Consolidation Quality Research Articles

Nanocrystalline NiAl intermetallic alloy with high hardness produced by mechanical alloying and hot-pressing consolidation

An Ni-50% Al elemental powder mixture was mechanically alloyed in a SPEX ball mill. The powders after various milling times were investigated by X-ray diffraction and differential scanning calorimetry. A nanocrystalline NiAl intermetallic phase with the mean crystallite size of 13 nm was formed after 8 h of milling. The produced powder was consolidated by high-pressure hot-pressing at 800 °C under the pressure of 7.7 GPa. The consolidated material was characterised by structural investigations. Hardness, density and open porosity as well as heat resistance measurements were also conducted. The mean crystallite size of the NiAl intermetallic phase in the bulk material was 24 nm, which shows that the nanocrystalline structure was maintained during the consolidation process. The hardness and heat resistance of the produced nanocrystalline NiAl were compared with those of a reference microcrystalline NiAl. The hardness of the nanocrystalline NiAl intermetallic is 971 HV1 (9.53 GPa) and it significantly exceeds the hardness of the reference microcrystalline NiAl. The relative density of the consolidated sample is 100%. The produced nanocrystalline NiAl intermetallic exhibits very good oxidation resistance at 900 °C in air. For this material, the mass gain per area after 100 h of exposure is 1.4 × 10−4 g and is smaller than that for the reference microcrystalline NiAl sample. The quality of consolidation with preserving NiAl nanocrystalline structure is satisfactory and the hardness as well as the oxidation resistance of the produced material are relatively high.

The mechanical properties of composite materials recycled from waste metallic chips under different pressures

The purpose of this study is to produce composite materials by utilizing the waste metallic chips. In this context, the metal matrix composite materials (MMCs) were produced at different production pressures and the effects of the different pressures on mechanical properties of MMCs were investigated. In the present investigation, spheroidal graphite cast iron (GGG-40) was used as reinforcement material in bronze (CuSn10) matrix system. The MMCs were produced by hot press with 20 wt% GGG-40 reinforcement ratio. The total time required for the production of one specimen was selected as 25 min and temperature was settled at 400 °C. In order to determine mechanical properties and consolidation mechanism of MMCs, Brinell and micro-Vickers hardness, porosity, compression and X-ray diffraction tests were conducted. In addition, microstructure views were examined to determine the consolidation quality of metallic chips. According to experimental results, it was observed that waste metallic chips can be successfully recycled into MMC final parts with approximately 40% porosity and almost 100% strength and 150% hardness with respect to bulk CuSn10 materials. Most of the presented studies in the literature present information about properties of MMCs fabricated by conventional production methods. However, no available data are found about the recycling of bronze-based MMCs which make this study more original. It is also shown in this study that waste metallic chips can be utilized by proposed recycling methodology, which is environmentally friendly in comparison with conventional recycling methods producing harmful gases for earth atmosphere.

Towards the combination of automated lay-up and stamp forming for consolidation of tailored composite components

A process route is proposed where automated lay-up is followed by stamp forming for the manufacturing of load carrying components of thermoplastic composite. The focus is on rapid lay-up, rather than in situ consolidation, while the final consolidation quality and shape are achieved by stamp forming. An experimental study offers improved understanding of the relation between blank preconsolidation quality and final quality and the role of the prepreg. Two C/PEEK prepregs are processed into blanks by ATL and AFP and subsequently stamp formed. The consolidation quality of the stamped blanks was characterized by C-scans, micrographs and density measurements, while the mechanical performance was evaluated based on flexural tests. The results demonstrate the key role of the prepreg, especially thickness variations, in the consolidation process, but also that high quality laminates can be obtained.

