The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Steven R. Nutt - One of the best experts on this subject based on the ideXlab platform.
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effects of resin distribution patterns on through thickness air removal in vacuum bag only Prepregs
Composites Part A-applied Science and Manufacturing, 2020Co-Authors: Sarah G.k. Schechter, Timotei Centea, Steven R. NuttAbstract:Abstract Prepregs with discontinuous resin patterns facilitate air removal and impart robustness to vacuum-bag-only processing of composites. However, optimal pattern characteristics have not yet been identified. A geometric model was developed to guide the fabrication of Prepregs with various discontinuous patterns and laminates with different orientations and ply counts. The model was used to evaluate metrics related to gas transport: projected surface area exposed, sealed interfaces, and tortuosity. Statistical analysis revealed that single layer surface area exposed and ply count had the greatest effect on projected surface area exposed; orientation had the greatest effect on sealed interfaces and tortuosity. From these insights, prototype Prepregs were fabricated to measure through-thickness permeability. Prepregs with a large percentage of sealed interfaces and high tortuosity exhibited lower permeability. The study demonstrated a methodology to differentiate/screen patterns for gas transport efficiency. The model can guide Prepreg design and support robust production of composites via out-of-autoclave manufacturing.
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2.4 Out-of-Autoclave Prepreg Processing
Comprehensive Composite Materials II, 2018Co-Authors: Pascal Hubert, James Kratz, Steven R. Nutt, Timotei Centea, Lessa Grunefelder, Arthur LevyAbstract:The objective of this chapter is to provide an overview of the processing aspects of out-of-autoclave (OOA) Prepregs. This chapter serves as a design guideline for the definition of tooling, bagging configuration, and processing conditions for making parts with OOA Prepregs. Section 1 presents an overview of the OOA materials, including their application, resins, and fibers. OOA Prepreg impregnation techniques are then discussed and typical properties of OOA composites are summarized. Section 2 covers OOA Prepreg characterization methods, techniques to measure resin impregnation, thermochemistry, out-time, permeability, and bulk factor are presented. Section 3 describes the infrastructure used to cure OOA Prepregs, such as ovens, heating systems, tooling, and process diagnostic tools. Section 4 provides basic processing guidelines, covering bagging configuration, debulking methods, and cure cycles to make simple monolithic OOA laminates, while Sections 5 and 6 provide processing guidelines for sandwich panels and complex shape laminates. The cost analysis of the manufacturing process with OOA Prepregs is reviewed in section seven. Finally, section eight discusses future developments for OOA Prepreg materials and processes.
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Effect of Prepreg format on defect control in out-of-autoclave processing
Composites Part A: Applied Science and Manufacturing, 2017Co-Authors: Lessa Kay Grunenfelder, A. Dills, Timotei Centea, Steven R. NuttAbstract:Prepreg format plays a key role in part quality for composites produced using vacuum bag only (VBO) techniques. To date, however, VBO Prepregs have been produced by modifying existing autoclave formats. In this work, we introduce USCpreg, a Prepreg format designed specifically for out-of-autoclave cure, featuring through-thickness permeability. We describe the fabrication and analysis of laminates processed with USCpreg, as well as laminates fabricated from traditional VBO Prepreg formats. The through-thickness pathways for air transport in USCpreg result in near-zero internal porosity and defect-free surfaces in parts cured under VBO conditions, even under challenging processing conditions. Results highlight the fact that surface and internal porosity depend on Prepreg format, and that through-thickness permeability is critical to achieving high quality parts in non-ideal manufacturing scenarios.
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A review of out-of-autoclave Prepregs - Material properties, process phenomena, and manufacturing considerations
Composites Part A: Applied Science and Manufacturing, 2015Co-Authors: Timotei Centea, Lessa Kay Grunenfelder, Steven R. NuttAbstract:Out-of-autoclave (OoA) Prepreg materials and methods have gained acceptance over the past decade because of the ability to produce autoclave-quality components under vacuum-bag-only (VBO) cure. To achieve low porosity and tight dimensional tolerances, VBO Prepregs rely on specific microstructural features and processing techniques. Furthermore, successful cure is contingent upon appropriate material property and process parameter selection. In this article, we review the existing literature on VBO Prepreg processing to summarize and synthesize knowledge on these issues. First, the context, development, and defining properties of VBO Prepregs are presented. The key processing phenomena and the influence on quality are subsequently described. Finally, cost and environmental performance are considered. Throughout, we highlight key considerations for VBO Prepreg processing and identify areas where further study is required.
