CompositesWorld

NOV 2017

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NOVEMBER 2017 46 CompositesWorld FOCUS ON DESIGN that, we need to accurately predict performance up front and know we'll achieve good correlation with physical testing. It's vital to have reliable predictive capabilities for all the materials we use, and that's another issue we still face with composites." From mono- to multi-material system e Gen 1 design was essentially a painted, structural SMC system with bonded metal stiffeners and molded-in mounting collars produced by Continental Structural Plastics (CSP, Auburn Hills, MI, US). To add features and reduce mass and costs for Gen 2, the team went with a multi-material system. While all load-bearing surfaces in the bed, trunk and liftgate inner remained in SMC with stiffeners and mounting collars, this time, the box's sidewalls and headboard were compression molded from molded-in-color (MIC) black, fiberglass- reinforced, direct-long-fiber thermoplastic (D-LFT) with a poly- propylene (PP) matrix. e spare-tire tray was injection molded from short-glass PP. "With any material, you have plusses and minuses," explains Ryan. "No single material is always right for every application across the board." Although researchers declined to provide details on the specific decision matrix used to specify the D-LFT and injection-PP formulations, team members did say that materials selection was driven by differences between the performance criteria for the box's vertically and horizontally oriented parts. e formulation was optimized jointly by Honda, CSP, and additive supplier Addcomp North America Inc. (Rochester Hills, MI, US). Even the carryover SMC parts went through considerable scrutiny to see how much more value could be added. One area that was identified was paint elimination. Although SMC is known for its toughness, stiffness, chemical resistance, weight reduction, low scrap, design flexibility and relatively fast compression molding cycle times (2-3 minutes, button-to-button, even for large parts), it is not considered weatherable in typical vinyl ester or unsaturated polyester (UP) formulations. For that reason, it is generally painted for applications that will involve outdoor exposure. However, paint adds cost and environmental burdens that Honda wished to avoid. anks to unique formulation work by resin supplier Ashland LLC (Dublin, OH, US) and additive supplier Chromaflo Technolo- gies LLC (Ashtabula, OH, US), all the Gen 2 Ridgeline's visible SMC box components use a new weatherable (UV-stable) struc- tural grade of fiberglass-reinforced UP SMC (specific gravity = 1.8). e MIC black material was compounded and molded by CSP, which also has produced SMC pickup boxes for Ford Motor Co. (Dearborn, MI, US) and Toyota Motor Corp. (Toyota City, Aichi, Japan). "Ashland has been doing development work on weatherable SMCs since the 1990s," notes Dan Dowdall, Ashland global business development manager – transportation composites. "Honda and CSP had interest in a weatherable grade for the Gen 2 Ridgeline to improve the bed's durability and scratch resistance, but had very demanding requirements for color stability, gloss retention and mechanical properties. After extensive trials and testing, the Ashland-CSP SMC 834UV formulation was approved for use." He says this application represents the first commercial use of the material in any industry. Read this article online | short.compositesworld.com/HondaR-G2 Molded-in-color D-LFT + unpainted SMC To add features and reduce mass and costs for the Gen 2 pickup box, the team went with a multi-material system. Load-bearing surfaces (bed, trunk and liftgate inner) remained in SMC, but the box's sidewalls and headboard were compression molded from molded-in-color (MIC) black, fiberglass-reinforced direct-long-fiber thermoplastic (D-LFT) with a polypro- pylene matrix. This time, SMC parts were incorporated without the need for paint, thanks to unique formulation work by suppliers that enabled the use of a new weatherable structural grade of fiberglass-reinforced UP-SMC in the Gen 2 box.

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