In-mould flow during manufacturing of Sheet Moulding Compounds (SMCs) heavily affects the material microstructure and its mechanical properties. This influence is studied here for carbon SMCs on panels compression moulded with limited charge coverage. The high in-mould flow caused severe in-plane tow distortions, while their planarity was preserved. Flow induced fibre orientation plays a paramount role in the material failure, whereas local manufacturing defects had no discernible influence. The properties difference between specimens with preferential orientation of 0° and 90° was 150% for tensile stiffness, 260% for tensile strength, 120% for compressive stiffness and 32% for compressive strength. The compressive strength and failure strain for 45° and 90° specimens were higher than those for tension, and comparable for 0° specimens. Compressive and tensile moduli were similar for specimens with the same orientation. A clear link between SMCs manufacturing and mechanical performance is highlighted, together with its implications on structural design.
The fibre orientation distribution controls the mechanical properties of random fibre composites. Generally accepted methods for its characterisation involve identification of fibres or their ellipsoidal cross sections as individual objects, requiring high image resolution and high computational resources. This paper investigates whether structure tensor analysis can be an alternative and whether it can work with lower resolution images. Micro-computed X-ray tomography images of random glass fibre/polypropylene injection moulded composites were processed using ellipsometry on 2D slices, 3D fibre identification (Avizo software) and analysis of the structure tensor (VoxTex software). The images had resolutions of 1.4, 3.2, 8 and 16 µm per pixel, compared to an average glass fibre diameter of 17 µm. All the methods yielded similar results for high-resolution images (1.4 and 3.2 µm). The high-fidelity, direct identification of fibres failed for low-resolution images, but the structure tensor analysis still yielded results close to the high-resolution scans.
Carbon Fibre Sheet Moulding Compounds (CF-SMCs) are lightweight materials very suitable for automotive parts. So far, their use was limited to thin components. This work presents a feasibility study on the compression moulding of a thick-walled SMC component, with a compound of randomly oriented chopped carbon fibre tapes.Bending tests were used to evaluate the effects of the manufacturing conditions on the mechanical performance. The choice of the charge pattern configuration played the paramount role in the final part performance, especially via the creation of weld surfaces, leading to a maximum strength difference of over 400%. The moulding temperature, pressure and cooling method showed no statistically significant influence on both strength and stiffness of the part. The results of this work can be used as a starting point in the design of manufacturing processes for thick SMC components.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.