Development of real-time visual monitoring system for vibration effects on fresh concrete

Abstract The consolidation of concrete is crucial to ensure the long-term strength and durability of concrete structures. Although fresh concrete can be consolidated properly via vibration, the consolidation quality heavily relies on construction workers' experience. Inexperienced workers tend to under-consolidate or over-consolidate concrete, resulting in indiscoverable and irreparable defects. It is necessary to establish a system that can track the real-time vibration activity and feedback vibration defects to the inspector and worker. In this paper, a real-time visual monitoring system of the vibration effects is developed and validated to solve the under-vibration issues of fresh concrete. The vibration trajectory is accurately tracked by Global Navigation Satellite System (GNSS). The vibration duration is calculated based on the alternation time of vibration status. The data is transmitted and stored in a cloud server by General Packet Radio Service (GPRS). The radius of action and effective vibration zone are determined by experiments and geometric models. The vibration effects are visualized in three dimensional at the control site. A mobile App is also developed to visualize defects to the inspector such that re-vibration can be timely conducted. Field experiments demonstrate that the tracking accuracy of the system satisfies the demand of construction applications. Through comparing the defect report of the system to the results of the nondestructive impact-echo method in a construction case study, the reliability of the system is verified.

Effects of Blank Quality on Press-Formed PEKK/Carbon Composite Parts.

The causes of delamination and porosities during press forming of pre-consolidated flat laminates (blanks) made of carbon fiber-reinforced poly(ether ketone ketone) (PEKK) were addressed in this study. In particular, the quality of the blank laminate was investigated before and after infrared heating. The consolidation quality was evaluated by thickness measurements, non-destructive inspection (NDI), and optical microscopy. The experimental results confirmed that deconsolidation phenomena can be related to residual stresses formed during blank forming in an autoclave, then released during infrared heating (IR) of the blank, determining most of the defects in IR heated blanks. These defects, generated at the pre-heating stage, were not fully removed in the consolidation stage of the press forming process. An annealing treatment, performed on autoclave-consolidated blanks above the glass transition temperature of the matrix, was proposed to reduce the formation of defects during IR heating. The stress relaxation phenomena during annealing were modelled using a simple viscoelastic model.

Effect of cooling rate on the interlaminar fracture toughness of unidirectional Carbon/PPS laminates

The effect of cooling rate on the interlaminar fracture toughness of Carbon reinforced PPS laminates was investigated experimentally. A typical stamp forming process was utilised in a novel manner to achieve high average cooling rates, of up to 3500 °C/min, while ensuring a good consolidation quality. Differential scanning calorimetry measurements were used to characterise the degree of crystallinity of the samples, while the interlaminar fracture toughness of the laminates was characterised under mode I using the Double Cantilever Beam test. Finally, micrographic analysis of the fracture surfaces was carried out to correlate the degree of crystallinity to the failure modes. A strong correlation between fracture toughness and degree of crystallinity was found. The samples with a low degree of crystallinity showed a high interlaminar fracture toughness and large plastic deformation of the matrix during fracture.

DTCF: deadline task consolidation first for energy minimisation in cloud data centres

The consumption of energy is a vital issue in the cloud, when more precisely administering a large-scale data centre. The cloud data centre accommodating more hosts consume an extent of energy for computation which increases the consumption of energy. To handle this issue, we propose a heuristics energy-efficient workload consolidation with deadline constraint to optimise energy in cloud data centre. The deadline task consolidation first algorithm ranks hosts for creating virtual machines (VMs) and validates the processing time of VMs and places the VM considering deadline of tasks, VMs can be placed in an increasing order of their respective processing time. Then, the decision for migrating VMs to other hosts is evaluated using Markov decision model. Through this process, for specific virtual machine necessities of workloads, we can reduce the number of hosts. The proposed algorithm is simulated in Cloudsim shows that it improves the workload consolidation quality, and is appropriate for deadline task consolidation in cloud data centre.

Development of multifunctional self-reinforced composites

Nanocomposites based on Polypropylene and carbon nanotubes were used as the matrix in self-reinforced composites. Morphological, thermal and mechanical characterization was performed. Electrical behavior was investigated to analyze the materials ability to monitor damage from strain-induced electrical changes. Nanocomposites obtained at high extrusion speed presented better filler dispersion and hence, improved tensile and electrical response. Processing conditions mainly affected the composites consolidation quality and thus, their failure mode. While poorer consolidated materials presented delamination, those better consolidated mostly failed by fiber fracture. Composites with an open PP fabric exhibited electrical resistivity values adequate for strain sensing but worse tensile properties.

