Mechanical properties of carbon black/poly (ε-caprolactone)-based tissue scaffolds

Carbon black (CB) spherical particles were added to poly(ε-caprolactone) (PCL) polymer to produce strong synthetic tissue scaffolds for biomedical applications. The objective of this paper is to study the mechanical behavior of CB/PCL-based nanocomposites using experimental tests, multi-scale numerical approaches, and analytical models. The mechanical properties of CB/PCL scaffolds were characterized using thermal mechanical analysis and results show a significant increase of the elastic modulus with increasing nanofiller concentration up to 7 wt%. Conversely, finite element computations were performed using a simulated microstructure, and a numerical model based on the representative volume element (RVE) was generated. Thereafter, Young's moduli were computed using a 3D numerical homogenization technique. The approach takes into consideration CB particles’ diameters, as well as their random distribution and agglomerations into PCL. Experimental results were compared with data obtained using numerical approaches and analytical models. Consistency in the results was observed, especially in the case of lower CB fractions

Periodic homogenization and damage evolution in RVE composite material with inclusion

This work deals with the coupling between a periodic homogenization procedure and a damage process occurring in a RVE of inclusion composite materials. We mainly seek on the one hand to determine the effective mechanical properties according to the different volume fractions and forms of inclusions for a composite with inclusions at the macroscopic level, and on the other hand to explore the rupture mechanisms that can take place at the microstructure level. To do this; the first step is to propose a periodic homogenization procedure to predict the homogenized mechanical characteristics of an inclusion composite. This homogenization procedure is applied to the theory based on finite element analysis by the Abaqus calculation code. The inclusions are modeled by a random object modeler, and the periodic homogenization method is implemented by python scripts. It is then a matter of introducing the damage into the problem of homogenization, that is to say; once the homogenized characteristics are assessed in the absence of the damage initiated by microcracks and micro cavitations, it is then possible to introduce damage models by a subroutine (Umat) in the Abaqus calculation code. The verifications carried out focused on RVE of composite materials with inclusions

Modeling and characterization of thermo-oxidative behavior of bismaleimide composites

High-temperature polymer matrix composites (HTPMCs) are susceptible to thermo-oxidation, which accelerates the composites\u27 degradation and reduces the service life. Mechanical properties of HTPMCs deteriorate due to coupled thermo-oxidation and cross-linking mechanisms. Bismaleimides (BMIs) are commonly used high-temperature resins for aerospace applications. This work presents the viability of using experimental weight loss to model the spatial distribution of oxidation when the oxidized polymer matrix is not discernible. Three tasks are introduced: (1) Anisotropic oxidation prediction using optimized weight loss behavior of bismaleimide composites, (2) A multi-scale modeling of thermo-oxidative effects on the flexural behavior of cross-ply bismaleimide composites, and (3) Thermo-oxidative induced damage in polymer composites: microstructure image-based multi-scale modeling and experimental validation. Task 1 deals with simulating the weight loss and oxidized layer evolution in unidirectional BMI composites exposed to a service temperature in the operating range, 176.67 °C (350 °F) and 200 °C (392 °F). In task 2, microstructural changes of the cross-ply BMIs composites were characterized using microscopy. A multiscale approach for modeling flexural modulus degradation was proposed. In Task 3, a multi-scale modeling approach is presented to simulate and validate thermo-oxidation shrinkage and cracking damage. The micro-scale shrinkage deformation and cracking damage are simulated and validated using 2D and 3D simulations. The meso-scale geometrical domain and the micro-scale geometry and mesh are developed using the object oriented finite element (OOF). The macro-scale shrinkage and weight loss are measured using unidirectional coupons and used to build the macro-shrinkage model --Abstract, page iv

Analysis of the Parameters Affecting the Stiffness of Short Sisal Fiber Biocomposites Manufactured by Compression-Molding

