International Journal of Automotive Composites (19 papers in press)
Study on strain-rate-dependent behaviour and constitutive model of long glass fiber reinforced polypropylene composite
by Shuyong Duan, Fuhao Mo, Kai Wei, Zhi Xiao, Sen Xiao, Xujing Yang
Abstract: Accurate material model under different strain rates is important for numerical simulations in vehicle design and crashworthiness assessment. Therefore, the objectives of this study are to develop the constitutive model of long glass fiber reinforced polypropylene composite (hereinafter referred to as LGFRP) which related to strain rate range of 10-3/s50/s. Tensile and compression tests are conducted at different strain rates. The experimental results show that the failure strain and ultimate strength increase as increasing strain rate. The elastic modulus is sensitive to strain rate in tensile tests, but less sensitive to strain rate in compression tests. According to the experimental results, a novel constitutive model proposed by the authors is used to represent stress-strain relationship related to strain rate of the LGFRP. The analysis results show that the novel constitutive model agrees well with the experimental results.
Keywords: long glass fiber; constitutive model; strain rate; thermoplastic resin.
Investigation on mechanical properties and stability of LGFRP strengthening ribs with different cross-section
by Shuyong Duan, Sen Xiao, Fuhao Mo, Maojun Li, Kai Wei, Zhi Xiao
Abstract: Long glass fiber reinforced polypropylene (LGFPP) strengthening rib with channel section has been increasingly applied in modern automotive structure to improve safety without adding weight of composite components. Hence, the objective of the current study is to investigate the influences of cross-section on mechanical properties and stability of LGFRP strengthening ribs with different cross-section shapes (semicircular, rectangular and trapeziform) by compression experimental tests for its application on automobile structural components. First, LGFRP strengthening ribs were prepared by hot compression moulding, and were tested by universal testing machine. Then, based on the experimental results, the elasticity stability theory of the open thin-walled axial compressive bar with uniform cross section was revised for the LGFRP strengthening ribs. The experimental results showed that the instability mode of the specimens is flexural-torsional bulking and the peak force decrease with increasing the length of specimens. The revised theoretical analysis results are in good agreement with experimental results.
Keywords: long glass fiber reinforced polypropylene; strengthening rib; mechanical properties; stability; elasticity stability theory.
On the calculation of the macroscopic stiffness of 2D triaxially braided composites
by Yifei Liu, Wei Ye, Huiming Ning, Ning Hu
Abstract: The elastic property of 2D triaxially braided composites (2DTBC) is of interest. This work proposes to formulate the global stiffness of 2DTBC for anisotropic fiber reinforcement based on concentric cylinder model (CCM). The results of the global stiffness from CCM, Quek's model and Shokrieh's model are compared and the usage of each model is clarified. It is found that Shokrieh's model predicts less agreeable result with experiment due to the improper calculation of the local stiffness. The results of CCM and Quek's model are consistent and either one is recommended for use in practical situations.
Keywords: Braided composites; Concentric cylinder model; Elastic property; CFRP; GFRP.
Ultimate in-plane strengths of two-dimensional tri-axial braided composites: experiments and numerical simulations
by Jian Wu, Yanjie Rui, Wei Ye, Huiming Ning, Ning Hu
Abstract: The ultimate in-plane strengths of a carbon/glass fiber reinforced tri-axial braided composite are studied by experiments and numerical simulations. The ultimate tensile, compressible and shear strengths are tested. Employing Tsai-Wu failure criterion, a progressive failure analysis is performed in finite element analysis. Reasonable agreement between the experiments and numerical simulations indicates that present finite element model has a potential to predict the ultimate strengths of a two-dimensional tri-axial braided composite.
Keywords: Tri-axial braided composites; In-plane strengths; Finite element analysis.
Special Issue on: ICAutoC 2016 Advances in Automotive Composites
Crush performance of foam filled tubular structures made of aluminium alloys at different loading conditions
by Isabel Duarte, Matej Vesenjak, Lovre Krstulović-Opara
Abstract: The aim of this research is to develop and characterise square and cylindrical foam filled tubular structures made of aluminium alloys. The thin-walled tubular structures were filled by a closed-cell foam during its in-situ foam formation using the powder metallurgy method. The deformation modes and compressive behaviour were studied using uniaxial compressive tests together with infrared thermography. The results demonstrate that the in-situ foam filled tubular structures have strong bonding and a high ductility that contributes to a progressive and stable axisymmetric deformation under compressive loads without the formation of cracks.
