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  • 1.
    André, Alann
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Kliger, R.
    Chalmers University of Technology.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Compression failure mechanism in small-scale wood specimens reinforced with CFRP: An experimental study2013In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 41, p. 790-800Article in journal (Refereed)
    Abstract [en]

    The optimal use of Carbon Fibre Reinforced Polymer (CFRP) when strengthening timber beams loaded in bending involves considering placing the reinforcement on both the tension and the compression side, in order to utilise the ductile compression failure of the wood to the full. In this respect, a knowledge and understanding of the compression failure mechanism of the timber/CFRP system becomes a point of paramount importance. However, no testing method specific to the compression loading of small wood specimens reinforced with CFRP is currently available. This investigation focuses on the experimental developments of the geometry and test set-up necessary in order to determine the compression failure mechanism of small wood block specimens reinforced with CFRP loaded in compression parallel to the grain. The method is based on an existing testing method for unreinforced wood specimens. The Digital Image Correlation (DIC) method is used to monitor deformation during experiments. The experimental results of reinforced specimens are compared with those of paired unreinforced specimens tested in a previous study. The experimental method presented in this study shows that specific geometry and test considerations must be implemented when compared with the existing method for unreinforced specimens. © 2012 Elsevier Ltd. All rights reserved.

  • 2.
    Asp, Leif
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Marklund, Erik
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Varna, J.
    Luleå University of Technology.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Multiscale modelling of non-crimp fabric composites2012Conference paper (Refereed)
    Abstract [en]

    Damage initiation and evolution in NCF composites leading to final failure includes a multitude of mechanisms and phenomena on several length scales. From an engineering point-of-view a computational scheme where all mechanisms would be explicitly addressed is too complex and time consuming. Hence, methods for macroscopic performance prediction of NCF composites, with limited input regarding micro- And mesoscale details, are requested. In this paper, multi-scale modelling approaches for in-plane transverse strength of NCF composites are outlined and discussed. In addition a simplistic method to predict transverse tensile and compressive strength for textile composites featuring low or no fibre waviness is presented. Copyright © 2012 by ASME.

  • 3.
    Bru, Thomas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Asp, Leif
    Chalmers University of Technology, Sweden.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Vyas, Gaurav
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Biaxial transverse compression testing for a fibre reinforced polymer material2018Conference paper (Refereed)
    Abstract [en]

    Unidirectional laminates have been tested under uniaxial transverse compression and under biaxialtransverse compression. Failure occurred by shear in an inclined failure plane parallel to the fibres.The transverse shear response of the material on the failure plane was evaluated from the tests. In thebiaxial tests, the failure load was considerably higher than in the uniaxial tests. For a given transverseshear strain the transverse shear stress was also higher in the case of biaxial compression. It is alsoshown that using waisted specimens instead of prismatic specimens does not seem to bring noticeablebenefits for through-thickness uniaxial compression tests. The experimental results presented here areimportant input to the development and the validation of damage models of fibre reinforced polymermaterials accounting for the matrix nonlinear response in shear and compression.

  • 4.
    Bru, Thomas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Gutkin, Renaud
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Vyas, Gaurav M.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Use of the Iosipescu test for the identification of shear damage evolution laws of an orthotropic composite2017In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 174, p. 319-328Article in journal (Refereed)
    Abstract [en]

    The experimental evaluation of the shear response of fibre-reinforced plies is a requirement for accurate material models predicting progressive damage. In the first part of the paper, the quality of the Iosipescu shear test is investigated with full-field strain measurements and finite element analyses. In the second part, the in-plane and through-thickness shear response of an orthotropic carbon/epoxy uni-weave non-crimp fabric composite are compared, and the stress–strain curves used as input for two continuum damage mechanics models. Both models were able to predict accurately the nonlinear shear behaviour of the material. The model parameters and the damage evolution laws could easily be extracted from cyclic Iosipescu tests.

  • 5.
    Bru, Thomas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Portugal, A
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Vyas, Gaurav
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Costas, Sérgio
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Validation of a novel model for the compressive response of FRP:experiments with different fibre orientations2017Conference paper (Refereed)
    Abstract [en]

    Crush tests have been performed on flat unidirectional non-crimp fabric (NCF) coupons with differentfibre orientations as part of the validation of a ply-based damage model for crash. The fibre off-axisangle with respect to the crushing direction ranged from 0º to 90°. The results of the tests indicate thatthe crush stress remains unchanged for off-axis angles between 0° and 15°. The failure mode in thesespecimens was out-of-plane kinking. For 20° and 25° off-axis angles the crush stress dropped 20% andevidence of out-of-plane kinking were harder to find. For 45° off-axis angle a network of matrixcracks develops in the specimen and for 90° off-axis angle a brittle shear failure is observed. It issuggested that the out-of-plane kinking is promoted because of the natural waviness of NCF materialsand that the high in-plane shear stress generated from 20-25° off-axis loading results in a transitionfrom out-of-plane kinking to in-plane kinking. These hypotheses need, however, to be verified by anextended failure analysis of the crush specimens.

