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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Fatigue Response of Centrally Notched APC-2 Composite Laminates at Elevated Temperature

Tseng, Yu-Chung 29 June 2006 (has links)
This thesis was concerned on the investigation of mechanical properties of centrally notched and unnotched AS-4/PEEK (APC-2) composite laminates due to static tensile and tension-tension (T-T) fatigue tests empirically and systematically. Then, statistical analyses were used to determine and quantify the significant thermomechanical variables that influence the durability/life of the composite laminates. Typical laminates were made from sixteen prepregs of APC-2 and manufactured by a modified curing process. After drilling one hole with various diameters in the center of the samples respectively, the lay-ups were conducted on tension fracture and T-T fatigue test at different temperatures. From the parametric study we achieved the important results as follows. The cross-ply laminate possesses the higher ultimate strength, fatigue strength and longitudinal stiffness than those of the quasi-isotropic at the same temperature. Notch effect decays the laminate strength seriously, but changes the stiffness irregularly. As test temperature rising both strength and stiffness of lay-ups degrade significantly. Combining both effects of notch and temperature under severe environmental condition, it is found the cross-ply laminate possesses more resistance than that of the quasi-isotropic to cyclic loading. However, the quasi-isotropic laminate is more capable of sustaining the original strength than that of the cross-ply. Finally, the multiple regression analysis results showed that the hygrothermal environmental effects and cyclic loading were decoupled for APC-2 composite system. A semi-empirical model, reliably set up after the said programs, predicts conservative values, and should be adequate for use in preliminary designs. That is the main contribution in this study. Also, for the purposes of design and application, the predicted models efficiently treat experimental data instead of conventional curve-fitting methods.

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