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The principles of mechanics are utilized for the description of the behavior of fiber-reinforced composites. Principal components of elastic moduli and strength for an orthotropic material are established as the intrinsic macromechanical properties. Micromechanics analyses provide a rational design basis of these properties from the material and geometric properties of the constituent materials. A bridge between the properties of the constituent materials and the structural behavior of a laminated anisotropic composite can then be established. Combined materials and structural design become feasible. Finally, test methods of composite materials are evaluated. The principles of mechanics can be used to select the material properties to be tested and the appropriate test procedures to be followed.

The principles of mechanics are utilized for the description of the behavior of fiber-reinforced composites. Principal components of elastic moduli and strength for an orthotropic material are established as the intrinsic macromechanical properties. Micromechanics analyses provide a rational design basis of these properties from the material and geometric properties of the constituent materials. A bridge between the properties of the constituent materials and the structural behavior of a laminated anisotropic composite can then be established. Combined materials and structural design become feasible. Finally, test methods of composite materials are evaluated. The principles of mechanics can be used to select the material properties to be tested and the appropriate test procedures to be followed.

The principles of mechanics are utilized for the description of the behavior of fiber-reinforced composites. Principal components of elastic moduli and strength for an orthotropic material are established as the intrinsic macromechanical properties. Micromechanics analyses provide a rational design basis of these properties from the material and geometric properties of the constituent materials. A bridge between the properties of the constituent materials and the structural behavior of a laminated anisotropic composite can then be established. Combined materials and structural design become feasible. Finally, test methods of composite materials are evaluated. The principles of mechanics can be used to select the material properties to be tested and the appropriate test procedures to be followed.

The principles of mechanics are utilized for the description of the behavior of fiber-reinforced composites. Principal components of elastic moduli and strength for an orthotropic material are established as the intrinsic macromechanical properties. Micromechanics analyses provide a rational design basis of these properties from the material and geometric properties of the constituent materials. A bridge between the properties of the constituent materials and the structural behavior of a laminated anisotropic composite can then be established. Combined materials and structural design become feasible. Finally, test methods of composite materials are evaluated. The principles of mechanics can be used to select the material properties to be tested and the appropriate test procedures to be followed.

Mechanics of Composite Materials and Structures 1996: Volume 3 , Issue CONTENTS. Digitized from IA1643510-07 . Next issue: sim_mechanics-of-advanced-materials-and-structures_1996-03_3_1 .

Mechanics of Composite Materials and Structures 1996: Volume 3 , Issue CONTENTS. Digitized from IA1643510-07 . Next issue: sim_mechanics-of-advanced-materials-and-structures_1996-03_3_1 .

Mechanics of Composite Materials and Structures 1996: Volume 3 , Issue CONTENTS. Digitized from IA1643510-07 . Next issue: sim_mechanics-of-advanced-materials-and-structures_1996-03_3_1 .

Mechanics of Composite Materials and Structures 1996: Volume 3 , Issue CONTENTS. Digitized from IA1643510-07 . Next issue: sim_mechanics-of-advanced-materials-and-structures_1996-03_3_1 .

Mechanics of Composite Materials and Structures 1996: Volume 3 , Issue CONTENTS. Digitized from IA1643510-07 . Next issue: sim_mechanics-of-advanced-materials-and-structures_1996-03_3_1 .

Mechanics of Composite Materials and Structures 1996: Volume 3 , Issue CONTENTS. Digitized from IA1643510-07 . Next issue: sim_mechanics-of-advanced-materials-and-structures_1996-03_3_1 .

This report presents the work performed under ONR contract number N00014-85-K-0733 during the period 1985-1990. The main objective of the project was to develop a computational facility for inelastic analysis of fibrous composite materials based on micromechanics. The theoretical work focused on development of micromechanical models for thermoplastic and thermoviscoplastic fibrous composites based on experimental observations of certain phenomena found in unreinforced and fiber reinforced metals. Implementation of the material models in computational procedures for analysis of composite materials and structures was an important part of the research. Accomplishments in these areas and in development of a layer-wise composite shell element, also performed under this contract, are described.