DTCF: deadline task consolidation first for energy minimisation in cloud data centres

The consumption of energy is a vital issue in the cloud, when more precisely administering a large-scale data centre. The cloud data centre accommodating more hosts consume an extent of energy for computation which increases the consumption of energy. To handle this issue, we propose a heuristics energy-efficient workload consolidation with deadline constraint to optimise energy in cloud data centre. The deadline task consolidation first algorithm ranks hosts for creating virtual machines (VMs) and validates the processing time of VMs and places the VM considering deadline of tasks, VMs can be placed in an increasing order of their respective processing time. Then, the decision for migrating VMs to other hosts is evaluated using Markov decision model. Through this process, for specific virtual machine necessities of workloads, we can reduce the number of hosts. The proposed algorithm is simulated in Cloudsim shows that it improves the workload consolidation quality, and is appropriate for deadline task consolidation in cloud data centre.

Integrating Fiber Optic Strain Sensors into Metal Using Ultrasonic Additive Manufacturing.

Ultrasonic Additive Manufacturing (UAM), a rather new three-dimensional (3D) printing technology, uses ultrasonic energy to produce metallurgical bonds between layers of metal foils near room temperature. This low temperature attribute of the process enables integration of temperature sensitive components, such as fiber optic strain sensors, directly into metal structures. This may be an enabling technology for Digital Twin applications, i.e., virtual model interaction and feedback with live load data. This study evaluates the consolidation quality, interface robustness, and load sensing limits of commercially available fiber optic strain sensors embedded into aluminum alloy (AA) 6061. Lastly, an outlook on the technology and its applications is described.

Controlling the Nanocontact Nature and the Mechanical Properties of a Silica Nanoparticle Assembly

Elaborating advanced nanomaterials based on the assembly of nanoparticles (NPs) is a versatile route for targeting and tuning a wide variety of properties like optical, magnetic, electrical properties or sensing. This route usually employs a so-called soft chemistry which has the advantage to be quite cheap and transferable to an industrial level. However getting quantitative informations on the quality of the mechanical consolidation of the nanoparticle assembly (ordered or disordered), in a non destructive manner is not often achieved although it is crucial for applications and integration of materials in devices. Therefore, we present in this article a complete method where we evaluate the elasticity of weakly (Van der Waals nanocontacts) to strongly (covalent-hydrogen nanocontacts) interacting nanoparticles assemblies. This complete work is realized on a disordered silica nanoparticles network obtained by sol-gel method. A precise control of the chemical and physical properties of the nanoparticles su...

Moisture and temperature influence on mechanical behavior of PPS/buckypapers carbon fiber laminates

In this work, multiwall carbon nanotubes (MWCNT) were dispersed in water with the assistance of water based surfactant and then sonicated in order to obtain a very well dispersed solution. The suspension was filtrate under vaccum conditions, generating a thin film called buckypapers (BP). Poly (phenylene sulphide) (PPS) reinforced carbon fiber (CF) and PPS reinforced CF/BP composites were manufactured through hot compression molding technique. Subsequently the samples were exposed to extreme humidity (90% of moisture) combined with high temperature (80 °C). The mechanical properties of the laminates were evaluated by dynamic mechanical analysis, compression shear test, interlaminar shear strength and impulse excitation of vibration. Volume fraction of pores were 10.93% for PPS/CF and 16.18% for PPS/BP/CF, indicating that the hot compression molding parameters employed in this investigation (1.4 MPa, 5 min and 330 °C) affected both the consolidation quality of the composites and the mechanical properties of the final laminates.