Timotei Centea - One of the best experts on this subject based on the ideXlab platform.
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effects of resin distribution patterns on through thickness air removal in vacuum bag only Prepregs
Composites Part A-applied Science and Manufacturing, 2020Co-Authors: Sarah G.k. Schechter, Timotei Centea, Steven R. NuttAbstract:Abstract Prepregs with discontinuous resin patterns facilitate air removal and impart robustness to vacuum-bag-only processing of composites. However, optimal pattern characteristics have not yet been identified. A geometric model was developed to guide the fabrication of Prepregs with various discontinuous patterns and laminates with different orientations and ply counts. The model was used to evaluate metrics related to gas transport: projected surface area exposed, sealed interfaces, and tortuosity. Statistical analysis revealed that single layer surface area exposed and ply count had the greatest effect on projected surface area exposed; orientation had the greatest effect on sealed interfaces and tortuosity. From these insights, prototype Prepregs were fabricated to measure through-thickness permeability. Prepregs with a large percentage of sealed interfaces and high tortuosity exhibited lower permeability. The study demonstrated a methodology to differentiate/screen patterns for gas transport efficiency. The model can guide Prepreg design and support robust production of composites via out-of-autoclave manufacturing.
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2.4 Out-of-Autoclave Prepreg Processing
Comprehensive Composite Materials II, 2018Co-Authors: Pascal Hubert, James Kratz, Steven R. Nutt, Timotei Centea, Lessa Grunefelder, Arthur LevyAbstract:The objective of this chapter is to provide an overview of the processing aspects of out-of-autoclave (OOA) Prepregs. This chapter serves as a design guideline for the definition of tooling, bagging configuration, and processing conditions for making parts with OOA Prepregs. Section 1 presents an overview of the OOA materials, including their application, resins, and fibers. OOA Prepreg impregnation techniques are then discussed and typical properties of OOA composites are summarized. Section 2 covers OOA Prepreg characterization methods, techniques to measure resin impregnation, thermochemistry, out-time, permeability, and bulk factor are presented. Section 3 describes the infrastructure used to cure OOA Prepregs, such as ovens, heating systems, tooling, and process diagnostic tools. Section 4 provides basic processing guidelines, covering bagging configuration, debulking methods, and cure cycles to make simple monolithic OOA laminates, while Sections 5 and 6 provide processing guidelines for sandwich panels and complex shape laminates. The cost analysis of the manufacturing process with OOA Prepregs is reviewed in section seven. Finally, section eight discusses future developments for OOA Prepreg materials and processes.
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Effect of Prepreg format on defect control in out-of-autoclave processing
Composites Part A: Applied Science and Manufacturing, 2017Co-Authors: Lessa Kay Grunenfelder, A. Dills, Timotei Centea, Steven R. NuttAbstract:Prepreg format plays a key role in part quality for composites produced using vacuum bag only (VBO) techniques. To date, however, VBO Prepregs have been produced by modifying existing autoclave formats. In this work, we introduce USCpreg, a Prepreg format designed specifically for out-of-autoclave cure, featuring through-thickness permeability. We describe the fabrication and analysis of laminates processed with USCpreg, as well as laminates fabricated from traditional VBO Prepreg formats. The through-thickness pathways for air transport in USCpreg result in near-zero internal porosity and defect-free surfaces in parts cured under VBO conditions, even under challenging processing conditions. Results highlight the fact that surface and internal porosity depend on Prepreg format, and that through-thickness permeability is critical to achieving high quality parts in non-ideal manufacturing scenarios.
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A review of out-of-autoclave Prepregs - Material properties, process phenomena, and manufacturing considerations
Composites Part A: Applied Science and Manufacturing, 2015Co-Authors: Timotei Centea, Lessa Kay Grunenfelder, Steven R. NuttAbstract:Out-of-autoclave (OoA) Prepreg materials and methods have gained acceptance over the past decade because of the ability to produce autoclave-quality components under vacuum-bag-only (VBO) cure. To achieve low porosity and tight dimensional tolerances, VBO Prepregs rely on specific microstructural features and processing techniques. Furthermore, successful cure is contingent upon appropriate material property and process parameter selection. In this article, we review the existing literature on VBO Prepreg processing to summarize and synthesize knowledge on these issues. First, the context, development, and defining properties of VBO Prepregs are presented. The key processing phenomena and the influence on quality are subsequently described. Finally, cost and environmental performance are considered. Throughout, we highlight key considerations for VBO Prepreg processing and identify areas where further study is required.
