Publications
78 results found
Micallef K, Soleiman-Fallah A, Curtis PT, et al., 2012, A study of early-time response in dynamically loaded visco-elastic composites, Vol: 94, Pages: 1366-1378
Ankersen J, Greenhalgh ES, Tsampas SA, et al., 2012, Dynamic fracture in CFRP panels under compressive loading, ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials
Little is known about compression crack velocities, and methods to arrest them. Here a sandwich panel was used for characterisation of rapid crack propagation under compressive loading by means of high speed video in conjunction with Digital Image Correlation (DIC). A finite element modelling approach was developed and compared with the test data. This investigation included plain skin panels and panels with thickened regions which showed evidence of crack retardation.
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.
Micallef K, Fallah AS, Pope DJ, et al., 2012, Mesh-insensitive finite element modelling of elastic-plastic composites
The aim of the present study is to investigate the behaviour of high-performance polypropylene based composites, such as Dyneema® and extract the response under tension, compression and shear. An energy-based approach to model the observed behaviour is presented. The proposed model is mesh-size independent by ensuring that the maximum element size does not exceed a computed value. Alternatively, the softening curve is adjusted such that the energy equivalence is maintained. A damage index is formulated to degrade material stiffness in each direction and also taking into account permanent plastic deformation under tensile loading. Compressive behaviour is accounted for by a simplified elastic-plastic response while shear deformation is characterised by a cubic stress-strain response. The proposed formulation will be implemented in a commercial finite element package, such as ABAQUS/Explicit, by means of a user-defined subroutine (VUMAT) and used to model extreme loading events on Dyneema® panels under localised and global blast loading.
Micallef K, Fallah AS, Pope DJ, et al., 2012, On constitutive modelling of rate-dependence in orthotropic elasto-plastic media
The aim of the present study is to develop a constitutive model which is able to capture full orthotropic behaviour of a laminated polymeric elasto-plastic composite as well as taking into account material strain-rate sensitivity, making it particularly suitable for investigation of dynamic response under high rate blast and impact loads. The formulation is an extension of the work by Ogihara and Reifsnider and including strain-rate effects using the method proposed by Thiruppukuzhi and Sun. The proposed model is implemented in incremental form as a VUMAT in ABAQUS/Explicit and a set of parametric studies assessing dependence on strain-rate and loading direction are carried out. From this study, it is found that the proposed model is suitable for characterisation of composites subjected to dynamic loads and by using appropriate values of material parameters, the model can also be used for various composite architectures, including woven and uni-directional.
Raimondo L, Iannucci L, Pope D, et al., 2012, Strategies for low, high and hyper velocity impact damage modelling of structural composites
Challenges and recent advances in the modelling of impact damage of polymer composites for aerospace and defense applications are discussed in the present paper, including: a novel damage mechanics formulation applicable to predicting mesh-size independent impact damage in unidirectional (UD) composite laminates; a novel physics-based approach to the modelling of strain-rate-dependent elastic and failure behavior of UD composites; the application of a sub-scaling technique for ballistic impact simulations of large laminated composite targets; and a novel approach to predicting hypervelocity impact damage in high-performance fibre composites. Conclusions indicate that the proposed original solutions are valid and result in more reliable and more cost efficient impact simulations when compared to classic approaches.
Ćwik TK, Iannucci L, Robinson P, et al., 2012, Dynamic testing of high performance composite materials
This paper presents work-in-progress in the area of tensile split Hopkinson bar testing of high performance composite materials and their constituents. Improvements in the design of yarn grips for dynamic tensile testing are presented. Examples of contactless measurements, such as strain measurement directly from the specimen, showed that 2D Digital Image Correlation can be used to extract strains from very small areas, however a number of problems have to be solved in order to obtain qualitative data.
Micallef K, Fallah AS, Curtis PT, et al., 2012, A study of early-time response in dynamically loaded visco-elastic composites, Composite Structures, Vol: 94, Pages: 1366 - 1378-1366 - 1378, ISSN: 0263-8223
Spalling is an important failure mode which triggers delamination, thus affects through-thickness integrity of a laminate and hinders the later integral plate action. The aim of the present study is to model the propagation of one-dimensional waves caused by a short-duration dynamic load through a visco-elastic medium. Two types of viscous effects are considered and described by means of partial differential equations. Four pulse load shapes are considered and four cases analysed. A higher order Lagrangian finite element is used to model the wave propagation and the weak-form Galerkin method is adopted to solve the differential equations. Numerical solutions are compared to analytical ones (where they exist) and excellent temporal and spatial correlation is achieved. It is found that damping leads to a decrease in peak stresses and strains by up to 11% for 5% of critical damping, even during the direct loading phase. It is shown that the inclusion of strain-rate did not have an effect on strains but led to an increase in stresses by almost 100%. The inclusion of damping and strain-rate effects increased stress values by up to 70% compared to the non-viscous cases, rendering strain-rate effects more pronounced than damping effects.