  • 6.
    Bru, Thomas
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Waldenström, Paul
    KTH Royal Institute of Technology, Sweden.
    Gutkin, Renaud
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Vyas, Gaurav M.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Development of a test method for evaluating the crushing behaviour of unidirectional laminates2017In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 51, no 29, p. 4041-4051Article in journal (Refereed)
    Abstract [en]

    More fundamental test methods are needed to assist the development of physically based and truly predictive simulation tools for composite materials under crash conditions. In this paper, a unidirectional flat specimen that can be used to validate the predicted behaviour from a simulation to the physical behaviour in the experiment is developed. A systematic experimental investigation is conducted to evaluate the influence of the trigger geometry on the crushing response by selecting two trigger types and different trigger angles. For longitudinal crushing, the traditional bevel trigger leads to out-of-plane failure by splaying with a limited amount of in-plane fracture, while the proposed trigger achieves a high amount of compressive fragmentation failure. For transverse crushing, the symmetry of the proposed new trigger improves the specimen stability during the crushing process. It is also observed that the weft threads of the unidirectional fabric reinforcement used for the tests have a strong influence on the longitudinal crushing response. The boundary conditions of the test and the information on the specimen failure gleaned from video recordings and microscopic inspections are discussed in order to facilitate a future correlation with modelling results. © 2017, © The Author(s) 2017.

  • 7.
    Costa, Sergio
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Bru, Thomas
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Portugal, André
    INOV Contacto Programme, Portugal.
    Improvement and validation of a physically based model for the shear and transverse crushing of orthotropic composites2019In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 53, no 12, p. 1681-1691Article in journal (Refereed)
    Abstract [en]

    This paper details a complete crush model for composite materials with focus on shear dominated crushing under a three-dimensional stress state. The damage evolution laws and final failure strain conditions are based on data extracted from shear experiments. The main advantages of the current model include the following: no need to measure the fracture toughness in shear and transverse compression, mesh objectivity without the need for a regular mesh and finite element characteristic length, a pressure dependency of the nonlinear shear response, accounting for load reversal and some orthotropic effects (making the model suitable for noncrimp fabric composites). The model is validated against a range of relevant experiments, namely a through-the-thickness compression specimen and a flat crush coupon with the fibres oriented at 45° and 90° to the load. Damage growth mechanisms, orientation of the fracture plane, nonlinear evolution of Poisson's ratio and energy absorption are accurately predicted.

  • 8.
    Costa, Sergio
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Gutkin, Renaud
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Mesh objective implementation of a fibre kinking model for damage growth with friction2017In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 168, p. 384-391Article in journal (Refereed)
    Abstract [en]

    A newly developed physically based model for the longitudinal response of laminated fibre-reinforced composites during compressive damage growth is implemented in a Finite Element (FE) software. It is a mesoscale model able to capture the physics of kink-band formation by shear instability, the influence of the matrix in supporting the fibres and the rotation of the fibres during compression, resulting in more abrupt failure for smaller misalignments. The fibre kinking response is obtained by solving simultaneously for stress equilibrium and strain compatibility in an FE framework. Strain softening creates pathological sensitivity when the mesh is refined. To make the model mesh objective, a methodology based on scaling the strain with the kink-band width is developed. The FE implementation of the current model is detailed with focus on mesh objectivity, and generalized to irregular meshes. The results show that the current model can be used to predict the whole kinking response in a 3D framework and thus account for the correct energy dissipation.

  • 9.
    Costa, Sérgio
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Portugal, André
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Vyas, Gaurav
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Bru, Thomas
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Validation of a novel model for the compressive response of FRP: numerical simulation2018Conference paper (Refereed)
    Abstract [en]

    A progressive damage model for matrix compression is complemented with matrix tension in a physically based manner. The interaction of damage mechanisms undergoes a preliminary validation using single elements. The crushing response is validated with two different flat specimens with the fibres oriented transversely and at 45 degrees to the load. The model combines friction with damage to model the shear response accurately, which is necessary for reliable crush simulations. The behaviour in tension is history dependent, i.e. the model accounts for the stiffness reduction and strength to carry load in tension when previously damaged occurs in compression.The validation is performed against different tests showing the reliability of the model for different fibre orientation, specimen geometry and multiaxial loading scenarios. The crush response is well captured as well as the geometry and location of the different damage mechanisms.

