Ändra sökning
Länk till posten
Permanent länk

Direktlänk
BETA
Publikationer (10 of 45) Visa alla publikationer
Singh, V., Larsson, R., Marklund, E. & Olsson, R. (2019). Effect of strain rate at compressive and tensile loading of unidirectional plies in structural composites. In: Turon A, Maimí P, Fagerström M (Ed.), Proc. 7th ECCOMAS Thematic Conf. on the Mechanical Response of Composites.: . Paper presented at 7th ECCOMAS Thematic Conf. on the Mechanical Response of Composites. (pp. 177-183). European Community on Computational Methods in Applied Science (ECCOMAS)
Öppna denna publikation i ny flik eller fönster >>Effect of strain rate at compressive and tensile loading of unidirectional plies in structural composites
2019 (Engelska)Ingår i: Proc. 7th ECCOMAS Thematic Conf. on the Mechanical Response of Composites. / [ed] Turon A, Maimí P, Fagerström M, European Community on Computational Methods in Applied Science (ECCOMAS) , 2019, s. 177-183Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
Abstract [en]

Fibre-reinforced polymer composites are widely used in structural applications due to their high specific stiffness and strength. In some applications the response of dynamically loaded composite components must be analysed. For example, in crash analyses of structural components, where very high loading rates occurs, the composite behaviour is not fully understood. For this, we present a novel transversely isotropic viscoelasticviscoplastic constitutive model for a unidirectional carbon-epoxy composite. The model is micromechanically motivated so that the matrix and fibre materials of the composite are treated as micromechanical constituents at the ply scale. Based on the Hill-Mandel condition, the phases are homogenized via the macroscopic and fluctuating strain fields. To arrive at a simple but still representative model, a simplistic ansatz is applied to the structure of the fluctuating strains leading to a non-standard homogenized response of the composite. The model is applied to the non-linear rate dependent anisotropic ply behaviour under quasi-static and dynamic loading at different off-axis angles. For a simple viscoelastic-viscoplastic prototype for the rate dependent matrix response, there is a good correlation between measured and model response of the IM7-8552 material system in compression and tension.

Ort, förlag, år, upplaga, sidor
European Community on Computational Methods in Applied Science (ECCOMAS), 2019
Nyckelord
Constitutive model, Strain rate effects, Unidirectional composites
Nationell ämneskategori
Teknisk mekanik
Identifikatorer
urn:nbn:se:ri:diva-42513 (URN)
Konferens
7th ECCOMAS Thematic Conf. on the Mechanical Response of Composites.
Projekt
ICONICFFI-Crash 2
Forskningsfinansiär
EU, Horisont 2020, Grant 721256Vinnova, Dnr 2016-04239
Tillgänglig från: 2020-01-09 Skapad: 2020-01-09 Senast uppdaterad: 2020-01-31Bibliografiskt granskad
Costa, S., Bru, T., Olsson, R. & Portugal, A. (2019). Improvement and validation of a physically based model for the shear and transverse crushing of orthotropic composites. Journal of composite materials, 53(12), 1681-1691
Öppna denna publikation i ny flik eller fönster >>Improvement and validation of a physically based model for the shear and transverse crushing of orthotropic composites
2019 (Engelska)Ingår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 53, nr 12, s. 1681-1691Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
Crushing, damage mechanics, friction, finite element analysis
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:ri:diva-36301 (URN)10.1177/0021998318807964 (DOI)
Tillgänglig från: 2018-11-15 Skapad: 2018-11-15 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
Bru, T., Asp, L., Olsson, R. & Vyas, G. (2018). Biaxial transverse compression testing for a fibre reinforced polymer material. In: : . Paper presented at 18th European Conference on Composite Materials ECCM-18.
Öppna denna publikation i ny flik eller fönster >>Biaxial transverse compression testing for a fibre reinforced polymer material
2018 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
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.

