The Experts below are selected from a list of 2745 Experts worldwide ranked by ideXlab platform
H.t. Hahn - One of the best experts on this subject based on the ideXlab platform.
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analysis of Vacuum Bag resin transfer molding process
Composites Part A-applied Science and Manufacturing, 2001Co-Authors: M. K. Kang, H.t. HahnAbstract:An analytical model is developed to analyze the resin flow through a deformable fiber preform during Vacuum Bag resin transfer molding (VBRTM) process. The force balance between the resin and the fiber preform is used to account for the swelling of fiber preform inside a flexible Vacuum Bag. Mold filling through multiple resin inlets is analyzed under different Vacuum conditions. The formation of dry spots is demonstrated in the presence of residual air. Molding of a three-dimensional ship hull with lateral and longitudinal stiffeners is simulated to demonstrate the applicability of the model.
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Analysis of Vacuum Bag resin transfer molding process
Composites - Part A: Applied Science and Manufacturing, 2001Co-Authors: M. K. Kang, W. I. Lee, H.t. HahnAbstract:An analytical model is developed to analyze the resin flow through a deformable fiber preform during Vacuum Bag resin transfer molding (VBRTM) process. The force balance between the resin and the fiber preform is used to account for the swelling of fiber preform inside a flexible Vacuum Bag. Mold filling through multiple resin inlets is analyzed under different Vacuum conditions. The formation of dry spots is demonstrated in the presence of residual air. Molding of a three-dimensional ship hull with lateral and longitudinal stiffeners is simulated to demonstrate the applicability of the model. © 2001 Elsevier Science Ltd. All rights reserved.
M. K. Kang - One of the best experts on this subject based on the ideXlab platform.
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analysis of Vacuum Bag resin transfer molding process
Composites Part A-applied Science and Manufacturing, 2001Co-Authors: M. K. Kang, H.t. HahnAbstract:An analytical model is developed to analyze the resin flow through a deformable fiber preform during Vacuum Bag resin transfer molding (VBRTM) process. The force balance between the resin and the fiber preform is used to account for the swelling of fiber preform inside a flexible Vacuum Bag. Mold filling through multiple resin inlets is analyzed under different Vacuum conditions. The formation of dry spots is demonstrated in the presence of residual air. Molding of a three-dimensional ship hull with lateral and longitudinal stiffeners is simulated to demonstrate the applicability of the model.
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Analysis of Vacuum Bag resin transfer molding process
Composites - Part A: Applied Science and Manufacturing, 2001Co-Authors: M. K. Kang, W. I. Lee, H.t. HahnAbstract:An analytical model is developed to analyze the resin flow through a deformable fiber preform during Vacuum Bag resin transfer molding (VBRTM) process. The force balance between the resin and the fiber preform is used to account for the swelling of fiber preform inside a flexible Vacuum Bag. Mold filling through multiple resin inlets is analyzed under different Vacuum conditions. The formation of dry spots is demonstrated in the presence of residual air. Molding of a three-dimensional ship hull with lateral and longitudinal stiffeners is simulated to demonstrate the applicability of the model. © 2001 Elsevier Science Ltd. All rights reserved.
Yoshihiro Mizutani - One of the best experts on this subject based on the ideXlab platform.
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Flow control by progressive forecasting using numerical simulation during Vacuum-assisted resin transfer molding
Composites Part A: Applied Science and Manufacturing, 2013Co-Authors: Ryosuke Matsuzaki, Seiji Kobayashi, Akira Todoroki, Yoshihiro MizutaniAbstract:Because slight differences in the wrinkle of a Vacuum Bag and other inherent variations in the preforms may cause unexpected resin flow in Vacuum-assisted resin transfer molding (VaRTM), flow control is strongly required to prevent dry spots. We propose an active flow control scheme by forecasting resin flow from the monitored time to the filling ends using numerical flow simulation and taking corrective action using dielectric heating at a specific targeted location to decrease the viscosity of the resin. Because dry-spot configuration can be forecasted early, the flow can be actively controlled before the occurrence of an adverse flow front. This method can be extended to forecasting load-bearing performance as the critical dry spot can be selectively prevented based on applied stress distribution information. We demonstrate the validity of the proposed method to improve uniaxial compressive buckling of plate structures by conducting virtual experiments based on a multifunctional interdigital electrode array film.
Pascal Hubert - One of the best experts on this subject based on the ideXlab platform.
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Vacuum-Bagged composite laminate forming processes: Predicting thickness deviation in complex shapes
Composites Part A-applied Science and Manufacturing, 2019Co-Authors: Arthur Levy, Pascal HubertAbstract:Abstract This paper focuses on the manufacturing of composite laminates using Vacuum-Bag processes. When forming complex shapes, such as corners, the laminate thickness may deviate from the nominal thickness obtained for flat plates. This is due to two phenomena that occur in corners: (i) because of the geometry, the available consolidation pressure differs from the expected pressure; and (ii) friction may prevent adequate conformation of the laminate to the mould. The thickness deviation is associated with defects (porosity, dry or resin-rich areas or fibre wrinkling). We propose an analytical model to describe these two phenomena, which relies only on two geometric ratio: radius to flange length and thickness to radius, and two material properties: bulk factor and inter ply friction coefficient. The model estimation was compared to an extensive experimental database including a variety of configurations: male or female tools and various flange lengths, weavings and corner radii.