  • 10.
    Craven, R.
    et al.
    Imperial College London.
    Iannucci, L.
    Imperial College London.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Buckling of a laminate with realistic multiple delaminations and fibre fracture cracks using finite element analysis2009Conference paper (Refereed)
    Abstract [en]

    This paper presents a finite element study of buckling and postbuckling of sub-laminates representative of an impact damaged laminate. Multiple realistic delaminations and fibre fracture cracks are considered under compression to identify the key parameters of impact damage that affect the residual compressive strength of the laminate.

  • 11.
    Craven, R.
    et al.
    Imperial College London.
    Iannucci, L.
    Imperial College London.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Delamination buckling: A finite element study with realistic delamination shapes, multiple delaminations and fibre fracture cracks2010In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 41, no 5, p. 684-692Article in journal (Refereed)
    Abstract [en]

    This paper presents a finite element model of a carbon fibre composite laminate with multiple delaminations of realistic shape and including fibre fracture cracks loaded under compression. The modelling technique is initially applied on circular and elliptical delaminations of single ply sublaminates, which are compared with existing analytical solutions. The techniques are then applied to models with multiple delaminations of realistic shape and their behaviour in buckling and post-buckling is captured. An inverse method is used to determine the stiffness reduction caused by the damage, and shows significant stiffness reduction caused by peanut shaped delaminations. When fibre fracture cracks are added, their contribution to further stiffness reduction is minimal but they have some significant effects on the buckling shapes. © 2010 Elsevier Ltd. All rights reserved.

  • 12.
    Craven, R.
    et al.
    Imperial College London.
    Iannucci, L.
    Imperial College London.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Homogenised non-linear soft inclusion for simulation of impact damage in composite structures2011In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 93, no 2, p. 952-960Article in journal (Refereed)
    Abstract [en]

    This paper presents the development of a homogenised non-linear soft inclusion which captures the geometric and material non-linearity of impact damage zone loaded in tension and compression. The homogenised non-linear soft inclusion can present a conservative worst case damage zone or use experimental data to mimic the behaviour of a particular damage zone in a simple and computationally efficient way that can be used as a structural design tool for composite structures subjected to impact. The development of the non-linear soft inclusion, implemented in an ABAQUS/Explicit VUMAT, is presented at element and coupon level. The non-linear soft inclusion is validated against experimental coupon data and produces a conservative worst case estimate in all cases investigated. © 2010 Elsevier Ltd.

  • 13.
    Farajzadeh Khosroshahi, S.
    et al.
    University of Padova, Italy.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Wysocki, Maciej
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Zaccariotto, M.
    University of Padova, Italy.
    Galvanetto, U.
    University of Padova, Italy.
    Response of a helmet liner under biaxial loading2018In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 72, p. 110-114Article in journal (Refereed)
    Abstract [en]

    Helmets are the most effective protective item for motorcyclists. The liner of the helmet is the part of the helmet which dissipates most of the impact energy and mitigates the risk of head injuries. It has been proposed that the helmet test standards should include assessment of the helmets for oblique impacts that is not currently addressed in the standards. A conventional uniaxial compression test method is still used for characterization of the helmet liner material. However, compressive tests of EPS foams provide reliable results for normal loading on EPS, but do not provide a realistic result for oblique impacts. Therefore, we carried out experimental tests to measure the response of EPS foams, which are commonly used for helmet liners, under biaxial loading. The result of our experiments show that the shear response of EPS foams is a function of axial compression, and increasing the axial strain leads to increased shear stiffness, and thus higher levels of shear stress. We also showed that including shear-stiffening of EPS in the FE assessment of helmets may change the headform rotational acceleration by 25%. Therefore, such behavior of EPS foams should be included in FE analysis of helmets in the case of oblique impacts for a more realistic assessment of their performance.

