Review of applications for advanced three-dimensional fibre textile composites

Current and future potential applications for three-dimensional (3D) fibre reinforced polymer composites made by the textile processes of weaving, braiding, stitching and knitting are reviewed. 3D textile composites have a vast range of properties that are superior to traditional 2D laminates, however to date these properties have not been exploited for many applications. The scientific, technical and economic issues impeding the more widespread use of 3D textile composites are identified. Structures that have been made to demonstrate the possible uses of 3D composites are described, and these include applications in aircraft, marine craft, automobiles, civil infrastructure and medical prosthesis.     

三维针刺C/C-SiC复合材料预制体工艺参数优化EI北大核心CSCD

基于误差反向传播(BP)神经网络与改进的遗传算法建立三维针刺C/C-SiC复合材料预制体工艺优化的代理模型,获得针刺工艺参数与复合材料刚度性能之间的关系。利用BP网络实现复合材料刚度性能预测,BP网络的预测值与有限元计算结果吻合程度较好,模型训练误差最大为0.526%,测试数据误差最大为0.454%,BP网络预测精度高。对传统遗传算法的遗传策略和优化策略进行改进,利用两种改进的遗传算法对针刺工艺参数进行优化。优化后的工艺参数显著提高了材料的刚度性能,其中面内拉伸模量分别提高了11.07%和11.48%,面外拉伸模量分别提高了49.64%和48.13%,复合材料的综合刚度性能分别提高18.17%和18.21%。     

A phenomenologically based damage model for textile composites with crimped reinforcement

A phenomenological damage model for textile composites with woven or braided reinforcement is presented and verified in this paper. Essential mechanical questions are clarified with regard to the dominant damage mechanisms and the definition of representative equivalent layers. Using the framework of continuum damage mechanics, damage is defined as the change of the tensor of elasticity. The initiation of damage is described using novel failure criteria based on the Failure-Mode-Concept. Damage variables and associated evolution laws are introduced to describe the subsequent degradation of the material stiffness. The capability of the proposed model is shown for woven thermoplastic composites made of hybrid glass–polypropylene yarns.     

Compaction modelling of textile preforms for composite structures

This paper deals with modelling the compaction behaviour of dry fibre assemblies using an energy minimisation scheme. Compaction behaviour of textile preforms can significantly influence the resin permeability, fibre volume fraction and the geometry of individual tows. Tow geometry will in turn affect the elastic properties of the laminate, mode of damage initiation and progression. In this work, constitutive properties of yarns in bending and transverse compression were measured using Kawabata Evaluation System, and used for computing the potential energy stored in individual yarn segments within a preform. The compaction model has been experimentally verified for single and multi-layer 2D fabrics and 3D fabrics.     

Drapability of dry textile fabrics for stampable thermoplastic preforms

Sandwiches based on stampable foam core and face sheets offer potential for cost-effective applications. Since the formability of such sandwich structures mainly depends on the drapability of the face sheets, the deformation behaviour of several types of textile preforms was evaluated. Glass fibre fabric preforms in the form of plain weave, twill, crowfoot and eight-harness satin as well as warp and weft-knitted architectures were studied. The tensile properties of the dry fabrics at various orientations and the locking angle of woven fabrics in the bias direction were determined. An analytical model is proposed to relate the fabric parameters to the locking angle. Drapability tests were performed on several woven and knitted fabrics in order to relate the forming energy to the preform architecture. Due to their high drapability and low forming energy, warp-knitted structures were selected as textile reinforcement for the sandwich face sheets.     

3D modeling of textile composite preforms

The purpose of this paper is to present three-dimensional models of fabric reinforcements for composite components by using computer aided geometric design (CAGD) techniques. A novel approach to structural representation of fabric preforms is described in both parametric and graphic forms. The philosophy behind the development of the computer generated model of a composite fabric reinforcement is discussed. The model described here is a general one, capable of producing a 3D representation of any 2D and 3D fabrics. The computer program also provides a very useful visualisation of the structure. Various structures of fabrics used as reinforcements for composite materials, such as woven, braided, knit, and multi-axial 3D weave, are demonstrated in virtual realistic forms.     