The Institute for Structural Mechanics of the German Aerospace Research Establishment (DFVLR) has conducted a research program aimed at the characterization of the fracture behavior of carbon-fiber-reinforced epoxy resins. The research effort encompassed a comprehensive experimental and analytical investigation of the response of test specimens under a broad range of material, loading and environmental parameters. By combining an evaluation of global laminate properties with an investigation of micro- and macroscopic modes of failure, the understanding of the fracture and fatigue behavior of carbonfiber-reinforced composites was enhanced. It is expected that the results of the research program and their representation in the form of tables, figures, graphs and maps will assist the design engineer and lead to improved engineering concepts. Volume 2 includes the following: Response of Mechanically Fatigued Notched Specimens; Response of Thermally Fatigued Un-Notched Specimens; Strain Capabilities and Strain Rate Effects in Epoxy Resins and Laminates; Radiative and Oxidative Effects; FractographicaL Investigations; Fracture Mechanics Aspects; Evaluation of Fracture Models; and Mechanisms of Fracture. Keywords: Fiber reinforced composites; Dynamic test; Thermal cycling; Quality control; Static test; Stress Concentration.

Mechanics of Composite Materials 2006: Volume 42 , Issue Index. Digitized from IA1642916-04 . Next issue: sim_polymer-mechanics_january-february-2006_42_1 .

The Institute for Structural Mechanics of the German Aerospace Research Establishment (DFVLR) has conducted a research program aimed at the characterization of the fracture behavior of carbon-fiber-reinforced epoxy resin. The research effort encompassed a comprehensive experimental and analytical investigation of the response of test specimens under a broad range of material, loading and environmental parameters. By combining an evaluation of global laminate properties with an investigation of micro- and macroscopic modes of failure, the understanding of the fracture and fatigue behavior of carbonfiber-reinforced composites was enhanced. It is expected that the results of the research program and their representation in the form of tables, figures, graphs and maps will assist the design engineer and lead to improved engineering concepts. This volume includes the following appendices: Fatigue Response of Notched Graphite-Epoxy Lamines; Influence of Simulated Space Environment on Carbon Fiber Reinforced Plastic (CFRP); Notched Strength of Composite Laminates; and Growth of Delaminations under Fatigue Loading. Keywords: Dynamic tests; Thermal cycling; Static tests; Quality control; Stress concentration.

Mechanics of Composite Materials is an active publication covering scientific research related to composite materials. It was established in 1965 and is published bi-monthly by Springer New York LLC. The journal presents experimental and theoretical research on the mechanical properties and behavior of composite materials as well as matrices and fibers. It includes original research articles, review papers, and technical notes covering topics such as stress analysis, applied mechanics, materials science, structural mechanics, and nanocomposites. Mechanics of Composite Materials can be found online at: https://www.springer.com/journal/11029 Publication History Polymer Mechanics 0032-390X Formerly (until 1979) USA United States

Mechanics of Composite Materials is an active publication covering scientific research related to composite materials. It was established in 1965 and is published bi-monthly by Springer New York LLC. The journal presents experimental and theoretical research on the mechanical properties and behavior of composite materials as well as matrices and fibers. It includes original research articles, review papers, and technical notes covering topics such as stress analysis, applied mechanics, materials science, structural mechanics, and nanocomposites. Mechanics of Composite Materials can be found online at: https://www.springer.com/journal/11029 Publication History Polymer Mechanics 0032-390X Formerly (until 1979) USA United States

Theoretical and experimental studies regarding the dynamics of composite materials are presented. Various methods for evaluating elastic constants (variational calculations, airy stress functions, elastodynamics) and recent methods of calculation for multilayers in the plastic state are described. A critical study of the various theories available for the propagation of waves and vibrations in composite materials was made (equivalent homogeneous media theory, microstructure theory, mixture theory, theory based on asymptotic development, etc. In addition, some experimental research is reviewed for the calculation of elastic constants in micropolar elasticity under a static and dynamic regime. (Author, modified-PL).

