Michael W. Hyer

Bio: Michael W. Hyer is an academic researcher from Virginia Tech. The author has contributed to research in topics: Buckling & Composite laminates. The author has an hindex of 27, co-authored 131 publications receiving 4784 citations. Previous affiliations of Michael W. Hyer include Areva & Langley Research Center.

Stress analysis of fiber-reinforced composite materials

Abstract: 1 Fiber-Reinforced Composite Materials2 Linear Elastic Stress-Strain Characteristics of Fiber-Reinforced Material3 Prediction of Engineering Properties Using Micromechanics4 The Plane-Stress Assumption5 Plane-Stress, Stress-Strain Relations in a Global Coordinate System6 Classical Lamination Theory: The Kirchoff Hypothesis7 Classical Lamination Theory: Lamination Stiffness Matrix8 Classical Lamination Theory: Additonal Examples9 Failure Theories for Fiber-Reinforced Materials Maximum Stress Criterion10 Failure Theories for Fiber-Reinforced Materials The TSAI-Wu Criterion11 Environmentally-Induced Stresses in Laminates12 Through-Thickness Laminate Strains13 Introduction to Fiber-Reinforced Laminated Planes14 Appendix Manufacturing Composite Laminates

Some Observations on the Cured Shape of Thin Unsymmetric Laminates

Abstract: This paper discusses the fact that the cured shape of thin unsymmetric laminates do not conform to the predictions of classical lamination theory. Rather than being saddle shaped, as predicted by the classical theory, the paper shows that thin unsymmetric laminates cure into a shape of a right circular cylinder. This anomalous behavior has been observed by many but the paper serves to quantify the effect and to inspire investigators to begin thinking about using the phenomenon to advantage. The paper indicates that the anomalous behavior is repeatable and that thicker laminates con form to the predictions of the classical theory. Laminates of the [0/902 /θ ]T, [02 /θ2 ] T and [04 /θ4 ] T families are investigated for this be havior and it is shown the principal curvature directions of the cylindrical shapes are predictable.

Calculations of the Room-Temperature Shapes of Unsymmetric Laminatestwo

Abstract: A theory explaining the characteristics of the cured shapes of unsymmetric laminates is presented. The theory is based on an extension of classical lamination theory which accounts for geometric nonlinearities. A Rayleigh-Ritz approach to minimizing the total potential energy is used to obtain quantitative information regarding the room temperature shapes of square T300/5208 (0(2)/90(2))T and (0(4)/90(4))T graphite-epoxy laminates. It is shown that, depending on the thickness of the laminate and the length of the side the square, the saddle shape configuration is actually unstable. For values of length and thickness that render the saddle shape unstable, it is shown that two stable cylindrical shapes exist. The predictions of the theory are compared with existing experimental data.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

Abstract: 1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Mechanics of Composite Materials with MATLAB

Abstract: Linear Elastic Stress-Strain Relations- Elastic Constants Based on Micromechanics- Plane Stress- Global Coordinate System- Elastic Constants Based on Global Coordinate System- Laminate Analysis - Part I- Laminate Analysis - Part II- Effective Elastic Constants of a Laminate- Failure Theories of a Lamina- to Homogenization of Composite Materials- to Damage Mechanics of Composite Materials

On the Role of Nonlinearities in Vibratory Energy Harvesting: A Critical Review and Discussion

Abstract: The last two decades have witnessed several advances in microfabrication technologies and electronics, leading to the development of small, low-power devices for wireless sensing, data transmission, actuation, and medical implants. Unfortunately, the actual implementation of such devices in their respective environment has been hindered by the lack of scalable energy sources that are necessary to power and maintain them. Batteries, which remain the most commonly used power sources, have not kept pace with the demands of these devices, especially in terms of energy density. In light of this challenge, the concept of vibratory energy harvesting has flourished in recent years as a possible alternative to provide a continuous power supply. While linear vibratory energy harvesters have received the majority of the literature’s attention, a significant body of the current research activity is focused on the concept of purposeful inclusion of nonlinearities for broadband transduction. When compared to their linear resonant counterparts, nonlinear energy harvesters have a wider steady-state frequency bandwidth, leading to a common belief that they can be utilized to improve performance in ambient environments. Through a review of the open literature, this paper highlights the role of nonlinearities in the transduction of energy harvesters under different types of excitations and investigates the conditions, in terms of excitation nature and potential shape, under which such nonlinearities can be beneficial for energy harvesting. [DOI: 10.1115/1.4026278]

In-plane response of laminates with spatially varying fiber orientations - Variable stiffness concept

Abstract: A solution to the plane elasticity problem for a symmetrically laminated composite panel with spatially varying fiber orientations has been obtained. The fiber angles vary along the length of the composite laminate, resulting in stiffness properties that change as a function of location. This work presents an analysis of the stiffness variation and its effects on the elastic response of the panel. The in-plane response of a variable stiff ness panel is governed by a system of coupled elliptic partial differential equations/Solving these equations yields the displacement fields, from which the strains, stresses, and stress resultants can be subsequently calculated. A numerical solution has been obtained using an iterative collocation technique. Corresponding closed-form solutions are presented for three sets of boundary conditions, two of which have exact solutions, and therefore serve to validate the numerical model. The effects of the variable fiber orientation on the displacement fields, stress resultants, and global stiffness are analyzed.