Self‐reinforced polypropylene composites based on low‐cost commercial woven and non‐woven fabrics

In the present paper, different self‐reinforced polypropylene (PP) composites based on low‐cost commercial woven (w) and non‐woven (nw) fabrics were obtained. Hot compaction (HC) and film stacking (FS) followed by compression molding were used to prepared the composites. The fracture and failure behavior of the different materials was determined under different testing conditions through quasi‐static uniaxial tensile tests, Izod impact experiments and by means of fracture mechanics tests on mode I double‐edge deeply notched tensile specimens. In the case of the composite obtained by film stacking + compression molding (rPP/nw/w‐FS) and the hot‐compacted composite (nw/w‐HC) containing simultaneously woven and non‐woven fabrics, the acoustic emission technique was applied in situ in the tensile tests to determine their consolidation quality and to identify the failure mechanisms responsible for their fracture behavior. It was observed that both composites exhibited relatively similar high consolidation quality. However, the hot‐compacted composite presented a more uniform distribution of failure mechanisms (debonding and fiber fracture) than the film‐stacked composite. The hot‐compacted composite containing both types of reinforcements exhibited the best combination of mechanical (tensile, impact, and fracture) properties. Therefore, this composite appeared as the most promising for structural applications among the different composites investigated.

Thermostamping of [0/90]n carbon/peek laminates: Influence of support configuration and demolding temperature on part consolidation

This work presents experimental results on the thermostamping of carbon/PEEK cross‐ply laminates made of unidirectional prepregs. The first objective was to evaluate the effect of the supporting frame and laminate thickness on the consolidation quality of the final part. Based on the use of a square frame mounted with constant‐force springs clamps, three support configurations are compared: (i) clamp a polyimide film with the springs and use it to support the blank, (ii) support the blank with the constant‐force springs without polyimide film and (iii) support both the blank and a polyimide film with the springs. Using the best of these configurations (configurations ii and iii), the second objective was to push further the analysis and evaluate how demolding at different temperatures affects the part thickness distribution, the interlaminar shear strength and the cycle time of the process. Good consolidation qualities were obtained with configurations (ii) and (iii). However, the latter allows for more uniformity in the part thickness and higher shear strength when demolding at higher temperatures. It also allows a reduction of the molding cycle time considering the part can be demolded at a higher temperature (reduced cooling time). POLYM. COMPOS., 39:3341–3352, 2018. © 2017 Society of Plastics Engineers

Modeling and optimization of interlaminar bond strength for composite tape winding process

The prepreg tape winding product of thermoset composite has been widely used in aerospace industry due to the favorable performance. The manufacturing process is the key to ensure the quality of product. This study is focused on the theoretical analysis of prepreg tape winding process. The mathematical model of thermal and consolidation process is established firstly. The influence mechanism of the major process parameters including heating temperature, consolidation force and winding velocity on consolidation quality is subsequently studied based on the simulation results. And the tape winding experiments and interlaminar shear strength tests are conducted to validate the predictive capability of the theoretical model. Moreover, the coupling role between the process parameters is explained based on the predicted model. In order to control the quality of winding product, the optimization of winding process is proposed, and the three-dimension process window of parameter settings is obtained.

Single-step manufacturing of curved polypropylene composites using a unique sheet consolidation method

Many techniques have been developed over the past few decades to manufacture curved fibre reinforced thermoplastic composites. Long-fibre composite parts have been mostly manufactured by either compression moulding or thermoforming in two or more steps. No effort has been put into single-step manufacturing of long fibre curved thermoplastic composite parts. This work develops a manufacturing plan that has the ability to produce fairly strong curved thermoplastic composites in a single step. The production of composites according to this plan is expected to be significantly cheaper than the composites produced by compression moulding or thermoforming. In this research, curved composites were manufactured from flax reinforcements and polypropylene sheets using a unique manufacturing cycle, where the composites were formed and consolidated simultaneously. The optimum processing parameters and the fibre volume fraction were found to manufacture curved flax reinforced polypropylene composites with acceptable tensile and shear strengths. An experimental setup was used to monitor and record the applied vacuum pressure and temperature during the experiments. Shear and tensile strength of the manufactured composites was found. The consolidation quality of the manufactured composites was assessed by examining the composite specimens’ cross-sections under an optical microscope. The results showed that the tensile and shear strengths of the manufactured composites were dependent on the fibre volume fraction, transverse permeability of the fibre reinforcement and also the magnitude and method of application of compaction pressure. There were optimum fibre volume fractions with respect to tensile and shear strengths for each of the three fibre reinforcements used in this research. The shear and tensile strengths of the composites produced in this research are comparable to compression moulded or thermoformed parts.

