Parametric study of automotive composite bumper beams subjected to low-velocity impacts Ramin Hosseinzadeh a , Mahmood M. Shokrieh b, * , Larry B. Lessard c a Department of Mechanical Engineering, Sharif University of Tech., Tehran, 11365-8639, Iran b Department of Mechanical Engineering, Composites Research Laboratory, Iran University of Science & Technology, Tehran, 16844, Iran c Department of Mechanical Engineering, McGill University, Montreal, H3A 2K6, Canada Abstract Fuel efficiency and emission gas regulations are the main causes for reducing the weight of passenger cars by using composite structures. Bumper beams are one of the main structures of passenger cars that protect them from front and rear collisions. In this paper, a commercial front bumper beam made of glass mat thermoplastic (GMT) is studied and characterized by impact modeling using LS-DYNA ANSYS 5.7 according to the E.C.E. UNITED NATIONS AGREEMENT [UNITED NATIONS AGREE- MENT, Uniform Provisions concerning the Approval of Vehicles with regards to their Front and Rear Protective Devices (Bumpers, etc.), E.C.E., 1994]. Three main design factors for this structure: shape, material and impact conditions are studied and the results are compared with conventional metals like steel and aluminum. Finally the aforementioned factors are characterized by proposing a high strength SMC [Composite and metallic crash performance, Hawaii University, 1999, Available from: http:// www.eng.hawaii.edu/~nejhad/BUMPER/bumper.html] (sheet molding compound) bumper instead of the current GMT. The advantages of the proposed model: equal strength and rigidity of the structure, reduction of material, ease of manufacturing by simplifying geometrical shape and reduction of production cost are studied and proved. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Bumper beam; Passenger car; Impact; Low velocity; GMT; SMC 1. Introduction Bumper beams are one of the key structures in pas- senger cars for which careful design and manufacturing should be considered in order to achieve good impact behavior [3,4]. Since suitable impact strength is the main expectation for such a structure [3–6], this research surveyed the parameters that directly affected impact characteristics and proposed easily achievable modifi- cations resulting from impact modeling on commercial bumpers. Thus, a commercial front bumper beam (used on two of the most highly sold Iranian passenger car models) was chosen. The bumper beam is the main structure for absorbing the energy of collisions. Efforts were taken to model the bumper as similar as possible to reality. Thus the Computer Aided Design (CAD) data of the bumper was imported directly to ANSYS 5.7 and meshed in order to make a precise model. The modeling was done according to the conditions stated in E.C.E. United Nations Agreement, Regulation No. 42, 1994 [1]. According to these conditions, the car should be placed on a flat surfaced with released gear and brake and impacted both from front and side directions. Since the real low-velocity test stated in the agreement requires laboratory equipment, simplifications were assumed to make finite element modeling possible. The simplifying assumptions were deemed not to change real conditions but to create more critical conditions, which could provide a reliable basis for the design and analysis of bumper beams. There were three main strategic parameters being studied during the test modeling. Firstly, the material, i.e., how the cross-selection of material can affect the impact specifications and what kind of materials can be used as a replacement in order to lower part costs. Secondly, the shape, i.e., how even small changes and modifications can result in easier manufacturing processes and lessening material volume without lowering the impact strength. Thirdly, the im- pact behavior, i.e., how test conditions other than the * Corresponding author. Tel./fax: +98-21-749-1206. E-mail address: shokrieh@iust.ac.ir (M.M. Shokrieh). 0263-8223/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.compstruct.2004.04.008 Composite Structures 68 (2005) 419–427 www.elsevier.com/locate/compstruct