Influence of three-dimensional (3D) fabric orientation on flexural properties of cement-based composites

This research studied the flexural behavior of textile reinforced cement-based composites reinforced with 3D fabrics. Three different 3D fabrics were examined, each with a different orientation of the spacer yarns. This work focused on the influences involved in the two plane fabric directions, weft and warp. Plain 2D fabrics (not in cement) and within the cement were also examined for comparison. It was found that the warp direction of the plain fabric has higher tensile strength than the weft direction. On the contrary, when the fabric is in a composite, the weft direction presents improved behavior in flexure due to three mechanisms: the tightening of the warp bundles by the loops, the waviness of the warp yarns, and the angle of the yarns located along the composite thickness to the loading direction. In general, compared with 2D fabrics, 3D fabrics are highly beneficial reinforcements for cement-based composites due to their greater reinforcing efficiency via mechanical anchoring.     

Fabrication and mechanical behaviors of cementitious composites reinforced by 3D woven lattice sandwich fabrics

Glass fibers were firstly woven to form three-dimensional (3D) woven lattice sandwich fabrics (WLSFs) which then were applied to reinforce cementitious foams and mortars to fabricate novel ductile cementitious composites. Failure behaviors of WLSF reinforced cementitious composite structures were studied through compression and three-point bending experiments. The WLSF greatly enhances the strength of cementitious foams at a level of four times. For cementitious mortars, compression strength of WLSF reinforced blocks is a little greater for the fraction of the textile is small as well as the compression strength of the textile pillars is not strong. But in flexure, excellent stretching ability of the glass fiber textiles greatly improves the flexural behavior of WLSF reinforced cementitious composite panels. Load capacity and ultimate deflection of these composite panels were greatly enhanced. Flexural capacity of the WLSF reinforced beam is four times greater. Reinforced by WLSF, failure of the cementitious composite is ductile.     

Mechanical properties of 3D printed interpenetrating phase composites with novel architectured 3D solid-sheet reinforcements

Interpenetrating phase composites (IPCs) are novel types of multifunctional composite materials. This work focuses on investigating experimentally and computationally the mechanical behavior of novel types of three-dimensional (3D) architectured two-phase IPCs. The current IPCs are architectured using several morphologies of the fascinating and mathematically-known triply periodic minimal surfaces (TPMS) that promote several multifunctional attributes. Specifically, the second hard reinforcing phase takes the architecture of one of the 3D non-intersecting and continuous TPMS-based solid sheets. The mechanical response of the 3D printed polymer-based IPCs is measured under uniaxial compression where the effect of varying the second-phase architecture and volume fraction is explored. Anisotropy induced by the 3D printing is also investigated. 3D finite element analysis has been performed and validated for predicting elastic properties of the various types of TPMS-based IPCs. The most effective TPMS architecture in enhancing the mechanical properties and damage-tolerance has been identified.     

3D mathematical modelling for robotic pick up of textile composites

An area of interest in the automated manufacture of composite components is the prediction in real-time of the deformed shape of a textile reinforcement in 3D space during robotic handling operations. The deformed shape can be used to guide robotic end-effectors to ensure accurate fabric placement and avoid collisions. In this paper, a nonlinear mathematical model using large deflection plate and shell theories is presented. The model is able to predict the 3D deformed shape of limp sheet materials being picked-up by multi robotic grippers for three boundary conditions. The main factors affecting the deformation behaviour of the sheet during the operation are identified and analysed, and the contributions of different energies during deformation are presented in detail. Good agreement is obtained when comparing the solutions of the model with FE simulation results. This study demonstrates the possibility of developing a modelling capability for material on-line response in automatic flexible material handling.     

On-machine interlocking of 3D laminate structures for composites

By using an adjacent-layer interlocking method on a weaving machine, multi-layer preform structures are developed. The on-loom interlocking method eliminates the yarn breakage resulting from needle penetration which is the case for off-loom interlocking of fabric layers. The concept of this three-dimensional (3D) fabric design is to bind each pair of adjacent layers at one connecting point in every other plain-weave repeat within each layer. The mechanical properties of the resulting composites are investigated by means of impact, short-beam shear and the long-beam flexural testing. The failure mechanisms found in 3D on-loom interlocked composites include fiber breakage, fiber debonding and fiber pull-out.     

