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Research Interests: Engineering, Signal Processing, Statistical Analysis, Modeling, Finite element method, and 15 moreStructural Health Monitoring, Damage detection, Fiber Optic Sensors, Finite element modelling, Outlier detection, Strain Measurement, Novelty Detection, Composite structures, Health monitoring, Composite Structure, Numerical Model, Experimental Tests, Diagnostic Accuracy, Fibre Bragg Grating, and Bragg Grating
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A finite difference method was used to model in near real-time, the deformed profile of rectangular composite plies manipulated by a combination of end-effector suction surfaces. A range of carbon and glass, dry, and prepreg fabrics were... more
A finite difference method was used to model in near real-time, the deformed profile of rectangular composite plies manipulated by a combination of end-effector suction surfaces. A range of carbon and glass, dry, and prepreg fabrics were modelled and compared with experimental results. As expected, the accuracy of the model increased with a decrease in the mesh-size of the finite
Research Interests: Materials Engineering, Mechanical Engineering, Robotics, Aerospace Engineering, Modeling, and 14 moreStratification, Numerical Simulation, Automation, Deformation, Collision Avoidance, Composite Material, Prediction Model, Real Time, Glass Fiber, Finite Difference, Finite Difference Method, Prepreg, Carbon Fiber, and Robot Manipulator
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ABSTRACT
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A preliminary study has been carried out to characterise the damage mechanisms associated with impact and postimpact loadings in a number of laminates manufactured from different fibre architectures and manufacturing techniques. This work... more
A preliminary study has been carried out to characterise the damage mechanisms associated with impact and postimpact loadings in a number of laminates manufactured from different fibre architectures and manufacturing techniques. This work has revealed that woven, uniweave and Unidirectional tape laminates all have fairly similar impact characteristics, i.e. they sustained increasingly larger damage zones with impact energy, with the
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INTRODUCTION A great deal of time and effort is spent by aircraft manufacturers in the identification and estimation of the parameters that properly describe the aerodynamics of a particular aircraft. The derivatives of the aircraft... more
INTRODUCTION A great deal of time and effort is spent by aircraft manufacturers in the identification and estimation of the parameters that properly describe the aerodynamics of a particular aircraft. The derivatives of the aircraft forces, with respect to the input state have been the basis of many design and development techniques and tools, such as dynamic stability analysis, performance, simulation and control. The system identification of the aerodynamic model using neural networks involves the selection of the necessary input and output states to the system, representation of the model, and parameter estimation of the characteristic quantities, and in this case the aerodynamic force and moment derivatives. The application of neural networks as both a model descriptor and parameter estimation technique also requires a close selection of model inputs, to most efficiently utilise the method. System identification of the entire dynamic system as opposed to the parameter esti
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The structural integrity and damage tolerance of typical composite T-joints found in ships constructed from glass fibre reinforced plastic was the subject of this investigation. The effect of the geometry of the T-joint on the strain... more
The structural integrity and damage tolerance of typical composite T-joints found in ships constructed from glass fibre reinforced plastic was the subject of this investigation. The effect of the geometry of the T-joint on the strain distribution was investigated using finite element (FE) analysis. The results, reported in this paper, showed that the critical strains were significantly affected by the joint geometry. Results of the FE analysis conducted to investigate the effect of disbonds between the filler and overlaminate are also reported. This showed that particular defects led to large changes in the strains in the T-joint structure, which would encourage disbond progression. The FE model was validated by mechanical tests on a representative T-joint, instrumented with surface strain gauges and displacement transducers, into which a range of defects was progressively introduced.
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ABSTRACT The propagation characteristics of Lamb waves activated and collected by an active piezoelectric (PZT) sensor network in a CF/EP composite panel of five stiffeners were investigated. In particular, wave attenuation in terms of... more
ABSTRACT The propagation characteristics of Lamb waves activated and collected by an active piezoelectric (PZT) sensor network in a CF/EP composite panel of five stiffeners were investigated. In particular, wave attenuation in terms of propagation distance and wave energy loss induced by reinforced stiffeners were evaluated. The interaction between Lamb wave modes and a through-thickness hole of 11.9 mm diameter was subsequently examined. Given the complexity of the captured wave signals, an inverse algorithm based on correlation between wave signals in the benchmark and damaged structures was developed. Different combinations of actuator-sensor paths were used to estimate the location of damage. The diagnostic results demonstrate that the proposed approach has a good capability for defining location of damage using the probability of occurrence of damage.