  • 14.
    Grauers, Lisa
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Gutkin, Renaud
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Energy absorption and damage mechanisms in progressive crushing of corrugated NCF laminates: Fractographic analysis2014In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 110, no 1, p. 110-117Article in journal (Refereed)
    Abstract [en]

    To develop reliable and physically based models for the crash behaviour of composite laminates, a thorough understanding of the failure mechanisms is crucial. Compression tests of corrugated Non-Crimp Fabric (NCF) laminates, made of carbon fibre unidirectional (UD) fabric with a [0/90]3S stacking sequence and epoxy, have been performed to study the energy absorbing damage mechanisms. Samples from the specimens have been studied with optical microscopy and Scanning Electron Microscopy (SEM) to identify the mechanisms involved in the crushing process. The specimens tested fail partly in bending and partly in pure compression with a mode I delamination separating these two regions. In the region failing in pure compression, the main damage mechanisms are kink band formation and matrix cracking of transverse bundles, whereas in the part failing in bending mixed mode delaminations, intralaminar shear fracture of axial bundles and kink band formation through parts of bundles are identified. © 2013 Elsevier Ltd.

  • 15.
    Juntikka, Rickard
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Experimental and modelling study of hail impact on composite plates2009Conference paper (Refereed)
    Abstract [en]

    Foreign object impact is a serious threat to aircraft, hail or bird impact may seriously degrade the performance of aircraft structures. This work focuses on hail impact experiments and modelling for characterising the impact event and damage initiation in composite material.

  • 16.
    Marklund, Erik
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Asp, Leif
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Transverse strength of unidirectional non-crimp fabric composites: Multiscale modelling2014In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 65, p. 47-56Article in journal (Refereed)
    Abstract [en]

    A multiscale approach is used to predict transverse tensile and transverse compressive strength of unidirectional non-crimp fabric (NCF) composites. Numerical analysis on fibre/matrix scale is performed to obtain the transverse strength of the fibre bundle to be further used in an analytical mesoscale model to predict the strength of the unidirectional NCF composite. Design of unidirectional layer composites with the same fibres, interface, matrix and volume fractions as in the bundle is suggested as an alternative method for bundle strength determination. Good agreement of both methods for bundle transverse strength determination is demonstrated. The simple analytical model used on mesoscale gives accurate predictions of the tensile transverse strength whereas the compressive strength is underestimated. The necessity of including bundle waviness in models when bidirectional NCF composites are analysed is demonstrated by FEM stress analysis and by experimental data showing differences in transverse cracking pattern due to bundle waviness. © 2014 Elsevier Ltd. All rights reserved.

  • 17.
    McElroy, Mark
    et al.
    NASA Langley Research Center, USA.
    Jackson, Wade
    NASA Langley Research Center, USA.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Hellström, Peter
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Tsampas, Spyros
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Pankow, Mark
    North Carolina State University, USA.
    Interaction of delaminations and matrix cracks in a CFRP plate, Part I: A test method for model validation2017In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 103, p. 314-326Article in journal (Refereed)
    Abstract [en]

    Isolating and observing the damage mechanisms associated with low-velocity impact in composites using traditional experiments can be challenging, due to damage process complexity and high strain rates. In this work, a new test method is presented that provides a means to study, in detail, the interaction of common impact damage mechanisms, namely delamination, matrix cracking, and delamination-migration, in a context less challenging than a real impact event. Carbon fiber reinforced polymer specimens containing a thin insert in one region were loaded in a biaxial-bending state of deformation. As a result, three-dimensional damage processes, involving delaminations at no more than three different interfaces that interact with one another via transverse matrix cracks, were observed and documented using ultrasonic testing and X-ray computed tomography. The data generated by the test is intended for use in numerical model validation. Simulations of this test are included in Part II of this paper.

  • 18.
    Nguyen, S.
    et al.
    Imperial College London.
    Greenhalgh, E.S.
    Imperial College London.
    Iannucci, L.
    Imperial College London.
    Longstaff, S.
    Imperial College London.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Curtis, P.T.
    Dstl Porton Down, Salisbury.
    Experimental characterisation of tyre indentation by simulated runway debris2011In: Strain, ISSN 0039-2103, E-ISSN 1475-1305, Vol. 47, no 4, p. 343-350Article in journal (Refereed)
    Abstract [en]

    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 inflated tyres and foreign objects. In this paper, experiments involving indentation of an inflated tyre to represent 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. © 2010 Blackwell Publishing Ltd.

