Design and manufacturing optimization of epoxy-based adhesive specimens for multiaxial tests. (15th December 2021)

• Record Type: Journal Article
• Authors: Wentingmann, Michael; Manousides, Nikolas; Antoniou, Alexandros; Balzani, Claudio
• Is Part Of: Materials & design. Volume 212(2021)
• Publication Date: 2021-12-15
• Subjects: Structural adhesives -- Multiaxial testing -- Porosity analysis -- Wind turbine rotor blades; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2021.110213
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: Finite Element based specimen geometry optimization resulted in smooth stress distributions and reduced measurement uncertainties of material properties. Combining vacuum speed mixing and 3D printed mold inserts led to low porosity specimens, which was verified with μ CT scanning. Machine-mixed specimens showed ductile behavior while hand-mixed specimens were rather brittle. Applied optimizations significantly reduced scatter in all measured material properties and increased strength and strain to failure. Abstract: Specimen design and manufacturing quality are decisive factors in the experimental determination of material properties, because they can only be reliably determined if all undesired influences have been minimized or are precisely known. The manufacture of specimens from highly viscous, two-component and fiber-reinforced structural adhesives presents a challenge from this point of view. Therefore, a design and manufacturing optimization procedure for fiber-reinforced structural adhesives and multiaxial testing was developed. It incorporated a finite element parametric study to minimize stress concentrations in the specimen geometry. Vacuum speed mixing was combined with 3D printed mold inserts to enable the manufacture of homogeneous specimens with negligible porosity. The method was demonstrated by means of a structural adhesive used to manufacture wind turbine rotor blades, while the manufacturing quality was verified with high-resolution X-ray microscopy ( μ CT scanning), enabling detailed detection of pores and geometrical imperfections. The results of uniaxial and biaxial static tests show maximized strength and stiffness properties, while the scatter was minimized in comparison to that stated in international literature. A comparison of the mechanical properties and associated manufacturing techniques is given. The comparison includes a porosity analysis of a specimen from an industrial dosing machine used for rotor blade manufacture.