Effect of fabric compaction and yarn waviness on 3D woven composite compressive properties

3D-woven fabrics incorporate through-thickness reinforcement and can exhibit remarkable inter-laminar properties that aid damage suppression and delay crack propagation. However, distortions in the internal architecture such as yarn waviness can reduce in-plane properties, especially in compression. The degree of yarn waviness present in a 3D woven fabric can be affected by a range of factors including weave parameters and manufacturing-induced distortions such as fabric compaction. This paper presents a thorough analysis of the effect of fabric compaction and yarn waviness on the mechanical properties and failure mechanisms of an angel-interlock fabric in compression. Tests were conducted on coupons moulded to different volume fractions and data compared to previous measurements of local yarn angle. Major findings show the importance of yarn straightness on compressive strength and how this can be affected by optimising moulding thickness. Failure initiation was also found to be heavily influenced by weave style and yarn interlacing.     

Compressibility of carbon woven fabrics with carbon nanotubes/nanofibres grown on the fibres

Growth of carbon nanotubes (CNT) or carbon nano-fibres (CNF) on carbon fibrous substrates is a way to increase the fracture toughness of fibre reinforced composites (FRC), with encouraging results reported in the recent years. If these nano-engineered FRC (nFRC) are destined to leave laboratories and enter industrial-scale production, a question of adapting the existing composite manufacturing methods will arise. The paper studies compressibility of woven carbon fibre performs (two types of fabrics) with CNT/CNF grown on the fibres using the CVD method. The results include pressure vs thickness and pressure vs fibre volume fraction diagrams for one and four layers of the fabric. Morphology of the nFRC is studied with SEM. It is shown that the pressure needed to achieve the target fibre volume fraction of the preform increases drastically (for example, from 0.05 MPa to more than 0.5 MPa for a fibre volume fraction of 52%) when CNT/CNF are grown on it. No change in nesting of the fabric plies is noticed. The poor compressibility can lower the achievable fibre volume fraction in composite for economical vacuum assisted light-RTM techniques and increase the pressure requirements in autoclave processing.     

Mechanical behavior of Kevlar/basalt reinforced polypropylene composites

In this study, mechanical behavior of thermoplastic composites reinforced with two-dimensional plain woven homogeneous and hybrid fabrics of Kevlar/basalt yarns was studied. Five types (two homogeneous and three hybrids) of composite laminates were manufactured using compression molding technique with polypropylene (PP) resin. Static tensile and in-plane compression tests were carried out to evaluate the mechanical properties of the laminates. The tension and in-plane compression tests had shown that the composites with the combination of Kevlar and basalt yarns present better tensile and in-plane compressive behavior as compared to their base composites. Improvement in the properties such as elastic modulus, strength and failure strain in both tension and in-plane compression was observed due to the hybridization. Numerical simulations were performed in ABAQUS/Standard by implementing a user-defined material subroutine (VUMAT) based on Chang-Chang criteria. Good agreement between the experimental and numerical simulations was achieved in terms of damage patterns.     

Experimental determination of the mode I delamination fracture and fatigue properties of thin 3D woven composites

The mode I delamination fracture toughness and fatigue strength of thin-section three-dimensional (3D) woven composite materials is experimentally determined. The non-crimp 3D orthogonally woven carbon–epoxy composites were thin (2 mm) and consequently their through-thickness z-binder yarns were inclined at a very steep angle (about 70°) from the orthogonal direction. The steep z-binder angle has a marked effect on the delamination toughening and fatigue strengthening mechanisms. Experimental testing revealed that the fracture toughness and fatigue resistance increased progressively with the volume content of z-binders. However, the steep angle caused the z-binder yarns bridging the delamination crack to deform and fail in shear and through-thickness tension, rather than in-plane tension which usually occurs in thick 3D woven composites. Mode I pull-off tests on a single woven z-binder yarn embedded within the composite revealed that the crack bridging traction load, strain energy absorption and failure mechanism were strongly affected by the steep angle.     

Effects of fabric parameters on the tensile behaviour of sustainable cementitious composites

The mechanical behaviour of fabric-reinforced composites can be affected by several parameters, such as the properties of fabrics and matrix, the fibre content, the bond interphase and the anchorage ability of fabrics. In this study, the effects of the fibre type, the fabric geometry, the physical and mechanical properties of fabrics and the volume fraction of fibres on the tensile stress–strain response and crack propagation of cementitious composites reinforced with natural fabrics were studied. To further examine the properties of the fibres, mineral fibres (glass) were also used to study the tensile behaviour of glass fabric-reinforced composites and contrast the results with those obtained for the natural fabric-reinforced composites. Composite samples were manufactured by the hand lay-up moulding technique using one, two and three layers of flax and sisal fabric strips and a natural hydraulic lime (NHL) grouting mix. Considering fabric geometry and physical properties such as the mass per unit area and the linear density, the flax fabric provided better anchorage development than the sisal and glass fabrics in the cement-based composites. The fabric geometry and the volume fraction of fibres were the parameters that had the greatest effects on the tensile behaviour of these composite systems.     

