The effects of HDPE matrix toughness on the brittle-ductile transition of HDPE/CaCO_3blends are investigated. Not all HDPE can be toughened by CaCO_3 particles. The ability of thematrix to yield plays a fundamental ro...The effects of HDPE matrix toughness on the brittle-ductile transition of HDPE/CaCO_3blends are investigated. Not all HDPE can be toughened by CaCO_3 particles. The ability of thematrix to yield plays a fundamental role in determing whether HDPE can be toughened or not.There exists a critical matrix toughness (I_(sc)≈45J/m) below which HDPE can not be toughenedobservably by CaCO_3 particle at given average size, and above which the critical matrix ligamentthickness (τ_?) is proportional to matrix impact strength.展开更多
In this paper,the Riccati transfer matrix method and the modal parameter identification tech-nique are applied to the dynamic analysis of the spindle system of a machine tool,the X62Wknee-type universal milling machin...In this paper,the Riccati transfer matrix method and the modal parameter identification tech-nique are applied to the dynamic analysis of the spindle system of a machine tool,the X62Wknee-type universal milling machine.With-the help of a computer,the lowest three critical speedsare calculated and these are compared with the values measured by a 7T17S analyzer,showing afairly good agreement.展开更多
An analytical methodology was developed to investigate the effect of fiber/matrix interface debonding on matrix multicracking evolution of fiber-reinforced CMCs(ceramic-matrix composites).The Budiansky-Hutchinson-Evan...An analytical methodology was developed to investigate the effect of fiber/matrix interface debonding on matrix multicracking evolution of fiber-reinforced CMCs(ceramic-matrix composites).The Budiansky-Hutchinson-Evans shear-lag model was adopted to analyse the micro-stress field of the damaged composites.The critical matrix strain energy criterion,which presupposes the existence of an ultimate or critical matrix strain energy with matrix,was obtained to simulate the matrix multicracking evolution of CMCs.With the increase of the applied stress,the matrix multicracking and fiber/matrix interface debonding occurred to dissipate the additional energy entered into the composites.The fiber/matrix interface debonded length under matrix multicracking evolution was obtained by treating the interface debonding as a particular crack propagation problem.The conditions for no-debonding and debonding during the evolution of matrix multicracking were discussed in terms of two interfacial properties,i.e.,the interface shear stress and interface debonded toughness.When the fiber/matrix interface was bonded,the matrix multicracking evolution was much more intense compared with the interface debonding;when the fiber/matrix interface was debonded,the matrix crack density increased with the increasing of interface shear stress and interface debonded energy.The theoretical results were compared with experimental data of unidirectional SiC/CAS(calcium alumina silicate),SiC/CAS-Ⅱand SiC/borosilicate composites.展开更多
基金This project is supported by the National Natural Science Foundation of China.
文摘The effects of HDPE matrix toughness on the brittle-ductile transition of HDPE/CaCO_3blends are investigated. Not all HDPE can be toughened by CaCO_3 particles. The ability of thematrix to yield plays a fundamental role in determing whether HDPE can be toughened or not.There exists a critical matrix toughness (I_(sc)≈45J/m) below which HDPE can not be toughenedobservably by CaCO_3 particle at given average size, and above which the critical matrix ligamentthickness (τ_?) is proportional to matrix impact strength.
文摘In this paper,the Riccati transfer matrix method and the modal parameter identification tech-nique are applied to the dynamic analysis of the spindle system of a machine tool,the X62Wknee-type universal milling machine.With-the help of a computer,the lowest three critical speedsare calculated and these are compared with the values measured by a 7T17S analyzer,showing afairly good agreement.
基金Supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20140813)Postdoctoral Science Foundation of China(Grant No.2012M511274)Introduction of Talents Scientific Research Foundation of Nanjing University of Aeronautics and Astronautics(Grant No.56YAH12034)
文摘An analytical methodology was developed to investigate the effect of fiber/matrix interface debonding on matrix multicracking evolution of fiber-reinforced CMCs(ceramic-matrix composites).The Budiansky-Hutchinson-Evans shear-lag model was adopted to analyse the micro-stress field of the damaged composites.The critical matrix strain energy criterion,which presupposes the existence of an ultimate or critical matrix strain energy with matrix,was obtained to simulate the matrix multicracking evolution of CMCs.With the increase of the applied stress,the matrix multicracking and fiber/matrix interface debonding occurred to dissipate the additional energy entered into the composites.The fiber/matrix interface debonded length under matrix multicracking evolution was obtained by treating the interface debonding as a particular crack propagation problem.The conditions for no-debonding and debonding during the evolution of matrix multicracking were discussed in terms of two interfacial properties,i.e.,the interface shear stress and interface debonded toughness.When the fiber/matrix interface was bonded,the matrix multicracking evolution was much more intense compared with the interface debonding;when the fiber/matrix interface was debonded,the matrix crack density increased with the increasing of interface shear stress and interface debonded energy.The theoretical results were compared with experimental data of unidirectional SiC/CAS(calcium alumina silicate),SiC/CAS-Ⅱand SiC/borosilicate composites.
