Mesostructural simulation of discontinuous prepreg platelet based carbon fibre sheet moulding compounds informed by X-ray computed tomography

ABSTRACT

Discontinuous prepreg platelet based carbon fibre sheet moulding compound (CF-SMC) materials offer huge potential for lightweight applications in the automotive industry. The composition of these materials and the flow behaviour during compression moulding result in a complex stochastic mesostructure, which presents a challenge in the modelling of the mechanical behaviour. The objective of the current work is to use the information obtained from multiscale X-ray computed tomography (XCT) scans to generate full-scale three-dimensional finite element models of tensile coupon specimens for the prediction of the elastic modulus. The models incorporate the stochastic distribution and discontinuous nature of the prepreg platelets. Defects such as porosity, resin-rich areas and fibre waviness can be observed by means of XCT. Porosity is found to be below 0.0076 vol.% and thus negligible. An average volume fraction of 6.48 vol.% of interlaminar resin-rich areas is considered in the mesostructural simulations. The predicted values of the tensile modulus are validated by experimental tensile tests on basis of a large series of specimens. The statistical analysis of variance methodology is employed to reach conclusive validation. The inherent stochasticity of prepreg platelet based CF-SMC materials is well captured with the proposed mesostructural simulation approach and the variability in their mechanical properties is accurately predicted.

KEYWORDS:

• Discontinuous reinforcement
• carbon fibre
• sheet moulding compound
• X-ray computed tomography
• porosity
• resin-rich areas
• fibre waviness

Acknowledgements

This research was performed within the framework of the 0-WASTE project and the authors wish to thank the company partners Alpex Technologies GmbH (Mils, Austria), Engel GmbH (Schwertberg, Austria) and Hexcel Composites GmbH (Neumarkt, Austria) for their contributions. The project was funded by the Austrian Research Promotion Agency (FFG) and the Climate and Energy Fund of the Austrian Federal Government under the program “Energieforschungsprogramm 3. Ausschreibung” with the grant number KR16VE0F13251. XCT scans and evaluations were performed within the projects “Interpretation and evaluation of defects in complex CFK structures based on 3D-XCT data and structural simulation - (DigiCT-Sim project number: 862015)” and “ Systematic analysis of three-dimensional pore structures in fibre-reinforced plastics using 3D X-ray methods - (pore3D project number: 868735)”. Both XCT projects were funded by the federal government of Upper Austria and Austrian Research Promotion Agency (FFG). The authors wish to acknowledge Volker Reisecker of Transfercenter für Kunststofftechnik GmbH (Wels, Austria) for the UD laminate testing as well as Markus Winklberger and Martin Tiefenthaler from JKU Linz (Linz, Austria) and Tokelo Shai for their support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Klima- und Energiefonds [KR16VE0F13251]; Österreichische Forschungsförderungsgesellschaft [862015, 868735, KR16VE0F13251].