Micromechanics

About: Micromechanics is a research topic. Over the lifetime, 6000 publications have been published within this topic receiving 162635 citations.

A Micromechanical Model for Textile Composite Plates

Abstract: A novel finite element based micromechanical method is developed for computing the plate stiffness coefficients (A, B, D matrices) and coefficients of thermal expansion (α's and β's) of a textile composite modeled as a homogeneous plate. Periodic boundary conditions for the plate model, which are different from those for the continuum model, have been derived. The micromechanics methods for computing the coefficients of thermal expansion are readily extended to compute the thermal residual stresses due to curing. The methods are first verified by applying to several examples for which solutions are known, and then applied to the case of woven composites. The plate stiffness coefficients computed from direct micromechanics are compared with those derived from the homogenized elastic constants in conjunction with the classical plate theory. It is found that the plate stiffness coefficients of textile composites, especially the B and D matrices, cannot be predicted from the homogenized elastic constants and ...

Fracture behaviour of wood and its composites. A review COST Action E35 2004–2008: Wood machining – micromechanics and fracture

Abstract: Abstract Fracturing of wood and its composites is a process influenced by many parameters, on the one hand coming from the structure and properties of wood itself, and on the other from influences from outside, such as loading mode, velocity of deformation, moisture, temperature, etc. Both types of parameters may be investigated experimentally at different levels of magnification, which allows a better understanding of the mechanisms of fracturing. Fracture mechanical methods serve to quantify the fracture process of wood and wood composites with different deformation and fracturing features. Since wood machining is mainly dominated by the fracture properties of wood, knowledge of the different relevant mechanisms is essential. Parameters that influence the fracture process, such as wood density, orientation, loading mode, strain rate and moisture are discussed in the light of results obtained during recent years. Based on this, refined modelling of the different processes becomes possible.

Micromechanics of plastic deformation and phase transformation in a three-phase TRIP-assisted advanced high strength steel: Experiments and modeling

Abstract: The micromechanics of plastic deformation and phase transformation in a three-phase advanced high strength steel are analyzed both experimentally and by microstructure-based simulations. The steel examined is a three-phase (ferrite, martensite and retained austenite) quenched and partitioned sheet steel with a tensile strength of ~980 MPa. The macroscopic flow behavior and the volume fraction of martensite resulting from the austenite–martensite transformation during deformation were measured. In addition, micropillar compression specimens were extracted from the individual ferrite grains and the martensite particles, and using a flat-punch nanoindenter, stress–strain curves were obtained. Finite element simulations idealize the microstructure as a composite that contains ferrite, martensite and retained austenite. All three phases are discretely modeled using appropriate crystal plasticity based constitutive relations. Material parameters for ferrite and martensite are determined by fitting numerical predictions to the micropillar data. The constitutive relation for retained austenite takes into account contributions to the strain rate from the austenite–martensite transformation, as well as slip in both the untransformed austenite and product martensite. Parameters for the retained austenite are then determined by fitting the predicted flow stress and transformed austenite volume fraction in a 3D microstructure to experimental measurements. Simulations are used to probe the role of the retained austenite in controlling the strain hardening behavior as well as internal stress and strain distributions in the microstructure.

Effective Elastoplastic Damage Mechanics for Fiber-reinforced Composites with Evolutionary Complete Fiber Debonding

Abstract: A micromechanical damage mechanics framework is proposed to predict the overall elastoplastic behavior and interfacial damage evolution of fiber- reinforced ductile composites. Progressively debonded fibers are replaced by equivalent voids. The effective elastic moduli of three-phase composites, composed of a ductile matrix, randomly located yet unidirectionally aligned circular fibers, and voids, are derived by using a rigorous micromechanical formulation. In order to characterize the homogenized elastoplastic behavior, an effective yield criterion is derived based on the ensemble area averaging process and the first-order effects of eigenstrains. The resulting effective yield criterion, together with the overall associative plastic flow rule and the hardening law, constitutes the analytical framework for the estimation of effective elastoplastic damage responses of ductile composites containing both perfectly bonded and completely debonded fibers. An evolutionary interfacial fiber debonding process, governed by the internal stresses of fibers and interfacial strength, is incorporated into the proposed framework. The Weibull's function is employed to describe the varying probability of fiber debonding. Further, comparison between predictions and available experimental data are presented to illustrate the potential of the proposed methodology.