A new stress-based multi-scale failure criterion is proposed based on a series of off-axis tension tests, and their corresponding fiber failure modes and matrix failure modes are determined at the microscopic level. I...A new stress-based multi-scale failure criterion is proposed based on a series of off-axis tension tests, and their corresponding fiber failure modes and matrix failure modes are determined at the microscopic level. It is a physical mechanism based, three-dimensional damage analysis criterion which takes into consideration the constituent properties on the macroscopic failure behavior of the composite laminates. A complete set of stress transformation, damage determination and evolution methods are established to realize the application of the multi-scale method in failure analysis. Open-hole tension（OHT） specimens of three material systems（CCF300/5228, CCF300/5428 and T700/5428） are tested according to ASTM standard D5766, and good agreements are found between the experimental results and the numerical predictions. It is found that fiber strength is a key factor influencing the ultimate strength of the laminates, while matrix failure alleviates the stress concentration around the hole. Different matchings of fiber and matrix result in different failure modes as well as ultimate strengths.展开更多
An experimental investigation was carried out on the damage resistance to a concen- trated quasi-static indentation force and low-velocity impact of four kinds of glass-reinforced aluminum laminates （GLARE for short...An experimental investigation was carried out on the damage resistance to a concen- trated quasi-static indentation force and low-velocity impact of four kinds of glass-reinforced aluminum laminates （GLARE for short）. Compared with the experimental results of the CFRP （Carbon Fiber Reinforced Plastics） laminates, the performance of GLARE was determined. By means of concentrated quasi-static indentation force test, typical force displacement response, the maximum contact force and dent depth were received, Through drop-weight low-velocity impact tests, impact force histories, indentation depths （through a new method） and dissipated energy were obtained. The test results show that the force-displacement response of GLARE 4 laminates under the concentrated quasi-static indentation force has an obvious fiat roof and the failure is instantaneous, which are different from CFRP laminates. The indention will be visible once the impact happens. C-scan results find that there is no delamination besides the impact area after both the concentrated quasi-static indentation and low-velocity impact. The dissipated energy approximately equals the impact energy.展开更多
A computational homogenization technique（CHT） based on the finite element method（FEM） is discussed to predict the effective elastic properties of honeycomb structures.The need of periodic boundary conditions（BCs...A computational homogenization technique（CHT） based on the finite element method（FEM） is discussed to predict the effective elastic properties of honeycomb structures.The need of periodic boundary conditions（BCs） is revealed through the analysis for in-plane and out-of-plane shear moduli of models with different cell numbers.After applying periodic BCs on the representative volume element（RVE）,comparison between the volume-average stress method and the boundary stress method is performed,and a new method based on the equality of strain energy to obtain all non-zero components of the stiffness tensor is proposed.Results of finite element（FE） analysis show that the volume-average stress and the boundary stress keep a consistency over different cell geometries and forms.The strain energy method obtains values that differ from those of the volume-average method for non-diagonal terms in the stiffness matrix.Analysis has been done on numerical results for thin-wall honeycombs and different geometries of angles between oblique and vertical walls.The inaccuracy of the volume-average method in terms of the strain energy is shown by numerical benchmarks.展开更多
基金the National Basic Research and Development Program of China: Basic Scientific Research of Advanced Composites in Aeronautic and Astronautic Application Technology (No. 2010CB631103)
文摘A new stress-based multi-scale failure criterion is proposed based on a series of off-axis tension tests, and their corresponding fiber failure modes and matrix failure modes are determined at the microscopic level. It is a physical mechanism based, three-dimensional damage analysis criterion which takes into consideration the constituent properties on the macroscopic failure behavior of the composite laminates. A complete set of stress transformation, damage determination and evolution methods are established to realize the application of the multi-scale method in failure analysis. Open-hole tension（OHT） specimens of three material systems（CCF300/5228, CCF300/5428 and T700/5428） are tested according to ASTM standard D5766, and good agreements are found between the experimental results and the numerical predictions. It is found that fiber strength is a key factor influencing the ultimate strength of the laminates, while matrix failure alleviates the stress concentration around the hole. Different matchings of fiber and matrix result in different failure modes as well as ultimate strengths.
文摘An experimental investigation was carried out on the damage resistance to a concen- trated quasi-static indentation force and low-velocity impact of four kinds of glass-reinforced aluminum laminates （GLARE for short）. Compared with the experimental results of the CFRP （Carbon Fiber Reinforced Plastics） laminates, the performance of GLARE was determined. By means of concentrated quasi-static indentation force test, typical force displacement response, the maximum contact force and dent depth were received, Through drop-weight low-velocity impact tests, impact force histories, indentation depths （through a new method） and dissipated energy were obtained. The test results show that the force-displacement response of GLARE 4 laminates under the concentrated quasi-static indentation force has an obvious fiat roof and the failure is instantaneous, which are different from CFRP laminates. The indention will be visible once the impact happens. C-scan results find that there is no delamination besides the impact area after both the concentrated quasi-static indentation and low-velocity impact. The dissipated energy approximately equals the impact energy.
文摘A computational homogenization technique（CHT） based on the finite element method（FEM） is discussed to predict the effective elastic properties of honeycomb structures.The need of periodic boundary conditions（BCs） is revealed through the analysis for in-plane and out-of-plane shear moduli of models with different cell numbers.After applying periodic BCs on the representative volume element（RVE）,comparison between the volume-average stress method and the boundary stress method is performed,and a new method based on the equality of strain energy to obtain all non-zero components of the stiffness tensor is proposed.Results of finite element（FE） analysis show that the volume-average stress and the boundary stress keep a consistency over different cell geometries and forms.The strain energy method obtains values that differ from those of the volume-average method for non-diagonal terms in the stiffness matrix.Analysis has been done on numerical results for thin-wall honeycombs and different geometries of angles between oblique and vertical walls.The inaccuracy of the volume-average method in terms of the strain energy is shown by numerical benchmarks.
