Compressive mechanical behaviour of E-glass/polyester composite laminates tailored with a thermoplastic preforming binder

Compressive mechanical behaviour and failure modes of E (electrical)-glass/polyester composite laminates tailored with a thermoplastic preforming polyester binder were investigated under ply-lay up and in-plane loading directions. Fiber preforms with various amount of the binder were consolidated under heat and pressure. The preform compaction experiments were performed by applying compressive pressure to the preforms, and the average thickness as a function of pressure was measured. It was found that the highest compaction of the preforms and therefore the highest fiber volume fraction can be obtained with 3 wt.% of the binder. Further increase of the amount of binder decreases the degree of compaction. Composite panels were fabricated by vacuum-assisted resin transfer molding using fabric preforms with various binder concentrations. The present investigation reveals that there are considerable effects of the binder on the compressive mechanical behaviour of the composites. Compression testing of the composites showed that the average strength values are in the range of 400-600 and 150-300 MPa for ply-lay up and in-plane directions, respectively. Also, both the strength and modulus values increase up to 3 wt.% of the binder, and these values decrease with further addition of the binder. Scanning electron microscopy showed that failure modes of the composites are altered significantly by the presence of the binder. Furthermore, the interaction between the binder and the reacting resin was followed to determine the extent of the binder dissolution and its effects on the viscosity of the resin and the mechanical behaviour of the matrix polymer. The results indicate that there is a partial dissolution of the binder within the matrix resin.Izmir Institute of Technology of Turkey under contract 2002 IYTE 06 projec

Modification of carbon fibre/epoxy composites by polyvinyl alcohol (PVA) based electrospun nanofibres

In this study, the effects of modifying interlaminar region of unidirectional carbon fibre/epoxy composites by the incorporation of electrospun polyvinyl alcohol (PVA) nanofibres were investigated. PVA nanofibres were directly deposited onto the carbon fabrics by electrospinning method to improve mechanical performance of those composites. The features of the electrospun nanofibres were characterized by microscopy techniques. The unidirectional carbon fibre/epoxy composite laminates with/without PVA nanofibre interlayers were manufactured by vacuum-infusion technique in a [0]4 configuration. Tensile, three-point bending, compression, Charpy-impact and Mode-I fracture toughness tests (Double Cantilever Beam (DCB)) were carried out in accordance with ASTM standards to evaluate mechanical performance of the composites. Scanning electron microscopy (SEM) observations were made on the specimens to evaluate microstructural features. It was observed that the carbon fabrics were successfully coated with a thin layer of PVA nanofibres by electrospinning technique. The results showed that P VA nanofibres improve the mechanical properties of unidirectional carbon/epoxy composite laminates when subjected to in-plane loading. On the other hand, PVA nanofibres slightly reduced the mode-I fracture toughness values although they led to more stable crack propagation.Scientific Research Projects of Izmir Institute of Technology with Project no.2015IYTE3

Silver and zinc oxide based nano powders and their polymer based nanocomposites for antibacterial application

The microorganisms cause some serious infections. It is a requirement and a necessity to create sterile fields such as hospital, food processing and public places. Composite stones are one of the main building materials that have been used in buildings due to their high resistant to abrasives, chemicals and mechanical impacts. The silver (Ag), zinc oxide (ZnO), and also nano Ag loaded ZnO (ZnO/Ag) nanopowders have demonsrated capability for the preparation of the polymer based antibacterial nanocomposite materials. In this study, Ag/polyester, ZnO/polyester, Ag/ZnO/polyester and their nanocomposites were prepared and tested with various weight fractions. The microstructure and surface morphology of these nanocomposites were investigated by means of scanning electron microscopy (SEM/EDX). The thermal properties were analyzed by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Finally, The antibacterial properties of nanocomposites were analyzed against gram positive (Bacillus subtilis) and gram negative bacteria (Escherichia coli).AKG Yalıtım and Ministry of Science and Technology of Industry, Repuplic of Turkey (SAN-TEZ, Project No. 1209-STZ.2012-1

