Implementation of New Process Models for Tailored Polymer Composite Structures into Processing Software Packages

Abstract

Recently, injection molded long-fiber thermoplastics (LFTs) have generated great interest within the automotive industry as these materials can potentially be used for structural applications to reduce vehicle weight. However, before our work on LFTs, injection-molding of these materials posed a great challenge because of two main reasons: (i) no process models for LFTs had been developed that could predict the injection-molding of an LFT part, and (ii) no experimental characterization methods had been developed to enable the characterization of the as-formed LFT microstructure to determine the fiber orientation and length distributions that are critical to any process model development. The objective of this project is twofold. First, the advanced process models for LFTs are developed that can accurately predict the composite microstructure governed by the flow-induced fiber orientation, fiber length distribution, and other features resulting from processing. Second, the models are implemented in the Autodesk Moldflow Insight software to enable the injection molding simulations of LFT structures. This report describes the work conducted under the Cooperative Research and Development Agreement (CRADA) (Nr. 260) between Battelle as Operator of the Pacific Northwest National Laboratory (PNNL) and Autodesk, Inc. PNNL has worked with the University of Illinois at Urbana-Champaign (UIUC) through subcontracts to develop process models for fiber orientation and length distributions in injection-molded LFTs. The UIUC has then developed and implemented the new process models for LFTs in an in-house code named ORIENT to enable first validations and applications of these models. Next, Autodesk, Inc. has implemented these new process models in Autodesk Moldflow Insight for LFT injection molding simulations. In addition, Autodesk, Inc. has performed rheological and mechanical tests to identify the rheological and physical properties for the pellet materials used in this CRADA. These properties are needed for injection-molding simulations using Autodesk Moldflow Insight. Autodesk, Inc. has delivered to PNNL the Autodesk Moldflow Insight research versions containing the newly implemented models for process simulations and also has provided PNNL with the technical support for the model validations. UIUC has assisted Autodesk, Inc. in the model implementations in Autodesk Moldflow Insight and also has assisted PNNL in the model validation using Autodesk Moldflow Insight by providing consultancy and reviews. Oak Ridge National Laboratory (ORNL) has performed microstructural characterizations for fiber length and orientation allowing the validations of the developed models.

The effect of fiber concentration on fiber orientation in injection molded film gated rectangular plates

“…Our calculations of N p , as described in the materials properties section, showed only insignificant variation of N p through the thickness of the plates. In addition, the variation between PA15, PA30, and PA50 was rather small [17][18][19][20][21][22][23][24][25][26][27] with no clear trend. Hence, N p is assumed to be constant in the following discussion and A yzyz is plotted as a measure of fiber-flow interaction in Fig.…”

“…The IRD term can be tuned to reduce the high degree of orientation predicted from the HD term, along the flow direction in the highly shear strained shell layer, by “pushing” fibers to all other directions. However, the IRD term has been found to give too high out‐of‐plane orientation and too low orientation in the in‐plane transverse to flow direction . To overcome this limitation of the FT model, Phelps and Tucker introduced the anisotropic rotary diffusion model (ARD) .…”

Validation of New Process Models for Large Injection-Molded Long-Fiber Thermoplastic Composite Structures

“…Phelps and Tucker suggest that accounting for such interactions with the anisotropic rotary diffusion (ARD) should allow us to better capture the fiber orientation distribution in LFTs. Such a model then replaces the scalar C I with a tensorial description C for the fiber-fiber interactions [3].…”

“…It was then used in the injection-molding analyses of small-size glass-fiber/PP samples. The ORIENT and Moldflow fiber orientation predictions were discussed and compared to the experimental results in our previous CRADA report [3].…”

“…PNNL/260), Battelle PNNL had worked with the University of Illinois at Urbana-Champaign (UIUC) through subcontracts to develop advanced process models for fiber orientation and length distributions in injection-molded LFTs [1][2][3]. These models are the Phelps-Tucker anisotropic rotary diffusion -reduced strain closure (ARD-RSC) model for predicting fiber orientation and the Phelps-Tucker fiber length attrition model.…”