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Full-Text Articles in Engineering
Non-Destructive Evaluation Of Aerospace Composites, Jeremy D. Johnson
Non-Destructive Evaluation Of Aerospace Composites, Jeremy D. Johnson
Theses and Dissertations
Five methods of non-destructive material evaluation (NDE) were used to inspect various forms of damage commonly found in aerospace fiberglass composites: voids, edge and sub-surface delaminations, surface burning, and cracking. The images produced by X-ray, X-ray Computed Tomography, terahertz (THz) imaging, ultrasound, and flash IR thermography were analyzed for the detection of defects. Test results and analysis of each NDE method's capabilities provide a comparison study of conventional techniques versus the emerging technology of THz imaging for the non-destructive evaluation of aerospace composite materials. A comparison guide to the five methods' damage detection effectiveness for fiberglass composites is provided by …
Effect Of Prior Aging On Fatigue Behavior Of Im7/Bmi 5250-4 Composite At 191°C, Christine G. Ladrido
Effect Of Prior Aging On Fatigue Behavior Of Im7/Bmi 5250-4 Composite At 191°C, Christine G. Ladrido
Theses and Dissertations
IM7/BMI 5250-4 with carbon fiber orientations [± 45] and [0/90] were aged in air at 191 °C for up to 1000 hours. The weight loss was analyzed during the aging process. Tension to failure tests were performed on both the unaged and aged specimens to establish a baseline for the Ultimate Tensile Strengths and Young's Modulus. Tension-tension cyclic load fatigue testing was conducted on the specimen to determine the effect of prior aging on the fatigue response of the composite. Cyclic strain accumulation was not influenced by prior aging, but it was influenced by the stress levels applied. [± 45] …
High Temperature Chemical Degradation Of Pmr-15 Polymer Resins, Grant W. Robinson
High Temperature Chemical Degradation Of Pmr-15 Polymer Resins, Grant W. Robinson
Theses and Dissertations
PMR-15 is a polymer resin for glass and carbon reinforced composites used for high temperature, civilian and military aerospace applications. The harsh environments of PMR-15 applications lead to long term structural degradation and, in turn, impact the readiness capabilities of the system. This study investigated the thermal and oxidative degradation of PMR-15 neat resin powder through the use of thermal gravimetric analysis (TGA) in oxygen, argon and air at isothermal hold temperatures of 260, 288, 316, and 343 °C for 250 hours. The TGA measured the degradation by recording the change in neat resin powder mass versus time. The qualitative …
Nonlinear Large Deformation Theory Of Composite Arches Using Truncated Rotations, Daniel A. Miller Ii
Nonlinear Large Deformation Theory Of Composite Arches Using Truncated Rotations, Daniel A. Miller Ii
Theses and Dissertations
This research has been directed toward capturing large cross sectional rotation during bending of composite arches. A potential energy based nonlinear finite element model that incorporates transverse shear strain was modified to include large bending rotations. Large rotation kinematics were derived in a vector format leading to nonlinear strain that was decomposed into convenient forms for inclusion in the potential energy function. Problem discretization resulted in a finite element model capable of large deformations. Riks method and displacement control solution techniques were used. Numerous problems and examples were compared and analyzed. Code vectorization and parallelization were briefly examined to improve …