Pub Date : 2016-07-01DOI: 10.3929/ETHZ-A-010691526
Daniel-Alexander Türk, R. Kussmaul, M. Zogg, C. Klahn, A. Spierings, H. Könen, P. Ermanni, M. Meboldt
The combination of additive manufacturing (AM) with advanced composites unlocks potentials in the design and development of highly integrated lightweight structures. This paper investigates two design potentials where the combination of AM and carbon fiber prepreg technology is applied to honeycomb sandwich structures: (i) Reduction of number of parts: The use of selective laser sintered cores allows the integration of various functions into one single part. These include structural as well as tooling, positioning and assembly functions. (ii) Tailored mechanical performance: With AM it is possible to adapt the mechanical properties of the core according to local load requirements. These potentials are demonstrated using the example of the development of an aircraft instrument panel. The approach of combining AM with advanced composites is evaluated by assessing the weight and the number of parts for the demonstrator panel compared to a state-of-the-art aluminum machined instrument panel. Weight savings of 40 % and parts reduction by 50 % indicate that the technology is competitive for complex low volume parts.
{"title":"Additive Manufacturing with Composites for Integrated Aircraft Structures","authors":"Daniel-Alexander Türk, R. Kussmaul, M. Zogg, C. Klahn, A. Spierings, H. Könen, P. Ermanni, M. Meboldt","doi":"10.3929/ETHZ-A-010691526","DOIUrl":"https://doi.org/10.3929/ETHZ-A-010691526","url":null,"abstract":"The combination of additive manufacturing (AM) with advanced composites unlocks potentials in the design and development of highly integrated lightweight structures. This paper investigates two design potentials where the combination of AM and carbon fiber prepreg technology is applied to honeycomb sandwich structures: (i) Reduction of number of parts: The use of selective laser sintered cores allows the integration of various functions into one single part. These include structural as well as tooling, positioning and assembly functions. (ii) Tailored mechanical performance: With AM it is possible to adapt the mechanical properties of the core according to local load requirements. These potentials are demonstrated using the example of the development of an aircraft instrument panel. The approach of combining AM with advanced composites is evaluated by assessing the weight and the number of parts for the demonstrator panel compared to a state-of-the-art aluminum machined instrument panel. Weight savings of 40 % and parts reduction by 50 % indicate that the technology is competitive for complex low volume parts.","PeriodicalId":14908,"journal":{"name":"Journal of Advanced Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76343786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-03-28DOI: 10.1002/9780470314500.CH64
U. Vaidya, H. Mahfuz, S. Jeelani
In the processing cycle of carbon-carbon (C/C) composites, transition of the precursor polymer matrix to a carbon matrix takes place at the stage of first carbonization. Matrix microcracking, interfacial debonding, and development of distributed porosity are some consequences of first carbonization. A key to assessing and optimizing these properties of the final material is to successfully define nondestructive evaluation (NDE) microstructure-process relationships for different material precursor systems at the stage of first carbonization. Here such a study is undertaken through a systematic consideration of structural and functional fiber reinforced phenolic matrix precursor material systems. Structural composite precursor systems consisted of woven fabric architectures, such as plain, satin, and stretch broken, while the functional systems included nonwoven thermal bonded carbon fiber. These materials were subjected to ultrasonic, acoustic, and vibration NDE at their polymer and carbonized matrix stages. NDE parameters from these methods were studied in light of various mechanisms ensuing first carbonization
{"title":"NDE of Structural and Functional Carbon‐Carbon Composites after First Carbonization","authors":"U. Vaidya, H. Mahfuz, S. Jeelani","doi":"10.1002/9780470314500.CH64","DOIUrl":"https://doi.org/10.1002/9780470314500.CH64","url":null,"abstract":"In the processing cycle of carbon-carbon (C/C) composites, transition of the precursor polymer matrix to a carbon matrix takes place at the stage of first carbonization. Matrix microcracking, interfacial debonding, and development of distributed porosity are some consequences of first carbonization. A key to assessing and optimizing these properties of the final material is to successfully define nondestructive evaluation (NDE) microstructure-process relationships for