Compression molding of Carbon/Polyether ether ketone composites: Squeeze flow behavior of unidirectional and randomly oriented strands

Abstract

Compression molding of randomly oriented strands (ROS) of thermoplastic composite is a new process that enabled the formation of complex shapes with high fiber volume fraction. During compression molding of ROS, several deformation mechanisms occurred. This article focused on the macroscopic squeeze flow mechanism. It ruled how the material will flow and fill intricate features of the mold. The squeeze flow behavior under large strain was investigated for Unidirectional (UD) and ROS. An experimental characterization was performed using an instrumented hot press. Also, to predict the associated thickness reduction, existing models using equivalent viscosity and lubrication assumptions were used. The results showed that large deformation of UD and ROS composite materials is mainly governed by two regimes: a Non‐Newtonian fluid behavior at low strain followed by a yielded phase at large strain. Quantitative indicators were defined to analyze these two phases. They showed that current models available in the literature fail to predict accurately the squeeze flow of thermoplastic composites under high strain (>50%). Also, strands size (especially strand length) has a large effect on the squeeze flow mechanism. This article provided basic process window guidelines in terms of minimum pressure and achievable strain for compression molding of ROS parts. POLYM. COMPOS., 38:1828–1837, 2017. © 2015 Society of Plastics Engineers

Insights into wide variations in carbon fibre/polyetheretherketone rheology data under automated tape placement processing conditions

“…The absence of a similar reduction for swept angular frequency tests may be related to the fact that these tests began at high value of ω (628 rad/s). The stabilisation of thickness reduction in the 313 kPa, 10 rad/s tests, after ∼4 min, can be explained by increased sample area, which reduces applied pressure below σy, as explained in Picher-Martel et al. 39 for similar behaviour of CF/PEEK randomly oriented strand material. Assuming CF/PEEK is incompressible, calculation of the associated increase in sample width leads to a more refined estimation of σy≅ 225 kPa.…”

Modelling of mechanical properties of randomly oriented strand thermoplastic composites

“…3 However, only a limited number of studies found in the literature discuss processability and mechanical properties of these materials. A new multi-disciplinary study [4][5][6][7][8] is being conducted to systematically evaluate, characterize and model the moulding process and mechanical properties of composites manufactured from carbon/polyetherether-ketone (PEEK) ROS.…”

The effect of moulding process parameters on interlaminar properties of CF/PEEK composite laminates

“…The selection of the process parameters was based on the result of the DSC test, the range of settings recommended by the prepreg supplier and other empirical parameters. 6,16 The laminates were heated from room temperature (approximately 25°C) to moulding temperatures (i.e. 360°C, 380°C and 440°C) at an average rate of 5°C min −1 and then the moulding pressures were adjusted to the set values (1, 2 and 3 MPa) within 2 min.…”