Ćwik TK, Iannucci L, Curtis PT, et al., 2011, Investigation of ballistic response of CFRP composites of various non-conventional reinforcement architectures
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Micallef K, Soleiman-Fallah A, Curtis PT, et al., 2011, Constitutive formulation of strain-rate sensitive deformation in orthotropic composites, Pages: 397-408, ISSN: 1743-355X
The aim of the current study is to develop a constitutive model which captures the full orthotropic behaviour of a laminated composite by employing 9 material parameters and also taking into account strain-rate sensitivity to loading. The formulation is an extension of the work by Ogihara and Reifsnider (DOI: 10.1023/A:1016069220255), whose model considers 4 parameters, and with the inclusion of strain-rate effect considerations using the method employed by Thiruppukuzhi and Sun (DOI: 10.1016/S0266-3538(00)00133-0). A plastic potential function which can describe plasticity in all directions, including fibre plasticity, is chosen and using an associated flow rule, the plastic strain-rate components are derived. The plastic compliance matrix is assembled, using a rate-dependent visco-plastic modulus. The elastic compliance matrix is combined with its plastic counterpart to give a rate-form constitutive law. It is found that the proposed model accounts for strain-rate dependence and by correct choice of model parameters, the model can also be used for various composite architectures, including woven and uni-directional architectures. © 2011 WIT Press.
Tsampas SA, Greenhalgh ES, Ankersen J, et al., 2011, Study of compressive failure in multidirectional fibre-reinforced composites, ICCM International Conferences on Composite Materials
In this study the compressive failure of multidirectional fibre-reinforced composites was investigated. Cross-ply (CP) and multidirectional (MD) compact compression (CC) specimens were tested to identify the failure mechanisms that occur during compressive loading. Experimental results and subsequent fractographic analysis revealed that the layup significantly influenced the performance of both CP and MD fibre-reinforced composites under compression. Delamination and in-plane shear fracture dictated the fracture processes. The sequence of failure events that led to global fracture is presented. The findings have important implications for predictive modelling of compressive failure and crack arrest.
Tsampas S, Greenhalgh ES, Ankersen J, et al., 2011, On compressive failure of multidirectional fibre-reinforced composites: A fractographic study, Composites Part A: Applied Science and Manufacturing, Vol: 43, Pages: 454-468
The compressive failure of multidirectional carbon fibre-reinforced composites is investigated in this paper. Cross-ply and multidirectional compact compression IM7/8552 specimens were tested to deduce the failure mechanisms that occurred during compressive loading. The experimental results and the subsequent fractographic analysis revealed that the stacking sequence had a significant effect on the performance of multidirectional composites under compression. Delamination and in-plane shear fracture were the dominant failure mechanisms both in cross-ply and multidirectional configurations. While multidirectional configurations exhibited a stiffer response and higher failure load compared to cross-ply configurations, they were also more prone to delaminations and post-failure damage. Multidirectional laminates also exhibited significantly more complex fracture morphologies, which made the failure process interpretation more difficult. The sequence of events that lead to global fracture in multidirectional fibre-reinforced composites is presented.
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
Gutkin R, Laffan ML, Pinho ST, et al., 2011, Modelling the R-curve effect and its specimen-dependence, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, Vol: 48, Pages: 1767-1777, ISSN: 0020-7683
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- Citations: 67
Gutkin R, Green CJ, Vangrattanachai S, et al., 2011, On acoustic emission for failure investigation in CFRP: Pattern recognition and peak frequency analyses, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, Vol: 25, Pages: 1393-1407, ISSN: 0888-3270
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- Citations: 386
Tsampas SA, Greenhalgh ES, Ankersen J, et al., 2011, Study of compressive failure in multidirectional fibre-reinforced composites
In this study the compressive failure of multidirectional fibre-reinforced composites was investigated. Cross-ply (CP) and multidirectional (MD) compact compression (CC) specimens were tested to identify the failure mechanisms that occur during compressive loading. Experimental results and subsequent fractographic analysis revealed that the layup significantly influenced the performance of both CP and MD fibre-reinforced composites under compression. Delamination and in-plane shear fracture dictated the fracture processes. The sequence of failure events that led to global fracture is presented. The findings have important implications for predictive modelling of compressive failure and crack arrest.
