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Suresh G Advani - One of the best experts on this subject based on the ideXlab platform.
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use of medial axis to find optimal channel designs to reduce mold filling time in resin transfer molding
Composites Part A-applied Science and Manufacturing, 2017Co-Authors: J Wang, Pavel Simacek, Suresh G AdvaniAbstract:Abstract In Resin Transfer Molding (RTM) process, pre-designed channels branching out like runners from the injection port can be used for faster resin distribution and impregnation as compared to traditional single gate injection to reduce the mold filling time. To search for the optimal channel design for maximum fill time reduction, the Medial Axis (MA) of the part surface is defined. Next, a methodology is developed to search for the topology of the MA using Finite Element based mold filling simulation software. The MA location is corrected for a part with non-homogeneous fabric permeability. Finally, some case studies are presented to illustrate the effectiveness and accuracy of the channel design approach for RTM with the objective of minimizing fill time, when fabricating composite parts that contain complexities in both the geometric features such as compound curvatures and corners and in material properties such as non-homogeneous and highly anisotropic Fiber Preform permeability.
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characterization of 3d Fiber Preform permeability tensor in radial flow using an inverse algorithm based on sensors and simulation
Composites Part A-applied Science and Manufacturing, 2011Co-Authors: K Okonkwo, Suresh G Advani, Pavel Simacek, Richard S ParnasAbstract:In Liquid Composite Molding (LCM), the Fiber Preform is placed in a mold and resin is injected through a gate to fill the empty spaces within the mold. LCM processes are modeled as resin flow through fibrous porous media in which if one knows the permeability values, one can determine the arrival times of the resin at any location. A mold with radial injection with 192 flow arrival detection sensors along 16 radial lines are mounted flush with the top and the bottom mold surface with an additional sensor on the top surface opposite to the injection hole of the bottom surface. The inverse problem addressed here is from the recorded resin arrival times at sensor locations, how accurately can one determine the permeability of the Preform? The proposed method uses correlation between the experimentally recorded resin arrival times and 3D flow simulation of the experiment. The optimization routine varies the permeability components in the simulation to achieve the best possible match with the experimental arrival times at all the sensor locations. Currently, all in-plane permeability components and through-the thickness permeability are characterized from a single experiment with the potential to evaluate the cross-thickness off-diagonal terms as well. In addition, the technique also demonstrates how one can reduce the variation in through thickness permeability by the use of a distribution media at the injection hole to avoid blockage of the inlet by the Fiber tows. The optimization routine sequentially optimizes the values of the individual components of the permeability tensor using golden search method, and then repeats the entire sequence until the best match is found. The validation and sensitivity of this method is explored and it has been shown that this technique is promising for characterization of all permeability components from a single radial flow experiment.
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role of processing on interlaminar shear strength enhancement of epoxy glass Fiber multi walled carbon nanotube hybrid composites
Carbon, 2010Co-Authors: V C S Chandrasekaran, Suresh G Advani, Michael H SantareAbstract:Abstract Interlaminar shear strength (ILSS) of hybrid composites made from glass Fiber and multi-walled carbon nanotube (MWCNT) modified epoxy is compared with unmodified epoxy/glass Fiber composites (control). By combining the techniques of high speed mechanical stirring and ultrasonic agitation, 0.5% MWCNT by weight was dispersed in epoxy to prepare a suspension. Composites were manufactured by both injection double vacuum-assisted resin transfer molding (IDVARTM) and the flow flooding chamber (FFC) methods. Compression shear tests were conducted on the manufactured samples to determine ILSS. The effect of processing history and batch-to-batch variability of materials – glass Fiber Preform, resin and carbon nanotubes – on ILSS of samples made by both techniques was investigated. Statistical analysis of the measured ILSS values for hybrid composites and their comparison with the control specimens clearly show that hybrid composites made by the FFC process resulted in (i) significant ILSS enhancement relative to the control and to IDVARTM specimens and (ii) better repeatability than the IDVARTM process. A description of both IDVARTM and FFC processes and their role in dispersing the nanotubes between the fabric layers was discussed.
