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Dissertation/Thesis Abstract

Evaluation of Electrical and Mechanical Properties of Carbon-Fiber Composites Using Interleaved Materials
by Rana, Akshaykumar A., M.S., California State University, Long Beach, 2018, 135; 10979176
Abstract (Summary)

Carbon-Fiber Reinforced Polymers (CFRPs) provides superior mechanical properties and low weight, enabling their extensive use in the aerospace industry. Susceptibility to internal damage due to out-of-plane loads and poor electrical properties are some of their major challenges that require to be addressed in order to increase the utilization of composites in further aerospace structures. Lightning strikes can lead to catastrophic damage, inflicting high repair and certification costs. Lightning Strike Protection (LSP) solutions such as integration of metallic meshes or foils into the composite structures, even though effective, impose extra costs and hinders the aircraft performance due to the increased weight of the aircraft.

This research aims at the development of a different LSP solution, by enhancing the electrical conductivity of composite, while maintaining a sufficient degree of mechanical properties. The use of non-woven conductive interlayers was proposed for manufacturing of conductive composites. Highly-conductive, low-aerial-weight carbon veil was utilized to manufacture prepreg-based CF/Epoxy laminates, which are generally toughened, in order to improve their conductivity using vacuum bag only (VBO) and heat-pressing techniques. Further, a bi-functional interlayer of graphene coated Polyamide (PA) was developed using interfacial trapping method. This conductive thermoplastic interlayer was then utilized for manufacturing Benzoxazine (BZ) infused carbon fabric laminate with Vacuum-assisted resin transfer molding (VARTM) method, which acted as a conductive toughener and improves the Inter-laminar Fracture Toughness (ILFT) as well as to increase the electrical conductivity.

The effects of the incorporation of non-woven interlayers on the electrical conductivity, thermal behavior of composites, and mechanical properties such as shear strength, compressive strength, and the ILFT (Mode-I and Mode-II) were investigated in this study. In both types of composites, an increase in electrical properties, as well as mechanical properties, were observed. The only exception was in the Mode-I ILFT of the CF/Epoxy prepregs, which decreased with the increase of the areal weight of the interleaved carbon veils. The mechanical properties increased in the range of 9%–138% with the only decrement observed in Mode-I ILFT of CF/Epoxy with carbon veils of 25%. The volume resistivity of the CF/Epoxy samples decreased significantly by approximately 50% due to the incorporation of the conductive interlayer. This added feature was used to develop a structural health monitoring (SHM) procedure. The conductive composite showed an increased sensitivity in detecting the pre-identified damage location in the composites.

Indexing (document details)
Advisor: Barjasteh, Ehsan
Commitee: Roy, Surajit, Yoozbashizadeh, Mahdi
School: California State University, Long Beach
Department: Mechanical and Aerospace Engineering
School Location: United States -- California
Source: MAI 58/05M(E), Masters Abstracts International
Subjects: Engineering, Aerospace engineering
Publication Number: 10979176
ISBN: 978-1-392-07403-9
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