Nyckelord
Polymer matrix composites, biaxial testing
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:ri:diva-36302 (URN)
Konferens
18th European Conference on Composite Materials ECCM-18
Anmärkning

Paper ID: 3.10(5)-24

Tillgänglig från: 2018-11-15 Skapad: 2018-11-15 Senast uppdaterad: 2020-01-10Bibliografiskt granskad
Olsson, R. (2018). Fibre lock-up and other mechanisms at large fibre rotations, and their effect on axial compression of composites.. In: Proc. 18th European Conf. on Composite Materials.: . Paper presented at 18th European Conf. on Composite Materials. Athens, Greece.. European Society for Composite Materials, Article ID 3.11-08.
Öppna denna publikation i ny flik eller fönster >>Fibre lock-up and other mechanisms at large fibre rotations, and their effect on axial compression of composites.
2018 (Engelska)Ingår i: Proc. 18th European Conf. on Composite Materials., European Society for Composite Materials , 2018, artikel-id 3.11-08Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

This paper studies the sequence of fibre kinking, the fibre lock-up and the subsequent constitutive behaviour. The conditions governing these phenomena are discussed with focus on the conditions for fibre lock-up. Lower bounds for the fibre lock-up angle a and the kink band angle b are derived purely from geometrical conditions for 3D arrays of fibres, with the aim to define the termination of fibre kinking in homogenized material models for FE analysis. It is concluded that the limit of the lock-up angle is 90° for low fibre volume fractions, decreases to about 50° for fibre volume fractions common in high performance composites, and reaches zero for fully packed fibres.

Ort, förlag, år, upplaga, sidor
European Society for Composite Materials, 2018
Nyckelord
fibre kinking, lock-up, 3D fibre array
Nationell ämneskategori
Teknisk mekanik
Identifikatorer
urn:nbn:se:ri:diva-42489 (URN)
Konferens
18th European Conf. on Composite Materials. Athens, Greece.
Projekt
Compcrash 2
Forskningsfinansiär
Energimyndigheten, 34181-2
Tillgänglig från: 2020-01-09 Skapad: 2020-01-09 Senast uppdaterad: 2020-01-20Bibliografiskt granskad
Farajzadeh Khosroshahi, S., Olsson, R., Wysocki, M., Zaccariotto, M. & Galvanetto, U. (2018). Response of a helmet liner under biaxial loading. Polymer testing, 72, 110-114
Öppna denna publikation i ny flik eller fönster >>Response of a helmet liner under biaxial loading
Visa övriga...
2018 (Engelska)Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 72, s. 110-114Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
Biaxial mechanical response, EPS, Helmet, Oblique impact, Compression testing, Safety devices, Shear stress, Compressive tests, Experimental test, Mechanical response, Reliable results, Rotational acceleration, Uni-axial compression tests, Accident prevention
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-35573 (URN)10.1016/j.polymertesting.2018.10.012 (DOI)2-s2.0-85054874584 (Scopus ID)
Anmärkning

 Funding details: FP7-PEOPLE-2013-ITN-608092, REA, Research Executive Agency; Funding text: The research leading to these results has received funding from the People Programme (Marie Sklodowska Curie Actions) of the European Union’s Seventh Framework FP7/2007-2013/under REA grant agreement n° [ FP7-PEOPLE-2013-ITN-608092 ] and from the ECCELLENZA programme of the CARIPARO foundation under the REDIPhE project.

Tillgänglig från: 2018-11-08 Skapad: 2018-11-08 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
Bru, T., Waldenström, P., Gutkin, R., Olsson, R. & Vyas, G. M. (2017). Development of a test method for evaluating the crushing behaviour of unidirectional laminates. Journal of composite materials, 51(29), 4041-4051
Öppna denna publikation i ny flik eller fönster >>Development of a test method for evaluating the crushing behaviour of unidirectional laminates
Visa övriga...
2017 (Engelska)Ingår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 51, nr 29, s. 4041-4051Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
Crushing, fractography, mechanical testing, non-crimp fabric composite, Fracture, Fracture mechanics, Video recording, Experimental investigations, Flat specimen, Non-crimp fabric composites, Out-of-plane failures, Physically based, Predictive simulations, Trigger angle, Unidirectional fabrics
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-33053 (URN)10.1177/0021998317697811 (DOI)2-s2.0-85037057642 (Scopus ID)
Tillgänglig från: 2018-01-11 Skapad: 2018-01-11 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
McElroy, M., Jackson, W., Olsson, R., Hellström, P., Tsampas, S. & Pankow, M. (2017). Interaction of delaminations and matrix cracks in a CFRP plate, Part I: A test method for model validation. Composites. Part A, Applied science and manufacturing, 103, 314-326
Öppna denna publikation i ny flik eller fönster >>Interaction of delaminations and matrix cracks in a CFRP plate, Part I: A test method for model validation
Visa övriga...
2017 (Engelska)Ingår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 103, s. 314-326Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
A. Laminates, B. Delamination, B. Transverse cracking, D. Mechanical testing, Carbon, Carbon fiber reinforced plastics, Computerized tomography, Cracks, Failure (mechanical), Fiber reinforced plastics, Laminates, Mechanical testing, Strain rate, Ultrasonic testing, Carbon fiber reinforced polymer, Damage mechanism, High strain rates, Low velocity impact, Model validation, Transverse cracking, Transverse matrix cracks, X-ray computed tomography, Delamination
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-33052 (URN)10.1016/j.compositesa.2017.09.011 (DOI)2-s2.0-85030465676 (Scopus ID)
Anmärkning