Self-reinforced composites based on commercial PP woven fabrics and a random PP copolymer modified with quartz

Self-reinforced composites based on commercial polypropylene (PP) woven fabrics and a random PP copolymer modified with quartz were obtained by film stacking. The effect of the incorporation of quartz on the materials fracture and failure behavior was studied through uniaxial tensile tests and quasi-static fracture experiments. Acoustic emission analysis was also performed in situ in the tensile tests. A higher consolidation quality was obtained for the composites containing quartz. In the composite with random PP modified with 5 wt% quartz, the higher consolidation and the better dispersion of quartz particles positively impacted on the materials tensile and fracture behavior. From the results of acoustic emission analysis, fiber fracture appears as the dominant failure mechanism in the investigated composites. Copyright © 2016 John Wiley & Sons, Ltd.

An empirical appraisal of the role of money in Nigerian politics

This study was conducted with the aim of ascertaining the impact of money on the quality of democracy and democratic consolidation in Nigeria. To achieve this major objective, the study employed the use of both primary and secondary data. The primary data consisted of questionnaires, while the secondary consisted of published materials. The study found that the use of money by politicians to influence the outcome of elections through vote buying among other malpractices in the country is firstly a consequence of the prevailing poverty and the expectation of the electorate for the aspiring politicians to dispense money. This development resulted in the lack of credibility of election results and in Nigeria's democracy. It is recommended that funding the electoral process must be reformed to make access and participation possible for a broader spectrum of society.

Real-time tracking of concrete vibration effort for intelligent concrete consolidation

Abstract Proper consolidation of concrete is critical to the long-term strength of concrete structures. Vibration is a commonly used method to make concrete flowable and to remove the excessive entrapped air, therefore contributing to proper concrete consolidation. To introduce vibrations to freshly placed concrete, various tools such as internal vibrators are widely used in the construction industry. Producing a dense concrete without segregation with these tools requires an experienced vibrator operator. Inexperienced vibrator operators tend to over-consolidate or under-consolidate concrete. Many of these quality problems have their roots in the lack of quality control methods that can provide real-time feedback on the quality of concrete consolidation to vibrator operators. A real-time wireless sensing-based internal vibrator tip tracking system was developed and validated in this research to support intelligent concrete consolidation operations. More specifically, the research explored the use of an ultra wideband (UWB) tracking system to realize precise localization of the tip of an internal vibrator. A series of indoor and outdoor experiments are conducted to validate and model the tracking accuracy. A novel visualization program was developed to visualize operators' vibration effort in real-time. The program is capable of displaying vibration location and time in real-time. A vibrator operator can leverage such information to visualize the distribution of his vibration effort, and spot areas that may need mitigation actions. This also provides an innovative construction inspection practice to owners and resident engineers. The new concrete consolidation tool will allow contractors to proactively address concrete consolidation issues, a problem common to many concrete construction projects.

Experimental investigation of carbon fiber reinforced poly(phenylene sulfide) composites prepared using a double-belt press

The high-performance carbon fiber reinforced poly(phenylene sulfide) composites were continuously fabricated using thermoplastic prepregs in a double-belt press. The effects of process velocity on the composite consolidation quality and mechanical properties were investigated. It is found that the tensile and interlaminar shear properties of composites prepared using the double-belt press are comparable to that of compression-molded composites when the process velocity is no more than 0.20 m·min−1. The composite fracture morphologies also show different failure mechanisms between different samples and indicate that the interfacial adhesion strength may play a vital role in the mechanical properties of CF/PPS composites. Furthermore, experimental results show that the heating time above 330 °C should be over 440 s and the void content should be lower than 2.38% in order to obtain high performance CF/PPS composites.