Anthony J. Kinloch

Imperial College London | Imperial · Department of Mechanical Engineering

Herein, we report a new method of mitigating cryogenic microcracking in carbon-fibre reinforced-plastics (CFRPs) using a negative thermal-expansion nanomaterial, zirconium tungstate (ZrW2O8), to simultaneously reduce the thermal residual stresses and enhance the fracture energy of the epoxy matrix of CFRPs. The results show that 1 wt.% of added ZrW...

The peeling apart of layered materials is common in nature and has been used by humans in myriad applications since prehistoric times. Over the past century, a wide range of peel tests has been proposed, standardized, and used to characterize important properties of materials, adhesives, and interfaces. Understanding the relative merits and limitat...

The patch-plug configuration has been widely used to repair composite structures and restore the structural integrity of damaged composites. In the present research, single-sided CFRP patch-repaired panels, with different patch-plug configurations, are prepared. This is where a circular-shaped damaged area has been removed and a CFRP patch has been...

Motivated by the need for an efficient fatigue crack growth prediction infrastructure for both legacy and novel materials, we have initiated the development of an automated computational framework capable of determining crack growth model parameters for an equationally defined model. As a first step in addressing this need, the present paper focuse...

To reduce the carbon footprint of many different applications, i.e. transportation, lightweight fiber-reinforced composites are the material of choice. The logical next step is to decarbonize composites as well. A promising approach is the use of natural fibers like flax in combination with a new bio-based matrix resin, based on waste from the pape...

A new analysis is proposed, and verified, to quantitively explain the recent experimental observations of a transition from unstable to slow, stable through-thickness crack growth in cross-ply laminates, as the ply thickness is decreased to 40 µm. The approach is prompted by the observed stable rise of crack opening under increasing applied strain...

Carbon-fibre reinforced polymer (CFRP) composites are replacing metal alloys in aerospace structures, but they can vulnerable to lightning strike damage if not adequately protected due to the poor electrical conductivity of the polymeric matrix. In the present work, to improve the conductivity of the CFRP, two electrically-conductive epoxy formulat...

A good dimensional stability is a crucial property of any base-platform structure for the attachment of high precision optical or mechanical devices, such as imaging equipment, satellite antennas, thermal sensors, etc., where the surrounding temperature may fluctuate substantially. The present study demonstrates how such a base-platform in a form o...

The present paper studies the low-velocity impact testing of carbon-fibre reinforced-plastic (CFRP) pristine and patch-repair CFRP panels. Firstly, the effect of repeated impacts on the pristine CFRP damage growth is considered at impact energies of 7.5, 10.5 and 30 J. Secondly, such tests lead to a single-sided, patch-repair panel being manufactur...

This paper first discusses the accuracy of the standard adhesively-bonded joint design code, the analytical A4EI code, that is used in the aircraft industry to determine the strain-energy density in a complex step-lap joint under shear loads. This joint geometry is then used to assess the ability of the A4EI code, and a standard finite-element anal...

The fusion bonding between individual filaments of 3D printed short carbon-fibre reinforced polyamide 6 (SCF/PA6) in thin films manufactured using the fused filament fabrication (FFF) process has been studied. The thin films were deposited by an ‘in-plane’ mode or an ‘interlayer’ mode. The main characterisation technique employed was the essential...

The present paper investigates the impact behaviour of both pristine carbon-fibre-reinforced-plastic (CFRP) composite laminates and repaired CFRP laminates. For the patch-repaired CFRP specimen, the pristine CFRP panel specimen has been damaged by cutting out a central disc of the CFRP material and then repaired using an adhesively bonded patch of...

In-service, composite sandwich structures, which consist of fibre-composite skins (also termed face-sheets) adhesively bonded to a polymeric foam core, can encounter extreme quasi-static flexural loading that may cause serious damage to the sandwich structure. The ability to model the flexural behaviour of such structures can lead to improved desig...

See at: https://www.youtube.com/watch?v=eBaugYOokFw&list=PLg7f-TkW11iXyrmX9k6beGGLJPsLfbTyO&index=19&t=821s - and at: https://royalsociety.org/science-events-and-lectures/2021/09/tough-materials/

Structural adhesives are widely used for joining composite components in many industries and crack growth in such materials is far more likely to occur when they are subjected to repeated cyclic loading than to monotonic loading. Whilst the Hartman- Schijve equation for fatigue crack growth (FCG) has been shown to hold for cohesive crack growth in...

