Understanding and modelling failure of laminated composites
Author(s)
Gutkin, Renaud
Type
Thesis
Abstract
In this thesis, experimental investigations together with analytical and numerical
work on the understanding and modelling of failure in laminated composites are
presented.
Failure of carbon fibre reinforced plastics is investigated using acoustic emission.
Signals are collected for various test configurations which give rise to specific failure
modes. The signals are then analysed using pattern recognition techniques and the
fast Fourier transform. An identi cation of the failure modes with their acoustic
signatures is proposed using the fast Fourier transform, which was found to be the
most suitable technique.
The failure modes in longitudinal compression are then studied using microscopy
techniques and finite element modelling. Experimental observations show that failure
results from an interaction between shear-driven compressive failure and kinkband
formation.
Micromechanical finite element analyses are used to explain the experimental observations.
The interaction of shear-driven compressive failure and kinking captured
by the model is used to explain the variation in characteristics typically measured
in failure envelopes for combined longitudinal compression vs. in-plane shear.
Based on the experimental and the numerical results, a failure criterion for fibre
kinking and splitting is developed and used to predict failure envelopes for combined
longitudinal compression vs. in-plane shear. The model correlates well with the
numerical predictions and experimental results.
The R-curve effect observed in mode I intralaminar matrix crack growth and its
specimen-dependence are then investigated. Relationships between crack extension
and crack opening displacement are obtained for the Double Cantilever Beam (DCB)
and Compact Tension (CT) specimens. Measured R-curves are used with the previous
relationships to define a trilinear cohesive law. The cohesive law is implemented
in finite element models and the load versus displacement curves predicted for the
DCB and CT specimens show that the R-curve effect is numerically well captured.
work on the understanding and modelling of failure in laminated composites are
presented.
Failure of carbon fibre reinforced plastics is investigated using acoustic emission.
Signals are collected for various test configurations which give rise to specific failure
modes. The signals are then analysed using pattern recognition techniques and the
fast Fourier transform. An identi cation of the failure modes with their acoustic
signatures is proposed using the fast Fourier transform, which was found to be the
most suitable technique.
The failure modes in longitudinal compression are then studied using microscopy
techniques and finite element modelling. Experimental observations show that failure
results from an interaction between shear-driven compressive failure and kinkband
formation.
Micromechanical finite element analyses are used to explain the experimental observations.
The interaction of shear-driven compressive failure and kinking captured
by the model is used to explain the variation in characteristics typically measured
in failure envelopes for combined longitudinal compression vs. in-plane shear.
Based on the experimental and the numerical results, a failure criterion for fibre
kinking and splitting is developed and used to predict failure envelopes for combined
longitudinal compression vs. in-plane shear. The model correlates well with the
numerical predictions and experimental results.
The R-curve effect observed in mode I intralaminar matrix crack growth and its
specimen-dependence are then investigated. Relationships between crack extension
and crack opening displacement are obtained for the Double Cantilever Beam (DCB)
and Compact Tension (CT) specimens. Measured R-curves are used with the previous
relationships to define a trilinear cohesive law. The cohesive law is implemented
in finite element models and the load versus displacement curves predicted for the
DCB and CT specimens show that the R-curve effect is numerically well captured.
Date Issued
2010
Date Awarded
2010-10
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Robinson, Paul
Pinho, Silvestre
Sponsor
EPSRC ; Ministry of Defence
Creator
Gutkin, Renaud
Grant Number
EP/E0Z3169/1
Publisher Department
Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)