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measuring the impregnation of an out of autoclave Prepreg by micro ct
Composites Science and Technology, 2011Co-Authors: Timotei Centea, Pascal HubertAbstract:Resin flow into dry reinforcement regions is the main microstructural change during the processing of out-of-autoclave Prepregs and influences air evacuation and void suppression. Such impregnation flow was investigated experimentally during the processing of a second-generation out-of-autoclave Prepreg. First, laminates were partially processed to different stages of a simple cure cycle. Then, samples from each laminate were scanned using X-ray microtomography (micro-CT) to obtain 3D microstructural data. This data was used to investigate the initial microstructure of the material and measure the extent of impregnation at each processing stage, the rate of impregnation, and the evolution of macro-porosity within the material.
Suresh G. Advani - One of the best experts on this subject based on the ideXlab platform.
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Prediction of process-induced void formation in anisotropic Fiber-reinforced autoclave composite parts
International Journal of Material Forming, 2020Co-Authors: Bamdad Barari, Shridhar Yarlagadda, Roger M Crane, Pavel Simacek, Suresh G. AdvaniAbstract:A numerical methodology is proposed to predict void content and evolution during autoclave processing of thermoset Prepregs. Starting with the initial Prepreg void content, the void evolution model implements mechanisms for void compaction under the effect of the applied pressure, including Ideal Gas law compaction, and squeeze flow for single curvature geometries. Pressure variability in the Prepreg stack due to interactions between applied autoclave pressure and anisotropic material response are considered and implemented. A parametric study is conducted to investigate the role of material anisotropy, initial void content, and applied autoclave pressure on void evolution during consolidation of Prepregs on a tool with single curvatures. The ability of the model to predict pressure gradient through the thickness of the laminate and its impact on void evolution is discussed.
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multi scale modelling of non uniform consolidation of uncured toughened unidirectional Prepregs
21st International ESAFORM Conference on Material Forming ESAFORM 2018, 2018Co-Authors: Giovanni Sorba, Elena Syerko, Adrien Leygue, Jonathan P Belnoue, Oliver J Nixonpearson, Sebastien Comascardona, Dmitry Ivanov, Christophe Binetruy, Stephen R. Hallett, Suresh G. AdvaniAbstract:Consolidation is a crucial step in manufacturing of composite parts with Prepregs because its role is to eliminate inter- and intra-ply gaps and porosity. Some thermoset Prepreg systems are toughened with thermoplastic particles. Depending on their size, thermoplastic particles can be either located in between plies or distributed within the inter-fibre regions. When subjected to transverse compaction, resin will bleed out of low-viscosity unidirectional Prepregs along the fibre direction, whereas one would expect transverse squeeze flow to dominate for higher viscosity Prepregs. Recent experimental work showed that the consolidation of uncured toughened Prepregs involves complex flow and deformation mechanisms where both bleeding and squeeze flow patterns are observed [1]. Micrographs of compacted and cured samples confirm these features as shown in Fig.1. A phenomenological model was proposed [2] where bleeding flow and squeeze flow are combined. A criterion for the transition from shear flow to resin bleeding was also proposed. However, the micrographs also reveal a resin rich layer between plies which may be contributing to the complex flow mechanisms during the consolidation process. In an effort to provide additional insight into these complex mechanisms, this work focuses on the 3D numerical modelling of the compaction of uncured toughened Prepregs in the cross-ply configuration described in [1]. A transversely isotropic fluid model is used to describe the flow behaviour of the plies coupled with interplay resin flow of an isotropic fluid. The multi-scale flow model used is based on [3, 4]. A numerical parametric study is carried out where the resin viscosity, permeability and inter-ply thickness are varied to identify the role of important variables. The squeezing flow and the bleeding flow are compared for a range of process parameters to investigate the coupling and competition between the two flow mechanisms. Figure 4 shows the predicted displacement of the sample edge with the multi-scale compaction model after one time step [3]. The ply distortion and resin flow observed in Fig.1 is qualitatively retrieved by the computational model.Consolidation is a crucial step in manufacturing of composite parts with Prepregs because its role is to eliminate inter- and intra-ply gaps and porosity. Some thermoset Prepreg systems are toughened with thermoplastic particles. Depending on their size, thermoplastic particles can be either located in between plies or distributed within the inter-fibre regions. When subjected to transverse compaction, resin will bleed out of low-viscosity unidirectional Prepregs along the fibre direction, whereas one would expect transverse squeeze flow to dominate for higher viscosity Prepregs. Recent experimental work showed that the consolidation of uncured toughened Prepregs involves complex flow and deformation mechanisms where both bleeding and squeeze flow patterns are observed [1]. Micrographs of compacted and cured samples confirm these features as shown in Fig.1. A phenomenological model was proposed [2] where bleeding flow and squeeze flow are combined. A criterion for the transition from shear flow to resin b...