See at: https://www.youtube.com/watch?v=8OI5T6CJ-2o&list=PLg7f-TkW11iXyrmX9k6beGGLJPsLfbTyO&index=17 - and at: https://royalsociety.org/science-events-and-lectures/2021/09/tough-materials/

This paper presents an experimental investigation into improvements to the interlaminar fracture toughness, low-velocity impact damage resistance and compression-after-impact (CAI) strength of continuous carbon fibre-epoxy composite laminates toughened with multi-scale carbon nano- and micro-fillers spanning the nanometer to millimeter length scale...

https://youtu.be/V4GiyI4L6Gc : Structural adhesives are being increasingly used in a very wide range of engineering applications, especially in the aerospace and automotive industries The present lecture will illustrate the wide and varied use of modern engineering adhesives and then consider three crucial aspects of their use, all of which have...

Structural adhesives are widely used for joining composite components in many industries and crack growth in such materials is far more likely to occur when they are subjected to repeated cyclic loading than to monotonic loading. Whilst the Hartman-Schijve equation for fatigue crack growth (FCG) has been shown to hold for cohesive crack growth in a...

This data is associated with cohesive crack growth in a toughened automotive adhesive

In the present seminar a novel methodology is proposed for predicting an ‘upper-bound’ (i.e. ‘worst case’) fatigue crack growth (FCG) rate curve from laboratory double-cantilever beam (DCB) test data which is representative of a composite laminate exhibiting no, or only very little, retardation (i.e. slowing) of the FCG rate under fatigue loading,...

Watch on: https://www.youtube.com/watch?v=-0RFT_o8KSM&feature=youtu.be The growth of delaminations in polymer-matrix fibre composites under cyclic-fatigue loading in operational aircraft structures has always been a very important factor which has the potential to significantly affect the service-life of such structures. The recent introduction b...

At cryogenic temperatures thermoset polymers suffer from low fracture toughness. Herein, we present a strengthening and toughening technique for cryogenic applications using cupric oxide (CuO) nanorods. These nanorods are synthesized via a hydrothermal reaction to give an average length of 1.64 and a diameter of 270 nm. They exhibit a low coefficie...

The present paper describes detailed analyses of experimental data for the cyclic-fatigue behaviour of epoxy nanocomposite polymers. It has been shown that the data may be interpreted using the Hartman–Schijve relationship to yield a unique, ‘master’, linear relationship for each epoxy nanocomposite polymer. By fitting the experimental data to the...

This paper discusses two approaches that have been proposed to account for the data scatter observed in delamination growth tests under cyclic-fatigue loading and thereby enable an estimate of a worst-case delamination growth curve for use in the damage tolerance and durability assessment of composite and adhesively-bonded airframes. The two approa...

Graphene due to its two-dimensional structure, large surface area and high impermeability is regarded as an excellent potential filler for the development of anti-corrosive coatings by creating a natural barrier to the diffusion of electrolytes. Epoxy polymers are widely used as protective coatings, and in the present study, commercially-available...

The extent and quality, i.e. consistency, of the fusion bonding between filaments that occurs during the fused filament fabrication (FFF) process plays an important role in determining the mechanical performance of 3D printed polymeric parts. This present research is designed to quantify these parameters of the fusion bonding between individual fil...

The present paper shows that the variability in the cyclic fatigue crack growth (FCG) rate in structural adhesives that is frequently observed in laboratory test results can be captured by using a Hartman-Schijve methodology. To this end the Hartman-Schijve equation has been used to access an 'upper-bound' FCG rate curve that (a) encompasses all th...

In the present research, a detailed experimental study of the impact behaviour of CFRP composites is performed. To investigate the effects of impactor velocity, a round-nosed steel impactor is employed to strike the composite specimens at two impact velocities (i.e. 2.40 m.s⁻¹ and 4.16 m.s⁻¹). To investigate the effects of the geometry of the head...

In the present paper a novel methodology is proposed for predicting an ‘upper-bound’ (i.e. ‘worst case’) fatigue crack growth (FCG) rate curve from laboratory double-cantilever beam (DCB) test data which is representative of a composite laminate exhibiting no, or only very little, retardation (i.e. slowing) of the FCG rate under fatigue loading, as...

