Methods for efficient modelling of progressive failure in laminated fibre-reinforced composites
Doktorsavhandling, 2019

To meet increasing demands on reduced CO2 emissions, the automotive industry is currently very active in research to reduce vehicle weight by incorporating laminated composites (primarily carbon fibre-reinforced polymers) into structural components.

Historically, composite materials have mainly been used in the aerospace industry, whereby CAE-based design and development tools for composite structures have been developed primarily to the specific needs and requirements in this industry. In general, the crashworthiness of aerospace structures is only assessed to a small extent compared to that of automotive structures. Consequently, no suitable numerical simulation tools, capable of assessing the crashworthiness of composite automotive structures, have been developed.

The fracture process of laminated composites is more complicated than that of metals, the dominant class of materials used in automotive crash protection systems today. Thus, numerical models developed for metals cannot be used to accurately predict the crashworthiness of composite structures. Instead, high-fidelity models that can resolve the complicated fracture process must be used. However, these models require excessive computational times, making industrial crash simulations infeasible. It is therefore crucial to develop computationally efficient numerical tools, which are able to accurately predict the crashworthiness performance of composite structures.

In this thesis, I will present a route towards full-scale vehicle crash simulations using a computationally efficient adaptive method. The method is based on an equivalent single-layer shell model which, during the analysis, is adaptively transformed to a high-fidelity model in areas where higher accuracy is required. This way, the increased computational cost, associated with the analysis of progressive damage in laminated composites, can be limited both in time and to the pertinent areas of the model.

The adaptive modelling method can successfully reproduce the same level of accuracy as a high-fidelity model, at lower computational cost. Consequently, this method can help to enable computationally efficient crash simulations of laminated structures, which in the long run will allow composite materials to have a widespread use in future automotive vehicles.

Composites

Progressive failure

Crash simulation

Adaptive modelling

Virtual Development Laboratory
Opponent: Prof. Stephen Hallett, University of Bristol, United Kingdom

Författare

Johannes Främby

Chalmers, Industri- och materialvetenskap, Material- och beräkningsmekanik

Assessment of two methods for the accurate prediction of transverse stress distributions in laminates

Composite Structures,; Vol. 140(2016)p. 602-611

Artikel i vetenskaplig tidskrift

Adaptive modelling of delamination initiation and propagation using an equivalent single-layer shell approach

International Journal for Numerical Methods in Engineering,; Vol. 112(2017)p. 882-908

Artikel i vetenskaplig tidskrift

Främby J, Fagerström M, Karlsson J, An adaptive shell element for explicit dynamic analysis of failure in laminated composites Part 1: Adaptive kinematics and numerical implementation

Främby J, Fagerström M, An adaptive shell element for explicit dynamic analysis of failure in laminated composites Part 2: Progressive failure and model validation

På grund av ökade krav på sänkta koldioxidutsläpp är fordonsindustrin starkt involverade i forskning med målet att sänka fordonsvikten med hjälp av lättviktsmaterial såsom laminerade fiberkompositer.

Historiskt sett har laminerade kompositer framförallt använts inom flygindustrin. Därför har virtuella utvecklingsverktyg för strukturer av kompositmaterial formats efter kraven inom just denna industri. Jämfört fordonsindustrin utvärderas krockegenskaperna hos flyg endast i liten utsträckning, vilket har innebär att lämpliga verktyg för virtuell utvärdering av krockegenskaperna hos strukturer av kompositmaterial saknas. Bristen på virtuella verktyg är ett stort problem eftersom utvecklingen av moderna fordon sker mer eller mindre helt virtuellt med hjälp av simulering. Utan tillgång till lämpliga krocksimuleringsverktyg, kan inte laminerade kompositer få en stor spridning inom fordonsindustrin.

Metaller är den klart dominerande materialtypen i krockskyddsstrukturer i dagens fordon. Moderna verktyg för krocksimulering är därför utvecklade för metaller och kan inte korrekt förutse den komplexa sprickbildningsprocess som sker vid progressivt brott i laminerade kompositer. För en korrekt förutsägelse krävs istället högupplösta och extremt beräkningstunga modeller, vilket omöjliggör krockutvärdering av ett helt fordon. Det är därför av yttersta vikt att utveckla beräkningseffektiva simuleringsverktyg som kan göra en korrekt utvärdering av krockegenskaperna hos laminerade kompositer.

I den här avhandlingen kommer jag att presentera en metod för automatisk modellförfining med syfte att åstadkomma krocksimulering av hela fordon av laminerade kompositer. Metoden är baserad på ett beräkningseffektivt skalelement, vilket under simuleringen automatiskt omvandlas till en högupplöst modell i områden där större noggrannhet krävs. På så sätt kan den ökade beräkningskostnaden för utvärdering av progressivt brott i laminerade kompositer begränsas.

Den föreslagna metoden kan reproducera samma grad av noggrannhet som en högupplöst modell, men till lägre beräkningskostnad. Följaktligen kan metoden möjliggöra beräkningseffektiv krocksimulering av laminerade kompositer, vilket i det långa loppet hjälper kompositmaterialen att få en stor spridning inom fordonsindustrin.

To meet increasing demands on reduced CO2 emissions, the automotive industry is currently very active in research to reduce vehicle weight by incorporating light-weight materials like laminated composites into structural components.

Historically, composite materials have mainly been used in the aerospace industry, whereby the virtual design and development tools for composite structures have been developed primarily to the specific needs and requirements in this industry. In general, the crashworthiness of aerospace structures is only assessed to a small extent. Especially, compared to that of automotive vehicles, where high rating in crash tests are a key selling argument. Consequently, no suitable virtual tools, capable of assessing the crashworthiness of composite automotive structures, have been developed. This lack of virtual tools is problematic since the development of modern automotive vehicles is almost exclusively driven by virtual developments. Without access to tools for crashworthiness assessment of composite materials, these materials will not be widespread in automotive vehicle structures.

The fracture process of laminated composites is far more complicated than that of metals, the dominant class of materials used in automotive crash protection systems today. Thus, virtual tools developed for metals cannot be used to accurately predict the crashworthiness of composite materials. Instead, highly refined models that can resolve the complicated fracture process must be used. However, these models require excessive computational resources, making full-scale vehicle crash simulations infeasible. It is therefore crucial to develop computationally efficient virtual tools, which can accurately predict the crashworthiness performance of composite structures.

In this thesis, I will present a route towards full-scale vehicle crash simulations using an automatic-refinement method. The method is based on a computationally efficient shell model which, during the simulation, is automatically transformed to a highly refined model in areas where needed. This way, the increased computational cost, associated with the analysis of progressive damage in laminated composites, can be limited.

The proposed method can successfully reproduce the same level of accuracy as a highly refined model, at lower computational cost. Consequently, this method can help to enable computationally efficient crash simulations of laminated structures, which in the long run will allow composite materials to have a widespread use in future automotive vehicles.

Modellering av krockbeteendet i framtida lättviktsfordon

VINNOVA, 2017-01-01 -- 2020-03-31.

VINNOVA, 2013-01-01 -- 2015-12-31.

Drivkrafter

Hållbar utveckling

Styrkeområden

Transport

Materialvetenskap

Ämneskategorier

Teknisk mekanik

Kompositmaterial och -teknik

Infrastruktur

C3SE (Chalmers Centre for Computational Science and Engineering)

ISBN

978-91-7905-233-1

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4700

Utgivare

Chalmers tekniska högskola

Virtual Development Laboratory

Opponent: Prof. Stephen Hallett, University of Bristol, United Kingdom

Mer information

Senast uppdaterat

2020-01-22