Keywords: lightweight structures; aluminium foams; foam filled tubular structures; deformation modes; uniaxial compression behaviour.
ANALYSIS AND DESIGN OF A CRASH ATTENUATOR FOR A LIGHTWEIGHT RACING CAR
by Simonetta Boria
Abstract: In this paper, the crash safety performance of a lightweight racing car is evaluated focusing on the optimization of its frontal impact attenuator from the geometrical and material point of view. After the definition of the 3D CAD model of the full vehicle, it was possible to convert it into finite elements applying the correct properties, materials, contacts, boundary and initial conditions for each body components in order to conduct an explicit dynamic analysis through LS-DYNA code. Therefore, the full vehicle front impact simulation against a rigid barrier is carried out considering different impact attenuator structures, that are the main parts of the front body subsystem which protect passengers from the collisions. Respect to previous literature works, the geometries taken into account for the attenuator design are much more complex. Moreover conventional and CFRP composite materials are used during modelling in order to do a comparison between them in term of safety. Overall vehicle deceleration responses obtained for these cases show, in accordance with previous literature, that also these lighter composite impact attenuators can be more competitive than conventional absorbers of similar geometry in terms of intrusion and energy absorption in an equivalent test condition.
Keywords: front impact; vehicle; crashworthiness; lightweight; composite material; FEA.
Optimisation of Fibre-Matrix Interface in Carbon Fibre Reinforced Light Metals via Liquid Phase Impregnation Coatings
by Miguel Jiménez Martínez, Rainer Gadow, Patrick Weichand
Abstract: Fibre reinforced metals are a potential alternative to replace steel components in the automotive industry due to their enhanced specific strength. Nevertheless, state of the art Metal Matrix Composites (MMC) are reinforced by expensive ceramic fibres, since the shaping and consolidation conditions by the classic manufacturing routes are quite severe in terms of thermal load and fibre-matrix chemical compatibility requirements. The Semi-Solid Forming and Shaping (SSFS) route, based on a densification process at the thixotropic temperature range of the employed alloy, is a promising alternative that enables the implementation of inexpensive high tenacity carbon fibres due to the reduced processing temperature. In this paper interfaces in carbon fibre reinforced AlSi6 are modified by Liquid Phase Impregnation (LPI) fibre coatings, improving the strength and strain to failure of composites by 45 % compared to reference materials. Fractographic analysis shows the reduction of brittle failure and the formation of pull-out phenomena in composites based on coated fibres.
Keywords: Metal Matrix Composites; Semi-Solid Forming; Thermal spraying; Carbon fibres; Fibre coating; Liquid phase impregnation.
Weight reduction through material changing in a commercial diesel engine: piston pin and connecting rod case studies
by Carlo Rosso, Cristiana Delprete
Abstract: In design of engine components, the demand for increasingly higher power combined with a growing awareness for environmental and energy saving, creates a number of conflicting design constraints that can be overcome with the use of new materials.rnThe present paper evaluates the possibility to use plastic materials for designing two parts of the crank mechanism: the connecting rod and the piston pin. In particular, the material used for the connecting rod design is PEEK filled with carbon fibre and that used for the piston pin design is carbon fibre prepreg epoxy.rnThe numerical analyses made by the authors prove that plastic materials can be useful for components weight reduction but a complete components revision and changing of design strategy are required.rnThe direct metal replacement with plastic material is not possible, and the improvement of plastic materials performance and the new technology for additive manufacturing can completely change the way of thinking about engine.
Keywords: Connecting rod; piston pin; weight saving; plastic materials.
ECO-SOLUTIONS FOR AUTOMOTIVE INTERIOR APPLICATIONS BY WAY OF THERMOPLASTIC BIOCOMPOSITES:
COST, WEIGHT AND GREEN ADVANCEMENTS
by Mihaela Mihai
Abstract: This paper discloses viable eco-solutions concerning formulation, processing, and performance of biocomposites and bioblends based on polypropylene (PP), polyamide (PA6), and acrylonitrile-butadiene-styrene (ABS) to be used in the fabrication of interior automotive parts. Biocomposites based on PP, PA6, and ABS containing up to 40 wt.% of three different types of cellulosic fibers were first formulated and compounded. PP, PA6 and ABS bioblends containing up to 30 wt.% polylactide (PLA) as bio-sourced polymer were also obtained. Finally, different formulations of biocomposites were also compounded using PP / PLA, PA6 / PLA and ABS / PLA alloys and cellulosic fibers. These biocomposites and bioblends were evaluated in terms of morphology, mechanical and thermal properties, as well as of cost and weight reductions. Tensile strength, tensile modulus, and heat deflection temperature (HDT) of bioblends and biocomposites presented at least equivalent values comparing to virgin PP, PA6 and ABS thermoplastics and to their corresponding commercial grades currently used in the fabrication of automotive interior parts. Furthermore, parts obtained by foaming through injection-molding process presented similar properties as the unfoamed and commercial grades counterparts while being up to 25 wt.% lighter, up to 37% less expensive, and up to 50 wt.% greener.