different material precursor systems at the stage of first carbonization. Here such a study is undertaken through a systematic consideration of structural and functional fiber reinforced phenolic matrix precursor material systems. Structural composite precursor systems consisted of woven fabric architectures, such as plain, satin, and stretch broken, while the functional systems included nonwoven thermal bonded carbon fiber. These materials were subjected to ultrasonic, acoustic, and vibration NDE at their polymer and carbonized matrix stages. NDE parameters from these methods were studied in light of various mechanisms ensuing first carbonization","PeriodicalId":14908,"journal":{"name":"Journal of Advanced Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2008-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73849536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The University of Texas at Austin Center for Electromechanics (UT-CEM) has developed a 2 kW-hr flywheel battery for energy management on a hybrid electric urban bus. The battery recovers braking energy and stores excess energy generated by the prime mover (e.g., internal combustion engine). The flywheel rotor, fabricated from high-strength composites, spins at 40,000 rpm at full charge (∼900 m/s tip speed), and is housed in a vacuum enclosure to minimize windage drag. Also integrated into the enclosure is a composite containment system that has been prooftested to provide additional safety. Ensuring flywheel safety is a major issue that must be addressed in using flywheels for transportation applications. A large leak caused by a service failure of the vacuum system could damage the flywheel before the energy dump system has time to act. A rapid loss-of-vacuum test on a rotor similar to that planned for the urban bus flywheel was conducted. Instrumentation, during the flywheel spin test recorded increasing flywheel surface temperature (>316°C or 600°F) following an intentional and abrupt loss of vacuum. No severe damage was noted on the surface of the flywheel, which was later retested to a higher speed to assess structural integrity. This paper provides an analysis of the data from that test and discusses the experimental results as they pertain to safety of the bus flywheel.
{"title":"Response of an urban bus flywheel battery to a rapid loss-of-vacuum event","authors":"R. Thompson, J. M. Kramer, R. Hayes","doi":"10.15781/T24H40","DOIUrl":"https://doi.org/10.15781/T24H40","url":null,"abstract":"The University of Texas at Austin Center for Electromechanics (UT-CEM) has developed a 2 kW-hr flywheel battery for energy management on a hybrid electric urban bus. The battery recovers braking energy and stores excess energy generated by the prime mover (e.g., internal combustion engine). The flywheel rotor, fabricated from high-strength composites, spins at 40,000 rpm at full charge (∼900 m/s tip speed), and is housed in a vacuum enclosure to minimize windage drag. Also integrated into the enclosure is a composite containment system that has been prooftested to provide additional safety. Ensuring flywheel safety is a major issue that must be addressed in using flywheels for transportation applications. A large leak caused by a service failure of the vacuum system could damage the flywheel before the energy dump system has time to act. A rapid loss-of-vacuum test on a rotor similar to that planned for the urban bus flywheel was conducted. Instrumentation, during the flywheel spin test recorded increasing flywheel surface temperature (>316°C or 600°F) following an intentional and abrupt loss of vacuum. No severe damage was noted on the surface of the flywheel, which was later retested to a higher speed to assess structural integrity. This paper provides an analysis of the data from that test and discusses the experimental results as they pertain to safety of the bus flywheel.","PeriodicalId":14908,"journal":{"name":"Journal of Advanced Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91158448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, a very ductile adhesive and a structural epoxy have been presented It has been shown that when designed correctly the ductile adhesive could take advantage of the epoxy, and that an adhesive which is relatively stronger in one mode, e.g. tension, is not necessarily so for the other mode, e.g. bending. Four Point Bending Test was carried out using a single lap joint configuration in which high strain concentrations were encountered at the ends of the overlap. It was found that in this mode the ductile adhesive having very low maximum tensile stress could break the hard steel having very high maximum tensile stress. Finite Element Analysis was also undertaken to investigate the stress distribution in the configuration.
