ABSTRACT PEEK matrix reinforced by carbon fibers as one thermoplastic composite material is studied. Thermoplastic composites have the advantages of high specific stiffness and strength, longer fatigue life, good resistance to moisture absorption and high temperature condition. The thesis is aimed to investigate the mechanical properties and fracture mechanism of the centrally notched AS-4/PEEK composite laminates subjected to tension-tension fatigue loading at elevated temperature. We use three common types of laminates, such as cross-ply , quasi-isotropic and angle-ply . After centrally notched, we first obtain the base-line data of mechanical properties by tensile tests at five different temperatures, such as 25¢J¡B75¢J¡B100¢J¡B125¢J¡B150¢J. Then, the fatigue tests are conducted, we receive the fatigue strength and life and establish the stress-life curves. The fatigue characteristics and fracture mechanism of a centrally notched composite laminate at elevated temperature are also recorded and observed. The empirical results can be concluded as follows. At the same temperature, the laminate of cross-ply possesses the largest ultimate strength and fatigue strength, quasi-isotropic the second angle-ply the smallest. As for the elastic modulus, the laminate of cross-ply is larger than that of quasi-isotropic. However, the large strain of angle-ply is within the plastic range that is out of the limit of the study. Thus, a further investigation is needed for angle-ply laminates alone. After centrally notched, the net area is reduced of the specimen, and then the elastic modulus is raised and the ultimate strength and fatigue strength of composite materials are lower. As the temperature increasing, the ultimate strength, fatigue strength and elastic modulus are all decreasing.

The Joint Architecture for Unmanned Systems (JAUS) is an emerging SAE standard for messaging between and within unmanned systems, enhancing interoperability, code reusability, and modularity. To date, most JAUS implementations have been produced by developers in the JAUS Working Group, who have an intimate understanding of the intent of the specification. As a result, the standards documents produced by the Working Group sometimes omit key implementation assumptions the developers had in mind. The work described in this thesis is intended to provide objective feedback from the viewpoint of a developer who began implementing JAUS independent of the standards committee and is now embedded in the Experimentation Task Group. This paper presents the lessons learned through this journey, from development of the first-ever JAUS software development toolkit for the LabVIEW programming language, through participation in Experimentation Task Group interoperability exercises 2.75 and 3.0, and to the establishment of the first internet-based testing environment for JAUS. The results of this experience are presented as a collection of recommendations to the standards committee, organized in a series of diverse implementation case studies. / Master of Science

ABSTRACT This thesis is aimed to investigate the fatigue life, strength, damage and fracture process in AS-4/PEEK APC-2 composite laminates subjected to both elevated temperature and loading sequences. Our main work is experiment. All specimens are 16-ply thick with lay-up of quasi-isotropic laminates. We accomplish static tensile test, fatigue test of constant stress amplitude, and two-step loading at elevated temperatures, i. e., 75¢Jand 125¢J. The residual strength and stiffiness are obtained. We also use Miner¡¦s rule to analyze the data acquired from experiment and to discuss the fatigue properties and fracture mechanism subjected to both elevated temperatures and loading sequences of combination. Finally, we perform ultrasonic C-Scan non-destructive test to examine laminates. In comparsion with experimental data, we can further understand the damage process and fracture mechanism in laminates. The experimental results can be concluded as follows. The damage of specimens at 125¢J is more serious than that at 75¢J.Furthermore, if the loading sequence is low-high, the cumulative damage value will be smaller than 1,whilst it will be larger than 1 due to reverse loading sequence. The sequence of decreasing residual strength and residual stiffiness of specimen associated with the temperature and stress level in combination is high temperature¡Ðlow stress, low temperature¡Ðlow stress, high temperature¡Ðhigh stress and low temperature¡Ðhigh stress.