The present paper describes the results from experimental and theoretical modelling studies on the behaviour of continuous carbon-fibre/polymer matrix composites subjected to a relatively low-velocity or high-velocity impact, using a rigid, metallic impactor. Drop-weight and gas-gun tests are employed to undertake the low-velocity and high-velocity...

Carbon-fibre/epoxy-matrix composites used in aerospace and vehicle applications are often susceptible to critical loading conditions and one example is impact loading. The present paper describes a detailed experimental and numerical investigation on the relatively low-velocity (i.e. <10 m/s) impact behaviour of such composite laminates. In particu...

A three-dimensional (3-D) finite-element analysis (FEA) model incorporating an elastic-plastic (EP) damage model, which was implemented as a user-defined material (‘VUMAT’) sub-routine in a FEA code (‘Abaqus/Explicit’), is developed to simulate the impact response of carbon-fibre reinforced-plastic (CFRP) composites. The model predicts the load ver...

In the present paper a novel methodology is proposed for predicting an ‘upper-bound’ (i.e. ‘worst case’) fatigue crack growth (FCG) rate curve from laboratory double-cantilever beam (DCB) test data which is representative of a composite laminate exhibiting no, or only very little, retardation (i.e. slowing) of the FCG rate under fatigue loading, as...

In the present paper numerical modelling results are described to predict the effects of the hardness of a projectile impacting a woven carbon-fibre reinforced thermoplastic-matrix composite. The projectiles are prepared from either relatively soft gelatine or hard high-density polyethylene (HDPE) materials, of the same mass, and are fired from a g...

In this study, the effects of adding nanofillers to an epoxy resin (EP) used as a matrix in glass-fibre reinforced-plastic (GFRP) composites have been investigated. Both 1D and 2D nanofillers were used, specifically (i) carbon nanotubes (CNTs), (ii) few-layer graphene nanoplatelets (GNPs), as well as hybrid combinations of (iii) CNTs and boron nitr...

This paper firstly reveals that when assessing if a bonded joint meets the certification requirements inherent in MIL-STD-1530D and the US Joint Services Standard JSSG2006 it is necessary to ensure that: (a) There is no yielding at all in the adhesive layer at 115% of design limit load (DLL), and (b) that the joint must be able to withstand design...

The present paper presents experimental and numerical studies on the behaviour of composite laminates subject to impact loading by soft projectiles to represent the impact of a small bird or hailstone. In this research, gas-gun experiments are performed to study woven carbon-fibre reinforced poly (ether-ether ketone) (CF/PEEK) composites subjected...

Watch on: https://www.youtube.com/watch?v=-0RFT_o8KSM&feature=youtu.be

The present paper investigates the impact performance of woven-fabric carbon-fibre composites based upon both thermoplastic- and thermoset-matrix polymers under high-velocity impact loading by conducting gas-gun experiments at impact velocities of up to 100 m.s-1. The carbon-fibre reinforced-polymers (CFRPs) are impacted using soft- (i.e. gelatine)...

This paper presents a detailed experimental investigation on the effects of projectile hardness on the behaviour of thermoplastic composites under impact loading. In this research, gas gun experiments employ gelatine and high-density polyethylene (HDPE) projectiles, of the same mass, to impact against woven carbon-fibre reinforced poly (ether-ether...

The impact performance of cross-ply thermoplastic and thermoset composites, under low-velocity and high-velocity impact loading, is assessed by conducting drop-weight and gas gun experiments. Typical load versus time and load versus displacement traces, for both types of composites, are obtained from the drop-weight experiments undertaken at variou...

The present paper describes analytical models to calculate the mode I fracture toughness of polymer composites reinforced with carbon nanoparticle. The model can predict the fracture toughness of nanocomposites reinforced with either one-dimensional (1D) nanofibres or two-dimensional (2D) nanoplatelets or hybrid combinations of nanofibres and nanop...

Composite and bonded aircraft structures are currently designed such that any delamination/disbond will not grow. However, it is now known that despite this design limit, delaminations and disbonds can both arise and grow when subjected to operational flight loads. In this context in 2009, the FAA Advisory Circular 20-107B introduced a slow growth...