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resin flow analysis with Fiber Preform deformation in through thickness direction during compression resin transfer molding
Composites Part A-applied Science and Manufacturing, 2010Co-Authors: Justin Merotte, Pavel Simacek, Suresh G AdvaniAbstract:Abstract Resin flow during Compression Resin Transfer Molding (CRTM) can be best described and analyzed in three phases. In the first phase, a gap is created by holding the upper mold platen parallel to the Preform surface at a fixed distance from it. The desired amount of resin injected into the gap quickly flows primarily over the Preform. The second phase initiates when the injection is discontinued and the upper mold platen moves down squeezing the resin into the deforming Preform until the mold surface comes in contact with the Preform. Further mold closure during the final phase will compact the Preform to the desired thickness and redistribute the resin to fill all empty spaces. This paper describes the second phase of the infusion. We assume that at the end of phase one; there is a uniform resin layer that covers the entire Preform surface. This constrains the resin to flow in through the thickness direction during the second phase. We model this through the thickness flow as the load on the upper mold forces the resin into the Preform, simultaneously compacting the Preform. The constitutive equations describing the compaction of the fabric as well as its permeability are included in the analysis. A numerical solution predicting the flow front progression and the deformation is developed and experimentally verified. Non-dimensional analysis is carried out and the role of important non-dimensional parameters is investigated to identify their correlations for process optimization.
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simulation and experimental validation of flow flooding chamber method of resin delivery in liquid composite molding
Composites Part A-applied Science and Manufacturing, 2007Co-Authors: Justin B Alms, Suresh G AdvaniAbstract:A new method of resin delivery, which we refer to as the flow flooding chamber (FFC), is investigated to improve infusion time and reduce material waste associated with the Vacuum Assisted Resin Transfer Molding (VARTM) process. The FFC method uses a rigid chamber that rests on top of the bagging material and a vacuum drawn inside the chamber stretches the bag to take the shape of the chamber above the Fiber Preform. Resin is then drawn into this chamber unimpeded, and once the chamber is full of resin, the release of the vacuum results in application of atmospheric pressure on top of the bag that drives the resin into the Fiber Preform. The distribution media and other subsequent materials for its removal are not needed in this modified VARTM process. This process is mathematically modeled using a two event model that couples them by using the output conditions from the first event to the input conditions of the second event. The model is implemented in a numerical simulation so one can track the movement of the resin into the chamber and the Preform. Experiments using the FFC process are conducted in complex geometries containing inserts and the flow fronts and fill times are recorded. The results compare very well with the predictions validating the assumptions made in the model to describe the flow.
Kuangting Hsiao - One of the best experts on this subject based on the ideXlab platform.
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effects of vacuum pressure inlet pressure and mold temperature on the void content volume fraction of polyester e glass Fiber composites manufactured with vartm process
Journal of Composite Materials, 2011Co-Authors: Vishwanath R Kedari, Basil I Farah, Kuangting HsiaoAbstract:Vacuum-assisted resin transfer molding (VARTM) process is one of the liquid composite molding (LCM) processes aimed at producing high-quality composite parts. The void content and Fiber volume fraction of a VARTM part can be affected by many parameters and is critical to the mechanical properties and the quality of the part. In this paper, a series of experiments were conducted with a heated dual pressure control VARTM setup for investigating the effects of vacuum pressure, inlet pressure, and mold temperature on the void content and Fiber volume fraction of polyester/E-glass Fiber composite. It was found that stronger vacuum and higher mold temperature can better control and increase the Fiber volume fraction; however, such a combination of strong vacuum and high mold temperature may also require a reduced inlet pressure for minimizing the void content. The need of pressure reduction can be explained with the compatibility between Darcy's flow and capillary flow in the Fiber Preform and can be calculated...
