Table of Contents
Journal of Composites
Volume 2014, Article ID 846962, 8 pages
http://dx.doi.org/10.1155/2014/846962
Research Article

Effect of Melt Temperature and Hold Pressure on the Weld-Line Strength of an Injection Molded Talc-Filled Polypropylene

Center for Lightweighting Automotive Materials and Processing, University of Michigan-Dearborn, Dearborn, MI 48128, USA

Received 12 June 2013; Revised 21 December 2013; Accepted 21 January 2014; Published 5 March 2014

Academic Editor: Mircea Chipara

Copyright © 2014 Yuanxin Zhou and P. K. Mallick. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Tensile stress-strain behavior coupled with fractography was used to investigate the weld-line strength of an injection molded 40 w% talc-filled polypropylene. The relationship between processing conditions, microstructure, and tensile strength was established. Fracture surface of the weld line exhibited skin-core morphology with different degrees of talc particle orientations in the core and in the skin. Experimental results also showed that the thickness of the core decreased and the thickness of the skins increased with increasing melt temperature and increasing hold pressure, which resulted in an increase of yield strength and yield strain with increasing melt temperature and increasing hold pressure. Finally, a three-parameter nonlinear constitutive model was developed to describe the strain softening behavior of the weld-line strength of talc-filled polypropylene. The parameters in this model are the modulus E, the strain exponent m, and the compliance factor β. The simulated stress-strain curves from the model are in good agreement with the test data, and both m and β are functions of skin-core thickness ratio.