This paper presents detailed experimental and numerical studies on the behaviour of composite laminates subject to impact loading by soft objectives. In this research, gas-gun experiments employ woven carbon fibre reinforced poly (ether-ether ketone) (CF/PEEK) and gelatine projectiles to study the response of composite laminates under soft impact l...

A liquid metal synthesis process provides a new low energy pathway avenue to synthesise various low-dimensional nanomaterials in order to improve the mechanical properties of polymer composites. This paper presents an investigation of the strengthening and toughening performances of two-dimensional platelets of boehmite (γ-AlO(OH)) and alumina (γ-A...

Composite airframes are currently designed such that any delamination will not grow. However, despite this design limit requirement, there have been a number of instances where delaminations and disbonds have grown in operational aircraft. To address this discrepancy between as designed and actual performance, in 2009 the FAA Advisory Circular 20-1...

The present paper examines crack growth in a range of structural adhesive joints under cyclic-fatigue loadings. It is shown that cyclic-fatigue crack-growth in such materials can be modelled by a form of the Hartman and Schijve crack-growth equation which aims to give a unique and linear 'master' representation for the fatigue data points that have...

Polymeric foams are extensively used as the core materials in sandwich structures and the core material is typically bonded between relatively thin fibre-composite skins. Such sandwich structures are widely used in the aerospace, marine and wind-energy industries. In the present work, various sandwich structures have been manufactured using glass-f...

This paper presents an experimental investigation into the electric field alignment of recycled/milled short carbon fibres (SCFs) to increase the electrical conductivity and fracture toughness of bulk epoxy and fibre reinforced epoxy composites. Subjecting the SCFs to an alternating current electric field while suspended within uncured liquid epoxy...

The present paper demonstrates that multi-scale fillers such as carbon nanofibres (CNFs) and short carbon fibres (SCFs) can significantly improve the mode I fracture toughness of epoxy composites by various toughening mechanisms. A comparative assessment on the toughening performance promoted by CNFs and SCFs is presented along with the effects of...

The fracture properties and toughening mechanisms of cellulose-and cellulose-rubber hybrid-modified epoxy polymers and glass-fibre (GF) composites are investigated. The cellulose modifiers used are microcrystalline cellulose (MCC) and cellulose nanocrystals (CNC), and the rubber modifiers are carboxyl-terminated butadiene-acrylonitrile (CTBN) and c...

An epoxy resin, cured with an anhydride, has been modified by the addition of silica nanoparticles. The particles were introduced via a sol-gel technique which gave a very well dispersed phase of nanosilica particles, which were about 20 nm in diameter, in the thermosetting epoxy polymer matrix. The glass transition temperature of the epoxy polymer...

Such windshields often employ chemically strengthened glasses and are required to withstand impact by birds, hail-stones and other foreign bodies. In the present study, windshields employing three different polymer interlayer materials were investigated under high-velocity impact by a soft projectile: Thermoplastic Polyurethane (TPU), Polyvinyl But...

The impact performance of thermoplastic and thermoset composites has been investigated by conducting gas gun tests, initial velocities up to 110 m s-1, employing with 3D Digital Image Correlation (DIC) technology. Woven fabric Carbon Fibre Reinforced Polyether-ether-ketone (CF/PEEK) and Carbon Fibre Reinforced Epoxy (CF/Epoxy) laminates, and the im...

The introduction, originally in 2009, by the FAA of a ‘slow growth’ approach to the certification of polymer-matrix fibre composites has focused attention on the experimental data and the analytical tools needed to assess the growth of delaminations under cyclic-fatigue loads. Of direct relevance is the fact that fatigue tests on aircraft composite...

Graphene nanoplatelets (GNPs) offer great potential for enhancing the multifunctional properties of epoxy polymers, including the cyclic-fatigue crack growth resistance. In the present work we investigate the effectiveness of electric-field alignment of GNPs in increasing the fatigue resistance of such epoxy nanocomposites. The GNPs were aligned in...

The fracture resistance, Gc, of adhesively bonded joints is known to vary significantly with loading mode and because joints are usually subject to mixed-mode loading in service, it is essential to be able to partition Gc into its I/II components so the appropriate failure criterion can be derived. Various partitioning schemes have been proposed in...