Nguyen S, Greenhalgh ES, Iannucci L, et al., 2011, Experimental Characterisation of Tyre Indentation by Simulated Runway Debris, Strain, Vol: 47, Pages: 343-350
As part of an investigation to assess the impact threat posed to vehicles by tyre-lofted runway debris, it is important to gain a quantitative understanding of the interaction between inflatedtyres and foreign objects. In this paper, experiments involving indentation of an inflated tyre torepresent over-rolling of a foreign object were used to estimate the energy that could be transferred to the over-rolled object. The maximum kinetic energy that a 24-mm diameter spherical stone could potentially attain from such an indentation-related loft mechanism by a tyre inflated to 0.34 MPa (50 psi) was 20 J.
Micallef K, Soleiman-Fallah A, Curtis PT, et al., 2011, Analytical and numerical study of early-time response in pulse-loaded visco-elastic composites, 3rd International Workshop on Performance, Protection and Strengthening of Structures Under Extreme Loading, Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 214-+, ISSN: 1660-9336
Foreman JP, Porter D, Behzadi S, et al., 2010, Predicting the thermomechanical properties of an epoxy resin blend as a function of temperature and strain rate, 10th International Conference on Deformation and Fracture of Composites (DFC-10), Publisher: ELSEVIER SCI LTD, Pages: 1072-1076, ISSN: 1359-835X
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- Citations: 38
Gutkin R, Pinho ST, Robinson P, et al., 2010, On the transition from shear-driven fibre compressive failure to fibre kinking in notched CFRP laminates under longitudinal compression, COMPOSITES SCIENCE AND TECHNOLOGY, Vol: 70, Pages: 1223-1231, ISSN: 0266-3538
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- Citations: 99
Gutkin R, Pinho ST, Robinson P, et al., 2010, Micro-mechanical modelling of shear-driven fibre compressive failure and of fibre kinking for failure envelope generation in CFRP laminates, COMPOSITES SCIENCE AND TECHNOLOGY, Vol: 70, Pages: 1214-1222, ISSN: 0266-3538
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- Citations: 71
Nguyen SN, Greenhalgh ES, Olsson R, et al., 2010, Parametric analysis of runway stone lofting mechanisms, INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, Vol: 37, Pages: 502-514, ISSN: 0734-743X
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- Citations: 6
Nguyen S, Greenhalgh ES, Iannucci L, 2009, Improved Aircraft Tire and Stone Models for Runway Debris Lofting Simulations, 50th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
Bloodworth V, Greenhalgh ES, Falzon B, et al., 2009, Observations on Local Strain Fields in CFRP Stiffened Element Tests Using Digital Image Correlation, 17th International Conference on Composite Materials
McCarroll CA, Robinson P, Pinho ST, et al., 2009, High rate fractue toughness test design for tensile fibre failure modes
The compact tension specimen has been investigated numerically for the measurement of Mode I fracture toughness associated with fibre tensile failure,GIc, at crack speeds of the order of 200 m/s. This paper develops a load-independent data reduction scheme for analysing such tests using the compressive strain measured at the back edge of the specimen.
Gutkin R, Pinho ST, Robinson P, et al., 2009, Investigation of kink-band formation under biaxial stress state
This paper investigates longitudinal compressive failure. Two failure modes were observed experimentally for pure longitudinal compression: shear-driven fibre compressive failure and kink-band formation. In a micromechanical numerical study, failure envelopes for combined longitudinal compression and in-plane shear were predicted.
Behzadi S, Curtis PT, Jones FR, 2009, Improving the prediction of tensile failure in unidirectional fibre composites by introducing matrix shear yielding, COMPOSITES SCIENCE AND TECHNOLOGY, Vol: 69, Pages: 2421-2427, ISSN: 0266-3538
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- Citations: 32
Nguyen SN, Greenhalgh ES, Iannucci L, et al., 2009, Improved models for runway debris lofting simulations, AERONAUTICAL JOURNAL, Vol: 113, Pages: 669-681, ISSN: 0001-9240
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- Citations: 5
Bloodworth VM, Greenhalgh ES, Falzon B, et al., 2009, Observations on Local Strain Fields in CFRP Stiffened Element Tests Using Digital Image Correlation, London, 17th International Conference on Composite Materials, Publisher: IOM Communications Ltd
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