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investigation on the spring in phenomenon of carbon nanoFiber glass Fiber polyester composites manufactured with vacuum assisted resin transfer molding
Composites Part A-applied Science and Manufacturing, 2008Co-Authors: Kuangting Hsiao, Sudhir GangireddyAbstract:Abstract Process-induced residual stress arises in polymer composites as a result of mismatched resin contraction and Fiber contraction during the cure stage. When a curved shell-like composite part is de-molded, the residual stress causes the spring-in phenomenon, in which the enclosed angle of the part becomes smaller than the angle of its mold. In this paper, a new approach is presented to control and reduce the spring-in angle by infusing a small amount of carbon nanoFibers (CNFs) together with liquid resin into the glass Fiber Preform using vacuum assisted resin transfer molding (VARTM) process. The experimental results showed that the spring-in angles of the L-shaped composite specimens were effectively restrained by the CNFs. An analytical model and a 3-D FEA model were developed to predict the spring-in phenomenon and to understand the role of CNFs in reducing the spring-in angle. The models agreed with the experimental results reasonably well. Furthermore, the analytical model explains how the CNF-enhanced dimensional tolerance control is accomplished through the reductions in the matrix’s equivalent coefficient of thermal expansion and linear crosslinking shrinkage.
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manufacturing carbon nanoFibers toughened polyester glass Fiber composites using vacuum assisted resin transfer molding for enhancing the mode i delamination resistance
Composites Part A-applied Science and Manufacturing, 2006Co-Authors: Ramin Banan Sadeghian, Sudhir Gangireddy, Bob Minaie, Kuangting HsiaoAbstract:Abstract Polymer composite materials reinforced by continuous Fibers have excellent in-plane strength but are usually weak against delamination. This paper presents an experimental study of using carbon nanoFibers (CNF) to improve the interlaminar fracture properties of polyester/glass Fiber composites. Surfactant-treated CNF were dispersed in polyester resin and then the CNF-resin suspension was infused to impregnate a glass Fiber Preform using vacuum assisted resin transfer molding (VARTM). The manufacturability of using VARTM for thick and large CNF toughened composite parts has been experimentally investigated. The influence of CNF concentration on the CNF filtration in the glass Fiber Preform, the resin viscosity, and the micro-void formation has been examined. By choosing appropriate manufacturing parameters, we were able to use VARTM process to infuse the surfactant-treated CNF/resin matrix into the glass Fiber Preform and successfully manufactured the CNF toughened polyester/glass Fiber composite specimens for mode-I delamination tests. The critical energy release rates of mode-I delamination ( G IC ) were characterized for several composite specimens with 1 wt% CNF concentrations and for those with pure resin. Significant improvement in the G IC was consistently observed as 1 wt% CNF were added to toughen the polyester resin. Microscopy pictures showed that the fracture surfaces of the 1 wt% CNF toughened polyester/glass Fiber composite samples were more complex than the fracture surfaces of regular polyester/glass Fiber composites.
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flow sensing and control strategies to address race tracking disturbances in resin transfer molding part ii automation and validation
Composites Part A-applied Science and Manufacturing, 2005Co-Authors: Mathieu Devillard, Kuangting Hsiao, Suresh G AdvaniAbstract:Abstract Resin Transfer Molding (RTM) is an advanced processing technology for composites manufacturing. In this process, the Fiber Preform is placed in a closed mold and the resin is injected into the mold to saturate the Preform. After the resin cures, the mold is opened and the net shape composite part is removed. RTM is capable of making complex and high quality composite parts in fairly short cycle times. However, by introducing more complexity into the part, one also introduces higher probability of disturbances, such as race tracking along Preform edges, into the molding system and increases the risk of failure. Part-I [Hsiao KT, Advani SG. Flow sensing and control strategies to address the race-tracking disturbances in resin transfer molding—Part I: design and algorithm development. Composites Part A: Appl Sci Manuf 2004;35(10):1149–59] outlined the methodology using process models and simulations along with sensing and control strategies to address flow disturbances. It was demonstrated in a virtual environment that one can increase the success rate significantly by selectively placing the sensors to identify the location of the disturbance and strategically opening and closing auxiliary gates to steer the resin flow to impregnate all the Fibers. In part-II, an automated system designed to implement the on-line control strategy of part-I is demonstrated. Once the design of on-line control strategy is completed as delineated in part-I, the results can be seamlessly interfaced with the manufacturing platform to communicate with the sensors in the mold and control the injection and vent valves on an experimental platform. Thus, this streamlines the feedback control in RTM from the design stage to the automation stage. An experimental case study is presented to validate the use of model based on-line control of the RTM process and to demonstrate how it lends itself to automation in the manufacturing process.
