Fatigue Behaviors of Carbon Fiber Reinforced Plastics Integrated with Carbon Nanotubes

open_access
Open Access
Author:
Barkauskas, Thomas
Area of Honors:
Aerospace Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Namiko Yamamoto, Thesis Supervisor
Puneet Singla, Thesis Honors Advisor
Keywords:
Carbon Nanotube
Carbon fiber reinforced plastics
Varying amplitude
Constant amplitude
Nanostitched
Fatigue Test
Stiffness
Fatigue Cycle
Abstract:
Carbon fiber reinforced plastics (CFRPs) are commonly used within next-generation structures due to their weight-saving and material properties which can be tailored to fit specific needs. Identifying factors to improve fatigue resistance and longevity within CFRPs to reduce the need for replacement, could have a measurable, beneficial impact on the use, safety and efficiency of aerospace structures. Preliminary studies have demonstrated that adding carbon nanotubes (CNTs) to CFRPs increases the number of fatigue cycles, but their performance under realistic loading cycles of varying amplitudes (VA) has not been fully tested. In this work, data will be analyzed from dynamic testing of CNT-integrated CFRPs under VA loading. The goal was to study the effect of VA loading and CNT implementation on fatigue cycle and fracture behaviors of CFRPs. The samples were subjected to either 90% or 70% of their static Short Beam Shear (SBS) strength Constant Amplitude (CA) testing or a 90%/70% mix of their SBS VA testing. In addition to fatigue cycles, the stiffness of each sample was recorded during the fatigue test until the sample reached failure. After the test, the samples were inspected under an optical microscope for fracture locations. The effect of CNTs were observed only with the initial stiffness. It stayed roughly comparable with constant and varying loadings, unlike the Baseline samples which changed between testing types. In terms of the fatigue cycles, it was found that the Nanostitched samples experienced a lower fatigue cycle due to a higher load being placed on them as a result of having a higher initial stiffness. This was a result of Nanostitched samples having a higher SBS strength as compared to Baseline samples.