Analysis of the Mechanical and Preforming Behaviors of Carbon-Kevlar Hybrid Woven Reinforcement

Carbon-Kevlar hybrid reinforcement is increasingly used in the domains that have both strength and anti-impact requirements. However, the research on the preforming behaviors of hybrid reinforcement is very limited. This paper aims to investigate the mechanical and preforming behaviors of carbon-Kevlar hybrid reinforcement. The results show that carbon-Kevlar hybrid woven reinforcement presents a unique “double-peak” tensile behavior, which is significantly different from that of single fiber type reinforcement, and the in-plane shear deformation demonstrates its large in-plane shear deformability. Both the tensile and in-plane shear behaviors present insensitivity to loading rate. In the preforming process, yarn slippage and out-of-plane yarn buckling are the two primary types of defects. Locations of these defects are closely related to the punch shape and the initial yarn direction. These defects cannot be alleviated or removed by just increasing the blank holder pressure. In the multi-layer preforming, the compaction between the plies and the friction between yarns simultaneously affect the quality of final preforms. The defect location of multi-layer preforms is the same as that of single-layer, while its defect range is much wider. The results found in this paper could provide useful guidance for the engineering application and preforming modeling of hybrid woven reinforcement.

The Dahl’s Model for the Inelastic Bending Behavior of Textile Composite Preforms. Analysis of its Influence in Draping Simulation

Most of the numerical simulations of dry textile reinforcements forming are based on a macroscopic approach and continuous material models whose behavior is assumed to be elastic (linear or nonlinear). On the one hand, the experience shows that under loading/unloading stresses, residual inelastic deformations are observed. On the other hand, among the deformations that a woven reinforcement undergoes during forming, in most cases, only bending is subject to loading/unloading stresses. The first objective of this work is to highlight the inelastic bending behavior of textile reinforcements during a forming process and to find the possible origins of inelasticity. The second objective is to find the cases generating bending loading/unloading during forming as well as to study the influence of the bending inelasticity on forming simulation. For this purpose, the inelastic bending behavior was characterized by three-point bending tests. Then, the Dahl friction model was adapted to bending to describe the inelastic behavior. Finally, this model was implemented in a finite element code based on shell elements allowing the study of the influence of taking into account the inelastic behavior in bending on the numerical simulation of forming.

Mechanical Testing of GFRP Composite Materials Used in Wind Turbine Blades Construction

The paper proposes to present the results of the evaluation of glass fiber reinforced plastics (GFRP) used in the construction of wind turbine blades. In a wind turbine, the blades are the most exposed to damages and the defects which appear are various and are connected with the type of manufacture, simple/complex loading, environmental conditions etc. In order to increase the lifetime span and to analyze the degradation phenomena during the materials functioning, destructive evaluation tests are performed to determine the mechanical property, by testing pure shear on specimens Iosipescu, from GFRP with woven reinforcement at [± 45°] and [0°/90°], with the shear fixture, endowment of Technical University Gh.Asachi Iasi.

Effect of particle sizes on the mechanical behaviour of limestone-reinforced hybrid plastics

The present research has been made to investigate the characteristics of a new composite material made up of limestone as particle reinforcement. New composites are made by taking limestone particles in five different sizes and jute as woven reinforcement in polypropylene matrix. Mechanical characteristics of the composites that include strengths against tension, compression, flexural, impact and hardness are evaluated and a comparative investigation is made among the composites. The effect of particle size on the properties is analysed and found that the composite with medium particle size bears the highest strength in all aspects. In addition, microscopic image analysis is carried out to investigate the distribution of particles, bonding capacity and other morphologies. The results showed that limestone will be apt particle reinforcement and its presence enhances all the characteristics of the composite.

Effects of Crimp and Textile Architecture on the Stiffness and Strength of Composites with 3D Reinforcement

The aim of this study is to experimentally determine how the weave architecture and yarn crimp affect the measured tensile stiffness and strength of composites containing 3D textile reinforcement. It is shown that both the stiffness and strength decrease nonlinearly with increasing 3D crimp. The ultimate strength of specimens containing nominally straight yarns and specimens containing crimped yarns can differ more than a factor of 3, and the stress causing onset of damage can be affected even more. Adding nominally straight stuffer yarns into a 3D-woven reinforcement significantly increases the fibre volume fraction, the stiffness, and the strength of the composite. However, since the stuffer yarns are virtually straight and thus stiffer than the warp yarns, they attract the load and reach their strength at relatively lower strain than the warp yarns. The reinforcement architecture varies between the surfaces and the interior of the studied textiles, which has corresponding influence on the local stiffness. The onset of failure is predicted satisfactorily accurate with relatively simple estimations. The ultimate strength is a result of extensive damage progression and thus more dubious to predict.

KOMPARASI KEKUATAN TEKUK PADA KOMPOSIT LAMINA DENGAN MATRIK DUA JENIS KAYU DAN REINFORCEMENT BAMBU

Natural materials are environmentally friendly materials that can be made as components of matrix and reinforcement. Wood is part of the stem or branches and twigs of hardened plant due to lignification. Bamboo is a type of grass plants belonging to the order Graminae, familia Bambuseae, rooted fibers, the trunk-shaped cylinder with a diameter that varies from base to tip, hollow, hard. The composite is a composite of two or more materials that are integrated macroscopically and form a new properties. The composite type used in the laminate composite consists of two different layers of material and combined together, using adhesive, the manufacturing process using the hand lay up method. Matrix used balsa and mahoni wood, for reinforcement used type of bamboo apus molded basket woven. Bending test, using ASTM D7264 / D7264M-07 standard. The results of the experiment by testing each test, using 3 test specimens, then taken the average value. For balsa wood matrix, with plain woven reinforcement, buckling strength with value 35.60 ± 2.30 MPa, for balsa wood matrix, with basket woven reinforcement, buckling strength with value 32.64 ± 4.20 MPa. For mahoni matrix, with plain woven reinforcement, buckling strength of 55.15 ± 4.89 MPa, for mahoni matrix, with basket woven reinforcement, buckling strength of 77.15 ± 4.88 MPa. From these data shows that by using mahoni matrix the buckling strength is greater than using balsa wood matrix, either using plain or basket woven.

Nonconformal mesh-based finite element strategy for 3D textile composites

A finite element procedure is developed for the computation of the thermoelastic properties of textile composites with complex and compact two- and three-dimensional woven reinforcement architectures. The purpose of the method is to provide estimates of the properties of the composite with minimum geometrical modeling effort. The software TexGen is used to model simplified representations of complex textiles. This results in severe yarn penetrations, which prevent conventional meshing. A non-conformal meshing strategy is adopted, where the mesh is refined at material interfaces. Penetrations are mitigated by using an original local correction of the material properties of the yarns to account for the true fiber content. The method is compared to more sophisticated textile modeling approaches and successfully assessed towards experimental data selected from the literature.