Showing papers on "Composite laminates published in 2017"

Bimaterial 3D printing and numerical analysis of bio-inspired composite structures under in-plane and transverse loadings

Abstract: This work presents a novel design, additive manufacturing and modeling approach of three dimensional voronoi-based composite structures that closely mimic nacre's multilayer composite structure. The hierarchical structure of natural nacre is mimicked to produce multilayer composite laminates assembled from three dimensional polygonal tablets bonded with organic adhesives. Furthermore, various complex geometries of the nacreous shells observed from the nature, such as the dome-shaped structure, are developed into three dimensional designs. A novel mapping algorithm is developed to generate complex structures of nacre-like composites that are readily fabricated by unique dual-material 3D printing technology. Preliminary 3D-printed prototypes with complex shapes and material combinations are presented. A novel numerical model of the nacreous composite is proposed, which includes tablet cohesive bonds and interlaminate adhesive layers to mimic the soft organic polymer matrix. The nacreous model is validated against a natural nacre specimen under uniaxial loading. To exemplify a potential application, a scaled model of a nacre-mimetic composite made of Aluminum tablets and Vinylester adhesive is constructed and assessed against blast-induced impulsive loading. The performance of the nacre-like composite panel is investigated in terms of deformation and energy dissipation.

Hybridization Effect of Sisal/Glass/Epoxy/Filler Based Woven Fabric Reinforced Composites

Abstract: Development of the Polymer based Composites from both natural and synthetic fibers is a sustainable alternative material for some engineering fields like automotive and aerospace. This work is aimed to incorporate the sisal and E-glass fabrics with the epoxy matrix and by adding silicon carbide filler to the sisal fabrics. Five different composite laminates were prepared by hand layup combined with vacuum bagging method as per laminate sequences. The physical and mechanical properties of composite laminates were evaluated according to ASTM. Results show that incorporation of E-glass and silicon carbide filler can reduce the voids and enhance the physical properties. As the amount of E-glass fibers slightly grows, tensile properties of composites grow. Effect of filler can enhance the flexural properties. Failure of composites mainly occurs due to the poor interfacial bonding between fabrics and matrix, fabrics pull out and fracture occurs in fabrics or matrix when load is applied.

Low velocity impact performance of stitched flax/epoxy composite laminates

Abstract: This paper presents an experimental investigation of the effect of through-thickness natural fibre stitches on the low-velocity impact response of the woven flax/epoxy composite laminates with the purpose of extending their use to higher performance applications. Two impact energy levels were selected to produce a perforated and a non-perforated damage state in stitched/unstitched composites for study. Twistless flax yarn and twisted cotton thread were used to stitch at an equivalent stitch areal fraction for all laminates of the same thickness. Unstitched cross-plies [0/90] 4s of continuous flax fibres were also manufactured at a similar thickness for benchmarking of energy absorption and fracture mechanisms. Comparison of the damage sustained in the unstitched and stitched natural fibre composites showed that while delamination was not the predominant damage mode in both laminates, stitching does facilitate the propagation of in-plane cracks. The experimental findings revealed that stitching with thicker yarn (Flax) led to a lower ratio of absorbed energy per area of damage as well as energy absorbed for full penetration.

Mechanical characterization of Basalt/epoxy composite laminates containing graphene nanopellets

Abstract: This paper presently investigates the influence of graphene nano-pellets (GnPs) inclusion on mechanical properties (tensile, flexural and impact resistance) of basalt/epoxy composite laminates. Variation of mechanical properties was explained by different GnPs loading by weight ratios (0.1, 0.2 and 0.3 wt %) between epoxy and filler, controlling with full basalt/epoxy laminates (unfilled). Failure characteristics of the prepared samples were also presented and compared along with GnPs filler loadings. Results indicated from this study that incorporation of GnPs fillers at 0.1 wt % significantly enhanced the mechanical properties of basalt/epoxy composites due to high bonding strength at the interphase between GnPs-epoxy-fiber interactions.

Drilling on fiber reinforced polymer/nanopolymer composite laminates: a review

Abstract: Among various machining operations, drilling is the most commonly employed machining operation for polymer composite laminates owing to the need for joining structures. Work with commercial composites has identified numerous parameters during the drilling operation that can influence the drilling factors and the material damage. The present paper gives a precise review of drilling on current state of fiber reinforced polymer as well as nanopolymer composite laminates. Specifically, the influence of machining parameters, tool geometry, tool materials and tool types on the cutting force generation and delamination mechanisms. Based on the comprehensive literature survey from the past few years, it is noticed that limited research has been made and published concerning to nanopolymer composite drilling and has led to a partial understanding of the cutting mechanics activated in machining/drilling. Some key contributions such as experimental and numerical studies are urgently demanded to address accurately various projections in drilling of nano-particle reinforced FRP composite laminates.