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Structural health monitoring (SHM) technology may be applied to composite bonded repairs to enable the continuous through-life assessment of the repair's efficacy. This paper describes an SHM technique for the detection of... more
Structural health monitoring (SHM) technology may be applied to composite bonded repairs to enable the continuous through-life assessment of the repair's efficacy. This paper describes an SHM technique for the detection of debonding in composite bonded patches based on frequency response. The external doubler repair, commonly used to patch aircraft structures, is examined in this paper. An experimental investigation was
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Research Interests: Damage detection and Csc
This paper uses one category of Structural Health Monitoring (SHM) which uses strain variation across a structure as the key to damage detection. The structure used in this study was made from Glass Fibre Reinforced Plastic (GFRP). This... more
This paper uses one category of Structural Health Monitoring (SHM) which uses strain variation across a structure as the key to damage detection. The structure used in this study was made from Glass Fibre Reinforced Plastic (GFRP). This paper discusses a technique developed called "Global Neural network Architecture Incorporating Sequential Processing of Internal sub Networks (GNAISPIN)" to predict the presence of multiple damage zones, determine their positions and also predict the extent of damage. Finite Element (FE) models of T-joints, used in ship structures, were created using MSC Patran(R) . These FE models were created with delaminations embedded at various locations across the bond-line of the structure. The resulting strain variation across the surface of the structure was observed. The validity of the Finite Element model was then verified experimentally. GNAISPIN was then used in tandem with the Damage Relativity Analysis Technique to predict and estimate the presence of multiple delaminations.
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The use of glass-reinforced plastics (GFRP) as a structural material is widespread because of their high strength and stiffness, low mass, excellent durability and ability to be formed into complex shapes. However, GFRP composite... more
The use of glass-reinforced plastics (GFRP) as a structural material is widespread because of their high strength and stiffness, low mass, excellent durability and ability to be formed into complex shapes. However, GFRP composite structures are prone to delaminations which can lead to a significant degradation in structural integrity. A number of non-destructive inspection methods have been devised to inspect
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This paper discusses a Real-Time Structural Health Monitoring (SHM) technique developed to predict the presence and extent of multiple delaminations in a composite structure. This technique was developed integrating Artificial Neural... more
This paper discusses a Real-Time Structural Health Monitoring (SHM) technique developed to predict the presence and extent of multiple delaminations in a composite structure. This technique was developed integrating Artificial Neural Networks (ANN) and the Damage Relativity Analysis Technique (DRAT). This SHM technique uses strain signatures emanating from the surface of the structure as damage features to facilitate damage detection
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The use of composite structures in engineering applications has proliferated over the past few decades due to its distinct advantages, namely: high structural performance, corrosion resistance, and high strength/weight ratio. However,... more
The use of composite structures in engineering applications has proliferated over the past few decades due to its distinct advantages, namely: high structural performance, corrosion resistance, and high strength/weight ratio. However, they also come with a set of disadvantages, i.e., they are prone to fiber breakage, matrix cracking, and delaminations. These types of damage are often invisible and if undetected, could lead to catastrophic failures of structures. Although there are systems to detect such damage, the criticality assessment and prognosis of the damage is often much more difficult to achieve. This article discusses the research study conducted, which resulted in the development of a Structural Health Monitoring (SHM) system for a 2D polymeric composite T-joint, used in maritime structures. The SHM system was found to be capable of not only detecting the presence of multiple delaminations in a composite structure, but also capable of determining the location and extent o...
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This paper presents a novel approach to computing minimum-time paths based on a technique originally developed for use in geophysics. The technique is based on a finite difference scheme and is quite efficient in terms of both computing... more
This paper presents a novel approach to computing minimum-time paths based on a technique originally developed for use in geophysics. The technique is based on a finite difference scheme and is quite efficient in terms of both computing effort and storage. A particular strength of the technique is that it provides optimal paths to all locations in the field, thus being useful in situations where the goal is not known at the outset of the search. Details are presented on the basic technique and extensions are derived to include the integrations of resources (such as fuel store), and to provide flexibility in the objective. Two examples are given: minimum-time planning for vehicles under the influence of drift, and planning to minimise the risk of detection for a stealthy vehicle in the presence of threats.
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Abstract Changes in fiber architecture which result from the compaction of fabric plies can be a major cause for scatter and inconsistencies in measured mechanical properties. The need to quantify and provide insight into the influence of... more
Abstract Changes in fiber architecture which result from the compaction of fabric plies can be a major cause for scatter and inconsistencies in measured mechanical properties. The need to quantify and provide insight into the influence of compaction on both the stiffness and strength of plain weave fabric composites, has led to the development of a model. The proposed model extends an existing modelling technique, a point-wise lamination approach using Classical Laminate Theory, to analyse the compaction problem. The analysis, which ...
