Design of experiment study of compression moulding of SMC

Abstract

The effect of vacuum assistance, mould temperature and ram velocity on the void transport and flow behaviour for sheet moulding compound (SMC) have been investigated with a design of experiment approach of the compression moulding phase. The relative amount of voids has been quantified with a high voltage insulation test and the flow behaviour has been quantified with image analysis of samples moulded with coloured SMC. In conclusion, the setting of high vacuum, low ram velocity and low mould temperature creates a homogeneous flow and minimises the amount of voids.

Review of the Numerical Modeling of Compression Molding of Sheet Molding Compound

“…Different speeds and temperatures of the plates were used and the uneven flow was captured by video recordings of the flow front as shown in Figure 2 for a relatively low speed of 2 mm/s, an lower plate temperature of 135 • C and an upper plate temperature of 165 • C. It should be noted that the compound starts to flow near the lower plate as it had been subjected to heat for a longer time. This phenomenon was first observed by Barone [8] from partial moldings and later confirmed by molding using sheets of varying color by Olsson [9], where it is obvious that the outer layers end up at the flow front. Hence, the outer layers do not stay as outer layers which results in a complicated three-dimensional flow in the front of the SMC during pressing.…”

“…Similar experiments have since been conducted by Olsson et al [9]. An important conclusion drawn by Olsson et al [9] is that a higher mold closing speed resulted in a more homogeneous flow, while a lower closing speed resulted in more mixing between the layers of the charge. Important early numerical work was performed by Tucker et al [10] and Lee et al [11], who developed a model for the flow of the charge based on Hele-Shaw flow (see for instance [12]).…”

“…Noteworthy early work on SMC was done by Barone and Caulk; including heat conduction in SMC [4,5], models of the flow [6,7], and experimental visualization of the flow [8]. Similar experiments have since been conducted by Olsson et al [9]. An important conclusion drawn by Olsson et al [9] is that a higher mold closing speed resulted in a more homogeneous flow, while a lower closing speed resulted in more mixing between the layers of the charge.…”

Coupled visco-mechanical and diffusion void growth modelling during composite curing

“…Afterwards void gas mass variation due to diffusion only is determined thanks to Eq. (18). Another loop stop is introduced in order to verify if the new gas mass inside void is positive.…”

“…Several authors have reported the influence of the manufacturing process on void content: for Resin Transfert Molding [12][13][14][15][16][17] (RTM), Sheet Moulding Compound (SMC) [18][19][20], or autoclave [21][22][23] processes.…”