The use of natural fiber-based composites is on the rise in many industries. Thanks to their eco-sustainability, these innovative materials make it possible to adapt the production of components, systems and machines to the increasingly stringent regulations on environmental protection, while at the same time reducing production costs, weight and operating costs. Optimizing the mechanical properties of biocomposites is an important goal of applied research. In this work, using a new numerical approach, the effects of the volume fraction, average length, distribution of orientation and curvature of fibers on the Young’s modulus of a biocomposite reinforced with short natural fibers were studied. Although the proposed approach could be applied to any biocomposite, sisal fibers and an eco-sustainable thermosetting matrix (green epoxy) were considered in both simulations and the associated experimental assessment. The results of the simulations showed the following effects of the aforementioned parameters on Young’s modulus: a linear growth with the volume fraction, nonlinear growth as the length of the fibers increased, a reduction as the average curvature increased and an increase in stiffness in the x-y plane as the distribution of fiber orientation in the z direction decreased

Changes of the Structural and Mechanical Properties on Nanocomposites based on Halloysite Nanotubes with the Optimization of Dispersion by Ultrasonic Waves

Nanoparticle refers to a particle within the scope of a hundred nanometers and nanoparticles have a wide specific surface area. By controlling their size or using nanoparticles of various types, the properties of material can be improved with only a small amount of particulate filler. Halloysite is a naturally occurring aluminosilicate in the form of nanotubes, also known as halloysite nanotubes (HNTs). The HNTs are odorless, white particles with the chemical formula H4Al2O9Si2·2H2O. Halloysite nanotubes are readily obtainable and are much cheaper than other tubular nanoparticles such as carbon nanotubes. There HNTs have been considered as a functionally effective material capable of mechanically strengthening resins by restrictive matrix dislocation movement. Especially, there are studies showing that adding HNTs to plastics improves tensile strength, impact resistance, fire retardancy and gives the added advantage of improved cycling time in production by injection molding. In this study, samples consisted of nanocomposites manufactured by adding HNTs to unsaturated polyester resin (UP). Herein, the contents of HNTs were 0.5, 1 and 3 wt.%. The purpose was to analyze the mechanical properties of nanocomposites on a function of HNTs content and through this, to find the optimal conditions for developing UP matrix HNT reinforced nanocomposites. The HNTs used in this study were treated by heat. Heat-treated HNTs were divided into 4 groups: untreated HNT (UTHNT), 300 (300HTHNT), 500 (500HTHNT), 700 (700HTHNT) and 1000 (1000HTHNT) heat-treated HNT, according to treating temperatures. To achieve a uniform distribution of nanoparticles in the matrix, the factors optimized for dispersion were considered and a suitable process environment for materials to be used was adopted by dividing these factors into constants and variables. The ultrasonic homogenization is used in the production of nano-size materials, dispersions and emulsions, because of the potential in deagglomeration. Ultrasonic homogenization is an easy way to separate particle aggregate, and obtain homogeneous phase. Ultrasonication was carried out by varying some parameters. The operating time and the volume of the sample were maintained at fixed values, namely 300 s and 18 ml, respectively. The output power was divided into two cases, at 45W and 60W. Finally we established the optimal dispersion condition of HNTs using ultrasonication, and the reinforcement effect of HNTs was studied by X-ray diffraction and evaluation of mechanical properties of nanocomposites such as impact strength and tensile strength. Also, the structural changes of HNT by heat treatment at various temperatures were evaluated.1. Introduction 1.1 Nanocomposites 1.2 Halloysite Nanotube (HNT) as an Eco-friendly Material 1.3 Effective Dispersion of Nanofillers in Nanocomposites 2. Experimental Work 2.1 Materials and Methods 2.1.1 Preparation of UP/HNT Nanocomposites 2.1.2 Heat Treatment of HNTs at Different Temperatures 2.1.3 HNT Dispersion by Ultrasonic Homogenization 2.2 Characterization of UP/HNT Nanocomposites 2.2.1 X-ray Diffraction 2.2.2 Transmission Electron Microscopy (TEM) 2.2.3 Impact Test 2.2.4 Tensile Test 3. Results and Discussion 3.1 Observation of Structural Changes by X-ray Diffraction and TEM Imaging 3.2 Changes in Mechanical Properties 3.2.1 Impact Properties 3.2.2 Tensile Properties 3.2.3 Considerations on the Effects of Nanoparticle Dispersion on Mechanical Strength 4. Conclusion Reference Acknowledgmen