Access Type

Open Access Dissertation

Date of Award

January 2016

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Mechanical Engineering

First Advisor

Golam M. Newaz

Abstract

STATIC AND DYNAMIC BEHAVIOUR OF CARBON FIBER REINFORCED ALUMINUM (CARALL) LAMINATES

by

GURPINDER SINGH DHALIWAL

Advisor: Dr. Golam Newaz

Major: Mechanical Engineering

Degree: Doctor of Philosophy

The main aim of this research work was to investigate the static and dynamic properties of carbon fiber reinforced aluminum laminates cured without using any external adhesive and acid treatment of aluminum layers. A comprehensive study was undertaken to study the effect of adding epoxy resin rich polyester synthetic surface veil cloth layers on the failure modes and flexural and tensile response of these fiber metal laminates (FMLs). The main purpose of adding veil cloth layers was to prevent the occurrence of galvanic corrosion by avoiding direct contact between aluminum and carbon fiber layers. The addition of veil cloth layers leads to the combined failure of all layers in carbon fiber reinforced aluminum laminates at the same time, whereas the carbon fiber/ epoxy layers break before the failure of aluminum layers in samples cured without using veil cloth layers under tensile loading. The delamination was found to be reduced to a great extent in these laminate configurations due to the addition of veil cloth layers. Thermal residual stress developed during the curing of fiber metal laminates were predicted by utilizing analytical equations and finite element modeling. It was found out that the veil cloth layer does not affect much in reducing the thermal residual stress. Low-velocity impact tests were carried out using a drop-weight impact tower by impacting these fiber metal laminates at the center with three different energy levels to address energy absorption characteristics of these composites. Results showed that these laminates give higher forces and smaller displacement with the addition of polyester veil cloth layers due to reduced delaminated area across all interfaces of aluminum and carbon fiber layers, thus increasing slightly the energy absorption capabilities of these laminates. Primary failure modes observed during impact tests in these FMLs were cracks in the non-impacted aluminum layer, carbon fiber (CFRP) layer breakage and delamination b/w aluminum & CFRP layers. The threshold impact energy, energy at which perforation failure was induced in all metallic and fiber reinforced layers for these laminates was found to be around 31J. Finite element analysis utilizing LS-DYNA software was performed to predict load-displacement history, delamination area, absorbed energy, damage morphologies on impacted and non-impacted sides and tensile failures of CFRP layers for an impact event at three different energy levels. Delamination at the aluminum and carbon fiber layers interfaces was modeled by using with traction separation law and damage criterion proposed by Benzeggagh–Kenane was used for interface damage evolution. Predicted impact behavior results match well with experimental results. Length-wise compression after impact static tests was conducted for impacted and non-impacted samples to determine the residual strength of these fiber metal laminates after the impact event. By comparing FMLs systems cured with and without using polyester surfacing veil cloth layers in terms of residual strength at the same impact energy, it is found that the FMLs having cloth layers provides higher residual strength than the regular FMLs cured without cloth layers composite system due to the higher interlaminar strength of the composite system. These results provide a clear understanding of the failure modes of these FMLs under different loading conditions and how they influence the overall composite behavior. A unique contribution of the thesis work is the investigation of the effect of resin rich polyester veil cloth on flexural, tensile, low-velocity impact & compression after impact characteristics of these carbon fiber reinforced aluminum laminates. These results can be used in designing lightweight automotive and aerospace components.

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