Keywords: Polypropylene; Polyamide; Acrylonitrile-butadiene-styrene; Thermoplastic biocomposites; Cellulosic fibers; Biocomposites; Automotive interior parts; Biocomposites formulation; Biocomposites processing; Lightweight biocomposites; Lower-cost biocomposites; Biocomposites for automotive applications; Bioblends for automotive applications.
Understanding the Contributions of Surface Morphology Transitions and the Phenomenon of Thermoelastic Instabilities on the Torque Output of a Carbon/Carbon Multi-Plate Clutch During Race-Start Conditions
by Ranvir Kalare, Peter Brooks, David Barton
Abstract: The torque output of a carbon/carbon multi-plate Formula One clutch during race starts has proved to be both unstable and inconsistent. A one-dimensional heat transfer model utilising a Taguchi analysis suggested that a close interdependency exists between surface temperature, surface morphology and coefficient of friction thus affecting torque output stability. Friction surface examination showed that a non-uniform friction surface height may lead to thermoelastic instabilities and effective friction radius migration which directly affects torque output. A single clutch-plate interface dynamometer confirmed the formation of narrow (~2mm), high-temperature (1300-1650
Keywords: Carbon/carbon composites; Formula One; F1; multi-plate clutch; torque instability; torque inconsistency; surface morphology; hot banding; thermoelastic instabilities; friction radius migration.
Methodical design process for structural composites to achieve lightweight vehicles
by Jonathan Schmidt, Georg Jacobs, Anna-Lena Beger, Dave Cadwell
Abstract: Integrating as many functions into a part as possible without compromising its function is a reliable and often applied way to reduce weight when introducing a composite part into a vehicle. By doing so a significant change of the product architecture (according to Pahl et al., 2013) is often inevitable. The current price pressure within in the automotive industry however leads to short development times and hence more carry over parts of previous models and derivates. In order to discuss concepts or necessary changes usually CAD-models are used. This implies a high amount of work and effort already put into the concept development which is inefficient and expensive for high level decisions. Thus a way to allow concept decisions at an early stage of the development is required especially to make the best decision regarding the material selection and to foster material conforming design from the concept phase on. This paper shows a way to support these decisions on both a macro and micro environmental point of view including a not-CAD-driven way to present the results adapting the contact and channel model developed by Matthiessen (2002) for the use on composite design.
Keywords: automotive composites; methodology; function integration; product architecture; lightweight design; structural composites; FRP.
Penetration impact behavior of hot-compacted self-reinforced polyamide 6 composite laminates
by Pietro Russo, Paolo Vecchione, Valentina Lopresto, Antonio Langella, Ilaria Papa, Francesco Cimino
Abstract: Polyamide 6 based sheets are produced by a typical hot compaction procedure and characterized in terms of compaction quality and penetration low-velocity impact performances. Starting from two commercial clothes, a yellow one fully constituted by PA6 fibers and a hybrid red one containing also 1% of secondary polyurethane fibers, single polymer composite (SPCs) plates involving 24, 30 and 36 layers of each fabric were prepared under controlled conditions and studied to define their potential applications. Ultrasonic C-scan results showed a quality of compaction always decreasing with the number of stacked fabric layers (thickness) and, with the same number of cloth layers, lower for red laminates compared to yellow ones, in line with previous morphological observations. Different damage propagation mechanisms occur as highlighted by typical load-deflection curves with hybrid systems showing a more pronounced ductile behavior and an evident deviation from the penetration energy-thickness linear relationship for red samples is detected.
Keywords: Self-reinforced composites; Hot-compaction; low-velocity impact tests; laminated structures; Ultrasonic C-scan.
