Retail price wars in the computer and consumer electronics market have led to massive cost reductions in case manufacture. Injection molded FRP costs have been reduced by using thinner walls. However, this has increased the risk of warpage. Whilst this can be predicted for given conditions, little work has been done on the ivnerse problem; how to achieve minimum warpage. With product lifetimes as short as six months, reducing time spent in the analysis loop by improving the accuracy of the 'first guess' is critical. A major cause of warpage in short fiber FRP is believed to be anisotropy in thermal expansion coefficients due to local fiber orientation. We have carried out a combined analytical and experimental research program, examining the effects of a wide range of structural and manufacturing variables on warpage of injection molded FRP. These included wall thickness, gate position and mold temperature. The analysis used an in-house system to examine flow induced effects on material properits and mechanical warpage for given injection conditions. These results were compared with samples from a specially designed mold which allowed variation of overal dimensions, thickness, gate position and layout, temperature and molding speed. The aim is to establish a reference catalog for the causes of FRP warpage, identifying preventative design measures and reducing the time needed for design iteration.
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