JEC COMPOSITES MAGAZINE - Issue #36 - October 2007 - 40

g…/… Mass transit application fibre-filled extruded PP charge in the mould cavity. Thermomechanical stresses, warpage, shrinkage, fibre distribution and flow fronts were predicted. The design cycle for the LFT bus seat is shown in figure 1. and the structural frames. A structural frame made of powderimpregnated carbon-fibre-reinforced polyphenylene sulphide (C/PPS) was developed, for assembly to a body panel. The body panel featured a load-bearing sandwich panel made of random chopped E-glass/PP face sheets and a hexagonal PP core. The frame was 60% lighter than the corresponding steel solution, and the body panel assembled to the frame was 40% lighter for equivalent structural performance. The conventional steel frame bus and the corresponding thermoplastic composite sub-elements of the body panel and structural frame are shown in figure 3. Fig 1: Integrated process and product development (IPPD) of glass/PP LFT mass transit bus seat Glass/PP tape consolidated floor segment The conventional floor on mass transit systems is made from steel and plywood. During the lifetime of a standard bus, the floor has to be replaced a number of times, because steel corrodes and plywood rots due to acid washes and moisture. For the thermoplastic floor segment, glass/PP woven tape material was consolidated on a double belt-press to form a face along with a vacuum-thermoformed, ribstiffened core. The woven fabric E-glass/PP floor segment was modular, and 40% lighter than the conventional metal/plywood floor. Steel frame b d Fig. 3: Thermoplastic structural side frame and body panel design; (a) conventional bus with welded steel frames; (b) modular thermoplastic composite concept–assembly of structural frame to body panels; (c) polypropylene core, thermoplastic glass/PP skins; (d) carbon/PPS structural frame LFT battery-box access door An LFT glass/PP battery-box door (figure 4) was designed and produced to replace a steel frame welded to sheet steel. The steel corrodes under corrosive battery-fluid environment. The LFT door featured ribs to support the structural loads, eliminating the steel frame entirely. The battery door is approximately 1 m long by 0.6 m wide, and the current design weighs about 12 kg. Adopting the thermoplastic composite technology can give weight savings of about 50 to 60% compared to the existing design. In order to reduce labour and therefore cost, the design approach for the LFTbased battery-box access door featured integrated stiffness to eliminate the steel frame as shown in figure 4. The ribs provide extra dimensional stability to the part by controlling out-of-plane Plywood Fig. 2: Floor segment replacement; (a) Conventional steel-plywood floor used in mass transit buses; (b) Modular tape reinforced glass/PP floor segment; (c) Design detail of hat-sine stiffened vacuum thermoformed glass/PP floor segment. Figure 2 illustrates the conventional floor as compared to a modular thermoplastic glass/PP floor segment. The thermoplastic composite floor was significantly more damage tolerant, easy to replace and install, and had an order of magnitude improved vibration and sound damping characteristics. Side body panel and structural frame segments Conventional buses possess a welded tubular steel frame, over which cosmetic body panels are mounted. In the thermoplastic design, the structural load bearing was shared across the body panel Fig. 4: Replacement of the welded steel battery-box access door on a mass transit bus with a glass/PP LFT battery access door; 50% weight savings; (a) location of battery-box access door on articulated bus; (b) form-fit function demonstrating replacement of steel door with LFT door JEC Composites Magazine / No36 October - November 2007

JEC COMPOSITES MAGAZINE - Issue #36 - October 2007

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #36 - October 2007