Numerical simulation of progressive damage and failure in composite laminates using XFEM/CZM coupled approach

Abstract: This study seeks to establish a high-fidelity mesoscale simulation methodology that can predict the progressive damage and resultant failure of carbon fiber reinforced plastic laminates (CFRPs). In the proposed scheme, the plastic behavior (i.e., pre-peak nonlinear hardening in the local stress-strain response) is characterized through the pressure-dependent elasto-plastic constitutive law. The evolution of matrix cracking and delamination, which result in post-peak softening in the local stress-strain response, is modeled through cohesive zone models (CZM). The CZM for delamination is introduced through an interface element, but the CZM for matrix cracking is introduced through an extended finite element method (XFEM). Additionally, longitudinal failure, which is dominated by fiber breakage and typically depends on the specimen size, is modeled by the Weibull criterion. The validity of the proposed methodology was tested against an off-axis compression (OAC) test of unidirectional (UD) laminates and an open-hole tensile (OHT) test of quasi-isotropic (QI) laminates. Finally, sensitivity studies were performed to investigate the effect of plasticity and thermal residual stress against the prediction accuracy in the OHT simulation.

Effects of cutting edge radius and fiber cutting angle on the cutting-induced surface damage in machining of unidirectional CFRP composite laminates

Abstract: Carbon fiber reinforced polymer composite laminates are anisotropic, inhomogeneous, and mostly prepared in laminate form before undergoing the finishing operations. The edge trimming process is considered as one of the most common finishing operations in the industrial applications. However, the laminate surface is especially prone to damage in the chip formation process, and the most common damage mode is burrs. Burrs may increase cost and production time because of additional machining; they can also damage the surface integrity. Many studies have been done to address this problem, and techniques for reducing burr size in material removal process has been the focus of the research. Nonetheless, the combined effects of the cutting edge radius and the fiber cutting angle on the burr formation have seldom been conducted, which in turn restricts to find out the mechanism of burr formation. The purpose of the present paper is to study the particular mechanism that leads to burr formation in edge trimming of CFRP laminates and investigate the effects of fiber cutting angle and cutting edge radius on burr formation. The results indicate that the burrs are prone to form in the fiber cutting angle range of 0° < χ < 90° when a large cutting edge radius of the tool is used for both milling and drilling of CFRP composites.

Hole making in natural fiber-reinforced polylactic acid laminates: An experimental investigation

Abstract: Natural fiber-reinforced composite materials are finding wide acceptability in various engineering applications. A substantial increase in the volume of production of these composites necessitates high-quality cost-effective manufacturing. Drilling of holes is an important machining operation required to ascertain the assembly operations of intricate composite products. In the present experimental investigation, natural fiber (sisal and Grewia optiva fiber)-reinforced polylactic acid-based green composite laminates were developed using hot compression through film stacking method. The drilling behavior of green composite laminates was evaluated in terms of drilling forces (thrust force and torque) and drilling-induced damage. The cutting speed, feed rate, and the drill geometry were taken as the input process parameters. It was concluded that all the three input process parameters affect the drilling behavior of green composite laminates. The drill geometry was established as an important input parameter ...

Characterization of indentation damage resistance of hybrid composite laminates using acoustic emission monitoring

Abstract: This paper focuses on the experimental investigation of impact damage resistance in hybrid composite laminates. In this case, the low velocity impact behaviour of quasi-isotropic glass/epoxy, glass/basalt/epoxy (G/B/G, B/G/B) and glass/carbon/epoxy (G/C/G, C/G/C) composite laminates was simulated by carrying out quasi-static indentation (QSI) tests with online acoustic emission (AE) monitoring. The dent depth, back surface crack size and load-deflection behaviors were examined and there is no distinct differences could be seen between low velocity impact tests and quasi-static indentation tests. The QSI tests were performed on specimens with rectangular section, of size 150 mm x 100 mm, which were loaded at the centre by a hemispherical steel indenter with 12.7 mm diameter. The indentation response was evaluated by measuring peak force, absorbed energy and linear stiffness. The residual strength of the laminates following indentation was measured by testing them under compression load in a 100 kN universal testing machine, once again with AE monitoring. AE parameters, such as amplitude, rise time, cumulative counts and cumulative energy were considered for monitoring damage progression during quasi-static indentation loading. Also other parameters linked to AE monitoring, such as the rise angle (RA) and Felicity ratio (FR) were measured for evaluating the damage resistance in each cycle of indentation. In addition, sentry function was also computed based on the combination of mechanical strain energy accumulated in the materials and of the acoustic energy propagates by fracture events made it possible to evaluate the amount of induced damage. These results showed that the combination of glass and carbon fibres in glass/carbon/epoxy (C/G/C) laminates improved their interlaminar shear strength at a level well above the other configurations tested.

