Effects of Polymer-Filler Properties on the Warpage of Injection Molded Automobile Door

Transcription

1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Effects of Polymer-Filler Properties on the Warpage of Injection Molded Automobile Door Qiuhui Liao a, Xiaoxun Zhang b and Qinchao Ruan c Material Engineering School, Shanghai University of Engineering Science, Shanghai, China a qiuhui@sues.edu.cn, b xx.zhang.cn@gmail.com, c xinda1118@163.com Keywords: Polymer Filler, Aspect Ratio, Modulus, Warpage, Thermal Displacement, PVT Displacement, Orientation Effect Displacement. Abstract. The accurate prediction of warpage of injection molded parts is important to achieve successful mold design with high precision. In this study, effects of polymer-filler properties, such as filler aspect ratio (L/D), filler modulus parallel to major axis (E1) and filler modulus perpendicular to major axis (E2), on warpage of automobile door were studied quantitatively by experimental investigation and numerical simulation. The numerical results are in good agreement with the experimental measurements. It is also found that: (1) the thermal decreases as E1 and E2 decrease, (2) the PVT is not influenced by change of L/D, E1 and E2, (3) the orientation effect is neglected small when L/D=1 and E1= E2, and it also increases as L/D and E1/E2 increase. Introduction One of the most important quality problems of plastic parts is warpage [1]. The direct cause of warpage is the uneven shrinkage, which results in internal stress and residual stress [1, 2]. Warpage appears when these stresses exceed the stiffness of the material [3]. The accurate prediction of warpage of injection molded parts is important to achieve successful mold design with high precision [4, 5]. Automobile door is an important vehicle interior structure, and its warpage must be controlled strictly since it needs to be assembled with other parts [6]. The main factors which influence the warpage of the automobile door are the parts design, mold construction, material properties and injection molding processes [7, 8]. The aim of this paper is to study the effects of polymer-filler properties, such as filler aspect ratio (L/D), filler modulus parallel to major axis (E1) and filler modulus perpendicular to major axis (E2), on warpage by experimental investigation and numerical analysis. Experimental Investigation and Numerical Simulation Processing conditions. The shape and structure of the automobile door, the runner system and the cooling channels are shown in Fig. 1. Hot runner system combined with cold runner and multi-gate is adopted in the production. The material of the automobile door is PP/EE260AE/Borealis and the content of polymer filler is 23 percent. The injection molding conditions are shown in Table 1. Table 1 Injection molding conditions of the automobile door Melt temperature [ C] Mold temperature [ C] Filling time [sec] Packing time [sec] Cooling time [sec] All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-09/04/16,07:51:21)

2 2512 Advanced Materials, CEAM 2011 Fig. 1. The model for injection molding of the automobile door Experimental measurement of the warpage. Injection molding experiments with different polymer-filler properties are carried out under the same processing conditions shown in Table 1. Totally 42 points for measuring warpage are set on the rim of each injection molded automobile door (see Fig. 2(a)). According to each measuring point, the warpage is measured using the 3D coordinate measuring machine after the part is ejected and cooled down to room temperature. The measured value is relative to the model coordinate. Numerical simulation of the warpage. Using the software package Moldex3D, numerical simulations of the injection molding process of the automobile door are conducted under the same processing conditions shown in Table 1. The total warpage s (all effects are considered) are calculated as shown in Fig. 2(b). The warpage s of the corresponding 42 points are compared with those values measured from experiments. It is found that the numerical results are in good agreement with the experimental measurements. In addition, effects of polymer-filler properties on the warpage of automobile door can be obtained from the simulation results. This will be discussed in detail in the next section. (a) (b) Fig. 2. The warpage of injection molded automobile door: (a) experimental measurement. (b) numerical simulation Effects of Polymer-Filler Properties on the Warpage In order to study the effects of polymer-filler properties on the warpage, a series of simulation cases are conducted with different polymer-filler properties. The detailed results of five cases are presented in Table 2. It can be seen that: (1) The Y-thermal and the total thermal of

