Molding Compounds

Discontinuous reinforcements come in various forms like chopped fibers and unidirectional tapes. A planar form of reinforcement with a woven structure is studied in this project. One of the goals is to capitalize the potential in the process scrap by recycling since a considerable amount of process/cutting scrap is generated in the production of thermoplastic composites. The prepreg cutting scrap is chopped to a bulk material form to be used as a standalone molding compound. Short-term objectives are defined to achieve a long-term goal of maximizing the benefit from scrap, such as to understand the nature of different scrap material forms, characterize the behavior of the discontinuous composite and finally derive guidelines for designing an efficient molding compound.

Contact: Iqbal Rasheed

TPRC
PhD student

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Objective

To develop guidelines for the processing of discontinuous thermoplastic composite material in order to achieve a robust manufacturing process for advanced parts with predictable and consistent material properties

Keywords: discontinuous, chopped, woven, flakes, integrated features, consolidation

Background/Introduction

The conventional production processes of continuously reinforced thermoplastic composites provide an excellent way to manufacture shell-shaped parts with high quality, but with limited geometrical complexity. And, significant amounts of high-value scrap are generated during prepreg cutting and laminate nesting operations for, respectively, autoclave consolidation and press forming. Currently, this waste is down cycled to particulate fillers or even incinerated. Even though the nesting and trimming processes can be optimized, the scrap generation is inevitable.

This project aims to develop guidelines for producing near net-shaped parts with complex geometries using chopped woven prepreg material. Potential applications include semi-structural and non-load bearing structures. Additionally, it enables to reclaim the virgin woven prepreg scrap from the conventional production process and thereby close one part of the manufacturing value chain.

Approach

The performance of a discontinuously reinforced composite part depends on the form of the discontinuous material, design of the part and the process used. In terms of processing, atypical flow mechanisms of chopped woven prepreg flakes were identified and explained with analytical models developed from the fundamentals of fluid mechanics. On the other end, the ability of the material to fill intricate design features such as integrated ribs were assessed with scaled molding experiments. A method to assess the variability of mechanical properties, such as tensile properties, and to arrive at the material allowable was established based on phenomenological models and statistical principles.

Finally, the processing strategy developed from the results was successfully put to test in molding a full-scale, net-shaped demonstrator part with complex features such as integrated ribs, as-molded holes with boss, joggles, thickness transitions, cut-outs and embossed logo.GIJS1844

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Contact

  • Interested in application of the developed knowledge? Please contact Sebastiaan Wijskamp.
  • Interested in the underlying scientific background? Please contact Iqbal Rasheed.

Research overview