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Manufacturing of 3C (Computer, Communication, and Consumer Electronics) products toward weight reduction, thin-wall, and minified-size is an inescapable trend for the future 3C industries. However, the induced damage information from drop impact, including exterior housing fracture, liquid crystal display (LCD) cracking, solder-joint breaking, or interior component failure, is still derived experimentally and involves very complicated parametric analyses, such as a dynamic impact process, drop orientation, contact behavior, and large deformation during the impact instance. In the present study, numerical simulations for the drop test and bending strength were applied to a thin-wall computer dictionary (Model CD-66) housing to understand the key factors that affect the part drop test performance. The appropriate modeling that would affect simulation accuracy as well as the associated nodal degree of freedom and computer time were also investigated. A housing of CD-66 was redesigned to be 1 mm thick and structurally verified with two different plastics: polycarbonate (PC) and acrylonitrile butadiene styrene (ABS). The simplification of the PC board and LCD backlight circuit in finite element modeling (FEM) only causes about a 10% difference, while saving many modeling costs. The numerical simulations also indicate that both its bending strength and drop-impact strength were decreased only about 5%, whereas the product quality still met its strength requirement if only the top housing plate thickness was reduced while the remaining sidewall thickness was kept unchanged. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3064–3071, 2002

Simulations of the injection-compression molding (ICM) process based on a Leonov viscoelastic fluid model has been employed to study the effects of processing conditions on the birefringence development and distribution in injection-compression molded parts. A numerical algorithm combined with a modified control-volume/finite-element method is developed to predict the melt front advancement and the distributions of pressure, temperature, and flow velocity dynamically during the injection melt-filling, compression melt-filling, and postfilling stages of the entire process. Part birefringence was then calculated from residual stresses following the thermal-mechanical history of the entire molding process. Simulations of a disk part under different process conditions including compression speed, switch time from injection to compression, compression stroke, packing pressure, and postfilling time were performed to understand their effects on birefringence variation. The simulated results were also compared with those required by conventional injection molding (CIM). It has been found that an ICM part shows a significant reduction of part birefringence near the gate area as compared with CIM parts. However, ICM parts exhibit higher birefringence values near the rim of the disk. The minimum birefringence occurs around the location where injection is switched over to compression. Although longer postfilling time and higher packing pressure result in higher birefringence values, their effects are not very significant. On the other hand, higher compression speed, larger compression stroke, and shorter switch time exhibit greater effects on the increase of part birefringence. Flow-induced residual stress is the major origin of birefringence formation in the present case. The simulated birefringence for both ICM and CIM parts show good coincidence with those obtained from measurements by using a digital photoelasticity technique. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 177–187, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10024

A numerical algorithm is developed to simulate the injection–compression molding (ICM) process. A Hele–Shaw fluid-flow model combined with a modified control-volume/finite-element method is implemented to predict the melt-front advancement and the distributions of pressure, temperature, and flow velocity dynamically during the injection melt filling, compression melt filling, and postfilling stages of the entire process. Part volumetric shrinkage was then investigated by tracing the thermal–mechanical history of the polymer melt via a path display in the pressure–volume–temperature (PVT) diagram during the entire process. Influence of the process parameters including compression speed, switch time from injection to compression, compression stroke, and part thickness on part shrinkage were understood through simulations of a disk part. The simulated results were also compared with those required by conventional injection molding (CIM). It was found that ICM not only shows a significant effect on reducing part shrinkage but also provides much more uniform shrinkage within the whole part as compared with CIM. Although using a higher switch time, lower compression speed, and higher compression stroke may result in a lower molding pressure, however, they do not show an apparent effect on part shrinkage once the compression pressure is the same in the compression-holding stage. However, using a lower switch time, higher compression speed, and lower compression stroke under the same compression pressure in the postfilling stage will result in an improvement in shrinkage reduction due to the melt-temperature effect introduced in the end of the filling stage. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1640–1654, 2000