Engineering Commons^™

Innovations In Aligned And Overmolded Long Fiber Thermoplastic Composites, Shailesh P. Alwekar

Doctoral Dissertations

Long fiber thermoplastic (LFT) composite materials are increasingly used in high performance lightweight automotive, sporting, and industrial applications. LFT composites are processed with extrusion-compression molding (ECM) and/or injection molding (IM). Melt extrusion offers unique opportunities to align long fibers in a thermoplastic polymer melt. The properties of LFT materials are highly influenced by processing techniques which leads to different porosity content, fiber length distribution, and fiber orientation distribution. Hence, it is important to understand the various LFT processing techniques and their effect on mechanical, thermal, and microscopic properties.

The fundamental process-property relationships in LFT composites are investigated in this dissertation. …

Interlaminar Damage Detection In Composite Materials, Hariharan Rangarajan

Williams Honors College, Honors Research Projects

Using ceramic matrix composites (CMCs) for high-temperature applications in jet engines increases durability and reduces weight and cooling requirements resulting in improved efficiency and fuel savings. Understanding, detecting, and monitoring different types of damage is essential to achieve optimal performance of CMC components. The Direct Current Potential Drop (DCPD) method is a non-destructive technique of estimating damage in composite materials.

DCPD technique works by measuring nodal potential differences when current is flown through the material. Direct current spreading in different woven and laminate composites is modeled to follow a ladder resistor network in which the nodal voltages decrease exponentially as …

Single-Sided Noninvasive Inspection Of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography, Matthew A. Lange

Theses and Dissertations

As aircraft age, corrosion forms upon unobservable surfaces, particularly at the junction of the sheet aluminum and the steel rivets used to attach the sheets to the airframe, degrading the aircraft s airworthiness. Previous research developed a noninvasive technique for the evaluation of the material composition of aluminum surfaces, utilizing the information encoded in the energy spectra of Compton-scattered gamma emissions. The spectra are gathered by a six-element, high purity germanium detector array. A, first principles, deterministic computer code is used to reconstruct a two-dimensional map of the electron density of aluminum samples. Previous efforts, to image pure aluminum samples, …