Microstructure,flexural properties and durability of coir fibre reinforced concrete beams externally strengthened with flax FRP composites

This study investigated the flexural behaviour of plain concrete (PC) and coir fibre reinforced concrete (CFRC) beams externally strengthened by flax fabric reinforced epoxy polymer (FFRP) composites. PC and CFRC beams without and with FFRP (i.e. 2, 4 and 6 layers) reinforcement were tested under three- and four-point bending. The microstructures of coir fibre, coir/cement matrix, flax/epoxy matrix, and FFRP/concrete interfaces were analysed using scanning electronic microscope (SEM). Test results indicated that the peak load, flexural strength, deflection and fracture energy of both PC and CFRC specimens enhanced proportional to an increase of FFRP layers. Coir further increased load, strength and energy of the specimens remarkably. It was also found that the thickness and coir influenced the failure modes while the test method influenced the load and energy of the specimens remarkably. SEM studies showed effective bond at coir/cement, flax/epoxy and FFRP/concrete interfaces. Therefore, it concluded that natural FFRP composites can be used to repair or retrofit existing concrete structures.     

Flax and polyparaphenylene benzobisoxazole cementitious composites for the strengthening of masonry elements subjected to eccentric loading

To address the structural problems caused by eccentric loads in unreinforced masonry, three different types of masonry were prepared based on clay bricks bonded with a natural hydraulic lime mortar combined with a flax or polyparaphenylene benzobisoxazole (PBO) fabric-reinforced cementitious matrix (FRCM) composite. The mechanical behaviour when subjected to concentric and eccentric loads was studied by performing axial compression tests, with eccentric load tests only carried out in instances of large eccentricities. Analysis of the load–displacement and moment–curvature response revealed that both the flax- and PBO-based strengthening systems improve the strength and deformability of masonry. However, compared to the PBO fabric composite, the use of flax fabric provides a greater deformability that helps prevent the composite and substrate debonding.     

Fabrication and characterization of three-dimensional PMR polyimide composites reinforced with woven basalt fabric

A PMR polyimide composite reinforced with three-dimensional (3D) woven basalt fabric is fabricated for medium high temperature applications. The PMR polyimide matrix resin is derived from 4,4′-methylenediamine (MDA), diethyl ester of 3,3′,4,4′-oxydiphthalic (ODPE) and monoethyl ester of Cis-5-norbornene-endo-2,3-dicarboxylic acid (NE). The rheological properties of the PMR polyimide matrix resin are investigated. Based on the curing reaction of the PMR type polyimide and the rheological properties, an optimum two-step fabrication method is proposed. The three dimensional fabric preforms are impregnated with the polyimide resin in a vacuum oven at 70 °C for 1 h followed by removing the solvent and pre-imidization. The composites are then consolidated by an optimized molding procedure. Scanning electron microscopy analysis shows that needle shaped voids are generated in yarns and the void volume fraction is 4.27%. The decomposition temperature and the temperature at 5% weight loss of the composite post-cured at 320 °C for 24 h are 440 °C and 577 °C, respectively. The dielectric constant and the dielectric loss of the composite are measured by circular cavity method at 7–12 GHz. The tensile strength and the modulus in the warp direction of the composite are 436 MPa and 22.7 GPa. The composite shows a layer-by-layer fracture mode in three-point bending test. The flexure strength and modulus in the warp direction of the composite are 673 MPa and 27.1 GPa, respectively.     

Hybrid 3D-textile reinforced composites with tailored property profiles for crash and impact applications

Novel 3D-textile reinforced composites with a stretched fibre arrangement have very good specific mechanical properties and outstanding energy absorption capabilities. With respect to the specific technical requirements, 3D-textile preforms can be adjusted with regard to stiffness, strength and crash-worthiness by the intelligent combination of different fibre materials in the textile preform. Thus, hybrid 3D-textile preforms with tailored property profiles are excellent candidates for the use in impact and crash components of innovative lightweight structures for the aircraft and vehicle industry as well as for mechanical engineering applications.     

