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Design of Additive Manufactured Thermoplastic Component as FMVSS 201U Countermeasure
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on November 21, 2019 by SAE International in United States
Event: NuGen Summit
Research and/or Engineering Questing/Objectives: Safety of the occupant in passenger cars is one of the regulatory requirements in many developed countries. This includes upper interior head impact load case of the unbelted occupant during crash (FMVSS 201U) as one of them. During a crash event the occupant head can collide with the interior parts of the vehicle, such as a headliner, pillar trim and other subsequent components in the loading direction. Injury on the head is quantified in terms of the Head Injury Criterion of a crash test dummy (HIC(d)) value which should be less than 1000 per standard. Several ways can be adopted to reduce the HIC(d) value. These include a change in the design of ribs in the safety plastic components, headliner profile change, use of countermeasure foam between headliner and the exterior sheet metal parts, or a combination of any of these to absorb the energy of impact. Recent developments in the field of manufacturing, such as the Additive Manufacturing (AM) method, have provided an opportunity to design and manufacture components with complex geometries which cannot be achieved with the conventional manufacturing methods. Current study focuses on the design of a thermoplastic component using the AM method as an alternative for the countermeasure foam used as an energy absorber for the head impact load case. Methodology Methodology includes understanding of AM capability, coupon manufacturing to characterize material properties, design a thermoplastic countermeasure in the form of lattice structure which can be manufactured using AM technique and can improve the value of the head injury criterion for FMVSS 201U. A special optimization technique is used to find the most suitable lattice structure, CAE analysis and component level verification is done. Results Characterization of additive manufactured Polycarbonate (PC) material shows small degree of anisotropy and lower failure strain compared to injection molded samples. Using the optimization technique few designs are obtained that has the potential to lower the HIC value. Such designs show the potential of the optimization technique to come up with even better designs if the DOE space is enlarged. Limitations of this study The performance of only few selected lattice designs were studied and other designs can be evaluated. Gauge optimization of lattice designs can further improve the performance which needs further study. The selected designs from this study should be evaluated with AM PC properties to assess the effect of lower ductility on the energy absorbing capacity. Prototype manufacturing and component level testing needs to be carried out for validation of the design. What does the paper offer that is new in the field including in comparison to other work by the authors? Anisotropic characterization of additive manufactured PC material and a unique way of obtaining lattice structure from optimization technique for FMVSS201U load case. Conclusions Few lattice structures from the optimization study are found to meet the HIC(d) criteria for 201U load case. However, a gauge optimization is needed to further improve the performance. Additive manufactured PC material demonstrates a small degree of anisotropy which needs to be accounted for design of components. It also has lower ductility compared to injection molded PC material. This needs a further investigation of the resins being used for AM and Injection molding.