In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in construct...In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in constructing the TiAl-based laminated composites.In this work,TiAl/Ti_(2)AlNb laminated composites are successfully synthesized by vacuum hot pressing combined with the foil-foil(sheet)metallurgy.Under the pressure of 65 MPa,different holding time and temperature of hot pressing are tried and the optimized fabrication parameter is acquired as 1050℃/120 min/65 MPa.Along with the changes of processing parameters,the defect,microstructure,interface,phase transformation and the corresponding mechanical properties are detailly discussed.The results show that the TiAl/Ti_(2)AlNb laminated composite fabricated at 1050℃ for 2 h achieves a good metallurgical interface bonding.The corresponding interface microstructure is composed of region I and region II.The region I consists of O,α_(2)and B2/βphase,and region II is made up ofα2.Subsequently,the tensile tests indicate that the composite synthesized at 1050℃ for 2 h possesses a maximum strength of 812 MPa and a total elongation of 1.31%at room temperature,and a strength of 539.71 MPa and the highest total elongation of 10.34%at 750℃.The well synergistic deformation ability between the interface and the two base alloys endows the composite an excellent tensile performance.Moreover,the composite processed at 1050℃ for 2 h behaves the best fracture toughness in both arrester orientation and divider orientation with the value of 32.6 MPa.m^(1/2)and 30.1 MPa.m^(1/2),respectively.The Ti_(2)AlNb alloy in the laminated structure effectively release the stress around the crack tip and plays a role in toughening.Further,crack deflection,crack bridging,crack blunting and fragmentation also make contributions to enhance the fracture toughness of the laminated composites.展开更多
The composite fabric is a new type of automobile fabric in recent years.The three-layer composite fabric was made of different materials that were linen weaving fabric,knitting fabric and warp-knitted spacer fabric.Th...The composite fabric is a new type of automobile fabric in recent years.The three-layer composite fabric was made of different materials that were linen weaving fabric,knitting fabric and warp-knitted spacer fabric.Through testing performances of three different adhesives,the thermoplastic urethanes(TPU)hot melt powder was selected to adhere every fabric.Then,the laminating process was designed and applied.The optimized process conditions were following:the temperature was 150℃,the pressure was 2.0 N·cm-2,the time was 80 s,and the dosage of adhesive was 20 g·m-2.This new laminated fabric has multi-functions,such as comfortability,permeability and physic mechanical properties.This lamination process will be used to be the basis for the study of functional laminated car seat fabric.展开更多
Recently, some new quadrilateral finite elements were successfully developed by the Quadrilateral Area Coordinate （QAC） method. Compared with those traditional models using isoparametric coordinates, these new model...Recently, some new quadrilateral finite elements were successfully developed by the Quadrilateral Area Coordinate （QAC） method. Compared with those traditional models using isoparametric coordinates, these new models are less sensitive to mesh distortion. In this paper, a new displacement-based, 4-node 20-DOF （5-DOF per node） quadrilateral bending element based on the first-order shear deformation theory for analysis of arbitrary laminated composite plates is presented. Its bending part is based on the element AC-MQ4, a recent-developed high-performance Mindlin-Reissner plate element formulated by QAC method and the generalized conforming condition method; and its in-plane displacement fields are interpolated by bilinear shape functions in isoparametric coordinates. Furthermore, the hybrid post-rocessing procedure, which was firstly proposed by the authors, is employed again to improve the stress solutions, especially for the transverse shear stresses. The resulting element, denoted as AC-MQ4-LC, exhibits excellent performance in all linear static and dynamic numerical examples. It demonstrates again that the QAC method, the generalized conforming condition method, and the hybrid post-processing procedure are efficient tools for developing simple, effective and reliable finite element models.展开更多
A mathematical model is made which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composite is devel...A mathematical model is made which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composite is developed. The model provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, and the void variation and the residual stress distribution. It can be used to illustrate the mechanism of curing process and optimize the cure cycle of composite material in order to ensure the quality of a product.展开更多
According to a mathematical model which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composites, t...According to a mathematical model which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composites, the solution method to the model is made and a computer code is developed, which for flat-plate composites cured by a specified cure cycle, provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, the void variation and the residual stress distribution.展开更多
With assumption of material inhomogeneity on meso level, a three-point bending beam model has been adopted to simulate crack propagation in two dimensional laminated composite and to verify the toughening mechanism of...With assumption of material inhomogeneity on meso level, a three-point bending beam model has been adopted to simulate crack propagation in two dimensional laminated composite and to verify the toughening mechanism of energy dissipation and crack deflection along the weak interlayer. Moreover, the effect of strength, elastic modulus and thickness of the weak interlayer on both strength and toughness of the laminated composite have also been investigated in this paper.展开更多
