Nano-Engineered Sandwich Interlayers for Simultaneous Functionalization and Delamination Resistance in CFRPs

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Carbon fiber-reinforced polymers (CFRP) are crucial in aerospace and automotive industries for their high strength-to-weight ratio.
• Integrating functionality into CFRP without compromising mechanical properties, especially delamination resistance, is a significant challenge.
• Functional interlayers offer a route to enhanced material performance but often increase structural complexity.

Purpose of the Study:

• To investigate the effectiveness of a novel sandwich-structured interlayer (GF/CNTs-CNTv/GF) for enhancing the Mode II interlaminar fracture toughness of CFRP.
• To examine the influence of interlayer architecture and carbon nanotube (CNT) loading on delamination resistance.
• To elucidate the toughening mechanisms responsible for improved interlaminar fracture toughness.

Main Methods:

• Fabrication of CFRP laminates with sandwich-structured interlayers containing varying CNT concentrations.
• Systematic evaluation of Mode II interlaminar fracture toughness using standardized testing methods.
• Microstructural analysis of delamination failure modes and toughening mechanisms via scanning electron microscopy (SEM) and ultra-depth-of-field 3D microscopy.

Main Results:

• An optimal CNT loading of 1.0 wt% in the interlayer resulted in a maximum Mode II interlaminar fracture toughness (G_IIC) of 1644.8 J/m².
• This represents a 103.06% increase in G_IIC compared to the reference CFRP laminate without the functional interlayer.
• Failure analysis revealed a transition from interfacial debonding to a robust mesh-block composite delamination pattern, indicating enhanced energy dissipation.

Conclusions:

• CNT-modified sandwich interlayers effectively enhance the interlaminar fracture toughness of CFRP.
• The improved performance is attributed to synergistic nano-engineering effects, including matrix toughening and CNT 'nano-anchoring'.
• This approach offers a promising strategy for developing multifunctional CFRP with superior delamination resistance for demanding applications.