Compression moulding of SMC: In situ experiments, modelling and simulation

Abstract

Compression mouldings of commercial SMC were performed with an instrumented industrial press under various process conditions. Results underline the influence of process parameters such as the initial SMC temperature, the axial punch velocity and the geometry of the mould on local normal stress levels. They also show negligible fibre-bundle segregation in the principal plane of the moulded parts. Thereby, a one-phase plug flow shell model is proposed as a direct extension of the plug flow model proposed by M.R. Barone and D.A. Caulk [J Appl Mech 53(191):1986;361-70]. In the present approach, the SMC is considered as a power-law viscous medium exhibiting transverse isotropy. The shell model is implemented into a finite element code especially developed for the simulation of compression moulding of composite materials. Simulation and experimental results are compared, emphasizing the role of the SMC rheology on the overall recorded stress levels. Despite the simplicity of the model, rather good comparisons are obtained.

Design of experiment study of compression moulding of SMC

“…This was carried out in order to minimise possible pregelation effects and obtain equal flow conditions since the placement of the charge can affect the flow. 9,18 The uniformed coloured charges were stacked in a similar fashion. For vacuum assisted mouldings, a switch was installed to turn on the vacuum so that it had reached full capacity just before the upper mould surface touched the charge.…”

Flow characteristics of carbon fibre moulding compounds

“…These materials are reported to be notch insensitive and exhibit a low sensitivity to defects [9,10], as stress concentrations present at the bundle ends are often larger than geometrical stress concentrations resulting from the notch [11]. A high viscosity epoxy matrix is required to avoid fibre/matrix separation during moulding [12], which can be a particular problem for ribbed parts [13]. However, a high viscosity can limit macroscopic charge flow due to higher friction levels at the mould-composite interface [14], increasing the required moulding pressures.…”

Towards the simulation of mould filling with polymer composites reinforced with mineral fillers and short fibres

“…Based on an experimental analysis of flow-induced microstructures, such a model could be in future replaced by more sophisticated rheological models dedicated to these types of fibre suspensions [4,24,32,33,38,51,52,56,58]. -This phenomenological model was implemented into a FE code dedicated to the compression of compounds [19]. Compared to heterogeneous compression moulding experiments, rather good trends were obtained from simulation.…”

“…Mechanical and numerical aspects related to this code are extensively described in [19]. Briefly, the flow of the compound during the compression is supposed to be equivalent to an incompressible and one-phase plug flow [1,7], so that the velocity of the suspension along the thickness of the BMC charge is uniform.…”