Numerical models of fabric behaviour using hybrids discrete elastic and hypoelastic modelling

This paper present two hybrids discrete continuous models for the simulation of woven fabric reinforcement preforming via explicit finite element analysis. There approaches are based 1D elements on a beam or nonlinear connectors, and 2D element account for shearing resistance of the fabric. The first developed model is built using linear and nonlinear connectors to take into account the tensile stiffness of the fabric, and a shell elastic isotropic element. The second model is based on nonlinear elements and the hypo-elastic behaviour. The determination of the material parameters is straightforward from tensile and bias extension tests. These proposed approaches have been implemented in the ABAQUS explicit finite element programs via subroutine VUMAT. There models allows the simulation of industrial part forming in a reasonable computational time. Simulations of the hemispherical shape of woven fabric 48600 C1300 have been implemented to highlight the performance of these model

Sensitivity analysis of composite forming process parameters using numerical hybrid discrete approach

The aim of this study is to investigate the influence of some important parameters in composite forming using a hybrid discrete hypoelastic computational model developed for simulation of the deformation behaviour of fibres materials. This model is based on elementary cell of shell or membrane type reinforced by nonlinear connectors. Moreover, it can follow the rotation of the fiber during the forming process. The constitutive model has been implemented in a commercial FE code (Abaqus Explicit) via a user material subroutine VUMAT. It has been shown that the forming simulation is affected by the process parameters like the binder force, the coefficient of friction and forming speed on the shear angle distribution

Experimental study of 48600 Carbons fabrics behavior using marks tracking technique method

Lightweight and energy saving are the main challenges in the aircraft industry production, that explain the increase of composite demand and the diversity of its applications. The investigation of the shear behavior and stiffness of technical woven fabric are essential to guarantee the performance of the final product. In case of forming process (for example RTM process), the in-plane deformability of the woven fabric is necessary for forming without creating defects. The change of the fiber orientation (warp and weft) have a significant impact on final mechanical properties. In this study, the use of marks tracking technique allow the determination of the rigidity of 48600 C 1300 carbon fabrics, and allow calculation of their shear angle, lock angle during tensile and bias-extension tests

Hybrid approach for woven fabric modelling based on discrete hypoelastic behaviour and experimental validation

A non-linear discrete hybrid approach based on the association of hypoelastic continuous elements (non-linear shear behaviour) with specific connectors (non-linear tension stiffness) is developed. It allows the simulation of a two-dimensional (2D) woven reinforcement forming via an accurate explicit finite element analysis. This approach allows the simulation of 2D unbalanced fabrics uncoupling tensile and shear behaviour. It only needs a few parameters to be identified, and shows a good agreement with the experiments. The identification of the model parameters is investigated, and their relevance is analysed in reference tests. To determine the continuous element behaviour, a VUMAT hypoelastic model is implemented in Abaqus/Explicit. This model allows the prediction of fibre stresses and the accurate determination of shear angle in large deformations. Identification and validation of the model are performed using standard characterisation fabric tests. The experimental characterisation provided the numerical data to produce a representational prediction of the deformed fabric geometry and shear angle distribution. Further, the behaviour of the carbon woven reinforcement is identified. A bias extension test is used to both calibrate and validate the model. The capability of the model is illustrated to simulate deep drawing, and to compare with the experimental results of hemispherical forming

Pacifica: Poetry International: Revolutions in Tunisian Poetry

A collection of contemporary poetry from Tunisia, including poems in translation with their French and Arabic original texts

A comprehensive review of natural fibers and their composites: An eco-friendly alternative to conventional materials

Breakthroughs in materials science are the driving force behind many of today's industrial advancements in our fast-changing high-tech world. Composite materials have proven valuable in numerous sectors, including automotive, aerospace, aeronautics, naval, and sports, due to their exceptional mechanical properties and lightweight nature. However, environmental concerns have led to a decrease in the use of fossil fuel-derived materials. Additionally, efforts to reduce greenhouse gas emissions and improve fuel efficiency require lightweight materials with a lower carbon footprint, highlighting the importance of natural fiber composites. Natural fiber composites are made from renewable resources, comprising reinforcements made of natural fibers such as jute, flax, ramie, hemp, cotton, sisal, and kenaf, and a matrix, preferably derived from biomass, which may or may not be biodegradable. However, plant fibers have certain drawbacks when combined with polymers. Due to the presence of hydroxyl groups in lignocellulose, plant fibers are hydrophilic, making them incompatible with hydrophobic thermoplastics and prone to moisture damage. These limitations pose challenges for using plant fibers as polymer reinforcement. To improve adhesion between fibers and the polymer matrix and reduce moisture absorption, surface modifications are typically required. Various methods, such as alkaline, silane, or other chemical treatments, have been developed to enhance fiber-matrix compatibility and improve composite quality. Although natural fiber composites are still in development and their applications are limited, they hold great promise as a sustainable alternative to conventional materials