Shear and compression behaviour of sheet moulding compounds

Abstract

International audienceAt the present time, the rheology of sheet moulding compounds (SMC) during forming is not well known. In order to provide better experimental data, an experimental program was carried out as a result of the development of a new rheometer especially dedicated to this kind of material. Homogeneous simple compression and simple shear tests are presented. They allow the evaluation of the influence of the main parameters on the SMC behaviour: strain rate, temperature and fibre fraction. It is shown that the SMC can be considered as a strongly anisotropic non-linear viscous medium

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

“…This was not observed for SMC [20,34], but was clearly established for BMC [41]. In such a case, (i) by performing two tests with two different initial radii R 0 and (ii) by assuming the lubrication layers act as Newtonian boundary layers (with a hydrodynamic friction coefficient λ), it is then possible [41] to estimate the Cauchy stress tensor:…”

“…The first apparatus is the simple compression rheometer initially developed for the rheology of sheet moulding compounds [20,34,41]. Tests consist in compressing lubricated cylindrical samples (initial radii R 0 = 35 mm and 55 mm, initial height h 0 = 20 mm) at constant axial average strain rates D 33 =ḣ/ h (compression direction given by the unit vector e 3 ) between two horizontal platens parallel to the (e 1 , e 2 ) plane, (e 1 , e 2 , e 3 ) being the usual orthogonal reference frame.…”

“…when the suspending fluid is also a concentrated granular suspension [15]. For example, some studies were carried out to understand the rheology of Sheet Moulding Compounds (SMC), a fibre-bundle reinforced thermoset polymer composites with a matrix, which is similar to that of the BMC [1,14,20,30,[34][35][36]50].…”

“…More recently, Orgéas et al [41] performed an extensive experimental study of the rheology of a BMC. BMC samples were deformed using lubricated simple compression experiments, similar to those initially proposed for SMC or other planar fibre or fibre-bundle reinforced polymer composites [20,21,34]. Provided both a good lubrication and samples with large dimensions (with respect to the fibre length), these tests allow the analysis of the rheology of compounds with reduced discrepancy and without any a priori constitutive assumptions.…”

Behavior of a net of fibers linked by viscous interactions: theory and mechanical properties

“…However, those theories cannot account properly for the e ects of local interactions between ÿbers, that may be due to dry friction e ects or localized viscous forces (Toll and Manson, 1994), and their validity is therefore limited to quite dilute suspensions, which is not the case of many industrial processes such as compression of Sheet Molding Compounds (SMC) or Glass Mat Transfer (GMT), or injection of Bulk Molding Compounds (BMC) (Dumont et al, 2003;Le Corre et al, 2002). Moreover, the complete solving of theoretical problems often requires further statistical assumptions that make the e ective calculation of the behavior possible only in the case of perfectly unidirectional or perfectly isotropic orientations of ÿbers (Fredrickson and Shaqfeh, 1989;Shaqfeh and Fredrickson, 1990).…”