better anti-exiting property of braided composites,and get an opposite effect on dissipation of vibration energy. The fiber volume fraction is an important factor for vibration performance design of braided composites. The comparison between the braided specimens and laminated specimens reveals that 3D braided composites have a wider range of damping properties than laminated composites with the same fiber volume fractions.

Prediction of three-dimensional elastic behavior of filament-wound composites based on the bridging model

This work provides a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization principle.In the meso-scale,a representative volume element(RVE)is defined and the bridging model is adopted to establish a theoretical predictive model for its three-dimensional equivalent elastic constants.The results obtained through this method for the previous experimental model are compared with the ones gained respectively by experiments and classical laminate theory to verify the reliability of this model.In addition,the effects of some winding parameters,such as winding angle,on the equivalent elastic behavior of the filament-wound composites are analyzed.The rules gained can provide a theoretical reference for the optimum design of filament-wound composites.

Synthesis and electrochemical properties of three-dimensional graphene/polyaniline composites for supercapacitor electrode materials

To improve the specific capacitance and rate capability of electrode material for supercapacitors, a three-dimensional graphene/polyaniline （3DGN/PANI） composite is prepared via in situ polymerization on GN hydrogel. PANI grows on the GN surface as a thin film, and its content in the composite is controlled by the concentration of the reaction monomer. The specific capacitance of the 3DGN/PANI composite containing 10 wt% PANI reaches 322.8 F.g-1 at a current density of 1 A.g-1, nearly twice as large as that of the pure 3DGN （162.8 F.g-1）. The capacitance of the composite is 307.9 F.g-1 at 30 A.g-1 （maintaining 95.4%）, and 89% retention after 500 cycles. This study demonstrates the exciting potential of 3DGN/PANI with high capacitance, excellent rate capability and long cycling life for supercapacitors.

Preparation of Three-Dimensional Carbon Network Reinforced Epoxy Composites and Their Thermal Conductivity

As a thermosetting resin with excellent properties,epoxy resin is used in many areas such as electronics,transportation,aerospace,and other fields.However,its relatively low thermal conductivity limits its wide application in more demanding fields.Here,a three-dimensional carbon(3DC)network was prepared through NaCl template-assisted in situ chemical vapor deposition(CVD)and used to reinforce epoxy resin for enhancing its thermal conductivity.The 3DC was prepared with a molar ratio of sodium atom to carbon atom of 100:20,and argon atmosphere in CVD led to an optimal improvement in the thermal conductivity of epoxy resin.The thermal conductivity of epoxy resin increased by 18%when the filling content was 3 wt.%of 3DC network because of the high contact area,uniform dispersion,and enhanced formation of conductive paths with epoxy resin.As the amount of 3DC addition increases,the thermal conductivity of composites also increases.As an innovative exploration,the work presented in this paper is of great significance for the thermal conductivity application of epoxy resin in the future.

Using Acoustic Emissions to Detect Damage in Three-Dimensional Braided Composites

Three-dimensional(3D)braided composites with better properties have been used in some particular industries.Some have had obvious signs of crack when they are braided.Others have had catastrophic failures occuring without warning.A new methodology for the analysis of failure modes in composite materials by means of acoustic emission techniques has been developed.The occurrence of fiber-breakage during tensile loading tests has been observed by the acoustic emission technology.Using acoustic emission technology is investigated as a means of monitoring 3D braided composites structures,detecting damage,and predicting impending damage.Some of the findings of the research project were presented.

Internal Strain Measurement in 3D Braided Composites Using Co-braided Optical Fiber Sensors

3D braided composite technology has stimulated a great deal of interest in the world at large. But due to the three-dimensional nature of these kinds of composites, coupled with the shortcomings of currently-adopted experimental test methods, it is difficult to measure the internal parameters of this materials, hence causes it difficult to understand the material performance. A new method is introduced herein to measure the internal strain of braided composite materials using co-braided fiber optic sensors. Two kinds of fiber optic sensors are co-braided into 3D braided composites to measure internal strain. One of these is the Fabry-Parrot (F-P) fiber optic sensor; the other is the polarimetric fiber optic sensor. Experiments are conducted to measure internal strain under tension, bending and thermal environments in the 3D carbon fiber braided composite specimens, both locally and globally. Experimental results show that multiple fiber optic sensors can be braided into the 3D braided composites to measure the internal parameters, providing a more accurate measurement method and leading to a better understanding of these materials.

Damage Initiation and Propagation in Composites Subjected to Low-Velocity Impact:Experimental Results,3D Dynamic Damage Model,and FEM Simulations

A three-dimensional dynamic damage model that fits both small and large damage sizes is developed to predict impact damage initiation and propagation for each lamina of T300-carbon/epoxy laminations.First,13 specimens of the same lamination sequence are subjected to three different impact energies(10 J,15 J,and 20 J).After the impact,the laminates are inspected by the naked eye to observe the damage in the outer layers,and subsequently X-rayed to detect the inner damage.Next,the stress analysis of laminates subjected to impact loading is presented,based on the Hertz contact law and virtual displacement principle.Based on the analysis results,a three-dimensional dynamic damage model is proposed,including the Hou failure criteria and Camanho stiffness degradation model,to predict the impact damage shape and area.The numerical predictions of the damage shape and area show a relatively reasonable agreement with the experiments.Finally,the impact damage initiation and propagation for each lamina are investigated using this damage model,and the results improve the understanding of the impact process.