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resin film impregnation in fabric Prepregs with dual length scale permeability
Composites Part A-applied Science and Manufacturing, 2013Co-Authors: Thomas A. Cender, Pavel Simacek, Suresh G. AdvaniAbstract:Abstract Prepregs are precursor materials for composites processing. Most Prepregs are fully impregnated however some Prepregs are only partially impregnated with resin. This study characterizes the resin impregnation process in a Prepreg consisting of a resin film laminated to one side of a woven fabric. Layers of such Prepregs are stacked on a tool surface to build thickness with low positive pressure. This assembly is then bagged and placed under vacuum pressure to remove the air and volatiles under vacuum before the resin impregnates these empty spaces. The assembly is then allowed to cure in an oven under vacuum pressure to form the composite. There is a need to understand resin flow in such fabrics with dual length scale permeability under the initial positive pressure and also the vacuum pressure. This paper focuses on understanding the under pinning flow mechanisms and presents an in situ method for characterizing fabric Prepregs under low positive pressures before vacuum bag processing. The proposed in situ method monitors the pattern of resin saturating the empty spaces between the fibers and the tows within the fabric over time, which allows for characterization of dual length scale permeability of such Prepregs. The experimental technique compresses a resin film into the fabric at a known temperature and pressure, during which the flow pattern is recorded from the opposite side through a transparent table with a CCD camera. The flow is modeled analytically to match the observed two stages: inter-fiber tow flow and intra-tow flow to characterize the dual length scale Prepreg permeability.
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Modeling of Resin Flow in Reinforced Dielectric Prepregs
Journal of Electronic Packaging, 2008Co-Authors: Pavel Simacek, Kossi Zonvide, Suresh G. Advani, Leonard W. BarrettAbstract:Manufacturing of printed circuit boards or chip-packaging substrates involves the use of resin-filled reinforcement materials, known as Prepregs, to bond together laminates with patterned copper layers and serve as dielectric material. In the circuit board or substrate lamination process, the Prepreg sheet is placed on top of the conductive copper patterns and pressure is applied to squeeze the resin out of the Prepreg to flow and fill the gaps between the baseboard and the copper as well as drilled holes and vias. The primary processing requirement is for resin to fill all the gaps within reasonable time and pressure limits before the resin cures to a hardened thermoset material. As the resin flow path may be nontrivial, it is desirable to model resin flow and filling of the gap as a function of applied pressure and lamination press closing rate so that one can successfully manufacture a variety of circuit board designs with different material systems. In this work, we model the flow during the filling of the gaps and justify noteworthy simplifications to provide a solution in closed form. This allows us to relate the material and process parameters such as Prepreg thickness and applied pressure to the circuit board design. It also permits prediction of the transient development of gap filling. We illustrate the factors that influence the flow and fill process and discuss their importance. Finally, we analyse the process with typical material and processing parameters and compare it with laboratory scale and industrial experiments.
Pascal Hubert - One of the best experts on this subject based on the ideXlab platform.
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2.4 Out-of-Autoclave Prepreg Processing
Comprehensive Composite Materials II, 2018Co-Authors: Pascal Hubert, James Kratz, Steven R. Nutt, Timotei Centea, Lessa Grunefelder, Arthur LevyAbstract:The objective of this chapter is to provide an overview of the processing aspects of out-of-autoclave (OOA) Prepregs. This chapter serves as a design guideline for the definition of tooling, bagging configuration, and processing conditions for making parts with OOA Prepregs. Section 1 presents an overview of the OOA materials, including their application, resins, and fibers. OOA Prepreg impregnation techniques are then discussed and typical properties of OOA composites are summarized. Section 2 covers OOA Prepreg characterization methods, techniques to measure resin impregnation, thermochemistry, out-time, permeability, and bulk factor are presented. Section 3 describes the infrastructure used to cure OOA Prepregs, such as ovens, heating systems, tooling, and process diagnostic tools. Section 4 provides basic processing guidelines, covering bagging configuration, debulking methods, and cure cycles to make simple monolithic OOA laminates, while Sections 5 and 6 provide processing guidelines for sandwich panels and complex shape laminates. The cost analysis of the manufacturing process with OOA Prepregs is reviewed in section seven. Finally, section eight discusses future developments for OOA Prepreg materials and processes.