The report consists of selected abstracts presented at All-Union Conference held from 30 May to 2 Jun 89 in Volgograd, USSR. The conference was designed to give a through review of current problems and methods of design of composite materials. The report additionally highlights their physical properties and also covers important issues related to technological mechanics of composite material products.

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Mechanics of Composite Materials and Structures 1998: Volume 5 , Issue CONTENTS. Digitized from IA1643510-07 . Previous issue: sim_mechanics-of-advanced-materials-and-structures_1996-12_3_4 . Next issue: sim_mechanics-of-advanced-materials-and-structures_january-march-1998_5_1 .

The present work is concerned with development of innovative damage mechanics models for constitutive modeling of modern composite materials. Special attention is focused on micromechanical damage theories to explain and model behavior of composites based on micromechanics and micro-geometry. In particular, basic studies are performed on the notion of isotropic and anisotropic damage variables in continuum damage mechanics. Furthermore, a micromechanical damage model is presented for uniaxially reinforced composites and is analytically derived based on micromechanical bi-material arc crack solutions. Finally, a novel three-dimensional statistical micromechanical theory is proposed to investigate the nonlinear behavior of microcrack-weakened brittle solids. The theory is fundamentally different from existing effective medium theories and deterministic microcrack interaction method.

JPRS-UMS-90-005 PREX 7.13:90/005 Digitized from IA1176811-06-0023 , IA1176811-06-0024 .

Composite materials have been used for several years in thermal protection systems such as reentry vehicle nosetips and heatshields as well as in more conventional aerospace structures such as laminated wings and stabilizers in the latest aircraft. Many composite materials, e.g., ATJ-S graphite, carbon-carbon, and graphite-epoxy, exhibit different strength and stiffness behavior in tension and compression. The moduli differences range from 20% for ATJ-S graphite to between 100% and 400% for carbon-carbon. The principal objective of this research is to model the behavior of solid bodies with different elastic moduli in tension and compression as well as the behavior of laminated plates and shells that have different elastic moduli in tension and compression and lamination asymmetries. The results of this work are coordinated with research sponsored by the Air Force Materials Laboratory on nonlinear stress-strain behavior of reentry vehicle materials. This report is a summary of work done during the last five years.

Abstracts of research work efforts presented at the Army Symposium on Solid Mechanics, 1976 are presented. Fracture mechanical studies on various composites used for various military applications are described.

The Institute for Structural Mechanics of the German Aerospace Research Establishment (DFVLR) has conducted a research program aimed at the characterization of the fracture behavior of carbon-fiber-reinforced epoxy resins. The research effort encompassed a comprehensive experimental and analytical investigation of the response of test specimens under a broad range of material, loading and environmental parameters. By combining an evaluation of global laminate properties with an investigation of micro- and macroscopic modes of failure, the understanding of the fracture and fatigue behavior of carbonfiber-reinforced composites was enhanced. It is expected that the results of the research program and their representation in the form of tables, figures, graphs and maps will assist the design engineer and lead to improved engineering concepts. Keywords: Fiber reinforced composites, Dynamic test, Thermal cycling, Quality control, Static test, Stress concentrations.

The effects of materials used in composites for army aircraft applications are experimentally studied. An assortment of mechanical testing results is presented for boron/epoxy, graphite, S glass/epoxy, Thornel/epoxy, and metal alloy/epoxy composites. In addition, the effects of shapes, ply, notching, and edging in the failure of the composites are studied.

The report covers some of the principles of the mechanics relevant to the description of composite materials. The contents of these notes may provide useful information for the understanding of current publications and reports related to composite materials. Emphasis is placed on the use of indicial notation and operations. The rules governing the use of the contracted notation are also outlined. The generalized Hooke's law and its transformation properties, material symmetries, and engineering constants are also discussed. The plane strain and plane stress problems are discussed in detail. Finally, the elastic moduli of laminated anisotropic materials, and the strength of both unidirectional and laminated composites are covered.

Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. to illustrate the basic nature of composite delamination, solutions are shown for edge- delaminated and graphite-epoxy systems under uniform axial extension. Three- dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. the basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined. Influences of lamination, geometric, and crack variables on the delamination behavior are investigated.

During this seven month project efforts continued on the development of advanced analytical and numerical techniques which can be effectively combined to provide advanced thermomechanical modeling of composite materials with nonlinear constituents. The areas of emphasis during this period were: development of thermoplastic and thermoviscoplastic models of composite materials using transformation strains; finite element formulation of bimodal plasticity model in combination with various forms of dimensional reduction; idealization control for composite materials.

This report summarizes the results of a theoretical study of wave propagation, diffusion, and damage accumulation in composite materials. (Author)

A 100 millimeter (4in) cubic billet of 3-dimensional cartesian weave carbon-carbon material was received in late December, 1977. A series of tests were performed to measure mechanical properties during uniaxial tension, compression, and shear loading. Extensive test development was required as standard tests for these materials do not exist. Strain gages and extensometers were used to measure strain during loading for determination of elastic coefficients. Acoustic emission measurements were performed on selected tests to determine damage thresholds. Failure surfaces were examined in a scanning electron microscope to study failure modes. (Author)

The principles of mechanics are utilized for the description of the behavior of fiber-reinforced composites. Principal components of elastic moduli and strength for an orthotropic material are established as the intrinsic macromechanical properties. Micromechanics analyses provide a rational design basis of these properties from the material and geometric properties of the constituent materials. A bridge between the properties of the constituent materials and the structural behavior of a laminated anisotropic composite can then be established. Combined materials and structural design become feasible. Finally, test methods of composite materials are evaluated. The principles of mechanics can be used to select the material properties to be tested and the appropriate test procedures to be followed.

This report summarizes the result of research done under NASA NAG3-882 Nonlinear Mechanics of Composites with Periodic Microstructure. The effort involved the development of non-finite element methods to calculate local stresses around fibers in composite materials. The theory was developed and some promising numerical results were obtained. It is expected that when this approach is fully developed, it will provide an important tool for calculating local stresses and averaged constitutive behavior in composites. NASA currently has a major contractual effort (NAS3-24691) to bring the approach developed under this grant to application readiness. The report has three sections. One, the general theory that appeared as a NASA TM, a second section that gives greater details about the theory connecting Greens functions and Fourier series approaches, and a final section shows numerical results.

Experimental and analytical investigations of scarf joints indicate that slight bluntness of adherend tips induces adhesive stress concentrations which significantly reduce joint strength, and the stress distribution through the adhesive thickness is non-uniform and has significant stress concentrations at the ends of the joint. The laminate stacking sequence can have important effects on the adhesive stress distribution. A significant improvement in joint strength is possible by increasing overlap at the expense of raising the repair slightly above the original surface. Although a surface grinder was used to make most experimental specimens, a hand held rotary bur can make a surprisingly good scarf. Scarf joints wit doublers on one side, such as might be used for repair, bend under tensile loads and may actually be weaker than joints without doublers.

Progress is reviewed with emphasis on a model of stress intensity factors in dynamic punch test. The specimen is assumed to be initially at rest and the projectile is rigid. Impact of the rigid projectile is modeled by a constant velocity condition on the impact surface. Three support geometries are considered for each specimen geometry: a free back surface, a fixed back surface, and a two dimensional punch. Analytical approximations for the stress intensity factor history are given for short times, while dynamic quarter point finite element solutions are included for longer times. The stress intensity factor is shown to increase with time due to wave reflection in the two dimensional punch and fixed back support geometries, while it decreases with time for the free back surface. The stress intensity factors in the plate specimen are also greater than those in the edge notched specimen in all tests. For applicability to manufacturing operations and increased chance of shear dominated failure, it is recommended that the two dimensional punch or fixed back surface geometries of the plate specimen be used in experimental studies.