3 Advanced Materials Research Vols the five cases decrease as E1 and E2 decrease. The thermal of case A is the smallest because the modulus of case A is the smallest. (2) The volumetric shrinkage, Y-differential area shrinkage and total differential area shrinkage are the same in the five cases since the volumetric shrinkage and differential area shrinkage are shrinkage behavior of polymer itself caused by PVT Effect. The change of aspect ratio and modulus of polymer-filler has no effect on them. (3) The fiber orientation effect s of cases A and B are neglected small, but those of cases C, D and E are much greater, since there is no fiber orientation Table 2 Effects of polymer-filler properties on the warpage Case A B C D E L/D: 1 L/D: 1 L/D: 20 L/D: 20 E1: 1.7e10 Pa E1: 7e10 Pa E1: 7e10 Pa E1: 7e12 Pa E2: 1.7e10 Pa E2: 7e10 Pa E2: 7e10 Pa E2: 7e10 Pa Filler properties Y 1 - Total Y-thermal Total thermal Volumetric shrinkage /% Y-fiber orientation effect Total fiber orientation effect Y-differential area shrinkage Total differential area shrinkage [-5.574, 4.834] 2 WA 3 = [1.677, ] WA= [-1.507, 1.445] WA= [0.010, 1.524] WA= [-0.127, 0.545] WA= [0.857, 1.234] WA= [-5.798, 4.951] WA= [2.265, ] WA= [-1.640, 1.474] WA= [0.007, 1.659] WA= [-0.289, 0.423] WA= [0.126, 0.673] WA= [ , 8.756] WA= [3.567, ] WA= [-1.510, 2.307] WA= [0.034, 2.330] WA= [ , 8.707] WA= [0.061, ] WA= Y direction is the mold opening direction; 2 [a, b] means the range of the warpage is from a to b; 3 WA means weighted average. [ , ] WA= [3.481, ] WA= [-1.726, 2.308] WA= [0.004, 2.330] WA= [ , ] WA= [0.428, ] WA= L/D: 40 E1: 7e12 Pa E2: 7e10 Pa [ , ] WA= [3.620, ] WA= [-1.839, 2.474] WA= [0.039, 2.500] WA= [ , ] WA= [0.334, ] WA= 4.589

4 2514 Advanced Materials, CEAM 2011 effect increases as L/D and E1/E2 increase. (4) For those plastics without filler or containing non-fibrous filler (L/D=1), the total warpage of the parts mainly comes from the shrinkage behavior of polymer itself caused by PVT Effect. For those plastics containing fibrous filler (L/D>>1), the total warpage not only comes from the uneven shrinkage behavior of polymer itself caused by PVT Effect, but the fiber orientation effect and anisotropy have a major impact on warpage. Conclusions Effects of polymer-filler properties on warpage of automobile door were studied quantitatively by experimental investigation and numerical simulation. The numerical results are in good agreement with the experimental measurements. It is also found that: (1) the thermal decreases as E1 and E2 decrease; (2) the PVT is not influenced by change of L/D, E1 and E2; (3) the orientation effect is neglected small when L/D=1 and E1= E2, and the orientation effect increases as L/D and E1/E2 increase. Acknowledgements This work is supported by Shanghai Leading Academic Discipline Project under grant J The authors would like to thank Mr. Ge J. from Yanfeng Visteon Automotive Tooling Co., Ltd and Mr. Xu from CoreTech System Co., Ltd. References [1] A. H. Ahmad, Z. Leman, M. A. Azmir: Optimization of Warpage Defect in Injection Moulding Process using ABS Material, in IEEE Int. Conf. on Modelling & Simulation, Bali, Indonesia, May 2009, p [2] Tuncay Erzurumlu, Babur Ozcelik: Materials & Design Vol. 27 (2006), p [3] Yih Cherng Chiang: J. Advanced Materials Research Vol. 154 (2010), p [4] Huang Guijian, Li Xuemei, Wu Xiaoyu, Li Jibin: Optimized Design of Injection Mould for Mobile Phone Front Shell Based on CAE Technology, in IEEE Int. Conf. on Artificial Intelligence, SanYa, China, April 2009, p [5] S.H.Tang, Y.J.Tan, S.M.Sapuan: J. Materials Processing Technology Vol. 182 (2007), p [6] RGW Pye: Injection Mould Design (Longman Group UK Limited, London 1989). [7] Ming-Chih Huang, Ching-Chih Tai: J. Materials Processing Technology Vol. 110(2001), p. 2. [8] X.T. Wang: Injection Molding Technology (Chemical Industry Press, Beijing 1989).(In Chinese)

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