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Technical Paper

A Novel Approach for Design and Optimization of Automotive Aluminum Cross-Car Beam Assemblies

Nowadays, moving toward more lightweight designs is the key goal of all major automotive industries, and they are always looking for more mass saving replacements. In this study, a new methodology for the design and optimization of cross-car beam (CCB) assemblies is proposed to obtain a more lightweight aluminum design as a substitution for the steel counterpart considering targeted performances. For this purpose, first, topology optimization on a solid aluminum geometry encompassing the entire design space should be carried out to obtain the element density distribution within the model. Reinforcing locations with high element density and eliminating those with density lower than the threshold value result in the conceptual design of the CCB. To attain the final conceptual design, the process of topology optimization and removal of unnecessary elements should be addressed in several steps.
Technical Paper

Effect of CO2 Content on Foaming Behavior of Recyclable High-Melt-Strength PP

This paper presents an experimental study on the foaming behavior of recyclable high-melt-strength (HMS) branched polypropylene (PP) with CO2 as a blowing agent. The foamability of branched HMS PP has been evaluated using a tandem foaming extruder system. The effects of CO2 and nucleating agent contents on the final foam morphology have been thoroughly investigated. The low density (i.e., 12~14 fold), fine-celled (i.e., 107–109 cells/cm3) PP foams were successfully produced using a small amount of talc (i.e., 0.8 wt%) and 5 wt% CO2.
Technical Paper

Effect of Fungal Modification on Fiber-Matrix Adhesion in Natural Fiber Reinforced Polymer Composites

Natural fiber reinforced polymer composites are beginning to find their way into the commercial automotive market. But, inadequate adhesion between hydrophilic natural fibers and hydrophobic matrix materials affects the performance of the resulting composites. In this study the effect of an environmental friendly fungal treatment on the adhesion characteristics of natural fibers is investigated. Firstly, changes in acid-base characteristics of the modified hemp fibers were studied using Inverse Gas Chromatography (IGC). Afterwards, composites were prepared using Resin Transfer Molding (RTM) process and the effect of modification on performance and durability of the composites was investigated.
Technical Paper

Eutectic Segregation and Cracking in AZ91 Friction Stir Spot Welds

Friction stir spot welding of Mg-alloy AZ91 is investigated. The temperature cycles within the stir zone and in the TMAZ region are examined using thermocouples, which are located within the tool itself and also by locating thermocouples in drilled holes at specific locations relative to the bottom of the tool shoulder and the periphery of the rotating pin. The measured temperatures in the stir zone range from 437°C to 460°C (0.98Ts, where Ts is the solidus temperature in degrees Kelvin) in AZ91 spot welds produced using plunge rates from 2.5 and 25 mm/s. The thermal cycle within the stir zone formed during AZ91 spot welding could not be measured by locating thermocouples within the workpiece in drilled holes adjacent to the periphery of the rotating pin.
Technical Paper

Microcellular Ceramic Foams: Manufacturing and Study of Acoustical Properties

A novel processing method for fabricating high porosity microcellular ceramic foams for sound absorption applications has been developed. The strategy for fabricating the ceramic foams involves: (i) forming some shapes using a mixture of preceramic polymer and expandable microspheres by a conventional ceramic forming method, (ii) foaming the compact by heating, (iii) cross-linking the foamed body, and (iv) transforming the foamed body into ceramic foams by pyrolysis. By controlling the microsphere content and that of the base elastomer, it was possible to adjust the porosity with a very high open-cell content (ranging between 43 - 95%), high microcellular cell densities (9 × 108 - 1.6 × 109 cells/cm3) and desired expansion ratios (3 - 6 folds). Sound absorption testing has been performed using ASTM C-384 standard test. The preliminary results show that ceramic foams are candidate sound absorption materials.
Technical Paper

The Effect of Surface Modification on the Mechanical Properties of Hemp Fiber/Polyester Composites

In this work hemp fibers were chemically treated in order to improve the fiber/matrix interaction in hemp fiber/unsaturated polyester composites prepared by a Resin Transfer Molding (RTM) process. Chemicals used for paper sizing (AKD, ASA, Rosin Acid and SMA) as well as a silane compound and sodium hydroxide were used to modify the fibers' surface. The tensile, flexural and impact properties of the resulting materials were measured. A slight improvement in mechanical properties was observed for the SMA, silane and alkali treated specimens. However close analysis of these tests and of the fracture surface of the samples showed that there was no amelioration of the fiber/matrix adhesion. It was found that predicted tensile strengths using the rule of mixture were very close to the experimental values obtained in this work. Finally the properties of an hybrid glass fiber/hemp fiber composite were found to be very promising
Technical Paper

The Effects of Nano-clay on Extrusion Microcellular Foaming of Nylon

This paper demonstrates the effects of nano-clay on the microcellular foam processing of nylon. First, Nylon 6 nanocomposites with 1 wt% clay were prepared by a twin screw extruder. The nanocomposite structures were characterized by XRD and TEM. Nylon and its nanocomposites were foamed in extrusion using CO2. The cell morphologies of nylon and its nanocomposite foams were investigated. It appeared that the nano-clay not only enhanced cell nucleation, but also suppressed cell deterioration in the microcellular foaming of nylon.
Technical Paper

The Influence of the Bauschinger Effect on Springback Prediction for Dual Phase Steel

Springback is one of the main concerns in sheet metal forming with the increased use of advanced high strength steels, among which dual phase steels are gaining popularity. Although finite element analysis (FEA) has been successfully used in simulating complicated forming processes, it is difficult to accurately predict springback due to certain complex material behaviors such as the non-linear recovery behavior. In this study, the tension-unloading-reloading (TUR) test and XRD analysis have been employed to investigate non-linear recovery through Bauschinger Effect (BE) measurement at different pre-strain levels. The results demonstrated that dual phase steels exhibited the strong BE. The FEA simulation of springback prediction in the deep-draw bending test showed that the simulation accuracy was significantly improved by incorporating the Bauschinger effect.