Resistive heating of multidirectional and unidirectional dry carbon fibre preforms

The electrical conductivity (EC) of continuous carbon fibre (CF) layers is highly anisotropic and is expressed by a second order tensor. In the present work, using continuity equation for anisotropic media, the electrical conductivity of a dry CF multilayer preform can be predicted. Hence, the electrical conductivity tensor of the CF preform can be calculated for any stacking sequence. By means of the calculated electrical conductivity tensor of the multilayer preform, the elliptical form of the governing equation can be solved numerically. Based on this, the generated heat (Joule effect) can be determined. Introducing the generated heat into the heat transfer equation, the temperature field over the CF preform can be predicted. For the experimental verification, a thermal camera was used to record the temperature field developed on a CF multilayer preform under given electric potential field. The experimental results were compared to the respective numerical calculations of the temperature field, where the electrical conductivity tensor was calculated analytically based on the proposed methodology. In all the tested cases the calculated electrical conductivity tensor leads to a numerical model which is in excellent agreement with the experimental results.     

Comprehensive drape modelling for moulding 3D textile preforms

A comprehensive drape model has been developed to deal with a range of 3D surfaces, from simple open surfaces to closed tubular sections with 3D bends. Existing drape algorithms, developed mainly for broadcloth composites, cannot cope with closed sections. These algorithms consider the woven fabric as a network of linkages with pin joints and perform kinematic mapping by solving a set of sphere-intersection equations. This method of kinematic drape assumes only in-plane shear deformation and hence cannot be readily applied to a number of 3D shapes, involving other modes of deformation. In the present work, a kinematic mapping algorithm was implemented at first and subsequently modified to drape two-layer tapered preforms to open surfaces. Following this work, a more general algorithm was developed to drape closed preforms on bent tubes, which the authors believe to be the first such attempt.     

Polysilane-derived porous SiC preforms for the preparation of SiC-glass composites

Three different types of SiC preforms, with open porosities between 60 and 70%, were prepared by pyrolysis of polysilanes and polycarbosilanes at 1670 K. some samples of each type of SiC structure were oxidized in air at 1070 K to promote wetting by the glass melt. Preforms were then applied for gas pressure infiltration with an alumosilicate glass melt at 1670 K in 3 MPa argon, and the influence of pore-size distribution and surface composition on infiltration time was investigated. The composition of the precursors was determined by chemical analysis, and pyrolysed SiC was analysed by thermal decomposition. The porosity and pore-size distribution of the SiC-preforms were measured on photographs of sample cross-sections. The SiC-glass composites were examined by light microscopy, scanning electron microscopy and electron scanning microanalysis.     

Compressive failure of hybrid multidirectional fibre-reinforced composites

In this paper, the hybridisation of multidirectional carbon fibre-reinforced composites as a means of improving the compressive performance is studied. The aim is to thoroughly investigate how hybridisation influences the laminate behaviour under different compression conditions and thus provide an explanation of the “hybrid effect”. The chosen approach was to compare the compressive performance of two monolithic carbon fibre/epoxy systems, CYTEC HTS/MTM44-1 and IMS/MTM44-1, with that of their respective hybrids. This was done by keeping the same layup throughout ((0/90/45/−45)_2S) while replacing the angle plies in one case or the orthogonal plies in the other case with the second material, thus producing two hybrid systems. To investigate the compressive performance of these configurations, compact and plain compression test methods were employed which also allowed studying the sensitivity of compressive failure to specimen geometry and loading conditions. The experimental results and the subsequent fractographic analysis revealed that the hybridisation of selective ply interfaces influenced the location and severity of the failure mechanisms. Finally, in light of this knowledge, an update of the generic sequence of events, previously suggested by the authors, which lead to global fracture in multidirectional fibre-reinforced composites under compression is presented.     

