Papers by Author: Min Shen

Abstract: Natural fiber reinforced composites have become excellent candidates for automotive applications and civil engineering facilities. The design procedures will require precisely evaluating the toughness of the materials, which demand accurate measurements of strain or displacement that are difficult to obtain for ductile materials. The primary objectives of this paper were to develop reliable experimental approaches which can effectively evaluate the fracture behaviors of random short natural fiber reinforced polypropylene (PP) composites. The digital image correlation method (DICM) was applied to compute the deformation fields around the crack tip of a compact-tension specimen in a process of loading. An experimental and numerical hybrid method was used to describe the fracture behaviors of the composites. The relationship between the micro-structure of random fibers and the macroscopic mechanical properties of the composites can also be understood.

Abstract: Natural short fiber reinforced polypropylene (PP) composite has great significance both in commercial and environmental and is widely used in motor industry. Its local inhomogeneity and interphase both affect the macroscopic properties of the composite. These phenomena are still difficult to observe and study accurately in the experiment. A cohesive zone model (CZM) based numerical simulation method is presented in this paper. The three-phase (matrix-interphase-fiber) model considering some different factors was developed to study the effects of interphase parameters on the mechanical properties of the composite.

Abstract: The spruce fiber reinforced thermoplastic polypropylene (PP) composite is studied in this paper aiming at inspecting the effect of micromechanics parameters on the effective elasto-plastic property of composite by the numerical methods. The local stress field changing with the fiber aspect ratio and volume fraction is detailed investigated. At the last the normal cohesive strength of the interface is predicted initially. The numerical results show good agreement with the theoretical prediction results and available data.

Abstract: Natural short fiber reinforced composite is promising in motor industry, it is meaningful to study the tensile property of spruce short fiber reinforced polypropylene (PP) composite. In this paper, the finite element model is developed with the consideration of the fiber random orientation, random distribution, fiber volume content and interphase effect, especially the cohesive zone model to simulate the interphase property. The tensile behaviors of the short spruce/PP composite with kinds of fiber volume content are predicted. The results show that both strength or stiffness and experimental data are well identical.

Abstract: The random spruce short fiber reinforced polypropylene composites is a type of thermoplastic bio-composites. It is considered as homogeneous, isotropic in macro-scale of its specimen, in fiber scale about 500μm, the composite material appears heterogeneity, anisotropy due to the influence of microstructures of random short fibers. The heterogeneous deformations near the crack tip of the compact tension (CT) specimen which made from spruce/PP composites were measured by means of the digital image correlation method (DICM) with high resolutions digital image. The crack tip fields of heterogeneous displacement and strain for spruce/PP composites with fiber volume content 49% were obtained. The effects of random fiber microstructures on macroscopic deformations were discussed.

Abstract: The results on a numerical and experimental study of graphite/epoxy composite plates [03/903]S are presented. Each specimen was firstly impacted by the low velocity with different energy level. Compression experiment based on carrier electronic speckle pattern interferometry (carrier-ESPI) is made for the post-impact composite plate. The finite element method (FEM) is used to gain further understanding of the deformation behavior of impacted specimens. The compressive deformation of various delaminated composite plates are analyzed with software ANSYS to see that the impact parameters and delamination damage data, such as impact energy, maximum impact force and delamination area, affect the deformation fields. In addition, the comparisons between the finite element results and experimental measurements are considered under different compression loads.

Abstract: The study on deformation in impact-damaged graphite-fibre/epoxy stitched composite plates subjected to compressive load is presented. A delaminated cross-ply laminate [03/903]S obtained in low-velocity impact test has been examined using a self-designed anti-buckling device in compressive experiment. The out-of-plane displacement field of the specimen has been measured with an optical whole-filed measurement technique, which is carrier electronic speckle pattern interferometry (carrier-ESPI). Finite element (FE) simulation is also carried out to predict the deformation. The effect of the stitching line on compressive deformation is discussed for various stitched laminates. Finally, the numerical results are compared with experimental measurement deformations under different compressive loads.

Abstract: The orthotropic mechanical behaviors of weft-knitted flax fiber fabric reinforced polypropylene (PP) composites, which were produced by hot pressing of knit layers composed of a commingled yarn with a flax fiber content of 50vol.%, are investigated in both meso- and macro-scales. In meso-scale, the repeating unit cell (RUC) finite element (FE) model is developed, in which impregnated yarns are assumed to be isotropic elastic while the matrix is modeled as an elastoplastic, isotropic solid. Then, stress-strain curves of the RUC are simulated for its elastoplastic orthotropic parameters. Finally, in macro-scale of its specimen, the tensile behavior of the composite laminates with six parallel plies is simulated by means of 3D elastoplastic FE method. The applicability and limitation of this model have been discussed.