  • 19.
    Nguyen, S.N.
    et al.
    Imperial College London, UK.
    Greenhalgh, E.S.
    Imperial College London, UK.
    Graham, J.M.R.
    Imperial College London, UK.
    Francis, A.
    Imperial College London, UK.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Runway debris impact threat maps for transport aircraft2014In: Aeronautical Journal, ISSN 0001-9240, Vol. 118, no 1201, p. 229-266Article in journal (Refereed)
    Abstract [en]

    Large transport aircraft are particularly susceptible to impact damage from runway debris thrown up by the landing gear. A methodology was developed to predict the trajectories of stones lofted by the nose wheel and subjected to aerodynamic forces due to the wake behind the nose landing gear and beneath the aircraft. In conjunction with finite element modelling of the stone/ground/tyre contact mechanics, an analytical model was used to perform a stochastic prediction of the trajectories of runway stones to generate impact threat maps which showed the relative likelihood of stones impinging upon various areas on the underside of a C-130 Hercules. The impact envelopes for the C-130 extended three to eighteen metres behind the nose wheel and two metres either side of the centre of the aircraft. The impact threat maps were especially sensitive to the values of the coefficients of lift and drag acting on the stone during its flight.

  • 20.
    Nguyen, S.N.
    et al.
    Imperial College.
    Greenhalgh, E.S.
    Imperial College.
    Graham, M.
    Imperial College.
    Francis, A.
    Imperial College.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Methodology for predicting the threat of runway debris impact to large transport aircraft2012Conference paper (Refereed)
    Abstract [en]

    Large transport aircraft are particularly susceptible to impact damage from runway debris thrown up by the landing gear. A methodology was developed to predict the trajectories of stones lofted by the nose wheel and subjected to aerodynamics forces due to the wake behind the nose landing gear and beneath the aircraft. In conjunction with finite element modeling of the stone/ground/tire contact mechanics, a Matlab model was used to perform a stochastic prediction of the trajectories of runway stones to generate impact threat maps which showed the relative likelihood of stones impinging upon various areas on the underside of a C-130 Hercules. The impact envelopes for the C-130 extended 2.4 to 17.5 meters behind the nose wheel and two meters either side of the center of the aircraft. The impact threat maps were especially sensitive to the values of the coefficients of lift and drag acting on the stone during its flight. © 2012 by Imperial College London.

  • 21.
    Nguyen, S.N.
    et al.
    Imperial College.
    Greenhalgh, E.S.
    Imperial College.
    Graham, M.
    Imperial College.
    Francis, A.
    Imperial College.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Methodology for predicting the threat of runway debris impact to large transport aircraft2012Conference paper (Refereed)
    Abstract [en]

    Large transport aircraft are particularly susceptible to impact damage from runway debris thrown up by the landing gear. A methodology was developed to predict the trajectories of stones lofted by the nose wheel and subjected to aerodynamics forces due to the wake behind the nose landing gear and beneath the aircraft. In conjunction with finite element modeling of the stone/ground/tire contact mechanics, a Matlab model was used to perform a stochastic prediction of the trajectories of runway stones to generate impact threat maps which showed the relative likelihood of stones impinging upon various areas on the underside of a C-130 Hercules. The impact envelopes for the C-130 extended 2.4 to 17.5 meters behind the nose wheel and two meters either side of the center of the aircraft. The impact threat maps were especially sensitive to the values of the coefficients of lift and drag acting on the stone during its flight. © 2012 AIAA.

  • 22.
    Nguyen, S.N.
    et al.
    Imperial College London.
    Greenhalgh, E.S.
    Imperial College London.
    Lannucci, L.
    Imperial College London.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Curtis, P.T.
    Physical Sciences Department, Salisbury, UK.
    Improved models for runway debris lofting simulations2009In: Aeronautical Journal, ISSN 0001-9240, Vol. 113, no 1148, p. 669-681Article in journal (Refereed)
    Abstract [en]

    Numerical models used to simulate the lofting mechanisms of runway stones were developed to assess the threat to aircraft structures from runway debris impacts. An inflated aircraft tyre model, which was validated by comparison with experimental indentation tests, showed that over-rolling of stones under typical take-off conditions led to only modest vertical loft velocities of less than 5 m/s. Experiments using a drop weight impactor simulated a section of aircraft tyre descending upon stones. These tests demonstrated that lofting was achieved for impacts with low rubber thickness. However, for impacts with greater rubber thickness, lofting was suppressed. Using more realistic tyre geometries resulted in launches with backspin, but only horizontally along the ground in the direction of the tyre axis. The speed at which launches occurred was proportional to the rate of descent of the tyre section and would consequently determine the loft speeds due to potential asperity lofting.