A new analytical model on predicting the elastic properties of 3D full five-directional braided composites based on a multiunit cell model

A new analytical model based on a multiunit cell model is proposed to predict the elastic properties of 3D full five-directional braided composites (F5DBC). The stiffness-volume averaging method is applied to predict the elastic properties of unit cell models in meso-scale and specimens in global-scale by using the multi-scale modeling procedures. The contribution of all unit cells to the elastic properties of specimen is considered in the analytical model. The predicted elastic properties are in good agreement with the available experimental data, demonstrating the applicability of the model. Also, the effects of the braiding angle and the fiber volume fraction on the elastic properties are discussed in detail. The elastic constants of each unit cell are analyzed and the effect of the number of yarn carriers on the mechanical properties is also investigated. Results indicate that it is convenient to apply the present analytical model to predict the elastic properties of 3D F5DBC due to high computational efficiency.     

Characterization of a novel natural cellulose fabric from Manicaria saccifera palm as possible reinforcement of composite materials

Identifying novel natural fibers/fabrics with proper properties as reinforcement material is a new challenge in the field of bio-composites. Hence, the aim of this paper is to study the possibility of using a natural fabric extracted from Manicaria saccifera palm as a novel reinforcement in composites. This fabric was extensively characterized by chemical composition analysis, infrared spectroscopy (FTIR) analysis, morphological studies (SEM), thermo-gravimetric analysis (TGA) and physical /mechanical properties studies. From SEM analysis it was identified globular protrusions spread uniformly over the fiber which could help the mechanical interlock with the resin. As well, Manicaria fabric showed good thermal stability, low density, low moisture content and good tensile properties. Further, their properties are comparable to most natural cellulose fabrics and some synthetic fabrics, such as fiber glass fabrics. Manciaria saccifera fabric showed to be a suitable candidate as natural reinforcement material for the development of bio- composite.     

Cellulosic fibers from rice straw and bamboo used as reinforcement of cement-based composites for remarkably improving mechanical properties

The cement-based composites reinforced with cellulosic fibers isolated from rice straw were fabricated by a slurry vacuum de-watering technique. The physical structures and mechanical properties of the composites with fiber contents ranging from 2% to 16% by weight (wt.%) were investigated. Moreover, the composites reinforced with bamboo cellulosic fibers and the control cement paste, sample without cellulosic fibers, were also fabricated as reference materials. As a result, the cement-based composites reinforced by cellulosic fibers showed a remarkable improvement in the mechanical properties. The measurements of the flexural strength and the fracture toughness of the optimal sample were found to be increased by 24.3% and 45 times, respectively. The bulk density of the composites was decreased by 12.4–37.3% as a result of the introduction of cellulosic fibers. Additionally, the field emission scanning electron microscope (FSEM) observations and energy dispersive spectroscopy (EDS) analyses revealed that the hydration products of Portland cement migrated to the fiber lumens, resulting in mineralizing the cellulosic fibers and decreasing the fracture toughness of the composites.     

Formability of a non-crimp 3D orthogonal weave E-glass composite reinforcement

In this paper, the formability of a single layer E-glass non-crimp 3D orthogonal woven reinforcement (commercialized under trademark 3WEAVE® by 3Tex Inc.) is experimentally investigated. The study involves the forming process of the 3D fabric on two complex moulds, namely tetrahedron and double-dome. The tests are assisted by 3D digital image correlation measurement to have a continuous registration of the fabric local deformation. Moreover, the results of bending tests in warp and weft direction are detailed to enlarge the mechanical properties data set of the 3D reinforcement, necessary for understanding its deformability capacities in forming processes. The elevated bending stiffness of the 3D fabric means that use of a blank-holder during forming is not required. The reinforcement has a good drapability and it is able to form complex shapes without defects (wrinkles and fibre distortions). The collected experimental results represent an important dataset for numerical simulations of any complex shape with the considered 3D fabric composite reinforcement.     

Smoothing artificial stress concentrations in voxel-based models of textile composites

Voxel meshing is an effective method to discretise the internal architectures of multi-phase materials. Spurious stresses are however introduced in the vicinity of a multi-material interface due to the stepped, block-like representation of smooth boundaries. A stress averaging technique is presented to eliminate artificial mesh-imposed stress concentrations. The effect of the local averaging domain size, averaging weight function, and mesh dependence is explored. The voxel finite element method with stress averaging is then further developed to study progressive damage propagation and failure analysis of composites. An additional control, based on the failure plane angle of each element, is included to ensure propagation of damage in the direction dictated by the physics of the process rather than mesh artefacts. It is found that the stress averaging technique is an effective way to alleviate local stress concentrations and can ensure correct damage and failure mode prediction when compared to a conformal mesh.     

Pull-through performance of carbon fibre epoxy composites

An investigation of the through-thickness properties of carbon fibre prepreg laminates, Non-Crimp Fabric laminates and non-crimp 3D orthogonal woven composites by pull-through testing was performed. Influence of matrix system and curing temperature on the performance of the 3D woven composites was investigated.