The effect of hybridization on significant characteristics of jute/glass and jute/carbon-reinforced composites:

Abstract: In this study, four plied jute, carbon, E-glass fabric-reinforced and their hybridized composites are manufactured. Nine composite laminates with different stacking sequences are manufactured by vacuum infusion technique. In order to understand the structure of the composites, fiber weight and fiber volume ratios in the laminate system are initially figured out. Furthermore, void fractions of samples are calculated by using theoretical and experimental densities of the composite samples to examine the impact of amount of fiber content on the void fraction. The effect of hybridizing jute fabric-reinforced polyester composite with E-glass fabric and carbon fabric and also the effect of stacking sequence of fabric layers on the mechanical properties (tensile strength, impact strength) of composite laminates are investigated. According to the outcomes of this investigation, it is realized that incorporating high impact resistant fibers to the outer layers of the composites leads to higher impact resistance, a...

Al-Mg-Si/SiC laminated composites: Fabrication, architectural characteristics, toughness, damage tolerance, fracture mechanisms

Abstract: Different architectures of layered laminates comprising two exterior layers of Al-Mg-Si/SiC metal matrix composite and an Al1050 ductile interlayer were fabricated by means of hot roll-bonding with applying different strains of er = 39%, 51%, and 63%. For monolithics production, ceramic particulate reinforcement contents of 0, 5, 10, and 15 vol% were utilized. The aim of introducing ductile metal interlayer was to compensate the low toughness of composite layers and consequently enhancement of damage tolerance of bundled structures along with prevention of their catastrophic failure through activation of extrinsic toughening mechanism. Effects of architectural characteristics and fabrication routes on toughness and fracture behavior of materials were studied by mechanical examinations including three-point bending (3PB) and shear tests. Fracture surfaces of 3PB examination were studied by SEM while associated mechanisms and correlations with debonded area (delamination), deformability, and SiC content were disclosed and discussed. Different analyses by deriving σm were performed and the role of reinforcement content, lamination and er were defined. Deformability of fabricated materials by identifying et, ei, and ep parameters were discussed. Based on results, et trend was obeyed ep rather than ei due to more ep contribution in materials' total ductility. Toughness change by accounting initiation and propagation values were surveyed considering the combined effects of σm, elongation, and stress-bearing capacity. Eventually, it was inferred that toughness was strongly controlled by elongation alteration. In addition, the contribution of propagation was more highlighted rather than initiation for laminates. Based on fracture surfaces, in monolithic samples, fracture morphology associated with SiC concentration. Fracture morphology of exterior composite layers had not been affected by er in laminates; since interlayer fracture was strongly influenced by rolling. This was due to distinct involved failure mechanisms. Al1050 deformability was governed by delamination length as an indication of constraint level. Interfacial strength which acquired by shear test revealed that composite laminates had not been influenced by er due to the weak bondings of layers beside presence of SiC particles; however, aluminum laminates showed enhanced shear strength.

Interlaminar toughening of woven fabric carbon/epoxy composite laminates using hybrid aramid/phenoxy interleaves

Abstract: The influence of a hybrid interleaf system based on aramid and phenoxy fibres on the interlaminar toughness and damage tolerance of epoxy based carbon fibre reinforced plastic (CFRP) laminates was studied. An interleaf consisting of a non-woven aramid mat was either used on its own or in combination with epoxy-dissolvable thermoplastic phenoxy fibres. These thermoplastic phenoxy fibres are miscible with the epoxy resin and phase separate upon curing to improve ductility and toughness. Tensile properties, Mode-I fracture toughness, interlaminar shear strength (ILSS), as well as compression after impact (CAI) properties of the toughened CFRP laminates have all been characterized and analysed. Fractography was used to identify the toughening mechanisms in the CFRP laminates with different interleaf compositions. At the optimal interleaf composition, obvious synergic effects were found in terms of the overall mechanical performance of these hybrid composite laminates, including a near 150% increment in interlaminar fracture toughness in comparison to a reference CFRP laminate.

The mechanical properties of natural fibre composite laminates: A statistical study

Abstract: The use of long natural fibres (LNF) as reinforcement in composite systems for structural applications has been steadily growing in the automotive and construction industries as these materials offer sustainability benefits combined with high specific strength and stiffness. However, the performance of natural fibres has been questioned by a high variability in their mechanical properties and design data for structural reliability analysis of LNF composites are not yet available. Here, we present a statistical study of the elastic modulus, strength and failure strain of a comprehensive set of LNF composite systems. We have found that the variability of LNF laminate properties is similar to that of carbon fibre laminates. We provide recommendations to apply the statistical parameters determined here to the design of natural fibre composite structures. Our findings provide a deeper understanding of LNF composites reliability and are important for the further acceptance of these materials by the industry.