The present paper describes improvements in the fracture resistance of epoxy polymers due to the addition of either (a) one-dimensional (1-D) carbon nanofibres (CNFs), or (b) two-dimensional (2-D) graphene nanoplatelets (GNPs), or (c) hybrid combinations of these carbon nanofillers (i.e. using both CNFs and GNPs). The effects of the dimensional sha...

The quasi-static flexural and impact performance, up to projectile impact velocities of about 270 m.s-1, of Fibre-Metal Laminates (FMLs), which consist of relatively thin, alternately stacked, layers of an aluminium alloy and a thermoset glass-fibre epoxy composite, have been investigated. The effects of varying (a) the yield strength, tensile stre...

An investigation is presented on increasing the fracture toughness of epoxy /short carbon fibre (SCF) composites by the alignment of short carbon fibres (SCFs) using an externally applied AC electric field. Firstly, the effects of the SCF length, SCF content and AC electric field strength on the rotational dynamics and alignment of the SCFs suspend...

Nail patches have a potential role as drug carriers for the topical treatment of nail diseases such as onychomycosis, a common condition. Our aim was therefore to develop a systematic and novel approach to the formulation of a simple drug-in-adhesive ungual patch. Twelve pressure-sensitive adhesives (PSAs), four backing membranes, two release liner...

The growth of delaminations in polymer-matrix fibre composites under cyclic-fatigue loading in operational aircraft structures has always been a very important factor which has the potential to significantly affect the service-life of such structures. The recent introduction by the Federal Aviation Administration (FAA) of a ‘slow growth’ approach t...

In 2009 the US Federal Aviation Administration (FAA) introduced a slow growth approach for certifying composite and adhesively-bonded structures. This approach requires that delamination or disbond is slow, stable and predictable under cyclic-fatigue loads. The present paper addresses the challenge of developing a methodology capable of enabling th...

This paper focuses on the ability of carbon nanofibre (CNF) networks to in situ monitor fatigue induced disbond damage in adhesive bonded composite joints. The inclusion of CNFs in the epoxy adhesive increases its conductivity by five orders of magnitude. The improved electrical conductivity is utilized to evaluate the ability of the CNF network to...

Two 'green modifiers', microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC), were treated using (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and added, via a three-roll milling process, to an epoxy resin which was then cured to give a thermosetting epoxy polymer. This route overcame the incompatibility between the NCC and MCC and...

The effect of backbone structure and conversion of polycyanurate networks on solid state properties has been studied and compared to co-curing with bisphenol-A. Dynamic mechanical behaviour, density, flammability properties, fracture toughness and long-term water uptake were investigated. The intensity of the γ-relaxation increases, room temperatur...

Presentation Abstract

An electric field is used to align carbon nanofibres (CNFs) in the matrix of a glass-fibre reinforced-polymer (GFRP) composite to simultaneously improve the (a) delamination toughness, (b) electrical conductivity and (c) damage-sensing capability. The CNFs are added to the epoxy resin prior to the manufacture of the GFRP composites. To align the CN...

Homogeneous and toughened cellulose-epoxy polymers were made by modifying an anhydride-cured epoxy with two green modifiers, microcrystalline cellulose (MCC) and cellulose nanocrystals (CNC). Without silane treatment, the MCC and CNC particles sedimented in the epoxy resin and formed either a gradient polymer or two distinct layers. This problem wa...

Improvements to the mode I fatigue resistance of epoxy nanocomposites containing randomly-orientated or aligned graphene nanoplatelets (GNPs) are examined in the present paper. The GNPs were aligned within an uncured (liquid) epoxy resin by applying an AC electric-field. Alignment of the GNPs (up to 2 wt.%) in the direction of the electric-field wa...

The growth of delaminations in polymer-matrix fibre composites under cyclic-fatigue loading in operational aircraft structures has always been a very important factor which has the potential to significantly affect the service-life of such structures. The recent introduction by the Federal Aviation Administration (FAA) of a ‘slow growth’ approach t...

A well-dispersed phase of exfoliated graphene oxide (GO) nanosheets was initially prepared in water. This was concentrated by centrifugation and was mixed with a liquid epoxy resin. The remaining water was removed by evaporation, leaving a GO dispersion in epoxy resin. A stoichiometric amount of an anhydride curing agent was added to this epoxy-res...