Powder binders used for the manufacturing of wind turbine rotor blades. Part 1. Characterization of resin‐binder interaction and preform properties

Abstract

Glass fiber reinforced plastics (GFRP) are the predominant materials used for wind turbine rotor blades. To manufacture blades in a vacuum-assisted resin infusion process (VARI), a binder is needed for fiber fixation and preform stability. Moreover, solubility and mechanical compatibility of the binder and the epoxy resin matrix are important parameters for processability and the mechanical properties of the composite. The present study therefore characterized and evaluated five chemically different binders with regard to their solubility in a rotor-blade-proven epoxy resin using microscopy, viscometry, and differential scanning calorimetry (DSC). The solubility tests enabled a binder-classification into critically soluble (KE-60, Epikote 05390), strongly soluble (Grilon MS), partially soluble (D 2433E), and nonsoluble (K-140) binder types. In subsequent mechanical and thermo-mechanical testing of resin-binder plates, the strongly soluble binder Grilon MS showed the best performance, followed by the nonsoluble binder K-140 and the partially soluble binder D 2433E. These results suggest that binders developing no interfaces within the resin should be preferred. Furthermore, interply adhesion for these three binders was investigated in a peeling test using fiber preforms. It was found that differences in peel strength might be controlled predominantly by different kinds of binder layer formations, but also to some extent by the different binder-fiber interaction (binder and fiber sizing correlation). Best performance was shown by D 2433E, followed by Grilon MS and K-140. All in all, the soluble binder Grilon MS exhibited the best results in mechanical testing of resin-binder plates and is therefore expected to also show the best mechanical performance in GFRP laminates. POLYM. COMPOS., 39:708-717, 2018.

Multifunctionality in Epoxy Resins

“…In the aviation and renewable energy sectors, epoxy resins are widely employed in fiber reinforced composites for the manufacture of structural parts of airplanes and wind turbines. [1][2][3][4][5][6] Epoxy resins are, to a large extent, utilized in more conventional applications such as engineering adhesives, coatings and paints as well as matrix for fabrication of electronic parts in consideration of the resins' excellent adhesion strength and processability. Since its discovery, the use of epoxy resins had become prevalent in composite research and development.…”

Influence of test fluids on the permeability of epoxy powder bindered non-crimp fabrics

“…Thereby, they focused on the influence of preforming conditions to adjust resin flow behavior. Schmidt et al [51] concentrated on the solubility of epoxy binders after infusing and curing of composite glass fiber plates. The influence on the mechanical behavior was characterized and concluded that interface formations due to partial solubility decrease interlaminar bonding.…”

“…When impregnating a Bindered Preform during an LCM process, binder dissolution is an expected phenomenon. The resulting solution deviates in terms of chemo-rheological properties and is still considered a major unknown factor [26,50,51]. The powder binder and the test liquid RIMR135 are both based on bisphenol-A and mainly differ in terms of their molecular length; hence, the binder is frozen at room temperature, while the resin is still in liquid form.…”

Characterisation of epoxy powders for processing thick-section composite structures

“…In relation to fibre-reinforced composite materials, polymer powders have also been investigated as binders which help to bond individual plies of fabric together and produce a preform for subsequent resin infusion [20,31,32]. For these studies, the main topics of interest were the solubility of the binder in the infusion resin and the effect of binders on both the processing parameters and the mechanical properties of composite materials.…”