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Joint Performance of Injection Molded Thermoplastic Bosses Containing Post Consumer Recyclate: Possible Squeak and Rattle Implications
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Abstract
Post Consumer Recyclate (PCR) or Post Industrial Regrind (PIR) use to manufacturer thermoplastic (or thermoset) automotive parts and components, has increased over the last 20 years. Therefore, automotive designers are challenged with the question of how recycled material differs in performance from virgin? In addition, automotive OEMs are requiring increased durability of thermoplastic parts and their attachments (joints), so that warranty costs, associated with interior squeaks and rattles are minimized. From this durability need there have grown several techniques for determining an attachment's performance capabilities, they are: strip-to-drive torque ratios, screw pull-out force, and clamp load fall-off. For example, if a boss has a low strip-to-drive torque ratio (< 3) there exists the potential for assembly and/or field failures. Also, a thermoplastic attachment (i.e. boss) which experiences clamp load fall-off (stress relaxation) will result in a loose fitting joint and would subsequently lead to interior squeaks and rattles.
Attachments/Joints, such as injection molded thermoplastic bosses, are on a variety of interior automotive components such as: instrument panel substrates, interior trim, consoles, package trays, cowl vents, side seat shields, and knee bolsters. To prevent squeaks and rattles these components must be robustly designed to survive extreme environmental conditions. Ford Motor Company evaluation vehicles, in Arizona, have experienced interior temperature variations between 66°C (for below the beltline interior trim) too as high as 114 °C (for package trays). Instrument panels can experience surface temperatures anywhere from 60 °C to 105 °C. These large variations in temperature will cause physical property changes in thermoplastics. Temperature changes will lead to expansions and contractions, due to the materials coefficient of thermal expansion (CTE), and reduction in the storage modulus (E), resulting in loose fitting joints.
The purpose of this paper is to evaluate the joint durability of virgin and PCR containing thermoplastic bosses, using the following metrics: 1.) pull-out forces, 2.) strip-to-drive ratios, and 3.) changes in the clamp load, with respect to environmental effects (i.e. thermal exposure). Our paper will emphasize the differences between virgin and PCR containing bosses and how this possibly relates to their squeak and rattle performance.
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Citation
Trapp, M., Rozmus, R., and Dapoz, A., "Joint Performance of Injection Molded Thermoplastic Bosses Containing Post Consumer Recyclate: Possible Squeak and Rattle Implications," SAE Technical Paper 972055, 1997, https://doi.org/10.4271/972055.Also In
References
- Hoy, R. Bartos C. Leung R. Rozmus R. Trapp M. “Determination of Dimensional Changes in Injection Molded Bosses Using Strain Gages: Effects on Joint Durability” SAE Paper # 940653 1994
- Bartos, C Leung R. Rozmus R. Trapp M. Hoy R. “Effect of Regrind on SMA Copolymer Bosses/Joint Performance” SAE Paper # 950810 1995
- Bartos, C. Leung R. Rozmus R. Trapp M. “Clamp Load and Strip-to-Drive Performance Measurements for Thermoplastic Bosses: Design of a Robust Joint” International Body Engineering Conference. Advanced Technologies & Processes 9 135 1995
- Hill, W. “Evaluating Boss Designs for Thermoset Glass-Riled Polyesters” Plastic Engineering 29 January 1996
- Bartos, C. Dapoz, A. Rozmus, R. Trapp, M. “Effect of Post Consumer Recyclate on SMA Copolymer Bosses/Joint Performance” SAE Paper # 960698 1996
- Clark, C. Florence, R. Locke, D. Bartos, C. Leung, R. Rozmus, R. Trapp, M. “Understanding the Mechanical Behavior of Threaded Fasteners in Thermoplastic Bosses Under Load” SAE Paper # 960293 1996
- Clark, C. Florence, R. Locke D. “The Behavior of Threaded Fasteners In Engineering Thermoplastics Under Load” International Body Engineering Conference, Body Design & Engineering 20 25 1996