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ABSTRACT
Research Interests: Mechanical Engineering, Civil Engineering, Structural Health Monitoring, Fatigue, Stress corrosion cracking, and 12 moreDamage Mechanics, Sensor Integration, Cyclic Loading, Experimental Study, Composite Structure, Carbon fibre, Optical Fibre, Glass Fibre, Fatigue Life, Fibre Bragg Grating, Bragg Grating, and Tensile Strength
... was to evaluate the mechanical properties and characterise the failure mechanisms of 2D triaxiallybraided carbon epoxy ... 1 illustrates the fibre architecture of a unit cell of the 2D triaxial braid used in ... are in the bias... more
... was to evaluate the mechanical properties and characterise the failure mechanisms of 2D triaxiallybraided carbon epoxy ... 1 illustrates the fibre architecture of a unit cell of the 2D triaxial braid used in ... are in the bias direction, referred to as the braider tows, which are braided in a ...
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An experimental evaluation has been undertaken to investigate the effect of transverse stitching on the strength of composite single-lap joints. Balanced single-lap joints were considered, and the lay-up for the adherends was (0/... more
An experimental evaluation has been undertaken to investigate the effect of transverse stitching on the strength of composite single-lap joints. Balanced single-lap joints were considered, and the lay-up for the adherends was (0/ ±45/90)s. Specimens were stitched with Kevlar® thread in a zigzag pattern and were manufactured by using the resin-transfer moulding (RTM) technique. Experimental results indicated that stitched joints
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ABSTRACT An investigation has been carried out on the in-plane tensile properties of two orthogonally woven structures with different binder paths. Measurements were made along both the longitudinal (warp) and transverse (weft) axes on... more
ABSTRACT An investigation has been carried out on the in-plane tensile properties of two orthogonally woven structures with different binder paths. Measurements were made along both the longitudinal (warp) and transverse (weft) axes on samples manufactured from two commercially available carbon fibres which are known to have different resistance to fibre damage induced through weaving. In general, this research revealed that the more damage-resistant fibre produces composites with higher strength and stiffness. It was also found that, independent of the fibres used, the in-plane fibre yarns in the structure with the longer binder path are less crimped and this, by and large, translates to better or unchanged tensile modulus, strength and strain-to-failure. In addition to fibre fractures, the superior strength of this composite was also observed to promote an extensive amount of longitudinal splitting, thus resulting in a relatively large failure zone. In the structure with the shorter path length where the in-plane fibres are more crimped, failure is due predominantly to fibre fractures. Groups of fibres are pulled out during failure of both structures, despite good fibre wetting and fibre/matrix adhesion having been achieved with either fibre.
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An experimental programme has been carried out to study the mechanical performance of resin transfer moulded composites comprising a weft-knit glass fabric of Milano-rib architecture. A number of mechanical properties ie tension,... more
An experimental programme has been carried out to study the mechanical performance of resin transfer moulded composites comprising a weft-knit glass fabric of Milano-rib architecture. A number of mechanical properties ie tension, compression, bearing, impact ...
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Two methods were proposed in order to correlate the test results and predict the compression-after-impact (CAI) strength of glass knitted textile composites. The Linear regression analysis was used to establish a linear relationship... more
Two methods were proposed in order to correlate the test results and predict the compression-after-impact (CAI) strength of glass knitted textile composites. The Linear regression analysis was used to establish a linear relationship between damage width and CAI strength. An important finding was that for a wide range of knit architectures, which had similar failure modes, the slope of the regression line for normalised CAI strength was constant, consequently, the slope of the regression line for actual CAI strength varied linearly with undamaged strength. This implies that increased damage tolerance for these knitted composites can be achieved only at the expense of the undamaged strength and CAI performance will be higher for the material with the lower undamaged strength. The second approach involved idealising the impact damage in the knitted composite as a circular hole. Using the semi-empirical failure criterion (point stress model), which necessitates the use of a characteristic length (determined from experiment), the CAI strength was predicted. Comparisons made between predicted and measured CAI strengths revealed good agreement, with differences less than 5% in most cases. A major finding from this work is that for knitted composites, one characteristic length is applicable for a range of damage geometries and knit architectures. This was not the case with composites made from unidirectional prepreg, where the characteristic length depends on the lay-up configuration and hole geometry. Comparing the predictions of the point stress model with the linear regression analysis, it was shown that the stress model generally provided a more accurate prediction of the CAI strength of the knitted composites.
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This research dealt with the impact resistance and tolerance of composite materials manufactured from weft-knitted E-glass fabrics. Three different styles of the weft-knit structures, Milano, 1×1 rib and plain knit, were investigated... more
This research dealt with the impact resistance and tolerance of composite materials manufactured from weft-knitted E-glass fabrics. Three different styles of the weft-knit structures, Milano, 1×1 rib and plain knit, were investigated together with two further variations of Milano and rib structure and one variation of plain knit. The effect of weft-knitted fabric style and knit- structural parameters upon the