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Vacuum-Bag-only co-bonding prepreg skins to aramid honeycomb core. Part II. In-situ core pressure response using embedded sensors
Composites Part A: Applied Science and Manufacturing, 2015Co-Authors: James Kratz, Pascal HubertAbstract:Miniature pressure sensors were embedded into the honeycomb core of sandwich panels featuring both tool-side and Bag-side skins. The pressure response was measured throughout the Vacuum hold and elevated temperature processing stages of both oven and autoclave manufacturing. The elevated temperature processing measurements validated the honeycomb core pressure model presented in Part I, confirming that gas flow primarily occurs through the Bag-side skin in semi-infinite panels. Aramid core panels showed much higher honeycomb core pressures than aluminum cores during elevated temperature processing. Higher core pressures during processing led to more gas flow and as a result, cured skins with interconnected porosity. The best sealed aramid core honeycomb skins were processed under one atmosphere of positive pressure with a vented Vacuum Bag, avoiding the continuous extraction of gas through the skins by the Vacuum pump while the resin was highly mobile.
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Corner consolidation in Vacuum Bag only processing of out-of-autoclave composite prepregs laminates
SAMPE, 2014Co-Authors: Arthur Levy, Jacques Stadlin, Pascal HubertAbstract:Out-of-autoclave (OOA) prepreg systems are of great interest for the aerospace industry, with mechanical properties similar to that of autoclave-processed prepregs. The processing of flat or low curvature parts is generally not problematic with Vacuum Bag only OOA prepregs. On the other hand, the moulding of parts with sharp corners often leads to significant thickness variations and voids concentrated at the corners. In this paper, the mechanisms that govern the compaction of complex shape composite laminates using OOA prepregs are investigated. The goal of this research is to develop guidelines and tools for the adequate design and manufacturing of parts with sharp corners, using Vacuum Bag only processing methods. Thickness variation at the corner of L-shape laminates with various radii and flange thicknesses were characterized. The quality of the manufactured parts was analyzed in terms of thickness deviation in the corner region, and the results compared with previous work done on L-shape laminates. Laminate thickening was observed at the corner. Results show that thickness variation of OOA L-shape laminates depends on tool radius, laminate thickness and flange length. A modelling of the corner thickness deviation was proposed. It accounts for the main deformation mechanisms: local compaction pressure differential and interply friction. To quantify these effects, the bulk factor was characterized and the interply slip behaviour was measured using a specifically designed testing fixture. A general analytical corner compaction model was obtained, and results were compared with the above experimental data. Copyright 2014. Used by the Society of the Advancement of Material and Process Engineering with permission.
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Processing out-of-autoclave honeycomb structures: Internal core pressure measurements
Composites Part A: Applied Science and Manufacturing, 2011Co-Authors: James Kratz, Pascal HubertAbstract:A strong desire to reduce manufacturing costs in the aerospace industry, coupled with recent advancements in out-of-autoclave prepreg materials, has created the potential to manufacture composites with only Vacuum pressure. As a step towards better manufacturing of sandwich structures, we focus on the behaviour of air inside a honeycomb core during Vacuum Bag processing. The pressure of the air inside the core was measured in a lab-scale test fixture to simulate full-scale manufacturing. The lab-scale tests revealed pressure fluctuations if the internal core pressure equalled atmospheric pressure during processing. Furthermore, an increasing number of pressure fluctuations were observed for increasing cure temperatures. Sandwich panels cured at higher temperatures had a higher void content and a worse bond between the skin and core. © 2011 Elsevier Ltd. All rights reserved.
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Air permeability of out-of-autoclave honeycomb structures during processing
26th Annual Technical Conference of the American Society for Composites 2011 and the 2nd Joint US-Canada Conference on Composites, 2011Co-Authors: James Kratz, Timotei Centea, Pascal HubertAbstract:Composite sandwich structures are desirable for aircraft applications because of their high stiffness-to-weight ratio. Manufacturing low-porosity honeycomb structures using out-of-autoclave prepreg and Vacuum Bag only curing requires a detailed understanding of the material and processing phenomena. In this study, the transverse air permeability of a honeycomb skin was measured at room temperature and at processing temperatures up to 100 °C. The air permeability was correlated to skin microstructure, visualized using micro-CT analysis. The micro-CT revealed that the fibre tows were infiltrated with resin as the honeycomb skin was compressed by the Vacuum Bag pressure at room temperature. Accordingly, the air permeability decreased. However, as temperature increased, the air permeability increased when the resin viscosity was sufficiently low to allow gas flow through the honeycomb skin, even though the fibre tows became progressively infiltrated with resin.
Chris Key - One of the best experts on this subject based on the ideXlab platform.
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Assessment of embedded fiber Bragg gratings for structural health monitoring of composites
Structural Health Monitoring, 2017Co-Authors: Mike Yeager, William Gregory, Michael Todd, Chris KeyAbstract:This work provides a system-level investigation into the use of embedded fiber Bragg grating optical sensors as a viable sensing architecture for the structural health monitoring of composite structures. The practical aspects of the embedding process are documented for both carbon fiber–reinforced polymer and glass fiber–reinforced polymer structures manufactured by both oven Vacuum Bag and Vacuum-assisted resin transfer method processes. Initially, embedded specimens were subject to long-term water submersion to verify performance in an underwater environment. A larger, more complex jointed specimen was also fabricated with a fully embedded sensor network of fiber Bragg gratings and subjected to incrementally induced bearing damage. Using commercially available interrogation hardware, a damage detection structural health monitoring algorithm was developed and deployed. The results permit statistically precise detection of low levels of connection damage in the composite specimen.
