Quadrant Plastic Composite have provided a lightweight reinforced thermoplastic (LWRT) composite solution in developing a load floor/trunk separator component featured on the 2005 Crossfire roadster by DaimlerChrysler.
The new Chrysler Crossfire sportscar is a low-slung, 2-seater with sculpted styling lines and is claimed to be one of the fastest concept-to production platforms in automobile history.
The new Crossfire roadster convertible model also boasts a 1-piece load floor/trunk separator moulded from a new low-density composite developed by Quadrant Plastic Composites called SymaLITE.
Designers of the Crossfire programme wanted to design a lightweight “”box”” with integral hinges that could stow the convertible top when retracted, yet fold flat when the top was closed. The novelty of this design and its deflection requirements demanded a new type of solution. Traditional loadfloor / trunk separator materials were considered first, but did not offer the option to integrate the convertible top rollback area with the trunk separator, create a living hinge to connect components yet let them flex in use, or in-mould decorate with carpet and scrim in a single production step (saving tooling and additional secondary operations).
The designers opted for a new type of low-density composite from Quadrant called SymaLITE, which enabled the innovative concept to become a reality because it offered the opportunity to change density locally across the part to maximize the stiffness/weight ratio, according to Quadrant.
The design and process versatility of this lightweight, glass reinforced thermoplastic composite enabled the part to be manufactured using a 2,000-g/m2 (gsm) grade for the truck separator and an 1,800-gsm grade for the load floor. The load floor’s cross-section is tailored via consolidation (degree of compression of the composite) to provide more rigidity in the centre by leaving the part thicker in that section. Quadrant said that natural fibre composites and sandwich constructions did not offer the flexibility to change density locally in the tool without adding weight. Additionally, SymaLITE composite offered the option to save weight, increase design freedom and functional integration, improve styling flexibility, save on tooling and assembly, and achieve easy processing and recyclability.
SymaLITE low-density composites offer significant opportunities to reduce mass and increase decorating options while maintaining stiffness and melt reprocessability for structural and semi-structural applications. The material makes use of a mat technology – a fleece comprised of long glass and polypropylene fibres – and low-pressure moulding to create long-fibre reinforced, air-permeated composite parts.
Altering either the ratio of fibres or the needling of the fleece allows Quadrant to optimize mechanical and physical properties for a given application. Because the higher the composite’s glass loading is, the higher its loft and the lower its density, it yields parts with higher stiffness and lower deflection than conventional GMT. This allows processors to use a technique called “”tailored consolidation”” where the density of SymaLITE composite can be reduced to one-third that of the original laminate and the thickness can be varied across the finished part while maintaining the same part weight. To maintain a thicker section with higher area stiffness, the tool is designed not to press as deeply into the material in that location. For sections where higher tensile strength is needed, the blank is more fully consolidated (pressed thinner) during moulding.
This large, complex LWRT composite part is produced in two tools, both using single-shot-technology, in about 90 sec. It is in-mould decorated with pressure-sensitive carpet on one side and polyester scrim on the other, with overlap of decoration layers. High design freedom allows for production of deep draws, sharp edges, and tight radii. A living textile hinge eliminates the need for fasteners and facilitates assembly.
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