{"title":"The Strength in the Weakness","authors":"F. Kadioglu, A. Özel, R. Sadeler, R. Adams","doi":"10.2307/j.ctvk12sp8.28","DOIUrl":"https://doi.org/10.2307/j.ctvk12sp8.28","url":null,"abstract":"In this paper, a very ductile adhesive and a structural epoxy have been presented It has been shown that when designed correctly the ductile adhesive could take advantage of the epoxy, and that an adhesive which is relatively stronger in one mode, e.g. tension, is not necessarily so for the other mode, e.g. bending. Four Point Bending Test was carried out using a single lap joint configuration in which high strain concentrations were encountered at the ends of the overlap. It was found that in this mode the ductile adhesive having very low maximum tensile stress could break the hard steel having very high maximum tensile stress. Finite Element Analysis was also undertaken to investigate the stress distribution in the configuration.","PeriodicalId":14908,"journal":{"name":"Journal of Advanced Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2003-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90667943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1201/9780367812720-15
B. Mauget, L. Minnetyan, C. Chamis
The large deformation behavior of fiber preform and angle ply composites with very soft matrix is the subject of this paper. For these materials, large strains and therefore significant changes in the fiber orientations occur due to the application of small traction, thus drastically changing their mechanical properties. The present method uses a laminate analogy model with very low stiffness matrix to compute the finite element properties. The assumptions are that fibers do not elongate, the laminate is made of symmetrically woven fibers and that during a finite element step the properties can be considered constant. Based on these assumptions, a simple way to compute the fiber angle changes is proposed. It is noted that a rectangular box on the soft matrix composite with fibers as its diagonal will deform into a box of different aspect ratio. The large displacement approach is valid since the properties depend on the global Poisson's ratio computation that is proved accurate. A traction test is simulated to demonstrate the method.
{"title":"Large Deformation Nonlinear Response of Soft Composite Structures via Laminate Analogy","authors":"B. Mauget, L. Minnetyan, C. Chamis","doi":"10.1201/9780367812720-15","DOIUrl":"https://doi.org/10.1201/9780367812720-15","url":null,"abstract":"The large deformation behavior of fiber preform and angle ply composites with very soft matrix is the subject of this paper. For these materials, large strains and therefore significant changes in the fiber orientations occur due to the application of small traction, thus drastically changing their mechanical properties. The present method uses a laminate analogy model with very low stiffness matrix to compute the finite element properties. The assumptions are that fibers do not elongate, the laminate is made of symmetrically woven fibers and that during a finite element step the properties can be considered constant. Based on these assumptions, a simple way to compute the fiber angle changes is proposed. It is noted that a rectangular box on the soft matrix composite with fibers as its diagonal will deform into a box of different aspect ratio. The large displacement approach is valid since the properties depend on the global Poisson's ratio computation that is proved accurate. A traction test is simulated to demonstrate the method.","PeriodicalId":14908,"journal":{"name":"Journal of Advanced Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78124131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eun U. Lee, K. George, V. Agarwala, H. Sanders, G. London
This study was conducted to identify the mechanical behavior of a wrought 62Be-38Al alloy and a cast 65Be-32Al-3Ni alloy. Tensile strength and elongation were measured at room and elevated temperatures. Fracture toughness was determined at room temperature. Fatigue resistance was characterized in terms of stress-life (S-N) and crack growth rate-stress intensity range (da/dN-ΔK) relations at room temperature. The resulting microstructures and crack paths of the aforementioned were also examined. The microstructure of the wrought and cast alloys consists of Be-phase particles dispersed within an Al-phase matrix. The Be-phase particles are aligned along the rolling direction in the wrought alloy, whereas they are coarser and round with no directionality in the cast alloy. Overall, the wrought alloy has better mechanical properties, including fatigue resistance, than the cast alloy. The conditional plane strain fracture toughnesses of the wrought alloy were determined to be 38. 8 and 22.4 MPa√m (35. 3 and 20.4 ksi√in) for the L-T and T-L orientations at room temperature, respectively. The crack path follows preferentially along the Al-phase and the Al/Be interfacial region for the wrought alloy at all temperatures and for the cast alloy at higher temperatures during tensile, fracture-toughness, and fatigue testing. However, while tensile testing at room temperature, the crack cuts through the Be- and Al-phases in the cast alloy.
