Publications
269 results found
Laffan MJ, Pinho ST, Robinson P, et al., 2012, Translaminar fracture toughness testing of composites: A review, POLYMER TESTING, Vol: 31, Pages: 481-489, ISSN: 0142-9418
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- Citations: 138
Pinho ST, Gutkin R, Pimenta S, et al., 2012, On longitudinal compressive failure of carbon-fibre-reinforced polymer: from unidirectional to woven, and from virgin to recycled, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 370, Pages: 1871-1895, ISSN: 1364-503X
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- Citations: 29
Pinho ST, Gutkin R, Pimenta S, et al., 2012, Fibre-dominated compressive failure in polymer matrix composites, Failure Mechanisms in Polymer Matrix Composites, Editors: Robinson, Greenhalgh, Pinho, Publisher: Woodhead Pub Limited, Pages: 183-224, ISBN: 9781845697501
Psarras S, Pinho ST, Falzon BG, 2012, Investigating the damage-tolerant design of stiffener run-outs
In this work, the use of a compliant web design for improved damage tolerance in stiffener run-outs is investigated. Three different configurations were compared to establish the merits of a compliant design: a baseline configuration, a configuration with optimised tapering and a compliant configuration. The performance of these configurations, in terms of strength and damage tolerance, was compared numerically using a parametric finite element analysis. The energy release rates for debonding and delamination, for different crack lengths across the specimen width, were used for this comparison. The three configurations were subsequently manufactured and tested. In order to monitor the failure process, Acoustic Emission (AE) equipment was used and proved valuable in the detection and analysis of failure. The predicted failure loads, based on the energy release rates, showed good accuracy, particularly when the distribution of the energy release rate across the width of the specimen was taken into account. As expected, the compliant configuration failed by debonding and showed improved damage tolerance compared to the baseline and tapered stiffener run-outs.
Gutkin R, Pinho ST, 2012, Predicting fibre kinking and splitting using a finite fracture mechanics formulation
This paper presents the development of a model to predict the strength associated with kinkband formation and fibre splitting based on a finite fracture mechanics approach. The model is derived to handle tri-axial stress states, namely longitudinal compression combined with in-plane shear and hydrostatic pressure. Correlations with experimental data from the literature show that the physics of the problem is correctly captured.
Robinson P, Greenhalgh E, Pinho S, 2012, Failure Mechanisms in Polymer Matrix Composites: Criteria, Testing and Industrial Applications, Failure Mechanisms in Polymer Matrix Composites: Criteria, Testing and Industrial Applications, Pages: 1-450
Polymer matrix composites are increasingly replacing traditional materials, such as metals, for applications in the aerospace, automotive and marine industries. Because of the relatively recent development of these composites there is extensive on-going research to improve the understanding and modelling of their behaviour - particularly their failure processes. As a consequence there is a strong demand among design engineers for the latest information on this behaviour in order to fully exploit the potential of these materials for a wide range of weight-sensitive applications. Failure mechanisms in polymer matrix composites explores the main types of composite failure and examines their implications in specific applications. Part one discusses various failure mechanisms, including a consideration of manufacturing defects and addressing a variety of loading forms such as impact and the implications for structural integrity. This part also reviews testing techniques and modelling methods for predicting potential failure in composites. Part two investigates the effects of polymer-matrix composite failure in a range of industries including aerospace, automotive and other transport, defence, marine and off-shore applications. Recycling issues and environmental factors affecting the use of composite materials are also considered. With its distinguished editors and international team of expert contributors Failure mechanisms in polymer matrix composites is a valuable reference for designers, scientists and research and development managers working in the increasing range of industries in which composite materials are extensively used. The book will also be a useful guide for academics studying in the composites field. © 2012 Woodhead Publishing Limited All rights reserved.
Melro AR, Camanho PP, Andrade Pires FM, et al., 2012, Modelling the micromechanical behaviour of 5-harness satin weaves obtained by RTM
An Offset-reduced Unit Cell (OrUC) model of a 5-harness satin weave is used to characterise damage evolution in this textile composite. Non-linear material models for both yarns and epoxy resin embedding the yarns are applied to the numerical analysis. The epoxy resin is represented by an elasto-plastic with damage constitutive model while the yarns are modelled making use of a transversely isotropic damage model recently proposed. Different loading conditions are applied to the OrUC, allowing for a detailed study of damage initiation and evolution inside the satin weave up until complete failure.
Wilmes AAR, Pinho ST, 2012, A molecular dynamics derived Finite Element Method for structural simulations and failure of graphene nanocomposites
The recent rise of 2D materials, such as graphene, has expanded the interest in nanoelectromechanical systems (NEMS). The increasing ability of synthesizing more exotic NEMS architectures, creates a growing need for a cost-effective, yet accurate nano-scale simulation method. Established methodologies like Molecular Dynamics (MD) trail behind synthesis capabilities because the computational effort scales quadratically. The equilibrium equations of MD are equivalent with those of the computationally more favourable Finite Element Method (FEM). However, current implementations exploiting this equivalence remain limited due to the FEM iterative solvers requiring a large number of lengthy force field derivatives and specifically tailored element topologies. This paper proposes a merged Molecular Dynamic Finite Element Method (MDFEM) which does not require the manual derivation of these derivatives. Hence, implementing MDFEM-specific element topologies is straightforwards and thus, different non-linear MD force field potentials can be solved exactly within the FEM, at reduced computational costs. The proposed multi-scale and multi-physics compatible MDFEM is equivalent to the MD, as demonstrated firstly by an example of brittle fracture in Carbon Nanotubes (CNT), and secondly by conformational analyses on Non-Equilibrium initial meshes of Pillared Graphene Structures (PGS).
