The impact behaviour of high performance fibre composites
File(s)
Author(s)
Syed Abdullah, Syed Idros Bin
Type
Thesis or dissertation
Abstract
The use of composite materials as structural reinforcements has increased significantly
throughout the years. In aircraft structures, composite materials have replaced conventional materials such as aluminium to more than 50% of the aircraft's total mass. The
advantages of composite materials include a high strength-to-weight ratio, and corrosion resistance. This has attracted designers to utilise these materials to enable a more
cost effective design, without compromising the aircraft's structural integrity. However,
composite materials are highly vulnerable to transverse impact loading. The need to
improve their impact resistance is essential to achieve a more reliable and safer design.
The research presented in this PhD aims to investigate the impact performance of
laminated composites, both in low and high-velocity regimes. The investigation involves impact loading on three different fibre composites, namely Carbon fibre (IM7),
Glass fibre (S2-Glass), and Thermotropic Liquid Crystal Polymer (Vectran), in a thermosetting epoxy matrix. Prior to this, all three laminates were characterised to obtain
their in-plane mechanical properties, as well as the Mode I and II interlaminar fracture
toughness. For the Vectran composite, the Mode I translaminar (fibre tensile) response
was characterised to obtain its strain energy release rate, Gc, as well as understanding
the complex failure mechanisms which contribute to its fracture toughness. All experimentally obtained properties were used for numerical modelling using the non-linear
explicit Finite Element Method (FEM) software, LS-Dyna. Finally, an energy-based
plane-stress User MATerial (UMAT) model was developed for the Vectran composite.
The UMAT was used to simulate the in-plane, as well as the low and high velocity
impact response of the Vectran composite. For carbon and glass composites, the commercially available energy-based material model in LS-Dyna was utilised to numerically
reproduce the experimentally obtained impact response.
throughout the years. In aircraft structures, composite materials have replaced conventional materials such as aluminium to more than 50% of the aircraft's total mass. The
advantages of composite materials include a high strength-to-weight ratio, and corrosion resistance. This has attracted designers to utilise these materials to enable a more
cost effective design, without compromising the aircraft's structural integrity. However,
composite materials are highly vulnerable to transverse impact loading. The need to
improve their impact resistance is essential to achieve a more reliable and safer design.
The research presented in this PhD aims to investigate the impact performance of
laminated composites, both in low and high-velocity regimes. The investigation involves impact loading on three different fibre composites, namely Carbon fibre (IM7),
Glass fibre (S2-Glass), and Thermotropic Liquid Crystal Polymer (Vectran), in a thermosetting epoxy matrix. Prior to this, all three laminates were characterised to obtain
their in-plane mechanical properties, as well as the Mode I and II interlaminar fracture
toughness. For the Vectran composite, the Mode I translaminar (fibre tensile) response
was characterised to obtain its strain energy release rate, Gc, as well as understanding
the complex failure mechanisms which contribute to its fracture toughness. All experimentally obtained properties were used for numerical modelling using the non-linear
explicit Finite Element Method (FEM) software, LS-Dyna. Finally, an energy-based
plane-stress User MATerial (UMAT) model was developed for the Vectran composite.
The UMAT was used to simulate the in-plane, as well as the low and high velocity
impact response of the Vectran composite. For carbon and glass composites, the commercially available energy-based material model in LS-Dyna was utilised to numerically
reproduce the experimentally obtained impact response.
Version
Open Access
Date Issued
2018-11
Online Publication Date
2019-04-09T13:03:46Z
Date Awarded
2019-04
Copyright Statement
Creative Commons Attribution NonCommercial No Derivatives licence.
Advisor
Iannucci, Lorenzo
Greenhalgh, Emile
Publisher Department
Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)