Composites: Part B 53(2013)103-111 Contents lists available at SciVerse Science Direct composites Composites: Part B ELSEVIER journalhomepagewww.elsevier.com/locate/compositesb fracture failure analysis of automotive accelerator pedal arms with Cross Mark polymer matrix composite material Yi Gong, Zhen-Guo Yang Department of Material Science, Fudan University, Shanghai 200433, PR China ARTICLE INFO A BSTRACT The booming automotive industry is undoubtedly not indep of the extensive applications of com- Received 4 January 2013 posite materials, especially the polymer matrix composite aiming to optimize the price versus erformance ratios. Actually, considering safety and reliabil he prior concerns of vehicles, evalu- Available online 25 April 2013 tion of the'performances'must never be stopped, from both laboratories and actual services. In this fracture failure incidents of the automotive accelerator pedal arms with matrix of long glass fiber reinforced polypropylene were systematically investigated. Based on the analysis results of matrix mate- A Polymer-matrix composites(PMCs) rials inspection and fractograph observation, root causes of the failure were identified, and the counter- B Microstructures measures were proposed from the manufacturing point of view. Achievements of this study would provide an actual and vivid example to understand how the processing of polymer matrix composite materials affects the microstructures, the properties and the performances, and would consequently help to prevent similar failures on automotive parts with such materials e 2013 Elsevier Ltd. All rights reserved 1 Introduction the root causes would help to clarify the actual duties. Finally, the countermeasures were proposed on basis of the analysis results. The increasing drive toward smaller and lighter vehicles for the Achievement of this paper would have a reference value for failure sake of higher fuel efficiency has been seeing the expanding appli- prevention of all the lGFPP automotive parts, and would even pro- cation of composite materials, which account for about 10-15% vide a vivid example of the relationship among processing, struc weight of a civilian vehicle nowadays. Among them, the long glass ture, performance, and application for polymer matrix composite fiber reinforced polypropylene(LGFPP)that owns superiorities like materials low-density, low-cost, and recyclable is the most used and faste growing one [1. mainly applied to the front end brackets, dash oards, pedals, and so on. Nevertheless, every coin has two sides. whether these composite automotive parts with optimized price It should be noted firstly that 1100 N was regarded as the qual- versus performance ratio are competent in practice still deserves ified fracture load for the pedal arms. Fig. la displayed the external to be investigated in detai appearances of two fractured samples, one was the failed pedal Besides abundance of experimental studies [2, 3]. failure analy- arm from the automaker, and the other was the unused pe is is relatively seldom reported, but it plays an even more impe tant role since its samples are all acquired from the actual service the manufacturer Learnt from Fig. 1b, the fracture positions were conditions. In this paper, several fracture failure incidents, which both locating at the joints between the pedals and the frames. took place under test loads lower than the design value during Then, referring to our previous experiences of engineeri ing failure tion after whole-vehicle assembly, of the automotive analysis 14-91. investigations were carried out from two aspects ccelerator pedal arms with LGFPP (GF, 50 wt%) polymer matrix n one hand, the matrix material of the failed pedal arm was char pose this fracture occurred in driving. untold sufferings would have lized to verify the chemical constituents; thermogravimetric been engendered From another point of view, as the automaker, analysis(TGA), melt index(MI)measurement, and high-temp the pedal arm manufacturer, and the GF/PP pellets supplier were ture sintering were employed to testify the content, detect the dis three different joint ventures from multiple countries, determining tribution condition, and help to observe the morphologies of the glass fibers; even the gF/PP pellets were examined for their phys- Corresponding author. Tel. +86 21 65642523: fax: +86 21 65103056 ical and mechanical properties. On the other hand, in order for E-mailaddress:zgyang@fudan.edu.cn(Z-G.Yang omparison, the fracture surfaces of both the two samples were 68/s-see front matter 2013 Elsevier Ltd. All rights reserved l/dx doiorg/10. 1016/j- composites. 