基金supported by Major Special Science and Technology Project of Yunnan Province 202002AB080001-3the National Natural Science Foundation of China(no.51704088)Fundamental Research and Development Program of China(Grant no.JCKY2017205B032)。
文摘In order to improve the intrinsic brittleness of TiAl alloys,Ti_(2)AlNb alloys with outstanding ductility and toughness at room temperature,and good high-temperature performance are competitive candidates in constructing the TiAl-based laminated composites.In this work,TiAl/Ti_(2)AlNb laminated composites are successfully synthesized by vacuum hot pressing combined with the foil-foil(sheet)metallurgy.Under the pressure of 65 MPa,different holding time and temperature of hot pressing are tried and the optimized fabrication parameter is acquired as 1050℃/120 min/65 MPa.Along with the changes of processing parameters,the defect,microstructure,interface,phase transformation and the corresponding mechanical properties are detailly discussed.The results show that the TiAl/Ti_(2)AlNb laminated composite fabricated at 1050℃ for 2 h achieves a good metallurgical interface bonding.The corresponding interface microstructure is composed of region I and region II.The region I consists of O,α_(2)and B2/βphase,and region II is made up ofα2.Subsequently,the tensile tests indicate that the composite synthesized at 1050℃ for 2 h possesses a maximum strength of 812 MPa and a total elongation of 1.31%at room temperature,and a strength of 539.71 MPa and the highest total elongation of 10.34%at 750℃.The well synergistic deformation ability between the interface and the two base alloys endows the composite an excellent tensile performance.Moreover,the composite processed at 1050℃ for 2 h behaves the best fracture toughness in both arrester orientation and divider orientation with the value of 32.6 MPa.m^(1/2)and 30.1 MPa.m^(1/2),respectively.The Ti_(2)AlNb alloy in the laminated structure effectively release the stress around the crack tip and plays a role in toughening.Further,crack deflection,crack bridging,crack blunting and fragmentation also make contributions to enhance the fracture toughness of the laminated composites.
基金Key Research Project of Shaanxi Province,China(No.2020GY-267)Directive Project of China Textile Industry Federation,China(No.2018061)。
文摘The composite fabric is a new type of automobile fabric in recent years.The three-layer composite fabric was made of different materials that were linen weaving fabric,knitting fabric and warp-knitted spacer fabric.Through testing performances of three different adhesives,the thermoplastic urethanes(TPU)hot melt powder was selected to adhere every fabric.Then,the laminating process was designed and applied.The optimized process conditions were following:the temperature was 150℃,the pressure was 2.0 N·cm-2,the time was 80 s,and the dosage of adhesive was 20 g·m-2.This new laminated fabric has multi-functions,such as comfortability,permeability and physic mechanical properties.This lamination process will be used to be the basis for the study of functional laminated car seat fabric.
基金The project is supported by the National Natural Science Foundation of China(10502028)the Special Foundation for the Authors of the Nationwide(China)Excellent Doctoral Dissertation(200242)the Science Research Foundation of China Agricultural University(2004016).
文摘Recently, some new quadrilateral finite elements were successfully developed by the Quadrilateral Area Coordinate （QAC） method. Compared with those traditional models using isoparametric coordinates, these new models are less sensitive to mesh distortion. In this paper, a new displacement-based, 4-node 20-DOF （5-DOF per node） quadrilateral bending element based on the first-order shear deformation theory for analysis of arbitrary laminated composite plates is presented. Its bending part is based on the element AC-MQ4, a recent-developed high-performance Mindlin-Reissner plate element formulated by QAC method and the generalized conforming condition method; and its in-plane displacement fields are interpolated by bilinear shape functions in isoparametric coordinates. Furthermore, the hybrid post-rocessing procedure, which was firstly proposed by the authors, is employed again to improve the stress solutions, especially for the transverse shear stresses. The resulting element, denoted as AC-MQ4-LC, exhibits excellent performance in all linear static and dynamic numerical examples. It demonstrates again that the QAC method, the generalized conforming condition method, and the hybrid post-processing procedure are efficient tools for developing simple, effective and reliable finite element models.
文摘A mathematical model is made which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composite is developed. The model provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, and the void variation and the residual stress distribution. It can be used to illustrate the mechanism of curing process and optimize the cure cycle of composite material in order to ensure the quality of a product.
文摘According to a mathematical model which describes the curing process of composites constructed from continuous fiber-reinforced, thermosetting resin matrix prepreg materials, and the consolidation of the composites, the solution method to the model is made and a computer code is developed, which for flat-plate composites cured by a specified cure cycle, provides the variation of temperature distribution, the cure reaction process in the resin, the resin flow and fibers stress inside the composite, the void variation and the residual stress distribution.
基金supported by the National Natural Science Foundation of China(No.50778046)the Science and Technology Planning of Guangdong Province(Nos.2006B14601004 and 2009A030302016).
文摘With assumption of material inhomogeneity on meso level, a three-point bending beam model has been adopted to simulate crack propagation in two dimensional laminated composite and to verify the toughening mechanism of energy dissipation and crack deflection along the weak interlayer. Moreover, the effect of strength, elastic modulus and thickness of the weak interlayer on both strength and toughness of the laminated composite have also been investigated in this paper.
