International Journal of Automotive Composites (7 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.
Finite Element Simulation for predicting the behaviour of Carbon Fibre Tubes for Automotive Side Structure.
by Balaji Pillai, Lakshmana Rao C, Naresh Kulkarni
Abstract: Carbon Fibre reinforced polymer (CFRP) composites are increasingly being used in automotive structures due to good strength to weight ratio. Digital product development for CFRP parts needs reliable simulation methods to predict the performance. The objective of this study to find the best simulation method to predict the behaviour of CFRP tube when subjected to lateral/bending forces. LS Dyna Explicit finite element code is used for simulation. CFRP square tube is subjected to three Point bend test experiment. The force displacement curves are obtained. The deformation pattern, cracks and failures are also closely observed. Various methods of Finite Element Simulation like layered thick shell, layered thin shell and delamination modelling methods like tiebreak contact and cohesive elements are simulated. Each simulation method is compared with experimental results. Finite Element Simulation method with Layered Thin Shell and delamination modelling using mixed mode material cohesive zone is found to be best validating with experimental results. This method is proposed to be used in the design and development of Carbon fibre parts for automotive structures. This can reduce time and cost involved in prototype preparation and testing.
Keywords: : FEA; Carbon Fibre; CFRP; Composite Tubes; Bending Experiment; Delamination; Tie Break; Cohesive Zone Modelling; LS Dyna; MAT_054; Thick Shell ; ThinShell.
Fracture simulation of an FRP tube with continuous random fibres at the initial stage
by Asao Koike, Reika Akita, Atsushi Yokoyama
Abstract: FRP composite materials are currently employed increasingly widely in vehicle body parts to reduce the weight and improve the fuel efficiency because these materials are lightweight and exhibit high stiffness. Another particularly interesting function of the materials is the continuous and stable fracture phenomenon known as the progressive crushing mode that occurs when an FRP tube with a trigger part is crushed in the axial direction. This phenomenon makes the FRP tube more effective to absorb crush energy than a conventional metal. Moreover, this benefit is considered for use in crush boxes of vehicles. In our previous studies, we conducted experimental analysis of the fracture mechanism at the initial stage of the FRP tube and made a test report publicly available. In this paper, we propose a finite-element model that is reasonably simple and accurate enough to simulate the initial fracture found experimentally.
Keywords: FRP tube; Progressive crushing mode; Trigger; GMT; Simulation; Cohesive element.
Fast and efficient automotive hybrid part manufacturing process using polyurethane-based prepregs
by Zuhal Tuncay
Abstract: A polyurethane-based prepreg with high metal adhesion is developed which enables a fast and efficient process route towards metal FRP hybrid parts. Due to thermoplastic processing of the thermoset matrix, forming of metal and FRP is achieved in a single step. Cycle times can be reduced to below one minute for body-in-white parts since the time-consuming post-curing step can be integrated into the cathodic dip coating process. The final demonstrator parts exhibit high bonding strengths between metal and FRP without the need for adhesives or metal pre-treatment.
Keywords: lightweight automotive design; multi-material approach; hybridrnpart; local patch reinforcement; carbon fibre composite; polyurethane prepreg;rnprepreg pressing; hat section;lap shear strength.