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anisotropic air permeability in out of autoclave Prepregs effect on honeycomb panel evacuation prior to cure
Composites Part A-applied Science and Manufacturing, 2013Co-Authors: James Kratz, Pascal HubertAbstract:Abstract Air evacuation is crucial to achieve low porosity for vacuum-bag-only manufacturing of out-of-autoclave Prepregs. In this paper, the air permeability of composite skins was evaluated for in-plane and transverse air evacuation. The air permeability and microstructure were evaluated for three common Prepreg fabric architectures: unidirectional, plain weave, and 5 harness satin. Since Prepreg permeability is anisotropic, a 3-D pressure gradient can arise in honeycomb skins. In-order to calculate the effective air permeability coefficients of honeycomb skins, the computational fluid dynamics software FLUENT was used to determine the 1-D pressure gradient and corresponding area normal to flow. The air permeability coefficients were correlated to the Prepreg microstructure using micro-CT imaging. The results showed that the in-plane air permeability was higher for fabrics with larger visible dry tow areas. The transverse air permeability was higher for Prepregs that formed connected macro-porosity networks after lay-up, compared to Prepregs with isolated macro-pores.
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measuring the impregnation of an out of autoclave Prepreg by micro ct
Composites Science and Technology, 2011Co-Authors: Timotei Centea, Pascal HubertAbstract:Resin flow into dry reinforcement regions is the main microstructural change during the processing of out-of-autoclave Prepregs and influences air evacuation and void suppression. Such impregnation flow was investigated experimentally during the processing of a second-generation out-of-autoclave Prepreg. First, laminates were partially processed to different stages of a simple cure cycle. Then, samples from each laminate were scanned using X-ray microtomography (micro-CT) to obtain 3D microstructural data. This data was used to investigate the initial microstructure of the material and measure the extent of impregnation at each processing stage, the rate of impregnation, and the evolution of macro-porosity within the material.
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a method for the direct measurement of the fibre bed compaction curve of composite Prepregs
Composites Part A-applied Science and Manufacturing, 2001Co-Authors: Pascal Hubert, Anoush PoursartipAbstract:Abstract A method to measure the fibre bed compaction curve directly from composite Prepreg is presented. The method was used to measure the compaction curve of unidirectional and quasi-isotropic AS4/3501-6 carbon–epoxy Prepregs. Similar compaction curves were obtained in all cases. The compaction curve obtained was used by a finite element process model, COMPRO, to simulate the uniaxial compaction of 8 and 16 ply laminates at different temperatures. The force–displacement response predicted by the model closely matched the experimental results. The method which can be used on both tape and fabric Prepregs, has the major advantages of being a direct measure of the Prepreg behaviour, and requires no special preparation of the sample.
James C Seferis - One of the best experts on this subject based on the ideXlab platform.
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Prepreg manufacturing under constant pressure of deformation
Journal of Advanced Materials, 1998Co-Authors: Frédéric U. Buehler, James C SeferisAbstract:A model epoxy resin was used to impregnate unidirectional carbon fibers with a hot-melt process under different processing conditions. The impregnation step ofthe process was the main focus ofthe study. In this step, resin and fibers are combined together on an impregnation plate under an impregnation roll. The impregnation roll can be controlled by either constant pressure, or by setting a constant gap between the roll and the impregnation plate. Ten different Prepregs were manufactured by varying either gap or pressure, keeping all other processing parameters constant. Prepregs were characterized in terms of resin content, grade, thickness, tack, permeability, and impregnation quality. Differences in Prepreg characteristics between gap and pressure control were assessed. Both gap and pressure were found to have an influence on resin content and grade. Under pressure control, it was observed that variations in thickness were severe. Tack was also affected by impregnation gap and impregnation pressure. The specific compressive power correlated well with the power input necessary for impregnation. This correlation could allow an on-line measurement of the specific compressive power, which could by very useful in Prepreg manufacturing for quality control.