Stocchi C, Robinson P, Pinho ST, 2012, Using strain gauges to monitor bolt clamping force and fracture in composite joints during fatigue tests
This paper presents an effective method to monitor the loss of clamping force and detect crack initiation and propagation in the fasteners of composite bolted joints during lap shear fatigue tests using strain gauges and an algorithm to process the data. The location of the strain gauges was determined to make their readings suitably sensitive to the effect of the clamping force and to reduce the effect of the external load on the strain readings. The algorithm recognises the load cycles and, using the superposition principle, extrapolates the strain associated only with the clamping force for each cycle. The method has been validated numerically and experimentally. In the experimental results, the clamping force has been observed to remain constant for most of the joint fatigue life and, subsequently, to drop rapidly as the bolt failure progresses. It was further observed that there is a load transfer and an interaction between the bolts during the failure process, which is related to the fast but stable fatigue crack propagation that takes place in the bolts before final failure of the joint.
Teixeira RF, Pinho ST, Robinson P, 2012, Translaminar fracture toughness of CFRP: From the toughness of individual plies to the toughness of the laminates
The translaminar fracture toughness of carbon-epoxy multidirectional composite laminates was measured using a compact tension (CT) configuration. Additionally, translaminar fracture toughnesses of individual plies orientated at angles of 90°, 0 °and ±45° were determined. The fracture surfaces of the CT specimens were analysed to investigate relationships between the features of these surfaces and the toughness measurements. Failure mechanisms found in the multidirectional laminates included a combination of the failure mechanisms found on bi-directional laminates (90=θ) made of its constituent plies. Ply splitting, fibre bridging and fibre pull were the main features characterizing the fracture surfaces. Three analytical predictive models were used to predict the translaminar toughness of the laminates from that of the constituent plies. The assumption of translaminar fracture toughness additivity by means of a law of mixtures correlated best with the experimental results.
Dizy J, Palacios R, Pinho ST, 2012, Homogenization of slender periodic composite structures
A homogenization technique is developed to obtain the equivalent 1-D stiffness properties of complex slender periodic composite structures with varying cross-sections. All this is done while removing the limitation of a constant cross-section often imposed in literature. The problem is posed using a unit cell approach and applying periodic boundary conditions such that: 1) the microscopic strain state averages to the macroscopic conditions, and 2) the deformation energy is conserved between scales. The methodology also allow for stress recovery and local buckling analysis. Numerical examples are shown to illustrate the diverse capabilities of the method: An isotropic ribbed prismatic beam is used to introduce the method, show the reinforcements and local buckling capabilities; a composite laminated cylinder is shown to demonstrate span-wise varying properties and parametric analysis and, finally, a composite blade section exemplifies it for complex geometries. © 2012 by Julian Dizy, Rafael Palacios and Silvestre T. Pinho.
Whiteside MB, Pinho ST, 2012, Stochastic modelling of woven composites
A reduced unit cell (rUC) structural/mechanical model of a 5-Harness satin weave is constructed and analysed deterministically in uniaxial and biaxial loading conditions. An algorithm is developed and implemented to fully automate the rUC construction such that stochastic variations of the crimp angle can be evaluated. Monte Carlo Simulation is employed to propagate the effect of the crimp angle through the deterministic model and the probabilistic response compared with data obtained experimentally. It is observed how simulated variability compares well in uniaxial compression, but under-predicts observed experimental variability in uniaxial tension. The influence of vertical stacking sequence of plies is also demonstrated through the study of in-phase and out-of-phase periodic boundary conditions in the through thickness direction.
Robinson P, McCarroll CA, Pinho ST, et al., 2012, Design and evaluation of a high rate mode i translaminar fracture toughness test for composite laminates
The compact tension (CT) specimen has been investigated for the measurement of the high rate Mode I translaminar toughness of a carbon epoxy composite laminate with a layup of [(90°/0°)890°] s. Finite element analyses using LS-DYNA showed that when loaded at high rates (up to 12 m/s) the CT specimen achieved virtually pure Mode I fracture. In additional analyses a data-reduction strategy was developed in which strain (measured at a specific position on the specimen) and crack length measured during a test could be used to determine the toughness in high rate tests. In an experimental programme the average propagation toughness exhibited a small overall decrease with increasing test speed but, in view of the considerable scatter, further testing will be required to confirm the significance of this trend. Examination of the fracture surfaces using a scanning electron microscope indicated that the fracture characteristics are essentially unchanged with increasing test speed.
