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Full-Text Articles in Engineering Science and Materials
Fatigue Response Of Cracked Aluminum Panel With Partially Bonded Composite Patch, Jason J. Denney
Fatigue Response Of Cracked Aluminum Panel With Partially Bonded Composite Patch, Jason J. Denney
Theses and Dissertations
More and more aircraft, both commercial and military, are being called upon to fly well beyond their economic and structural service lives. Budget cuts and dwindling new aircraft development has forced the United States Air Force (USAF) to look toward more reliable structural repairs. One of these repair techniques, which was the subject of this study, is the repair of metallic aircraft structures using high strength composite materials. This study investigated the fatigue response of a precracked, 508x1 52x1 mm, 2024-T3 aluminum panel repaired with a partially bonded, unidirectional, three-ply boron/epoxy composite reinforcement with ply lengths of 68, 56 and …
Thermal Stresses In End-Heated Layered Media, Jerry R. Couick
Thermal Stresses In End-Heated Layered Media, Jerry R. Couick
Theses and Dissertations
Thermal stresses in semi-infinite layered beams heated on the end are calculated using an extension to simple bimetallic thermostat theory. Recently, researchers have used the concept of interfacial compliance to determine interlaminar stresses in a simple thermostat of finite length subjected to a uniform temperature increase. In the present work, the thermostat theory is extended to apply to the beams of interest. A closed-form solution to the problem is obtained. It is not applicable within about one beam thickness (St Venant boundary region) of the end. Various classes of layered materials are analyzed to determine if significant stresses exist outside …
Investigation Of Residual Strength And Fatigue Life Of Unstiffened Aluminum Panels With Multiple Site Damage, Mark C. Cherry
Investigation Of Residual Strength And Fatigue Life Of Unstiffened Aluminum Panels With Multiple Site Damage, Mark C. Cherry
Theses and Dissertations
Multiple Site Damage MSD is the occurrence of small fatigue cracks at several sites within aircraft structures. This is important since it may lower the residual strength and fatigue life of the structure beyond what can be predicted using the damage tolerance technique based on a single crack, currently in use to design aircraft structures. This study investigated the effects of MSD on unstiffined panels. MSD usually occurs at rivet holes, or other stress concentration locations within an aircraft structure. This study simulated rivet holes with MSD, by using holes of constant diameter with small cracks, evenly spaced across the …
Thermo-Mechanical Fatigue Behavior Of Cross-Ply Ceramic Matrix Composite Under Tension-Tension Loading, Dana G. Allen
Thermo-Mechanical Fatigue Behavior Of Cross-Ply Ceramic Matrix Composite Under Tension-Tension Loading, Dana G. Allen
Theses and Dissertations
The purpose of this study was to investigate the combined effect of cyclic temperature and loading on the fatigue life of a ceramic matrix composite with a cross ply lay-up. The material used in this study was a potassium borosilicate glass (BSG) doped magnesium aluminosilicate (MAS) cordierite matrix reinforced with Nicalon (silicon carbide, SiC) fibers in a [0/90]4s lay-up. Thermomechanical fatigue (TMF) tests were performed with a period of 180 seconds/cycle, or 0.00556 Hz, and a triangular wave-form. The temperature was cycled between 566°C and l093°C, and the stress levels varied between 60 MPa and 145 MPa. All tests …
Nonlinear Geometric And Material Behavior Of Composite Shells With Large Strains, Scott A. Schimmels
Nonlinear Geometric And Material Behavior Of Composite Shells With Large Strains, Scott A. Schimmels
Theses and Dissertations
A two-dimensional, geometrically and materially nonlinear shell theory applicable to arbitrary geometries described by orthogonal curvilinear coordinates and encompassing large displacements, moderate rotations for large strain situations has been developed. Additionally, the theory includes Jacobian transformation matrices, based upon displacement parameters, for the Cauchy - 2nd Piola-Kirchhoff stress-state and the Cauchy (Almansi) - Green strain-state transformations, and a layered material approach is included for the elastoplastic analysis to allow for variation of plasticity through-the-thickness. Doubly curved 20, 28, and 36 degree-of-freedom finite elements are defined based on specialization of the theory to spherical coordinates. The computer program includes algorithms for …