There is tremendous need to integrate carbon fiber composites for light-weighting in the transportation sector, especially for automotive composites and in energy generation space associated with wind turbine manufacturing. Tensile properties of carbon fibers are fundamental to designing fiber reinforced polymers and carbon/carbon composites. Carbon fiber suppliers typically follow general guidelines prescribed in the relevant standards (ASTM D4018) to prepare resin reinforced carbon fiber tows for determining the tensile properties. In this study, the effect of manufacturing process associated with carbon fiber tows was evaluated using two methods involving manual tensioned strands or using automated spool method. Important effects associated with fiber spacing, cross-sectional morphology of the infused tows are reported in this study. Single fiber mechanical properties are determined to obtain relationship from multiple length scales and the role of interfacial behavior between the carbon fiber and resin system using single fiber fragmentation. These results, for the first time, revealed important relationships between single fiber, interface, and infused tow based mechanical properties. A new concept for deformation response of infused tows, limit stress, demonstrated a connection in the nonlinearity nature of tensile modulus seen for carbon fibers in single fiber state and in tow format. Limit stress showed good representation of the relative role of relationships (interfacial behavior, crack propagation, and stress transfer) from limit stress to failure stress. Three low-cost precursors, oxidized PAN, and carbon fiber, from the Carbon Fiber Technology Facility with differences in spin finish and/or tenacity are studied in detail through various stages of oxidative stabilization and carbonization to develop improved understanding of the precursor properties and final textile PAN based carbon fiber properties. A systematic approach consisting of DSC, TGA, FT-IR, XRD, single fiber testing, and infused tow testing were considered in evaluating the process-structure-tensile property relationship for the three precursors. The results identified the role of spin finish and tenacity on the performance of low-cost carbon fiber. This part of the research provides an important conclusion that the carbon fiber manufacturing process using textile PAN precursors is industrially robust and is not strongly dependent on precursor tenacity or surface finish.