Effect of adhesive on the strengthening of aluminum foam-filled circular tubes

Studies of the crushing behavior of closed-cell, aluminum foam-filled aluminum and steel tubes have shown an interaction effect between tubewall and foam filler [1, 2, 3]. The crushing loads of foam-filled tubes are, therefore, found to be higher than the sum of the crushing loads of foam (alone) and tube (alone) mainly due to this effect. Santosa et al. [1], based on FEM results, proposed the following equation for the average crushing load of foam-filled square tubes of length b

Compression behavior of Al-foam filled compesite/aluminum hybrid tubes

Tüp sarma yöntemiyle hazırlanan ince duyarlı cam fiber takviyeli polyester kompozit/Alüminyum ikili tüplerin ezilme davranışları statik basma hızlarında (25 mm/dak) deneysel incelenmiştir. Tüplerde dolgu malzemesi olarak kullanılan Al köpüğün ezilme yük değerlerine ve deformasyon mekanizmalarına etkileri belirlenmiştir.The quas-static (25mm/min) crushing behayior of thin walled rolled tubes of glass fiber reinforced polyester composite/Aluminum hybrid tubes were investigated experimentlly. The effects of AI-foam filler on the crushing loads and deformation mechanisms were determined

Effect of blending conditions on the properties of EPDM/organoclay nanocomposites

17th International Conference on Composite Materials, ICCM-17; Edinburgh; United Kingdom; 27 July 2009 through 31 July 2009The effects of blending conditions on the microstructural and mechanical properties of EPDM / organo modified montmorillonite (OMMT) nanocomposites at various clay loadings were investigated. The effects of the processing conditions were manifested in both the morphology and mechanical properties, which showed significant increase when optimized process conditions are applied.TÜBİTAK-MAG project 106M15

Porous nanocomposites prepared from layered clay and PMMA [poly(methyl methacrylate)]

The aim of the present work is the preparation of PMMA based porous nanocomposites that contain clay (montmorillonite, MMT) platelets as reinforcements within the cell walls of the porous structure. To render the clay layers organophilic, MMT was surface treated by an ion exchange reaction between interlayer cations of the clay and ammonium ions of a surfactant. Clay/PMMA based porous nanocomposites were prepared by polymerization of water-in-oil emulsions with and without clay addition. The microstructure and compressive mechanical behavior of the nanocomposites were investigated. The results of mechanical tests showed that the porous systems with the addition of 1 wt.% of organoclay (OMMT) exhibited a 90% and 50% increase of collapse stress and elastic modulus values, respectively, as compared to neat porous PMMA

Polymethyl methacrylate based open-cell porous plastics for high-pressure ceramic casting

The aim of the present study is to investigate the microstructure-property relation in polymethyl methacrylate (PMMA)-based porous mould materials used for high-pressure casting of ceramic articles. For this purpose, porous plastic materials were produced by the polymerization of water-in-oil emulsions with various compositions of emulsion constituents and particle sizes of the filler PMMA beads. Pore morphology, porosity and water permeability of the materials were measured. The compressive stress-strain behavior, collapse stress and elastic modulus values of the macroporous materials were determined by performing compressive mechanical testing. Fracture toughness values of the materials were also measured using the single-edge notched bending method. The results showed that the concentration of emulsion constituents and PMMA bead sizes has significant effects on the pore morphology, porosity, water permeability and mechanical properties of the porous plastics

Mechanical and energy absorption behaviors of metal/polymer layered sandwich structures

This article considers the sandwich structures with aluminium (Al) foams of various thicknesses in conjunction with skins composed of fibre-metal laminates (FML). The FMLs with Al sheet and glass fiber reinforced polypropylene (GFPP) composites were integrated with Al foam for composing the sandwich panels. The FML-foam sandwich systems were manufactured by hot pressing in a mold at 200°C under 1.5 MPa pressure. The bonding between the components of the sandwich was achieved by various surface modification techniques, i.e., silane surface treatment, PP adhesive film additition, and their combination. The Al sheet/Al foam sandwiches were also prepared by bonding the components with an epoxy adhesive for comparing the effect of GFPP on the mechanical performance of the sandwich structures. The energy absorption capacities together with compressive mechanical behavior of both Al foams and FML-foam sandwich systems were evaluated by flatwise compression tests. Experiments were performed on samples of varying foam thicknesses.TÜBİTAK (107A015

Effect of polyamide-6,6 (PA 66) nonwoven veils on the mechanical performance of carbon fiber/epoxy composites

In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness