Band 31, Heft 8-9

As it offers a wide range of benefits, assembly injection molding of plastics represents an innovative technology. In a material, cost efficient and integrative process, the most diverse products for mechatronics applications can be manufactured. The technique can generate multi-material systems combining different parts with special functionality, e.g., plastics casings and circuit boards, in a fully automated process. This automated integration of part structure and functionality makes these products superior to others. However, it implies a great challenge in terms of technology for part development and production. Of vital importance for a media tight and durable connection between individual materials/parts of the assembly, are factors such as the components’ compatibility and chemical-physical adhesion. Thermal stress in hybrid assemblies due to different thermal expansion coefficients is often the reason for part failure. An approach to meeting these challenges is the investigation of the process-integrated application of functional interlayers, in order to improve the formation of adhesion along with the optimization of the stress distribution. The following article will present findings obtained on the bond strength generated by different types of interlayers (hot-melt and pressure-sensitive adhesives) between circuit cards and different types of casing plastics. A fundamental understanding of underlying effects and the tools for predicting process dependent effects is required for the optimization of the systems’ functionality. For this purpose, the interactions between material, system design and process conditions are considered in relation to bond strength.

This study develops an effective approach to measure real-time mold plate flexion, namely a displacement of a cavity plate. A mold-filling program was used to simulate the injection molding process. The predicted cavity pressure was then applied as an input for the subsequent mold deflection analysis. In this work, an amorphous polymethyl methacrylate (PMMA) was injection-molded into a 6-inch light guide plate (LGP) cavity, with cavity plate thicknesses of 35 mm, 55 mm, and 100 mm. To validate the predicted mold deflection, an inductive displacement sensor was placed underneath the cavity plate, and experiments were conducted using process variables identical to those of the simulation. Comparison between the simulated results and the experimental data shows that when the cavity plate thickness is reduced, the mold deformation increases significantly, and results in an increase in part thickness. In addition, an increase in packing pressure caused a rise in mold deformation. This study demonstrates that the proposed approach is able to measure the mold deflection.

This paper describes an opportunity to compute the surface waviness of compression moulded sheet moulding compound (SMC) parts by simulating residual stresses. First, different types of surface defects occurring on SMC parts are discussed. A method for calculating the surface waviness of the compression moulded part is presented, which combines the simulation of the production process and the structural computation. Modelling of the curing reaction and the development of mechanical properties are discussed and implemented. The potential of the computation method is shown for an automotive fender made of SMC. The results state that the curing reaction of SMC can be well described using the approach of Ng and Manas-Zloczower. The position of the measured waviness on the examined fender is in good agreement with the calculated stress distribution.

A superabsorbent composite was synthesized via polymerization in a complete aqueous environment. A polymeric composites was fabricated effectively by varying the concentration of natural gum and crosslinker. Reinforcing of the polymer chains with bentonite sheets was confirmed by Fourier transform infrared (FTIR) spectra. X-ray diffraction (XRD) revealed that bentonite was exfoliated and dispersed in the polymeric matrix. Scanning electron microscopy (SEM) and thermal analysis (TGA/DSC/DTA) were used to study the morphology and thermal stability of the composites, respectively. The effects of natural gum and crosslinker were investigated. Results showed that introducing organic-inorganic composites improved the swelling capability and water retention ability of the superabsorbent.