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Solving Nonlinear Composite Material Problems Using The Automated Structural Optimization System (Astros), Robert Bolha
Solving Nonlinear Composite Material Problems Using The Automated Structural Optimization System (Astros), Robert Bolha
Theses and Dissertations
Most advanced composite materials have nonlinear stress versus strain curves--grossly so in the laminas shear direction. If linear approximations are used, overly conservative design will result. This thesis expands the usefulness of the Automated Structural Optimization System (ASTROS) finite element (FE) program by incorporating a newly developed capability to include material nonlinearities. By dividing a FE problem into several intervals, and incorporating the changing nature of the nonlinear material properties within each element, a good approximation of the laminate's actual stresses and strains can be obtained without the undue experimentation involved in testing every individual configuration. Each material property is …
Behavior Of A Titanium Matrix Composite Under Quasi-Static Tensile And Compressive Loading, Keith L. Bearden
Behavior Of A Titanium Matrix Composite Under Quasi-Static Tensile And Compressive Loading, Keith L. Bearden
Theses and Dissertations
Quasi-Static tensile and compressive testing was performed on a unidirectional titanium matrix composite. The specific material was SCS-9/β 21S. The initial tensile and compressive modulus for both laminates was the same. The ninety degree laminate had a tensile and compressive modulus of 115.89 GPa. The zero degree laminate had a tensile and compressive modulus of 197.51 GPa. The ninety degree laminate exhibited a three stage stress/strain response in tension. The first stage is completely linearly elastic, however, partial debonding of the fiber from the matrix was observed. This partial debased did not effect the stress/strain response. The second stage is …
Stratified Plate Model For Composite Plate Analysis, Richard A. Coveno
Stratified Plate Model For Composite Plate Analysis, Richard A. Coveno
Theses and Dissertations
This study continues the investigation of the stratified plate model for the analysis of composites plates. The strata theory models a composite plate as a stack of isotropic matrix and orthotropic, fiber dominated layers. Energy methods are used to derive a set of partial differential equations and boundary conditions as a function of the displacement. An assumed displacement field, of a polynomial in z and a Sine/Cosine function in x and y, generates a solution to a simply supported composite plate with cross plies. A cylindrical bending example is also solved with a polynomial in z and Sine/Cosine function in …
Effect Of Thickness And Ply Layup On The Collapse Characteristics Of Cylindrical Composite Shells With Large Cutouts, James C. Hatfield
Effect Of Thickness And Ply Layup On The Collapse Characteristics Of Cylindrical Composite Shells With Large Cutouts, James C. Hatfield
Theses and Dissertations
This study involved a numerical and experimental investigation of the geometric instability(collapse loads/displacements) of vertically unsupported graphite/epoxy cylindrical shell panels undergoing axial compression. Symmetric quasi-isotropic and cross-ply laminates, with and without 4 X4 centralized cutouts, were investigated for three thicknesses:8,16,and 24 plies. The experimental data was compared to results from SHELL, a geometrically nonlinear finite-element computer program which incorporates a parabolic transverse shear strain distribution through the thickness. Good correlation was obtained for shells with large cutouts between the SHELL numerical data and the experimental results. This research verified that the SHELL program will provide good predictions of the collapse …