Compression molding process analysis

Kim et al. (2009,2011) proposed a structural optimization considering processing parameters in the case of compression molding process. While the conventional structural design and analysis has been based on the assumption of isotropic properties in the final part, they integrated the structural analysis with the simulation of fiber orientation and separation into the optimization scheme. This structure-process coupled optimization is useful to further improve the product quality compared to the conventional separate structural design and process optimization procedures. 

Yoo, Y. E. (1997) A study on the analysis of compression molding process of composite material structures , PhD thesis. Department of Mechanical Engineering, Seoul National University, Seoul, Korea. 

Kang M K and Lee W I (1999) Analysis of resin transfer/compression molding process, Polym Compos 20 293-304,... 

Mobius T, Eilbracht S, Rudolph N, Osswald TA. Analysis of fiber orientation and fiber matrix separation in a compression molding process with an equi-biaxial flow front. J Plast Technol 2013 9(2) 101-28. 

The degree of bonding analysis has been verified for both compression molding and online consolidation of thermoplastic composites. In these studies, composite test specimens were consolidated under controlled processing conditions. The most common types of tests performed to measure the interply bond strength were the interlaminar (short beam) shear test [21,25] or the lap shear test [12,21,26]. 

Additional source of information for UHMWPE acetabular cups arises from the quantitative analysis of polarized Raman spectra. Figure 17.6 shows photographs and the outcome of such analysis for two acetabular cups, which were retrieved after substantially different in vivo lifetimes. The retrieved acetabular cups were both belonging to male patients and sterilized by y-rays, but produced by different processes. One acetabular component (manufactured in 2002 by Biomet Inc.) was prepared by isostatic compression molding and sterilized before implantation by a dose of 33 kGy of y-rays. It was retrieved due to infection after 2 years 5 months. This cup will be referred to as the short-term retrieval. The other retrieval (manufactured in 1995 by Zimmer Inc.) was prepared by Ram-extruded molding and sterilized in air by a dose of 25-37 kGy of y-rays. For this latter cup, the follow-up pe-... 

Savastano H Jr, Santos SF, Radonjic M, Soboyejo WO et al (2009) Fracture and fatigue of natural fibre-reinforced cementitious composites. Cement Concr Compos 31 232-243 79. Rahman WA, Tin SL, Razak RA et al (2008) Injection moulding simulation analysis of natural fibre composite window frame. J Mater Process Technol 197 22-30 Toledo FRD, Andrade SF, Fairbaim EMR, Melo FA et al (2009) Durability of compression molded sisal fibre reinforced mortar laminates. Construct Build Mater 23 2409-2420 Pillai MS (2006) Applications of natural coir fibre, proceedings, natural fibres vision 2020, New Delhi 8-9th December... 

The modeling of resin curing is one of the most important issues in the analysis of compression molding because the cure cycle constitutes a major portion of the total process cycle time and an incompletely cured part should be discarded. Material flovy in mold filling is also an important topic because knit line formation can be avoided by optimizing the precharge location. Moreover, mold filling analysis is indispensable to predict the fiber... 

Bhat, R, Merotte, J., Simacek, P. and Advani, S. G., Process analysis of compression resin transfer molding , Composites Part A Applied Science and Manufacturing, 40(4), 431 41, 2009. 

Figure 1.20 is adapted from Composites Part A, Vol. 40, 2009, Authors Bhat P, Merotte J, Simacek P and Advani S G, Title Process analysis of compression resin transfer molding, pp. 431-441, Copyright (2011), with permission from Elsevier Ltd. 

Although an old process, compression molding is not well described technically or analytically in the literature. Basically, what is needed is an analysis that combines rheology, heat transfer, chemical reaction (the curing process), and even mass transfer (outgassing) in a dynamic (time-dependent) system. The situation is also complicated by changing temperatures and pressures. 

The analysis of the effect of the molding process show that, at the surface of compression-molded "physical blends", the EP nodules are present at the outermost surface. On the contrary, FM measurements reveal that the surface EP nodules in injection-molded "reactor blends" are covered by a thin PP surface layer. 

The processes we have considered thus far - extrusion, wire coating, and injection and compression molding - are dominated by shear between confined surfaces. By contrast, in fiber and film formation the melt is stretched without confining surfaces. It is still possible to gain considerable insight from very elementary flow and heat transfer models, but we must first parallel Section 2.2 and develop some basic concepts of extensional flow. The remainder of the chapter is then devoted to an analysis of fiber formation by melt spinning. 

A sample which had been heated in bulk at 150°C for 3 h (see Fig. 5) was treated with boiling xylene for a long period of time. A gel fraction was actually found whose IR spectrum, obtained on a film compression-molded at 150°C, shows a high content of anhydride. In contrast, the soluble fraction, recovered from xylene, shows an IR spectrum similar to that of the starting material, i.e., before any heat treatment, with a very small anhydride band. We can conclude that the bulk cyclization reaction proceeds via an inter-chain anhydride formation, which is a bimolecular process. A similar treatment with boiling xylene was made on a sample of EPR-g-MES after solution cyclization. Also in this case the sample shows a small gel fraction which presents at IR analysis no differences from the soluble fraction, thus indicating that both mechanisms of inter- and intra-chain anhydride formation can occur in this case, even if the monomolecular mechanism is preferred, due to the dilution of the system. 

This need for thin films for quantitative analysis usually means that polymer film samples should be prepared in the 10-100-p,m range of thickness. Solvent casting or compression molding of the samples is usually required to prepare such thin films and, unfortunately, these sample preparation techniques transform the sample through melting or dissolution, with the loss of the thermal and process history of the polymer sample. The film samples must be randomly oriented, because nonrandom chain orientation influences the value of the measured absorbances. 

A comprehensive dimensional analysis was developed in order to study the influence of processing variables on the final quality of the part. Figure 3. shows a schematic of the compression molding of a ribbed part. An upper platen is lowered with a force F which exerts a pressure p on the charge. The charge is squeezed at a closing speed... 

A rectangular shaped composite extrudate was immediately further processed by compression molding using a positive mould and a hydraulic 25t press. Specimens of 150x100x4 mm were produced for the further analysis. 

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