Polymer-based laminated composite materials are widely used in many industries due to their superior mechanical properties. The main disadvantage of using composites is their delamination failure that occurs due to poor interlaminar properties because of a lack of reinforcement through the thickness direction. One of the unique ways to address this problem in traditional composites is the use of nanoscale reinforcements such as carbon nanostructures that has demonstrated promising results during the past two decades. In the first part of this report, closed-form analytical solutions were developed for effective transverse Young’s modulus and Poisson’s ratios of a three-phase carbon nanotube (CNTs)-based orthotropic nanocomposite cylindrical model subjected to a uniform external pressure, and then solutions for deformations, strains, and stresses were obtained. In the second part of this research, design of experiment (DOE) was used to study the effects of process parameters on the tensile properties of epoxy resin per ASTM D638. The test results were used to carefully optimize the process parameters for the fabrication of our nanocomposite materials which was the main subject of this dissertation. Our previous studies had demonstrated that helical CNTs (HCNTs) perform much better than straight CNTs (SCNTs), due to a mechanical interlocking mechanism that the Heli-coil geometry of the HCNTs provides between the microfiber reinforcements and within the solidified polymeric resins. In this research, various weight percentages of HCNTs were processed and used to fabricate laminated nanocomposite panels and then mechanically tested and characterized (as per ASTM D790, D5868, D2344, D3039, and E384 standard test methods) to study the effectiveness of the HCNTs reinforcements. Overall, the test results showed significant improvements in several material properties that demonstrate the benefits of HCNTs as an effective reinforcement for highperformance structural applications of composite laminates.