Thermal and crystallinity profiles in laminates manufactured with automated thermoplastic tow placement process

Automated Tow Placement (ATP) is an increasingly desirable manufacturing technique for composite materials for aerospace applications. Historically, thermoset composites have been the desired material for ATP. However, high performance thermoplastics have proven they can perform as well as the thermoset matrix. The three main goals to further the research on thermoplastics used in ATP are the following. First, to model the crystallinity level of a thermoplastic composite material with Differential Scanning Calorimetry (DSC) experiments on thermoplastic films. Second, to provide a thermal analysis through the thickness of the material profile and determine cooling rates that occur in carbon fiber-thermoplastic matrix laminates during processing. Last, to measure by DSC method the post processing crystallinity levels through the thickness of a laminate manufactured in ATP.;Generally, the material properties are related to the crystallinity level found in the thermoplastic matrix. Since it does not require the secondary post cure step as thermoset composites require, the ATP manufacturing process for thermoplastic composites is an in-situ method. This thesis seeks to provide more clarity in modeling crystallinity levels and the ATP manufacturing process for thermoplastic composites.;A set of DSC experiments using isothermal and dynamic cooling measured the crystallinity levels in thermoplastic films. Each experiment was compared with models from literature. After comparing three different models, none fit well to the experimental data. In order to fit properly, the constants in the literature models had to be refit to the data collected by method of least squares; however, the models fit well for the slower cooling rates only. Experiments on ATP to measure the temperatures and calculate the cooling rates through the part thickness showed that the cooling rate is affected by the material that the composite tow is laid onto. The same manufactured parts that had thermocouples implanted were also used to test the crystallinity levels through three sections of the part thickness. There was not much difference in crystallinity level through the thickness since the material used is a high crystalline material.