Kiefer K, Robinson P, Pinho ST, 2012, Simulation of high-cycle fatigue-driven delamination in carbon/epoxy laminates using cohesive elements
This paper discusses the implementation of a model for the high-cycle fatigue-driven delamination of a carbon/epoxy composite into the finite element software ABAQUS. The model was first tested using a non-FE technique which enabled an extensive investigation of its sensitivity and accuracy to be rapidly performed. It was then implemented as a user- defined element in the ABAQUS and will be used to predict the fatigue delamination of structural details for aerospace applications such as stiffener runouts.
Potter E, Pinho ST, Robinson P, et al., 2012, Mesh generation and geometrical modelling of 3D woven composites with variable tow cross-sections, COMPUTATIONAL MATERIALS SCIENCE, Vol: 51, Pages: 103-111, ISSN: 0927-0256
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- Citations: 42
Vyas GM, Pinho ST, 2012, Computational implementation of a novel constitutive model for multidirectional composites, COMPUTATIONAL MATERIALS SCIENCE, Vol: 51, Pages: 217-224, ISSN: 0927-0256
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- Citations: 17
Laffan MJ, Pinho ST, Robinson P, et al., 2011, Translaminar fracture toughness: The critical notch tip radius of 0° plies in CFRP, COMPOSITES SCIENCE AND TECHNOLOGY, Vol: 72, Pages: 97-102, ISSN: 0266-3538
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- Citations: 48
Gutkin R, Pinho ST, 2011, Practical application of failure models to predict the response of composite structures
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- Citations: 3
Teixeira RF, Pinho ST, Robinson P, 2011, Translaminar ply fracture toughness of advanced composites
The translaminar fracture toughness of fibre reinforced polymers (FRP) is important to characterise the failure resistance and response of notched composite structures. Compact Tension (CT) tests of UD 90° [(90 6/0)2/903]s, [(90/0) 8/90]s and [(906/-45/906/+45)/ 903]s laminates were conducted in order to investigate the crack development and measure the translaminar fracture toughnesses values for three plies of interest:90°,0° and ± 45° A quasi-isotropic layup with 90°,0° and ±45°plies was also investigated. Testing was monitored with digital image correlation (DIC). The test method and data reduction scheme are the result of extensive background work [1]. Failure sequence was analysed using optical micrography, SEM, C-Scan and X-ray.
Stocchi C, Robinson P, Pinho ST, 2011, A detailed finite element investigation of composite bolted joints with countersunk fasteners
This paper presents a very detailed FEM model of a single lap shear composite bolted joint, with countersunk fasteners, under static tensile load. Parametric studies have been performed to study the influence of clamping force, coefficient of friction and clearance on the joint behaviour. It has been found that the model is able to identify correctly the joint critical locations and that the joint behaviour can be divided in five stages, which are deeply influenced by the three studied parameters.
Whiteside MB, Pinho ST, 2011, Stochastic modelling of UD and 2D woven composite response
Pinho ST, De Carvalho NV, Robinson P, 2011, Analytical model to predict failure of woven composites
Vyas GM, Pinho ST, Robinson P, 2011, Failure prediction and damage modelling of matrix cracking in quasi-isotropic laminates at the ply level
Kiefer K, Robinson P, Pinho ST, 2011, Comparison of models for the simulation of fatigue-driven delamination using cohesive elements
In this pape,r two formulations for introducing fatigue damage into cohesive elements have been examined to determine their mesh sensitivity and numerical stability in mode I. A simple, non-FE model has been used to quickly assess a wide range of parameters associated with the fatigue degradation routines developed for cohesive elements. The model has been used to explore the sensitivity of two fatigue degradation strategies to changes in key parameters. For small element and cycle increments, both models predict the fatigue crack growth rate accurately for various applied loads where the Paris law is valid. However the models exhibit significant mesh sensitivities. The analysis has shown that in order to obtain a numerically stable algorithm, the models need to be improved.
Chen B, Tay TE, Baiz PM, et al., 2011, Size effects in progressive damage of notched and holed composites
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- Citations: 1
Canturri C, Greenhalgh ES, Pinho ST, et al., 2011, Delamination growth mechanism from embedded defects in compression, ICCM International Conferences on Composite Materials
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- Citations: 5
Gutkin R, Pinho ST, Robinson P, et al., 2011, A finite fracture mechanics formulation to predict fibre kinking and splitting in CFRP under combined longitudinal compression and in-plane shear, MECHANICS OF MATERIALS, Vol: 43, Pages: 730-739, ISSN: 0167-6636
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- Citations: 29
Pimenta S, Pinho ST, Robinson P, 2011, Micromechanics of recycled composites for material optimisation and eco-design, 18th International Conference on Composite Materials
Bui VQ, Iannucci L, Robinson P, et al., 2011, A coupled mixed-mode delamination model for laminated composites, JOURNAL OF COMPOSITE MATERIALS, Vol: 45, Pages: 1717-1729, ISSN: 0021-9983
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- Citations: 11
Psarras S, Pinho ST, Falzon BG, 2011, Design of composite stiffener run-outs for damage tolerance, FINITE ELEMENTS IN ANALYSIS AND DESIGN, Vol: 47, Pages: 949-954, ISSN: 0168-874X
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- Citations: 10
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