The effect of thin film adhesives on mode II interlaminar fracture toughness in carbon fiber composites with shape memory alloy inserts

In the current study, the production of multifunctional hybrid-stitched composites with improved interlaminar fracture toughness and electromagnetic interference shielding effectiveness is reported. Unidirectional carbon fiber-epoxy composite laminates stitched with Kevlar, nylon, hybrid stitched with both Kevlar and nylon and unstitched were prepared using resin infusion process. Representative specimens from unstitched and stitched composites were tested using rectangular waveguide and Mode I double cantilever beam tests. The Mode I experimental results showed that composite stitched with Kevlar exhibited the highest crack initiation interlaminar fracture toughness (GIC-initiation), whereas composite stitched with nylon exhibited the highest maximum crack propagation interlaminar fracture toughness (GIC-maximum). The four-hybrid stitching patterns exhibited higher GIC-initiation than the unstitched and stitched with nylon composites and lower than stitched with Kevlar composite, whereas they had higher GIC-maximum than the unstitched and stitched with Kevlar composites, although lower than stitched with nylon composite. The electromagnetic shielding effectiveness experimental results showed that stitched composites exhibited improved shielding effectiveness compared to unstitched composites. For example, composite stitched with nylon had highest shielding effectiveness value of 52.17 dB compared by the composite stitched with Kevlar which had 40.6 dB. The four hybrid-stitched composites exhibited similar shielding effectiveness with an average value of 32.75 dB compared to the unstitched composite shielding effectiveness of 22.84 dB. The experimental results comply with the initial goal of this study to manufacture multifunctional hybrid stitching composites with combined properties between Kevlar and nylon-stitched composites.

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Enhancement of fracture toughness of hierarchical carbon fiber composites via improved adhesion between carbon nanotubes and carbon fibers

Composites Part A Applied Science and Manufacturing ◽

10.1016/j.compositesa.2014.12.014 ◽

2015 ◽

Vol 71 ◽

pp. 72-83 ◽

Cited By ~ 42

Author(s):

Hansang Kim ◽

Eugene Oh ◽

H. Thomas Hahn ◽

Kun-Hong Lee

Keyword(s):

Carbon Nanotubes ◽

Fracture Toughness ◽

Carbon Fiber ◽

Carbon Fibers ◽

Fiber Composites ◽

Carbon Fiber Composites ◽

Hierarchical Carbon

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The Importance of the Mode II Term on the Analysis of Angled Cracks in Unidirectional Carbon Fiber Composites

10.1115/detc2021-67236 ◽

2021 ◽

Author(s):

Jacob Biddlecom ◽

Garrett J. Pataky

Keyword(s):

Stress Intensity Factor ◽

Regression Analysis ◽

Stress Intensity ◽

Carbon Fiber ◽

Intensity Factor ◽

Fiber Composites ◽

Shear Loading ◽

Mode Ii ◽

Carbon Fiber Composites ◽

Displacement Fields

Abstract Carbon fiber reinforced polymers (CFRP) have been used in many high-performance applications where strength to weight ratio is an important characteristic. The goal of this research was to analyze the effects of Mode II, also known as shear loading, on the displacement fields surrounding a crack for unidirectional carbon fiber composites. Tensile and fatigue experiments were conducted on angled unidirectional CFRP coupled with digital image correlation (DIC) to analyze the full field displacement. Angled CFRP cracks experienced mixed mode loading which required addition insight due to the complex stresses on the fiber/matrix interface. The experimental displacement fields acquired from DIC were used as inputs for an anisotropic regression analysis to determine the mode I and mode II stress intensity factor ranges. The results from the regression analysis were used to predict the displacement fields around a crack. When comparing the experimental results with the predicted results, the inclusion of Mode II increased the agreement between predicted and experimental displacement fields around a crack tip for two different fiber orientation angles. Crack growth rate analysis and analytical stress intensity factor ranges were used to expand on the agreement of the results as well as bring to light CFRP specific fracture mechanisms that lead to disagreements.

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