  • 23.
    Nguyen, S.N.
    et al.
    Imperial College London.
    Greenhalgh, E.S.
    Imperial College London.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Analytical modeling of runway stone lofting2011In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 48, no 4, p. 1412-1421Article in journal (Refereed)
    Abstract [en]

    This investigation aims to develop a closed-form analytical model to understand and predict runway stone lofting processes by considering the rigid-body interaction of a tire partially rolling over a stone. Any leading-edge aircraft structures impinging into the path of such stones could experience impacts at speeds up to the aircraft takeoff velocity, despite being some distance from the sides of the wheels. The results of the analytical model provide upperbound envelopes of the vertical loft speeds obtained in previous numerical simulations and modified drop-weight experiments. Parametric studies conclude that the vertical loft speeds rise with increasing stone-tire overlap, stone size, and aircraft speed and with deceasing tire diameter. The outcomes of this model form a basis for vehicle designers to assess the runway stone impact threat by better understanding the physics of lofting. © 2010 by S. N. Nguyen, E. S. Greenhalgh, and R. Olsson. Published by the American Institute of Aeronautics and Astronautics, Inc.

  • 24.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Analytical model for delamination growth during small mass impact on plates2010In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 47, no 21, p. 2884-2892Article in journal (Refereed)
    Abstract [en]

    An analytical model is presented for delamination initiation and growth and the resulting response during small mass impact on orthotropic laminated composite plates, which typically is caused by runway debris and other small objects. The solution is obtained by a fast stepwise numerical solution of a single integral equation. Delamination size, load and deflection history are predicted by extension of an earlier elastic impact model by the author. Good agreement is demonstrated in comparisons with finite element simulations and experiments. © 2010 Elsevier Ltd. All rights reserved.

  • 25.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Analytical model for small mass impact with delamination growth2009Conference paper (Refereed)
    Abstract [en]

    An analytical model is presented for small mass impact on orthotropic composite laminates with delamination growth, which typically is caused by runway debris and other small objects. Delamination size, load and deflection history are predicted by extension of an earlier elastic impact model by the author. Comparisons with finite element simulations and experiments are provided.

  • 26.
    Olsson, Robin
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Juntikka, Rickard
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Asp, Leif
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    High velocity hail impact on composite laminates - Modelling and testing2013In: Solid Mechanics and its Applications, ISSN 9250042, Vol. 192, p. 393-426Article in journal (Refereed)
    Abstract [en]

    Hail impact on composite structures during flight occurs at high velocities and is a serious concern as it may cause matrix cracking, large internal delaminations, and eventually fibre fracture not visible on the impacted surface. The present paper gives an introduction to hail impact on composite laminates and an overviewof experiments andmodellingwork on this topic, performed during several years at Swerea SICOMP. Ice balls of different sizes and velocities have been shot with an air gun on composite laminates of different thickness and reinforcement architecture. High speed photography and measurement of strain and deflection histories of the laminates have been used to validate the models developed. Models involve dynamic explicit finite element (FE) simulations with cohesive elements to allow for delamination in the laminate, and simplified but fast analytical models. The experimental response has also been compared with predictions from the FE model and the analytical models using various material models of the ice. FE models using a calibrated elastic-plastic ice model are capable of accurately predicting the response and delamination initiation, while the current analytical models are unable to simulate the initial part of the impact. A main conclusion is that delamination occurs at a very early stage of the impact (first 10-50 μs) where three-dimensional wave propagation and the initial elastic-plastic behaviour of the ice are important. Closed form models are capable of predicting the peak contact stresses at the first instance of contact, but further work is required to allow simulation of the decay of contact stresses observed in the FE simulations. © Springer Science+Business Media Dordrecht 2013.

  • 27.
    Olsson, Robin
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Marklund, Erik
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Jansson, N.
    Volvo, Sweden.
    Testing of carbon/epoxy NCF strength under mixed in-plane loading2012Conference paper (Refereed)
    Abstract [en]

    The measured stiffness and strength of a carbon/epoxy unidirectional NCF system in shear, tension and compression are compared with test results for the pure resin and for impregnated bundle material under various combinations of in-plane compressive and tensile loading. The study is a part of a project to develop mesomechanics models to predict failure of NCF materials under triaxial loading by use of data for the pure resin and for bundles impregnated by resin. A simplified analytical rule-of-mixtures model is suggested for stiffness and strength of the NCF material. Good agreement is shown for shear and tension along and transverse to the bundles. Compressive strengths are significantly underestimated, apparently due to deficiencies in the compressive test method used for the bundle material.

1 - 27 of 27
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