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Experimental and numerical evaluation of force transduced by interactive fiber rubber composite structures
(Wydawnictwo Politechniki Łódzkiej, 2022) Annadata, Achyuth Ram; Lohse, Felix; Gereke, Thomas; Cherif, Chokri
Shape memory alloys (SMA) represent a category of smart materials and are widely used as actuators for many applications ranging from aircraft-automotive as vibration dampers to medical stents mainly because of their high energy density and their ability to generate high actuating forces. One of the potential applications of use of SMA is in robotics. SMA integrated composites provide a light-weight solution for conventional grippers but have their fair share of disadvantages such as minimal movements due to constrained degrees of freedom, less gripping force towards irregular structures, durability reduction etc. In this work, SMAs are integrated into glass fiber reinforced fabrics with tailored properties with the help of flat-knitting technology creating an Interactive Fiber Rubber Composite by infiltrating the fabrics with liquid silicone. To determine the range of force induced, a simulation model is developed to capture the transduced force of the composite when SMA is activated and the model is calibrated with respect to a test set-up specifically tailored to determine the force exhibited. The results obtained are utilized in a future study in determining the twisting behaviour of the composite, which would further help in a better grip for small and irregular shaped objects.
Flowable 2D textile structures for the production of thermoplastic 3D FRP parts with continuous fiber reinforcement between shell and rib
(Wydawnictwo Politechniki Łódzkiej, 2022) Hellmann, Sven; Overberg, Matthias; Pham, Minh Quang; Häntzsche, Eric; Gereke, Thomas; Cherif, Chokri
Nature shows evolutionary fiber-reinforced solutions, e.g. a peanut shell that enables a high stiffness with extremely low component masses by using complex shell and rib arrangements. Lightweight shellshaped components made of fiber-reinforced plastic (FRP) are often stiffened with ribs. In this work, a new method is proposed to produce directional fiber reinforcement in the transition area from shell to rib and within the rib by a direct thermal pressing process. Numerical calculations are initially used to demonstrate the potential of this type of structure. The source material is a flowable 2D textile hybrid structure consisting of continuous glass fibers and discontinuous recycled carbon fibers. The arrangement of the fibers leads to a defined flow movement of matrix and fibers and thus the production of a 3D FRP component with continuous fibers in the shell area and staple fiber-based reinforcement in the rib area and in between.
Micromechanical models for fabrics and composites made of hybrid yarns from recycled carbon fibers
(Wydawnictwo Politechniki Łódzkiej, 2022) Lang, Tobias; Hasan, Mir Mohammad Badrul; Huynh, Thy Anh My; Gereke, Thomas; Abdkader, Anwar; Cherif, Chokri
Although the great potential of carbon fibers for use in lightweight applications has been demonstrated in the past, their cost and environmental impact remain a barrier to their widespread use [1]. Recycling of carbon fibers from end-of-life components and combining them with thermoplastic fibers to form hybrid yarns addresses both issues. Due to the stochastic nature of hybrid yarns in terms of recycled carbon fiber (rCF) length and orientation [2], their influence on drapability and performance of rCF composites needs to be investigated. In this paper, a micromechanical model for analysing the dry and composite properties of yarns made from rCF is presented. By using a self-developed framework for generating representative volume elements (RVE) based on parameters such as fiber length, orientation, waviness, and fiber volume content, a variety of idealised random yarn geometries is created. A subsequent simulation step of the compaction of the RVE assures a more realistic RVE geometry. The models are validated by carrying out virtual tests and comparing the results with real tensile tests. The modelling approach can be used for further analyses.