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Showing papers on "Micromechanics published in 1980"


Journal ArticleDOI
TL;DR: In this paper, the self-consistent approach originally proposed by Hill has been adopted to derive the effective elastic stiffness constants of unidirectional short-fiber composites.
Abstract: The self-consistent approach originally proposed by Hill has been adopted to derive the effective elastic stiffness constants of unidirectional short-fiber composites. The short-fibers are modeled as ellipsoidal inclu sions uniformly distributed in the matrix and the transverse isotropy of the composite has been taken into account. The method of analysis is valid for multi-component systems and hence, applicable to hybrid composites. Comparisons of this analysis with existing theories are made for binary composites.

135 citations


01 Jun 1980
TL;DR: In this paper, an elastoplastic finite element micromechanics computer program is used to model a unidirectional composite subjected to any combination of longitudinal, transverse, and hygrothermal loadings.
Abstract: : The analysis uses an elastoplastic finite element micromechanics computer program to model a unidirectional composite subjected to any combination of longitudinal, transverse, and hygrothermal loadings. Time-dependent effects are included by means of nonlinear viscoelastic constitutive equations. The method of solution is based upon the conditions for generalized plane strain which permits a pseudo-three-dimensional analysis. It also contains two failure criteria, viz., an octahedral shear stress criterion and a hydrostatic criterion. Application of load or changes in temperature or moisture are input through time-independent increments. A plotting package is also included which allows the user to obtain a total of eight different plots; octahedral shear stress and strain, maximum and minimum principal stress, in-plane shear stress, out-of-plane longitudinal stress, and normal and tangential shear stress on the fiber-matrix interface. The study demonstrates that the associated program is able to model essentially any type of stress input or hygrothermal history. (Author)

11 citations


Book ChapterDOI
01 Jan 1980
TL;DR: In this paper, the influence of variations in fiber and matrix constituent material properties on the moisture and thermal expansion coefficients of a unidirectional composite is demonstrated, using a finite element, inelastic micromechanics analysis.
Abstract: The influence of variations in fiber and matrix constituent material properties on the moisture and thermal expansion coefficients of a unidirectional composite is demonstrated, using a finite element, inelastic micromechanics analysis. Three of the commonly utilized graphite/epoxy material systems are selected for detailed analysis, using available experimental values of the constituent material properties wherever possible. The epoxy matrix is assumed to be Hercules 3501-6 in all cases, a polymer which is fully representative of the various structural epoxies in current use. The three graphite fibers are Celanese GY-70, Hercules HMS, and Hercules AS, representative of high, medium, and low modulus graphite fibers, respectively.

10 citations


ReportDOI
01 Oct 1980
TL;DR: The BILAM as discussed by the authors program uses constant strain laminate analysis to generate in-plane load/deformation or stress/strain history of composite laminates to the point of laminate failure.
Abstract: The BILAM code which uses constant strain laminate analysis to generate in-plane load/deformation or stress/strain history of composite laminates to the point of laminate failure is described The program uses bilinear stress-strain curves to model layer stress-strain behavior Composite laminates are used for flywheels The use of this computer code will help to develop data on the behavior of fiber composite materials which can be used by flywheel designers In this program the stress-strain curves are modelled by assuming linear response in axial tension while using bilinear approximations (2 linear segments) for stress-strain response to axial compressive, transverse tensile, transverse compressive and axial shear loadings It should be noted that the program attempts to empirically simulate the effects of the phenomena which cause nonlinear stress-strain behavior, instead of mathematically modelling the micromechanics involved This code, therefore, performs a bilinear laminate analysis, and, in conjunction with several user-defined failure interaction criteria, is designed to provide sequential information on all layer failures up to and including the first fiber failure The modus operandi is described Code BILAM can be used to: predict the load-deformation/stress-strain behavior of a composite laminate subjected to a given combination of in-plane loads, and make analytical predictions ofmore » laminate strength« less

2 citations