Enhancement of the mechanical properties and bonding of composite laminates and assemblies using carbon nano-coils

Abstract

Composite materials are known for their low weight, high damage tolerance, multifunctionality, and excellent mechanical properties that can be tuned based on the application. However, their main disadvantages are their poor interlaminar properties and difficulties to assemble and join them together using adhesive bonds and mechanical fasteners. Generally, the assembly and joining of composite parts require machining and drilling that will cause certain damages to the machined or drilled areas (e.g., fiber breakage, fiber pull-out, resin cracking, and delamination). Due to their exceptional mechanical, thermal, electrical, optical, and absorption properties carbon nanotubes nanomaterials can be used as additional reinforcements to improve the overall mechanical properties and performance of the composite parts and assemblies. Our previous research has demonstrated that carbon nanotubes (CNTs) with Heli-coil geometries are more effective than straight CNTs [1] for the improvement of the overall mechanical properties of polymeric epoxy resin. In this report, Heli-coil CNTs (HCNTs) were used as a nanoscale reinforcement to improve the overall mechanical properties of the laminated composites and assemblies. The presence of HCNTs with a coil-like interlocking mechanism between the fiber filaments, fabric layers, and composite bonded assemblies can provide an interlocking mechanism that is expected to effectively improve the mechanical performance of the laminated composites and assemblies. Composite and HCNTs reinforced nanocomposite panels were fabricated, cut, and prepared for mechanical testing and analysis, as per ASTM standards (i.e., ASTM D790-17, ASTM D2344/2344M-16, ASTM D3039/D3039M-17, and ASTM D5868-01). The test results for flexural strength, short-beam strength, tensile strength, and single-lap shear strength of the composite and nanocomposite test samples with and without Heli-coil CNTs reinforcements were evaluated and compared, and promising results were obtained. This report simply demonstrates that Heli-coil CNTs can be used as an effective reinforcement for the enhancement of the mechanical properties of traditional composite parts and assemblies.