Elasto-plastic response of graphene nanoplatelets reinforced polymer composite materials
by Wiyao Azoti, Ahmed Elmarakbi, Hisham Elhage, Mustafa Elkady
Abstract: In this paper, graphene nanoplatelets GNPs have been used as continuum phases within polymer composite materials. For such a purpose, a multi-scale strategy embedding the constitutive law of each material phase is accounted for to obtain the effective properties. The elasto-plastic response is established in the framework of the J2 plasticity. An expression of the algorithmic tangent operator for each phase is obtained and used as uniform modulus for homogenisation purpose. Using the Mori-Tanaka scheme, the effective non-linear behaviour is predicted for micro-parameters such as the aspect ratio and volume fractions. The results are compared to available experimental data as well as modelling from the literature. They show an enhancement of the equivalent macro stress-strain response with respect to low aspect ratio corresponding to platelet-like inclusions. Also, the volume fraction is seen to improve the composite response.
Keywords: Graphene composites; Mori-Tanaka scheme; Elasto-plasticity; Effective properties.
Design of a composite crash box for a Formula Student team car: preliminary testing and model tuning
by André Santos, Aurelio Araujo, José Madeira, Hernâni Lopes
Abstract: In this work, preliminary studies towards the development of a struc-
tural carbon fibre nose for a Formula Student team car are presented. Numerical
and experimental approaches have been considered to evaluate the impact behav-
iorof compositetubes. Then,finiteelementsimulations areusedto determinethe
crush stress by fitting the numerical results to the experimental data. The crush
stress is also validated using quasi-static compression tests. The obtained results
are compared and discussed in the framework of the future structural nose and
Keywords: Crash box; Impact simulation; Experimental tests; High speed imaging; Composite tube.
Function Integration concept design applied on CFRP Cross Leaf Spring Suspension
by Andrea Airale, Alessandro Ferraris, Shuang Xu, Lorenzo Sisca, Paolo Massai
Abstract: In automotive systems, lightweight design is nowadays a mandatory target. Suspension systems, which are a safety system and contribute to overall vehicle performance (dynamic, comfort, noise and vibration, etc), are one of the most complex systems in which to achieve lightweight targets. This article discusses the development of a CFRP Cross Leaf Spring Prototype (TRL 6). The entire workflow, starting from Kinematic Design, Multibody Vehicle Dynamics Analysis, FEM Structural Analysis, Prototype Construction, Testing and Correlations is shown. Also studied in this project is the integration and applications of advanced Continuous Fiber Reinforced Thermoplastic Polymer (CFRTP). This system, in comparison to traditional solutions, could guarantee: around 75% weight savings, suspension component optimization, an optimization of the suspension volume (resulting in more space for vehicle occupants), easy integration of advanced process using CFRTP, and a sustainable cost solution.
Keywords: Cross Leaf Spring Suspension; Thermoplastic Composite; CFRP; Innovative Suspensions; FEM Analysis; Engineering Methodology.
EVOLUTION FP7 FUNDED PROJECT - BODY STRUCTURE DESIGN STRATEGIES USING NEW COMPOSITE AND ALUMINIUM MATERIALS AND ENABLED TECHNOLOGIES
by Elena Cischino, Cristina Elizetxea, Iratxe Lopez, Zina Vuluga, Mikelis Kirpluks, Peteris Cabulis, Jesper DeClaville Christiansen, Catalina-Gabriela Sanporean, John Deverill, Francesca Di Paolo, César Maestro, Enrico Mangino
Abstract: Funded by the EC FP7 Program and based on Pininfarina Nido EV concept, EVolution aims to reduce the vehicle weight through new materials and process technologies, focused on five demonstrators: underbody, front crossbeam, mechanical subframe, shotgun system and door. This paper refers to body structure design strategies using new composite, Al materials and enabled technologies, focusing in particular on demonstrators design and manufacturing. The new front crossbeam geometry of the front shell is adapted starting from the Nanotough design, keeping in account the characteristics of the several raw materials selected and the different manufacturing processes, while the rear shell is specific for EVolution. A core of specific rigid polyurethane foam is inserted in selected beam sections to improve crash performances. The subframe demonstrator is redesigned to fulfil mechanical requirements of the part and manufacturing feasibility either. The raw material used consisted of polyamide with different sheets of carbon fiber fabrics positioned as a lay-up. The orientation of the fibres disposed in twelve layers is conceived to assure the mechanical properties. The EVolution door concept consists of two semistructural composite skins (inner and outer) including a structural Al frame. The idea of the door is an unconventional concept, assuring the main structural and functional performances, cheaper and light weighted respect to baseline Nido door. The underbody is conceived through an integrated approach, leveraging new process technologies to merge in a unique new component as much parts as possible, optimizing each element for its function. This methodology allowed the maximum potential in weight saving with respect to Nido underbody: proposed technologies enabled complex geometries with reduced thickness and a consistent part count reduction. The shot gun component is designed to be a media to link parts obtained with different manufacturing technologies (extrusion, standard profiles, stamping) and several aluminium alloys in one single component: the structural node demonstrator. It has the relevant function to absorb the energy in the case of a frontal collision.
