During the fabrication of a filament-wound composite case, which includes the winding and cure stages, the tension in the fiber can change significantly. If the level of fiber tension decreases excessively during fabrication, fiber slippage and clumping can occur. The resulting resin rich areas can significantly decrease the strength of the composite case. The objectives of the present investigation were 1) to measure the change in fiber tension during the winding and cure of a composite case wound with prepreg material, and 2) to calculate the change in tension during cure using a simulation computer program. Of particular interest was the loss of fiber tension due to resin flow (RFTL). A total of twenty-four tension loss experiments were performed using Amoco’s Thornel T40 fiber and T40/1908 prepreg materials. The parameters which were varied in the experiments were spool tension, oven heating rate, and the number of composite layers. Some of the experiments were designed to isolate and measure RFTL by comparing the changes in tension of winds of dry fiber and prepreg material. This method was not successful due to a similarity in prepreg and dry fiber tension loss characteristics. Low spool tensions were found to result in more tension loss due to resin flow (RFTL). RFTL was also greater for an increased number of layers, but was not affected by oven heating rate. During winding, significant tension loss occurred, probably due to deformation of the prepreg tow at room temperature. The change in fiber tension during cure was calculated using an existing cure simulation code (FWCURE) which was modified in this work to include the contribution to fiber tension made by the thermal expansion of the mandrel during cure. The revised code is called FWEXPAND. By adjusting the permeability model in FWEXPAND, the fiber tension during the cure of a single layer wind was accurately calculated. The predicted total RFTL of two multi-layer winds agreed reasonably well with the measured RFTL, but the rate of tension loss was overpredicted. Complete RFTL and full compaction occurred during the first ramp of the cure cycle in all of the experiments. / Master of Science