MECHANICAL CHARACTERIZATION OF E-GLASS FIBER REINFORCED POLYESTER/ MWCNTS NANOCOMPOSITES

Mechanical properties of polyester/glass fiber reinforced by multiwalled carbon nanotubes (MWCNTs) were studied. MWCNTs nano particles are mixed within resin in various weight fractions of 0.1, 0.2, 0.4 and 0.6 % using sonication. E-Glass fiber (chopped strand mat) is used in various weight fractions within the composite like 80/20 wt%, 70/30 wt%, 50/50 wt% to fabricate polyester/CSM/MWCNTs composites. The effect of the addition of MWCNTs nanoparticles on the mechanical characteristics such as hardness and tensile strength were investigated. The effect of various E-glass fiber chopped strand mat (CSM) wt.% reinforcement is also investigated. A scanning electron microscope (SEM) was used to show the nanocomposites morphological properties such as reinforcement orientation and the bonding between matrix and fiber. It was found that the addition of 0.4 wt% MWCNTs improves the mechanical properties of composites, especially the 50 wt% polyester / 50 wt% CSM composite. The tensile strength improved by 39.8%, and the hardness improved by 38%. ABSTRAK: Ciri-ciri mekanikal bagi poliester / gelas fiber diperkukuh dengan dinding berbilang karbon nanotiub (MWCNTs) dikaji. Partikel nano MWCNT telah dicampur ke dalam resin pelbagai berat pada pecahan 0.1, 0.2, 0.4 dan 0.6 % menggunakan sonikasi. Gentian Kaca-E (potongan lembaran) telah digunakan dalam pelbagai pecahan berat dalam komposit 80/20 wt%, 70/30 wt%, 50/50 wt% bagi menghasilkan komposit poliester/CSM/MWCNT. Kesan penambahan nanopartikel MWCNT pada ciri-ciri mekanikal seperti kekerasan dan kekuatan tensil diuji. Kesan pelbagai gentian Kaca-E (potongan lembaran) (CSM) wt.% bersama agen pengukuh turut dikaji. Pengimbas Mikroskop Elektron (SEM) digunakan bagi menilai ciri-ciri morfologi komposit nano seperti orientasi pengukuh dan ikatan antara matrik dan gentian. Dapatan kajian menunjukkan dengan penambahan sebanyak 0.4 wt% MWCNT dapat memperbaiki ciri-ciri mekanikal komposit terutama komposit campuran (50 wt% polyester / 50 wt% CSM). Ketahanan tensil meningkat sebanyak 39.8%, dan kekerasan telah bertambah sebanyak 38%.

The Effect of High Glass Fiber Content and Reinforcement Combination on Pulse-Echo Ultrasonic Measurement of Composite Ship Structures

Ship structures made of glass fiber-reinforced polymer (GFRP) composite laminates are considerably thicker than aircraft and automobile structures and more likely to contain voids. The production characteristics of such composite laminates were investigated in this study by ultrasonic nondestructive evaluation (NDE). The laminate samples were produced from E-glass chopped strand mat (CSM) and woven roving (WR) fabrics with different glass fiber contents of 30–70%. Approximately 300 pulse-echo ultrasonic A-scans were performed on each sample. The laminate samples produced from only CSM tended to contain more voids compared with those produced from a combination of CSM and WR, resulting in the relative density of the former being lower than the design value, particularly for high glass fiber contents of ≥50%. The velocity of the ultrasonic waves through the CSM-only laminates was also lower for higher glass fiber contents, whereas it steadily increased for combined CSM–WR laminates. Burn-off tests of the laminates further revealed that the fabric configuration of the combined CSM–WR laminates was of higher quality, prevented the formation of voids, and improved inter-layer bonding. These findings indicate that combined CSM–WR laminates should be used to achieve more accurate ultrasonic NDE of GFRP composite structures.

Mechanical Properties of GFRPs Exposed to Tensile, Compression and Tensile–Tensile Cyclic Tests

Currently there are many applications for the use of composites reinforced with fiberglass mat and fabrics with polyester resin: automotive, aerospace, construction of wind turbines blades, sanitary ware, furniture, etc. The structures made of composites have a complex geometry, can be simultaneously subjected to tensile–compression, shear, bending and torsion. In this paper we analyzed the mechanical properties of a polyester composite material reinforced with glass fiber (denoted GFRP) of which were carried out two types of samples: The former contains four layers of plain fabric (GFRP-RT500) and the second type contains three layers of chopped strand mat (GFRP-MAT450). The samples were subjected to tensile, compression and tensile–tensile cyclic loading. The results highlight the differences between the two types of GFRP in terms of initial elastic modulus, post yield stiffness and viscoelastic behavior under cyclic loading. Thus, it was observed that the value of the modulus of elasticity and the value of ultimate tensile stress are approximately twice higher in the case of GFRP-RT500 than for the composite reinforced with short fibers type GFRP-MAT450. The tensile–tensile cyclic test highlights that the short glass fiber-reinforced composite broke after the first stress cycle, compared to the fabric-reinforced composite in which rupture occurred after 15 stress cycles. The elasticity modulus of GFRP-RT500 decreased by 13% for the applied loading with the speed of 1 mm/min and by 15% for a loading speed of 20 mm/min.