{"title":"Mechanical behavior of Be-Al alloys","authors":"Eun U. Lee, K. George, V. Agarwala, H. Sanders, G. London","doi":"10.21236/ada378014","DOIUrl":"https://doi.org/10.21236/ada378014","url":null,"abstract":"This study was conducted to identify the mechanical behavior of a wrought 62Be-38Al alloy and a cast 65Be-32Al-3Ni alloy. Tensile strength and elongation were measured at room and elevated temperatures. Fracture toughness was determined at room temperature. Fatigue resistance was characterized in terms of stress-life (S-N) and crack growth rate-stress intensity range (da/dN-ΔK) relations at room temperature. The resulting microstructures and crack paths of the aforementioned were also examined. The microstructure of the wrought and cast alloys consists of Be-phase particles dispersed within an Al-phase matrix. The Be-phase particles are aligned along the rolling direction in the wrought alloy, whereas they are coarser and round with no directionality in the cast alloy. Overall, the wrought alloy has better mechanical properties, including fatigue resistance, than the cast alloy. The conditional plane strain fracture toughnesses of the wrought alloy were determined to be 38. 8 and 22.4 MPa√m (35. 3 and 20.4 ksi√in) for the L-T and T-L orientations at room temperature, respectively. The crack path follows preferentially along the Al-phase and the Al/Be interfacial region for the wrought alloy at all temperatures and for the cast alloy at higher temperatures during tensile, fracture-toughness, and fatigue testing. However, while tensile testing at room temperature, the crack cuts through the Be- and Al-phases in the cast alloy.","PeriodicalId":14908,"journal":{"name":"Journal of Advanced Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88202723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Ng, R. Boswell, S. J. Claus, F. Arnold, A. Vizzini
The heat of reaction for the cure, degree of cure, and viscosity of Hexcel 8552, and Cytec Fiberite 977-3 HM neat resins were measured using a modulated differential scanning calorimeter (MDSC) and a rheometric digital analyzer (RDA). Expressions were developed using isothermal tests for correlating the rate of degree of cure and the viscosity with the degree of cure using a Lee, Loos, and Springer approach. The models were used to predict the kinetic behavior of the resins using the respective manufacturer s cure cycle. Data were collected and a good correlation was found with the model. In addition, the kinetic behaviors of these systems were compared to Hercules 3501-6 data. A second study was also performed to compare cure models developed based on neat and prepreg forms of the resin viscosity data. Vastly different viscosity behaviors were found indicating further physical insights are necessary to account for fiber/resin content and material properties difference.
{"title":"Degree of Cure, Heat of Reaction, and Viscosity of 8552 and 977-3 HM Epoxy Resin","authors":"S. Ng, R. Boswell, S. J. Claus, F. Arnold, A. Vizzini","doi":"10.21236/ada377439","DOIUrl":"https://doi.org/10.21236/ada377439","url":null,"abstract":"The heat of reaction for the cure, degree of cure, and viscosity of Hexcel 8552, and Cytec Fiberite 977-3 HM neat resins were measured using a modulated differential scanning calorimeter (MDSC) and a rheometric digital analyzer (RDA). Expressions were developed using isothermal tests for correlating the rate of degree of cure and the viscosity with the degree of cure using a Lee, Loos, and Springer approach. The models were used to predict the kinetic behavior of the resins using the respective manufacturer s cure cycle. Data were collected and a good correlation was found with the model. In addition, the kinetic behaviors of these systems were compared to Hercules 3501-6 data. A second study was also performed to compare cure models developed based on neat and prepreg forms of the resin viscosity data. Vastly different viscosity behaviors were found indicating further physical insights are necessary to account for fiber/resin content and material properties difference.","PeriodicalId":14908,"journal":{"name":"Journal of Advanced Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2000-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75173005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-01-01DOI: 10.1007/978-1-4613-0669-6_27
R. E. Southward, D. S. Thompson, D. W. Thompson, A. K. Clair
{"title":"Enhancement of Dimensional Stability in Soluble Polyimides via Lanthanide (III) Additives","authors":"R. E. Southward, D. S. Thompson, D. W. Thompson, A. K. Clair","doi":"10.1007/978-1-4613-0669-6_27","DOIUrl":"https://doi.org/10.1007/978-1-4613-0669-6_27","url":null,"abstract":"","PeriodicalId":14908,"journal":{"name":"Journal of Advanced Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1990-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75830469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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