Development and characterization of composites consisting of woven fabrics with integrated prismatic shaped cavities

Composites are extensively used in automotive, construction, airplanes, wind turbines etc. because of their good mechanical properties such as high specific stiffness, high specific strength and resistance against fatigue. The main issues with composites are delamination and the manual labour in the production process. If hollow structures like stiffeners need to be manufactured, these problems become even more apparent. As a result, there is a lot of interest in woven fabrics with integrated prismatic shaped cavities for composites as they reduce the manual labour, have a higher resistance against delamination and can lead to special properties and applications. In this work several of these woven fabrics with integrated prismatic shaped cavities are designed and produced in high-tenacity polyester yarns. Then, the possibility to use these fabrics in composites is explored: reproducibility of the production process is assessed and static testing is performed. A reproducible production process is developed and static testing shows promising results

Quasi-static behavior of three-dimensional integrated core sandwich composites under compression loading

In the current study, the effect of the thickness and the foam density in three-dimensional integrated woven sandwich composites on quasi-static properties was investigated. For this purpose, produced samples were subjected to uniaxial flatwise compression tests and their compression strength and moduli were determined. Obtained results were optimized by taking core thickness, foam density and panel weights into consideration. Damages that occurred on the tested samples were reported. When compared to conventional foam core sandwich composites, it was found that three-dimensional integrated sandwich composites have better compression properties and due to the fact that the pile yarns in the core and the foam support each other

Research in textile composites at KU, Leuven

An overview is presented of the research on textile composites at Katholieke Universiteit Leuven. Three dimensionally woven sandwich fabric preforms are investigated for delamination resistant sandwich structures, velvet woven 2.5 dimensional fabrics for delamination resistant laminates, and knitted fabrics with good drapability for laminates of complex shape

A material interpolation technique using the simplex polytope

The Discrete Material Optimization (DMO) and the Shape Function with Penalization (SFP) constitute the state-of-the-art material interpolation techniques for identifying from a list of pre-defined candidate materials the most suitable one(s) for the structural domain. The candidate materials are represented on this list through their mechanical properties, and are interpolated within the domain of interest (DOI), whether that is the finite element (FE) domain or groups of FEs, so-called patches. Depending on the technique preferred to interpolate the mechanical properties within the DOI, a different type of weights is selected. Goal of the discrete material optimization problem (MOP) is to solve for these weights and determine for each FE/patch a unique material from the list. The current work extends the concept of the SFP technique by employing as weights the shape functions of the hyper-tetrahedral FE, the dimension of which is dynamically adapted depending on the number of candidate materials considered for the structural domain. This generalized hyper-tetrahedral FE constitutes what is defined as a simplex, and similar to the SFP technique each of its nodes is tied to a specific candidate material. In the context of discrete optimization and utilizing the shape functions of an abstract high-dimensional FE as weights for the candidate materials, the proposed interpolation technique secures the continuity between the number of candidate materials that can be considered for the structure, a feature lacking in the SFP technique. Additionally, given that the number of nodes forming the simplex FE is always one unit greater than the dimension of the space it is defined within, the dimension of the resulting MOP drops by one per DOI. The developed material interpolation technique is combined with the topology optimization problem (TOP) to formulate the concurrent material and topology optimization problem for compliance minimization of the structure. Finally, the latter is examined on the academic case study of the 3D Messerchmitt-B¨olkow-Blohm (MBB) beam for the case of the concurrent topology and discrete fiber orientation optimization problem

Novel thermoplastic composites strengthened with carbon fiber-reinforced epoxy composite waste rods: development and characterization

The increasing use of carbon fiber and epoxy resin composite materials yields an increase in the amount of waste. Therefore, we present a solution consisting of composites manufactured by hot pressing, employing polyamides (either PA11 or PA12) and a mechanically recycled carbon fiber-reinforced polymer (CFRP) as reinforcement. The main objectives are to study the manufacturing of those composites, to evaluate the fiber distribution, and to perform a mechanical, dynamical, and thermomechanical characterizations. The X-ray micro-computed tomography (muCT) shows that the fibers are well-distributed, maintaining a homogeneous fiber volume fraction across the material. The variability in the results is typical of discontinuous fiber composites in which the fibers, although oriented, are not as homogeneously distributed as in a continuous fiber composite. The mechanical and dynamic properties barely differ between the two sets of composites. A dynamic-mechanical analysis revealed that the glass transition temperature (Tg) increases slightly for both composites, compared to the polymers. These results illustrate the viability of the recycling and reuse route for preventing the deterioration of carbon fibers and promoting the subsequent reduction in the environmental impact by employing a thermoplastic matrix.This research was carried out with financial support from the University Carlos III Madrid and Álvaro Alonso Barba Institute of Chemistry and Materials Technology (IAAB)