Viscoelastic Behavior of Glass-Fiber-Reinforced Silicone Composites Exposed to Cyclic Loading

Abstract

The aim of this work was to analyze the influence of fibers on the mechanical behavior of fiber-reinforced elastomers under cyclic loading. Thus, the focus was on the characterization of structure–property interactions, in particular the dynamic mechanical and viscoelastic behavior. Endless twill-woven glass fibers were chosen as the reinforcement, along with silicone as the matrix material. For the characterization of the flexible composites, a novel testing device was developed. Apart from the conventional dynamic mechanical analysis, in which the effect of the fiber orientation was also considered, modified step cycle tests were conducted under tensile loading. The material viscoelastic behavior was studied, evaluating both the stress relaxation response and the capability of the material to dissipate energy under straining. The effects of the displacement rate of the strain level, the amplitude of the strain applied in the loading–unloading step cycle test, and the number of the applied cycles were evaluated. The results revealed that an optimized fiber orientation leads to 30-fold enhanced stiffness, along with 10 times higher bearable stress. The findings demonstrated that tailored reinforced elastomers with endless fibers have a strong influence on the mechanical performance, affecting the structural properties significantly.

The Tension-Twist Coupling Mechanism in Flexible Composites: A Systematic Study Based on Tailored Laminate Structures Using a Novel Test Device

“…For better comparability and to minimize any negative influences concerning the manufacturing of the composite test specimens, a vacuum resin infusion (VARI) process was chosen [33,47]. The maximum feasible pressure during the impregnation and consolidation phase was set with about 0.1 MPa (atmosphere pressure) [2,55].…”

“…To ensure equal test and the same initial starting conditions during the experiments, a preload of 1 N was considered. For the evaluation of the load-coupling, further effects of viscoelasticity in flexible composites [33,49] are reduced by the constant set test speed. Due to that, a methodically validated test plan was developed, where the fiber orientation was set depending on the considered reinforcing structure.…”

“…The interaction of all individual elements in total generates and quantifies the intended load-coupling mechanism [34]. The stiffness towards twist as well as the in-plane shear strength of the flexible composite related to different directions is controlled by the force transmission of the anisotropic oriented fibers versus the viscoelastic behavior of the matrix [33,49]. Hence, the CLT represents a computational tool to describe overall deformations.…”

“…For the evaluation of the load-coupling, further effects of viscoelasticity in flexible composites [33,49] [58] were chosen for the composite lay-up with textile. In order to determine the maximum bearable twist angle and corresponding torque, both gauge lengths were considered in addition due to the high flexible behavior of these composites, since the form stability and the distinct textile-like character can be influenced significantly.…”

“…Therefore, profound knowledge and an adequate quantitative investigation regarding the performance and mechanical behavior of fiber reinforced elastomers combined with an external trigger is necessary. Since the ability of load transfer between the fibers and the matrix is crucial to analyze load-coupling mechanisms, a tailored fiber orientation as well as an optimized interfacial fiber-matrix bonding is indispensable to ensure an adequate adhesion with an intended load-coupling [23,33].…”