Computational implementation of a novel constitutive model for multidirectional composites

This paper details the numerical implementation of a constitutive model for unidirectional (UD) polymer-matrix fibre-reinforced composites, which is able to accurately represent the full non-linear mechanical response. Features such as hydrostatic pressure sensitivity, the effect of multiaxial loading and the dependence of the yield stress on the applied pressure are often neglected in constitutive modelling, but are included in this model.The constitutive model includes a novel yield function, non-associative flow rule and a non-linear kinematic hardening rule. It is combined with suitable failure criteria and associated damage model. The complete model is implemented in an explicit finite element code.Experimental test data is used to show that the model is able to predict the non-linear response of both unidirectional and multidirectional composite laminates. The model is shown to accurately predict the constitutive response under complex multiaxial loading and unloading, including significant hydrostatic pressure. Predictions are also shown to compare favourably for the evolution of matrix cracking after initial matrix cracking is detected by the failure criteria.     

Highly aligned flax/polypropylene nonwoven preforms for thermoplastic composites

A major challenge for natural fibre composites is to achieve high mechanical performance at a competitive price. Composites constructed from unidirectional yarns and woven fabrics are known to perform significantly better than composites made from random nonwoven mats, but unidirectional yarns and fabrics are much more expensive to manufacture than random nonwoven mats. Here, we report on highly aligned natural fibre nonwoven mats that can be used as a replacement for unidirectional woven fabrics. A drawing operation is added to the conventional nonwoven process to improve fibre alignment in the nonwoven preforms and the final composites. The modified nonwoven manufacturing process is much simpler and cheaper than the unidirectional woven fabric process because of the elimination of expensive spinning and weaving operations. The composites fabricated from the highly aligned nonwoven mats showed similar mechanical strength as the composites made from unidirectional woven fabrics.     

Dynamic response of multidirectional composites in hygrothermal environments

Drilling is an essential operation in the assembly of the structural frames of automobiles and aircrafts. The life of the joint can be critically affected by the quality of the drilled holes. The main objective of the present paper is to investigate the influence of some parameters on the thrust force, torque and surface roughness in drilling processes of fiber-reinforced composite materials. These parameters include cutting speed, feed, drill size and fiber volume fraction. The quasi-isotropic composite materials were manufactured from randomly oriented glass fiber-reinforced epoxy, with various values of fiber volume fractions (V_f), using hand-lay-up technique. Two components drill dynamometer has been designed and manufactured to measure the thrust and torque during the drilling process. The dynamometer was connected with a data acquisition, which installed in a PC computer. This set-up enable to monitor and record the thrust force and torque with the aid of a computer program that designed using Lab View utilities.

The results indicate that the start point of torque cycle is delayed by few seconds (depending on the value of feed) than the thrust force. This time is consumed to penetrate the specimen by chiseling edge. After the thrust force reached its maximum value it is gradually decreased during the full engagement of the drill and goes to zero when both the chisel edge and the cutting lips have exit of the laminate. In contrast the torque was gradually increased up to the end of the cycle and sudden jump to a value about 10 times the peak value. Cutting speed has insignificant effect on the thrust force and surface roughness of epoxy resin. For glass fiber-reinforced epoxy composites (GFREC) with V_f=9.8–23.7% the thrust force and torque were decreased with increasing cutting speed. On contrast increasing feed, drill size and fiber volume fractions lead to increase the thrust force and torque. The drilled holes of GFREC with lower V_f ratio at lower feed have greater roughness than that drilled at higher feed. Specimens with high V_f ratio have a contrary behavior. Drill diameter combined with feed has a significant effect on surface roughness.     