Keywords: Body in White; Lightweighting; Composites; Aluminium; Electric Vehicles.
A Composite Chassis for a Formula Student Vehicle
by Ricardo Ferreira, Luis Sousa, Virgínia Infante
Abstract: The present work aims to analyse different types of chassis used in Formula Student vehicles. This analysis is done under the same circumstances for all structures: the suspension lines and packaging of main components are fixed and a target value for torsional stiffness is estimated based on the cars handling balance.
A tubular space frame from previous prototype (named FST 04e) is re-analysed using structural optimization methods, aiming for weight reduction while considering the new torsional stiffness target. This new arrangement is used as a benchmark for comparison with the composite structures.
When using composite materials, it is mandatory to prove equivalency to a steel base frame structure to comply with the competition rules. A quick overview of this type of composite materials is presented, the equivalency process is explained and a model to identify lay-ups for the different zones is developed.
After identifying the candidate lay-up cases, several arrangements are analysed for the semi-monocoque and monocoque structures, considering two manufacturing processes: vacuum infusion and Prepreg. The final lay-up arrangements for each process are analysed under the critical load case scenarios.
Additionally, a local study is developed in order to define the dimensions for the inserts that must be used in the monocoques pickup points.
A study is also performed on bonded joint when the vacuum infusion monocoque process is analysed. This study is important since most of the monocoque chassis structures are obtained from two bonded parts.
Keywords: Tubular space frame; semi-monocoque; full monocoque; torsional stiffness; composite material; Vacuum infusion.
An Iterative Approach for the Determination of Tailored Blanks for Waste-Free Composite Forming by Means of FE Forming Simulation
by Dominik Dörr, Lukas Lipowsky, Fabian J. Schirmaier, Luise Kärger, Frank Henning
Abstract: Forming of composite pre-products into complexly shaped geometries is one of the most determining process steps in manufacturing of continuously fibre-reinforced composites. An educated guess of the tailoring of the pre-product (tailored blank), which leads to a desired contour after forming, is in the most cases not possible. An iterative and a direct approach, which facilitate the determination of a tailored blank, based on Finite Element forming simulation, is presented. Both approaches are successfully applied to a box-shaped, generic geometry and thermoplastic UD-tapes, as well as to a light pod of an automotive boot-lid and a woven engineering textile. It is shown, that the iterative approach is necessary for a reliable determination of a tailored blank, if there is an influence of the areas outside the desired contour for the non-tailored blanks.
Keywords: Composite forming; Process simulation; Finite Element analysis (FE); Finite Element (FE) forming simulation; Iterative tailoring determination.
Experimental and numerical investigation of full scale impact test on fibre-reinforced plastic sandwich structure for automotive crashworthiness
by Dirk Lukaszewicz, Lourens Blok, James Kratz, Carwyn Ward, C. Kassapoglou
Abstract: In this work the application of fibre reinforced plastic (FRP) sandwich structures, with particular focus on aramid fibre tufted sandwiches is being studied for automotive crashworthiness during edgewise impact using impact testing and numerical simulation. This work uses prior coupon data for scaling into a subsystem of a vehicle floor. A novel manufacturing process where Kevlar tufting is inserted through the dry preforms and the core is introduced. Subsystem testing then demonstrates the scalability of the sandwich system into a floor assembly. The specimen exhibits crushing with significant energy absorption. Numerical modelling is then used to validate the test result and demonstrate the simulation capability. Using commercial finite element software (Abaqus) with composite crushing add-in (CZone), the crushing of the sandwich and facesheets can be simulated with good agreement to the test results.
Keywords: Sandwich; Testing; Crashworthiness; Axial Impact and Tufting.