H.E.N. Bersee

Sustainable Vacuum-Infused Thermoplastic Composites for MW-Size Wind Turbine Blades—Preliminary Design and Manufacturing Issues

This paper addresses the feasibility of using innovative vacuum infused anionic polyamide-6 (PA-6) thermoplastic composites for MW-size wind turbine blades structures. To compare the performance of this fully recyclable material against commonly used less sustainable thermoset blade materials in a baseline structural MW-size blade configuration (box-spar/skins), four different blade composite material options were investigated: Glass/epoxy, carbon/epoxy, glass/PA-6, and carbon/PA-6. Blade characteristics such as weight, costs, and natural frequencies were compared for rotor blades ranging between 32.5 and 75 m in length, designed according to both stress and tip deflection criteria. Results showed that the PA-6 blades have similar weights and natural frequencies when compared to their epoxy counterpart. For glass fiber blades, a 10% reduction in material cost can be expected when using PA-6 rather than epoxy while carbon fiber blades costs were found to be similar. Considering manufacturing, processing temperatures of PA-6 are significantly higher than for epoxy systems; however, the associated cost increase is expected to be compensated for by a reduction in infusion and curing time.

Improving Erosion Resistance of Polymer Reinforced Composites

This article reports on solid particle erosion tests performed on glass fiber reinforced polyphenylene sulphide (PPS) for use on an all-composite ice-protection system for aircraft structures. The idea was introduced to use a metal mesh as a convenient way of toughening the surface layer thereby increasing erosion resistance. The erosion rates of the composites were evaluated at different impingement angles and with different erodent particle size. An aircraft-grade aluminium sheet was also used to provide a comparison for the composites. It was found that the erosion rate of the composites drastically reduced upon the introduction of an impregnated mesh onto the surface of the baseline glass/PPS laminate, to values similar to that of the aluminium sheet. In addition, the erosion rate was found to be dependent not only on the volume fraction of the matrix on the surface, but also the properties of the metal used for the mesh. The solution to use a metal mesh was shown to have multifunctional uses for composite based ice-protection system.

Consolidation of Thermoplastic Composites

The consolidation of CETEX® glass-PEI prepreg has been investigated at a micro level, which is the flattening of the prepreg layers and the inherent establishing of intimate contact between two adjacent layers. The consolidation phenomena were investigated by C-scanning of 2-layer laminates, in which the standard deviation was taken as an indication of the presence of voids within the laminate and of the homogeneity in laminate thickness. The decrease in standard deviation with pressure and temperature is for a large extent caused by straightening of the fabric. A further increase in pressure and temperature, therefore, does not result in a large decrease of standard deviation. The increase of the standard deviation above the critical temperature is most likely to be caused by matrix flow.

Structure and Mechanical Properties of Nanocomposites with Rod- and Plate-Shaped Nanoparticles

Particle-reinforced polymer composites or compounds have been used for decades to increase the stiffness and strength of polymers and to reduce thermal expansion. Polymer nanocomposites based on exfoliated layered silicates have been developed more recently [11, 23, 24] for improved mechanical properties, barrier properties, and reduced flammability. Polymer nanocomposites are polymers filled with finely dispersed particles that have at least one dimension in the nanometer range. Compared to composites containing larger dispersed particles, nanocomposites have the advantage of achieving the optimal properties at relatively low filler content, resulting in a lower density and better surface smoothness and transparency. This is due to the large aspect ratio and high stiffness of the particles, resulting from the exfoliation of the layered silicate particles. This can be especially favorable for moisture-sensitive polymers like polyamides, which loose a lot of their stiffness under moist conditions [10, 12]. The types of polymer nanocomposite that will be discussed here are the plateshaped layered silicate nanocomposites, and polymer nanocomposites containing rod-shaped high aspect ratio boehmite needles. In both cases we will consider polyamide-6 (PA6) as the matrix material. For the layered silicate polymer nanocomposites, the increase in stiffness depends strongly on the degree of exfoliation of the silicate layers, see Fig. 1.

Understanding piezoelectric composite–based actuators with nonlinear and 90° domain walls effects

Piezoelectric materials possess nonlinear behavior when actuated in a large electric field and show a large deflection when embedded inside a composite laminate such as a LIghtweight Piezoelectric Composite Actuator. Linear and nonlinear COMSOL multi-physics finite element models were developed and validated using the actuation response of three different layups of LIghtweight Piezoelectric Composite Actuators under a cantilever beam configuration. The linear model incorporated the linear piezoelectric coefficient given from the manufacturer, while the nonlinear model incorporated the nonlinear piezoelectric coefficient plus permanent strain offset in the piezoelectric material as a result of a high applied electric field. The linear model significantly underestimated the experimental values of the actuator response and it showed that taking nonlinearity and permanent strain offset into account is an essential practice when an actuator is operated in high electric fields and accurate prediction is required.

Structural Evaluation of Woven Composites

*† ‡ § In the design of new curved woven reinforced composites parts, it is necessary to have a good understanding of the behavior of the material through its manufacturing stage, especially if a deformation process is involved. On e of the most important fabric deformation mechanisms is intraply shear, and it is responsible for the formability of the desired part. This mechanism provides information about the manufacturability of the product and the final fiber orientation distributio n of the woven plies. This paper presents a method to investigate the real fiber orientation of woven reinforced composites and its effect in the mechanical performance of the part. The method is based on an Infrared Square Grid Analysis technique (IRSGA), which uses embedded Heat Emitting Layers (HELs) into the composite. The HELs have a regular pattern that deforms with the fabric and this deformation is used to reconstruct the real fiber o rientation per layer through-the-thickness of the composite. As an application case, hemispher es were diaphragm formed and the gathered information was compared against conventional manufacturing simulations like Drape. Then, a structural analysis of the shapes, b ased on the real fiber orientation, was performed in ABAQUS and the results were compared with tensile tests of the hemispheres.