Aluminum matrix composites based on preceramic-polymer-bonded SiC preforms

Polymethylsiloxane (PMS) was used as a binder to make self-supporting SiC preforms for pressurized aluminum melt infiltration. The SiC particles were coated with preceramic polymer by spray drying; this ensured a fine and homogeneous distribution coupled with a high yield of the binder. The conditioned SiC powder mixtures were processed into preforms by warm pressing, curing and pyrolysis. A polymer content of 1.25 wt.% conferred sufficient stability to the preforms to enable composite processing. Using this procedure, SiC preforms with various SiC particle size distributions were prepared. The resulting Al/SiC composites with SiC contents of about 60 vol.% obtained by squeeze casting infiltration exhibit a 4-point bending strength of ∼500 MPa and Young’s moduli of ∼200 GPa. These values are comparable to those of compositionally identical, but binder-free composites. It is thus shown that the PMS-derived binder confers the desired strength to the SiC preforms without impairing the mechanical properties of the resulting Al/SiC composites.     

Low-volume-fraction particulate preforms for making metal-matrix composites by liquid metal infiltration

A preform technology for making particulate metal-matrix composites with a low particulate volume fraction (as low as 18%) by liquid metal infiltration is provided. This technology used a non-combustible reinforcement (SiC) as the primary particulate and combustible particles (carbon) as the secondary particulate in the preform. The secondary particulate was removed from the preform by oxidation prior to liquid metal infiltration.     

Mechanics of textile composites: Micro-geometry

Textile fabric geometry determines textile composite properties. Textile process mechanics determines fabric geometry. In previous papers, the authors proposed a digital element model to generate textile composite geometry by simulating the textile process. The greatest difficulty encountered with its employment in engineering practice is efficiency. A full scale fiber-based digital element analysis would consume huge computational resources. Two advances are developed in this paper to overcome the problem of efficiency. An improved contact-element formulation is developed first. The new formulation improves accuracy. As such, it permits a coarse digital element mesh. Then, a static relaxation algorithm to determine fabric micro-geometry is established to replace step-by-step textile process simulation. Employing the modified contact element formulation in the static relaxation approach, the required computer resource is only 1–2% of the resource required by the original process. Two critical issues with regards to the digital element mesh are also examined: yarn discretization and initial yarn cross-section shape. Fabric geometries derived from digital element analysis are compared to experimental results.     

Micromechanical modeling of imperfect textile composites

After fabrication the carbon-carbon (C/C) plain weave textile composites often show a certain degree of geometrical or material disorder including yarn waviness and misalignment or nesting of individual fiber tows together with intrinsic material porosity observed at all relevant scales. A brief survey of recently developed approaches for estimating overall elastic stiffnesses or thermal conductivities of such composite systems is presented in this paper. Depending on the source and type of available geometrical data the homogenization scheme usually relies either on finite element (FEM) simulations performed for a suitable Periodic Unit Cell (PUC) or employs one of the popular averaging techniques such as the Mori-Tanaka (MT) method. While existing applications of both methodologies are encouraging, there still exists a number of steps to be completed in the course of the future research.     

Mechanics of non-orthogonally interlaced textile composites

The present paper focuses on geometric and micromechanical modelling of non-orthogonal structures. Braided structure and sheared woven structures have similar interlacement geometry. However, tow wavelength in a woven fabric remains constant during in-plane shear, where as, in the case of a braid, tow wavelength deceases with an increase in interlacement angle. In the present work, lenticular geometry has been used for describing the unit cell geometry, and relations for various geometrical parameters have been derived. Three braided composite tubes with angles of 31°, 45° and 65° were prepared for experimental validation of geometric and mechanical models. Almost all the published work was based on orthogonal repeating unit cells suitable only for un-sheared woven structures. In this work, we identified a non-orthogonal representative volume element (RVE) that can deal with any interlaced tow architecture. Experimental results for three braided tubes were compared with the data obtained using modified laminate theory and finite element analysis.