This report summarizes the results of a theoretical study of wave propagation, diffusion, and damage accumulation in composite materials. (Author)

The fundamental mechanics of delamination in fiber composite laminates is studied. Mathematical formulation of the problem is based on laminate anisotropic elasticity theory and interlaminar fracture mechanics concepts. Stress singularities and complete solution structures associated with general composite delaminations are determined. For a fully open delamination with traction-free surfaces, oscillatory stress singularities always appear, leading to physically inadmissible field solutions. A refined model is introduced by considering a partially closed delamination with crack surfaces in finite-length contact. Stress singularities associated with a partially closed delamination having frictional crack-surface contact are determined, and are found to be diferent from the inverse square-root one of the frictionless-contact case. In the case of a delamination with very small area of crack closure, a simplified model having a square-root stress singularity is employed by taking the limit of the partially closed delamination. The possible presence of logarithmic-type stress singularity is examined; no logarithmic singularity of any kind is found in the composite delamination problem. Numerical examples of dominant stress singularities are shown for delaminations having crack-tip closure with different frictional coefficients between general (1) and (2) graphite-epoxy composites.

Composite mechanics disciplines are presented and described at their various levels of sophistication and attendant scales of application. Correlation with experimental data is used as the prime discriminator between alternative methods and level of sophistication. Major emphasis is placed on: (1) where composite mechanics has been; (2) what it has accomplished; (3) where it is headed, based on present research activities; and (4) at the risk of being presumptuous, where it should be headed. The discussion is developed using selected, but typical examples of each composite mechanics discipline identifying degree of success, with respect to correlation with experimental data, and problems remaining. The discussion is centered about fiber/resin composites drawn mainly from the author's research activities/experience spanning two decades at Lewis.

Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extenstion. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined.

The Institute for Structural Mechanics of the German Aerospace Research Establish (DFVLR) has conducted a research program aimed at the characterization of the fracture behavior of carbon-fiber-reinforced epoxy resins. The research effort encompassd to comprehensive experimental and analytical investigation of the response of test specimens under a broad range of material, loading and environmental parameters. By combining an evaluation of global laminate properties with an investigation of miro-and macroscopic modes of failure, the understanding of the fracture and fatigue behavior of carbonfiber-reinforced composites was enhanced. It is expected that the results of the research program and their representation in the form of tables, figures, graphs and maps will assist the design engineer and lead to improved engineering concepts. Keywords: Fiber reinforced composites, Dynmaic test, Thermal cycling, Quality control, Static test, Stress concentrations, Notched specimens, Nondestructive testing.

The fundamental mechanics of delamination in fiber composite laminates is studied. Mathematical formulation of the problem is based on recently developed laminate anisotropic elasticity theory and interlaminar fracture mechanics concepts. Stress singularities and complete solution structures associated with general composite delaminations are determined. For a fully open delamination with traction-free surfaces, oscillatory stress singularities always appear, leading to physically inadmissible field solutions. A refined model is introduced by considering a partially closed delamination with crack surfaces in finite-length contact. Stress singularities associated with a partially closed delamination having frictional crack-surface contact are determined, and are found to be different from the inverse square-root one of the frictionless-contact case. In the case of a delamination with very small area of crack closure, a simplified model having a square-root stress singularity is employed by taking the limit of the partially closed delamination. The possible presence of logarithmic-type stress singularity is examined; no logarithmic singularity of any kind is found in the composite delamination problem. Numerical examples of dominant stress singularities are shown for delaminations having crack-tip closure with different frictional coefficients between general theta sub 1 and theta sub 2 graphite-epoxy composites.

This bibliography is comprised of approximately 1,600 reference citations related to four problem areas in the mechanics of failure in aerospace structures. The bibliography represents a search of the literature published in the period 1962-1976, the effort being largely limited to documents published in the United States. Listings are subdivided into the four problem areas: Hydrogen Embrittlement; Protective Coatings; Composite Materials; and Nondestructive Evaluation. An author index is included.