2013.04.047Fracture failure analysis of automotive accelerator pedal arms with polymer matrix composite material Yi Gong, Zhen-Guo Yang ⇑ Department of Materials Science, Fudan University, Shanghai 200433, PR China article info Article history: Received 4 January 2013 Accepted 7 April 2013 Available online 25 April 2013 Keywords: A. Polymer–matrix composites (PMCs) A. Glass fibers B. Microstructures D. Fractography abstract The booming automotive industry is undoubtedly not independent of the extensive applications of com￾posite materials, especially the polymer matrix composite materials, aiming to optimize the price versus performance ratios. Actually, considering safety and reliability are the prior concerns of vehicles, evalu￾ation of the ‘performances’ must never be stopped, from both laboratories and actual services. In this paper, fracture failure incidents of the automotive accelerator pedal arms with matrix of long glass fiber reinforced polypropylene were systematically investigated. Based on the analysis results of matrix mate￾rials inspection and fractograph observation, root causes of the failure were identified, and the counter￾measures were proposed from the manufacturing point of view. Achievements of this study would provide an actual and vivid example to understand how the processing of polymer matrix composite materials affects the microstructures, the properties and the performances, and would consequently help to prevent similar failures on automotive parts with such materials. 2013 Elsevier Ltd. All rights reserved. 1. Introduction The increasing drive toward smaller and lighter vehicles for the sake of higher fuel efficiency has been seeing the expanding appli￾cation of composite materials, which account for about 10–15% weight of a civilian vehicle nowadays. Among them, the long glass fiber reinforced polypropylene (LGFPP) that owns superiorities like low-density, low-cost, and recyclable is the most used and fastest growing one [1], mainly applied to the front end brackets, dash￾boards, pedals, and so on. Nevertheless, every coin has two sides, whether these composite automotive parts with optimized price versus performance ratio are competent in practice still deserves to be investigated in detail. Besides abundance of experimental studies [2,3], failure analy￾sis is relatively seldom reported, but it plays an even more impor￾tant role since its samples are all acquired from the actual service conditions. In this paper, several fracture failure incidents, which took place under test loads lower than the design value during the inspection after whole-vehicle assembly, of the automotive accelerator pedal arms with LGFPP (GF, 50 wt%) polymer matrix composite materials were systematically analyzed. Evidently, sup￾pose this fracture occurred in driving, untold sufferings would have been engendered. From another point of view, as the automaker, the pedal arm manufacturer, and the GF/PP pellets supplier were three different joint ventures from multiple countries, determining the root causes would help to clarify the actual duties. Finally, the countermeasures were proposed on basis of the analysis results. Achievement of this paper would have a reference value for failure prevention of all the LGFPP automotive parts, and would even pro￾vide a vivid example of the relationship among processing, struc￾ture, performance, and application for polymer matrix composite materials. 2. Experimental It should be noted firstly that 1100 N was regarded as the qual￾ified fracture load for the pedal arms. Fig. 1a displayed the external appearances of two fractured samples, one was the failed pedal arm from the automaker, and the other was the unused pedal arm (with qualified fracture load in test) directly obtained from the manufacturer. Learnt from Fig. 1b, the fracture positions were both locating at the joints between the pedals and the frames. Then, referring to our previous experiences of engineering failure analysis [4–9], investigations were carried out from two aspects. On one hand, the matrix material of the failed pedal arm was char￾acterized. Fourier transform infrared spectroscopy (FTIR) was uti￾lized to verify the chemical constituents; thermogravimetric analysis (TGA), melt index (MI) measurement, and high-tempera￾ture sintering were employed to testify the content, detect the dis￾tribution condition, and help to observe the morphologies of the glass fibers; even the GF/PP pellets were examined for their phys￾ical and mechanical properties. On the other hand, in order for comparison, the fracture surfaces of both the two samples were 1359-8368/$ - see front matter 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.compositesb.2013.04.047 ⇑ Corresponding author. Tel.: +86 21 65642523; fax: +86 21 65103056. E-mail address: zgyang@fudan.edu.cn (Z.-G. Yang). Composites: Part B 53 (2013) 103–111 Contents lists available at SciVerse ScienceDirect Composites: Part B journal homepage: www.elsevier.com/locate/compositesb