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flow sensing and control strategies to address race tracking disturbances in resin transfer molding part i design and algorithm development
Composites Part A-applied Science and Manufacturing, 2004Co-Authors: Kuangting Hsiao, Suresh G AdvaniAbstract:In the resin transfer molding process for advanced polymer composites manufacturing, the Fiber Preform is placed in the mold cavity and a thermoset resin is injected into the mold to impregnate the stationary Preform. The resin displaces the air in the mold through openings called vents. Once the resin emerges out of the vents, the injection is discontinued. The near net-shaped composite part can be demolded after the resin cures. Ideally, the vents should be placed at the locations where the resin arrives last to ensure the complete saturation of the Preform. However, the racetracking phenomenon, in which the resin flows faster along the minuscule channels induced by imperfect fits between the Preform edges and the mold walls, can dramatically change the resin infiltration process. The ramifications of racetracking are that the resin may arrive at the vents before completely impregnating the Preform and create undesired dry spots, which are Fiber regions devoid of resin. The racetracking strength is not repeatable and may vary from one injection trial to next. Hence, the online strategic flow control can be useful in improving the processing reliability and the parts quality by re-directing the flow to arrive last at the vents. In this article, an online strategic flow control system consisting of a flow sensing network and a flow actuation network is proposed. A flow pattern recognition technique, which is based on the dimensionless time vector collected by the flow-sensing network, is developed in order to perform the online flow characterization effectively. Flow simulations are utilized to off-line design the flow control system. An evaluation function is formulated to optimize the flow sensing network design. A multi-tier genetic algorithm is implemented to optimize the locations of vents and gates along with the necessary control actions. A numerical case study for testing the computer-generated flow control solutions is presented. It was found that there was significant improvement in the success rate (fewer dry spot regions) due to the use of the strategic flow control and the automated design approach.
C A Back - One of the best experts on this subject based on the ideXlab platform.
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fabrication of sic sic composites for fuel cladding in advanced reactor designs
Progress in Nuclear Energy, 2012Co-Authors: Christian P Deck, H E Khalifa, B Sammuli, T Hilsabeck, C A BackAbstract:Abstract Both advanced fission reactor concepts and fusion energy systems demand materials that can survive extremely harsh operating environments having persistent high temperature and high neutron flux conditions. Silicon carbide Fiber/silicon carbide matrix (SiC–SiC) composites have shown promise for these applications, which include fuel cladding and reactor structural components. However, the composite fabrication process is time consuming and the fabrication of complicated geometries can be difficult. In this work, SiC–SiC and carbon Fiber–SiC composite samples were fabricated using chemical vapor infiltration (CVI), and the mechanical and thermal properties of samples with a range of densities and total infiltration times were characterized and compared. Both sample density and the reinforcing Fiber material were found to have a very significant influence on the composite mechanical and thermal material properties. In particular, internal porosity is found to have a significant effect on the mechanical response, as can be observed in the crack propagation in low density samples. In order to better understand the densification of the composites, a computer model is being developed to simulate the diffusion of reactants through the Fiber Preform, and SiC deposition on the Fiber surfaces. Preliminary modeling has been correlated with experimental results and shows promising results.
Litong Zhang - One of the best experts on this subject based on the ideXlab platform.
