Carbon nanotubes (CNTs) are a potential new component to be incorporated into existing aerospace structural composites for multifunctional (mechanical, electrical, thermal, etc.) property enhancement. Although CNT properties are extraordinary when measured individually, they tend to degrade by a large factor when integrated in system (often in polymer matrices). Mechanisms and effectiveness of nano-scale CNT implementation into macro-scale structural composites are not well understood. Non-mechanical aspects of these composites are the focus of this work. As a CNT hybridized fiber polymer composite, fuzzy fiber reinforced plastic (FFRP) is developed using a scalable fabrication method that achieves uniform CNT distributions for thermal and electrical conductive networks without requiring intensive mixing which can damage CNTs. At small CNT volume fractions (∼0.5-8% V f), characterization shows significant enhancement in electrical conduction (x10 6-10 8) but limited enhancement in thermal conduction (xl.9). In addition, aligned-CNT polymer nanocomposites (A-CNT-PNCs) are being characterized as a representative volume element (RVE) of the FFRP. Experimentally obtained data on consistent A-CNT-PNC samples sets provide engineering knowledge and to achieve effective utilization of CNTs' multifunctional properties. Theoretical studies, both analytical and numerical, have been recently developed, suggesting interface effects may be a key to explaining the above limitations, including electron tunneling/hopping or phonon scattering at CNT-CNT and CNT-polymer interfaces. Multiple test techniques and property extraction methods for A-CNT-PNCs are developed and/or employed for cross-comparison. Applications of nano-engineered composites enhanced with CNTs can include lightning protection layers, electromagnetic interference shields, thermal management layers, and thermoelectrical sensor layers for airplane structures.