Funding details: Langley Research Center

Tillgänglig från: 2018-01-11 Skapad: 2018-01-11 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
Costa, S., Gutkin, R. & Olsson, R. (2017). Mesh objective implementation of a fibre kinking model for damage growth with friction. Composite structures, 168, 384-391
Öppna denna publikation i ny flik eller fönster >>Mesh objective implementation of a fibre kinking model for damage growth with friction
2017 (Engelska)Ingår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 168, s. 384-391Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
Crushing, Damage mechanics, Fibre kinking, Friction, Mesh objectivity, Energy dissipation, Fiber reinforced plastics, Fibers, Laminated composites, Mesh generation, Fibre reinforced composites, Kink band formations, Longitudinal response, Meso-scale modeling, Physically based modeling, Strain compatibility, Finite element method
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-29316 (URN)10.1016/j.compstruct.2017.02.057 (DOI)2-s2.0-85013781749 (Scopus ID)
Tillgänglig från: 2017-05-12 Skapad: 2017-05-12 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
Bru, T., Olsson, R., Gutkin, R. & Vyas, G. M. (2017). Use of the Iosipescu test for the identification of shear damage evolution laws of an orthotropic composite. Composite structures, 174, 319-328
Öppna denna publikation i ny flik eller fönster >>Use of the Iosipescu test for the identification of shear damage evolution laws of an orthotropic composite
2017 (Engelska)Ingår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 174, s. 319-328Artikel i tidskrift (Refereegranskat) Published
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.

Nyckelord
Continuum damage mechanics CDM, Fabrics/textiles, Finite element analysis (FEA), Shear testing, Thermosetting resin, Carbon, Continuum damage mechanics, Damage detection, Elasticity, Thermosets, Continuum damage mechanics model, Experimental evaluation, Full-field strain measurement, Non-crimp fabric composites, Orthotropic composites, Through-thickness shears, Finite element method
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:ri:diva-30816 (URN)10.1016/j.compstruct.2017.04.068 (DOI)2-s2.0-85018974882 (Scopus ID)
Anmärkning

 Funding details: 34181-1/2, Energimyndigheten; Funding text: The funding for this research from the Swedish Energy Agency (Energimyndigheten), project number 34181-1/2, is gratefully acknowledged.

Tillgänglig från: 2017-09-06 Skapad: 2017-09-06 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
Costa, S., Portugal, A., Olsson, R., Vyas, G. & Bru, T. (2017). Validation of a novel model for the compressive response of FRP: numerical simulation. In: : . Paper presented at 21st International Conference on Composite Materials ICCM-21.
Öppna denna publikation i ny flik eller fönster >>Validation of a novel model for the compressive response of FRP: numerical simulation
Visa övriga...
2017 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
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.

Nyckelord
Crushing, Damage modes, Friction, Damage mechanics
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
urn:nbn:se:ri:diva-36298 (URN)2-s2.0-85053166997 (Scopus ID)
Konferens
21st International Conference on Composite Materials ICCM-21
Anmärkning

Paper ID. 4280

Tillgänglig från: 2018-11-15 Skapad: 2018-11-15 Senast uppdaterad: 2020-01-10Bibliografiskt granskad
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-2627-3280

Sök vidare i DiVA

Visa alla publikationer
v. 2.35.10