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Variable temperature cure polyetherimide epoxy-based Prepreg systems
Polymer Engineering and Science, 1998Co-Authors: Brian S. Hayes, James C SeferisAbstract:This work identifies the necessary attributes of variable temperature cure epoxy-based Prepreg systems as they relate to high performance Prepreg systems capable for composite repair. Model polyetherimide epoxy blend resins were developed and hot-melt impregnated into woven carbon fabric and compared with a commercial Prepreg system. It was found that when the PEI content was increased from 0 to 14 wt% in the base resin of the Prepregs, the G IC and G IIC fracture toughness increased by over 70%. The fracture toughness was found to be similar when the model Prepreg was cured at either 121°C or 177°C, a result of only a 9% difference in conversion and complete phase separation of the PEI at both cure temperatures. Void content in vacuum cured laminates were found to decrease as the PEI content was increased because of a large quantity of resin in the interstitial areas between the longitudinal and transverse tows. A comparison of the model and commercial Prepreg system demonstrated many similarities and some significant differences. For example, the commercial Prepreg had a 15% difference in conversion when cured at 121°C versus 177°C and very little PEI phase separation after both cure cycles. As a result, a significant difference in G IIC for the commercial Prepreg was observed for the two cure temperatures.
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thermal characterization and comparison of structural Prepregs with different cure temperatures
Thermochimica Acta, 1997Co-Authors: Sangbeom Shim, James C Seferis, Yi Taek ShimAbstract:Abstract Two different epoxy based Prepreg systems were characterized and compared using thermal analysis. A Prepreg system presently used in the commercial airplane industry was compared with a Prepreg system that is a prospective candidate for the same applications. The commercial system in use is a controlled flow resin Prepreg system which is a 177°C cure system, while the prospective Prepreg system is marketed as a dual Prepreg system that can be cured at either 121°C or 177°C. Thermal characterization techniques including differential scanning calorimetry (DSC), dielectric analysis (DEA), and dynamic mechanical analysis (DMA) were used to investigate these systems. The difference in the curing mechanisms of both Prepreg systems were identified through these thermal analysis techniques. Although, the kinetics of these systems were found to be vastly different their heats of reactions were very similar. The activation energies for the Prepreg systems were determined by DSC using Kissinger's method and were found to be quite different. DMA measurements on autoclave cured composites demonstrated that the Prepregs obtained a different degree of cure as well as different glass transition temperatures ( T g ). Furthermore, the use of DEA and DMA demonstrated a difference in gelation of the two Prepreg systems examined.
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Effect of impregnation conditions on Prepreg properties and honeycomb core crush
Polymer Composites, 1997Co-Authors: C. J. Martin, J. W. Putnam, M J Turner, Brian S. Hayes, James C Seferis, G. E. GreenAbstract:The effects of fiber tension, line speed, and impregnation temperature and pressure in the Prepregging process used to manufacture a commercial high temperature toughened epoxy Prepreg were investigated in a Design of Experiments (DOE) to understand core crush in honeycomb composite structures. The Prepregs developed in this DOE were characterized by tack, permeation, optical microscopy, and frictional resistance. Of these methods, frictional resistance was found to correlate with core crush. Tack, permeation, and optical microscopy provided a basis for understanding this relationship through impregnation and morphology. Prepregs manufactured with high fiber tension showed greater crush and less frictional resistance than Prepregs with manufactured low fiber tension. These low tension Prepregs were found to have more fibers at the Prepreg surface, allowing them to grip the adjacent surface and resist slippage. By identifying the key factors influencing honeycomb core crush, the Prepregging process was modified, producing a crush-resistant Prepreg for end use manufacture.
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frictional resistance of thermoset Prepregs and its influence on honeycomb composite processing
Composites Part A-applied Science and Manufacturing, 1996Co-Authors: C. J. Martin, James C Seferis, M A WilhelmAbstract:Abstract A testing device was developed to measure the frictional resistance of woven Prepregs at temperatures and consolidation pressures typical of those used in honeycomb sandwich processing. To demonstrate the use of this new device, the frictional resistance of three woven carbon fibre/epoxy Prepreg systems were measured. It was found that frictional characteristics vary between Prepregs and that these differences do not exhibit a one-to-one correlation with the viscosity of the matrix resin or Prepreg. Further, Prepreg exhibiting lesser frictional resistance showed greater degrees of core crush. These observed differences were shown to be dependent on both resin viscosity and distribution of the resin on the Prepreg surface. Finally, integration of these results into the manufacture of test panels suggests that core crush observed in honeycomb production may be strongly influenced by frictional resistance changes during cure.