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low cost preparation and frictional behaviour of a three dimensional needled carbon silicon carbide composite
Journal of The European Ceramic Society, 2009Co-Authors: Yongdong Xu, Laifei Cheng, Litong Zhang, Bin Li, Lin YuAbstract:Abstract A low-cost carbon/silicon carbide (C/SiC) composite was manufactured by phenolic resin impregnation–pyrolysis combined with liquid silicon infiltration. The carbon Fiber Preform was prepared by three-dimensional needling. A carbon/carbon composite with a density of 1.22 g/cm3 after only one impregnation–pyrolysis cycle was achieved by using hot-pressing curing. The density of the final C/SiC was 2.10 g/cm3 with a porosity of 4.50% and SiC-content of 45.73%. The C/SiC composite had a high thermal conductivity of 48.72 W/(m K) perpendicular to the friction surface and demonstrated good friction and wear properties. The static and average dynamic friction coefficients were 0.68 and 0.32 (at a braking velocity of 28 m/s). The weight wear rates of the rotating disk and stationary disk were respectively 7.71 and 5.60 mg/cycle with linear wear rates, 1.67 and 1.22 μm/cycle, at a braking velocity of 28 m/s.
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effect of sic coating and heat treatment on damping behavior of c sic composites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Qing Zhang, Laifei Cheng, W L Wang, Litong ZhangAbstract:Three groups of 2D and 3D C/SiC composites were fabricated by chemical vapor infiltration (CVI) process: the first group was as received, the second group was treated at 1500 °C in vacuum atmosphere for 2 h, and the third group was deposited with a chemical-vapor-deposited (CVD) SiC coating. Damping properties of these composites were measured by dynamical mechanical analyzer (DMA) at different frequencies from room temperature to 400 °C in air atmosphere. The results show that SiC coating and heat treatment decrease damping capacity of C/SiC composites and the damping peak disappears or decreases in the testing temperature range. The effect of CVD SiC coating on damping behavior of 2D and 3D C/SiC composites is mainly related to the change of porosity and is independent of Fiber Preform architecture. However, the effect of heat treatment on damping behavior of 2D and 3D C/SiC composites is mainly attributed to the change in the SiC matrix and interphase bonding, and it is dependent on Fiber Preform architecture. Both of CVD SiC coating and heat treatment studied in this paper have no influence on relationship between damping behavior of C/SiC composites and frequency.
Frank W. Zok - One of the best experts on this subject based on the ideXlab platform.
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in situ 3d visualization of composite microstructure during polymer to ceramic conversion
Acta Materialia, 2018Co-Authors: Natalie M. Larson, Frank W. ZokAbstract:Abstract One route for producing Fiber-reinforced ceramic-matrix composites entails repeated impregnation and pyrolysis of a preceramic polymer in a Fiber Preform. The process relies crucially on the development of networks of contiguous cracks during pyrolysis, thereby allowing further impregnation to attain nearly-full densification. The present study employs in-situ x-ray computed tomography (XCT) to reveal in three dimensions the evolution of matrix structure during pyrolysis of a SiC-based preceramic polymer to 1200 °C. Observations are used to guide the development of a taxonomy of crack geometries and crack structures and to identify the temporal sequence of their formation. A quantitative analysis is employed to characterize effects of local microstructural dimensions on the conditions required to form cracks of various types. Complementary measurements of gas evolution and mass loss of the preceramic polymer during pyrolysis as well as changes in mass density and Young's modulus provide context for the physical changes revealed by XCT. The findings provide a foundation for future development of physics-based models to guide composite fabrication processes.
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effects of Preform shear on tensile properties of a woven c sic composite
Journal of the American Ceramic Society, 2016Co-Authors: John H. Shaw, David B. Marshall, Michael N. Rossol, Frank W. ZokAbstract:This article addresses effects of weave defects in an angle-interlock C-Fiber Preform on the tensile properties of the resulting fully processed C-Fiber/SiC-matrix composite. For this purpose, a Preform was intentionally sheared in a controlled manner after weaving. The resulting distortions were quantified by analyzing high-resolution images of the Preform surface after the first step of matrix processing, while the tows were still clearly visible. Comparisons are made of tensile test results on specimens cut from this composite panel and from a pristine panel in select loading orientations. Strain maps obtained by digital image correlation are used to identify local strain variations that are attributable to weave defects. The results are discussed in terms of: (i) the shear-normal coupling that arises in loading orientations of present interest, and (ii) the geometric effects of tow misalignment on tow continuity along the specimen gauge length. The composite is found to perform in a robust manner, in the sense that the tensile properties are not sensitive to the presence of the defects.