STUDI PERBANDINGAN KEKUATAN TARIK KOMPOSIT BERBAHAN CHOPPED STRAND MAT METODE HAND LAY-UP DAN VACUUM ASSISTED RESIN INFUSION

Sifat fisik dan mekanik sebuah produk komposit ditentukan oleh beberapa faktor yang diantaranya adalah proses manufaktur dan jenis material penyusun. Material penguat dan matriks yang memiliki kekuatan tarik tinggi akan berpeluang menghasilkan komposit yang memiliki kekuatan tarik yang tinggi pula dan begitupun sebaliknya. Pada penelitian ini dilakukan perbandingan pembuatan komposit dengan proses manufaktur yang sederhana selain hand lay-up, yaitu dengan Vacuum Assisted Resin Infusion. Penelitian ini menggunakan material yang paling murah dan mudah ditemukan di pasaran. Hasil pengujian kekuatan tarik komposit hasil proses manufaktur hand lay-up sebesar 2.22 MPa sedangkan kekuatan tarik komposit hasil proses manufaktur Vacuum Assisted Resin Infusion adalah 55.54 MPa. Hal tersebut terjadi dikarenakan tingginya fraksi volume void dari komposit yang dibuat dengan proses manufaktur hand lay-up yang disebabkan oleh gerakan dua arah rol pada saat proses manufaktur. Hal ini diharapkan dapat menjadi referensi bagi para pelaku usaha kecil dan menengah di bidang pembuatan produk komposit. Dengan menggunakan metode Vacuum Assisted Resin Infusion kekuatan tarik dapat ditingkatkan secara signifikan namun metode wet hand lay up mampu menghasilkan komposit dengan elongasi yang lebih tinggi.

Characterization and numerical simulation of laminated glass fiber–polyester composites for a prosthetic running blade

The objective of this work was to explore different types of deformations (buckling, bending, and relaxation) on the properties of laminated composites based on polyester as the matrix and glass fiber in two forms: woven and chopped strand mat. The specimens were produced with the same thickness but with different number of ply. Also, a thin gelcoat based on clay particles was applied on the chopped strand mat samples to get a third series. The results showed that using the same thickness, the mechanical properties, especially in terms of bending and buckling, are influenced by the layers’ number. Furthermore, a sports application, which is the main objective of this work, is presented as an applied investigation for a leg prosthesis. Three different running blades “Flex-foot Cheetah” were manufactured to be experimentally and numerically (ANSYS ACP software) characterized to simulate real conditions. The results showed a good agreement between the experimental and numerical values in terms of total displacement, which is around 50 mm, the produced blade has been tested in quasi-static and dynamic compression, and results showed that the relaxation behavior depends on the structure design and the used materials.

Hybrid-modelling of Mechanical Properties and Thermo-mechanical Behaviour of Chopped Strand Mat Reinforced Thermoset Composites

The concern of this paper is to develop simple workshop application models for predicting the mechanical properties and the evaluation of the thermo-mechanical behaviour of chopped strand fibre-mat reinforced thermoset composites. A hybrid of empirical and strength of materials approach was used at macro- and micro-mechanics levels to model the random fibres which were treated as simple bars within the mat preform and the resulting composite material. The model was validated experimentally by testing wet lay-up produced samples with varying fibre volume fractions and they were found to agree well. The toughness modulus of the composite was also modeled using the secant modulus obtained from the sample’s stress – strain curves of uniform material composites produced at different temperature histories. The toughness modulus determined using the new model was compared with that obtained using the area under the same stress – strain curve computed by Simpson’s rule and the results agreed very well.

Influence of nanoclays on water uptake and flexural strength of glass–polyester composites

Fiber-reinforced polyester composites have received significant attention in a variety of applications due to their considerable potential due to such characteristics as high strength, stiffness, and modulus. However, one of the most important concerns about polymeric composites is their sensitivity to moisture attack. This work has been conducted to investigate the effects of nanoclay addition on reinforcing glass/polyester composites against water absorption and the resultant deterioration of flexural strength. Therefore, chopped strand mat and woven fiberglass polyester specimens were fabricated by using the hand lay-up technique with varying weight percentages of Cloisite 20A nanoclays (0, 1.5, and 3 wt%) and immersion in water for a time duration of 21 days. The specimens were weighed for the water absorption test. The results showed a remarkable drop in water absorption of the composite samples with the increase of nanoclay content. Moreover, although all the pure and nanocomposite specimens underwent degradation in flexural strength due to the water absorption, the strength was found to significantly increase with increasing the percentage of nanoclay at all immersion periods. The experimental results were confirmed by scanning electron microscopy (SEM). SEM images indicated that the presence of nanoclay protected the fiber/matrix interfaces.

Effect of Fibers Configuration and Thickness on Tensile Behavior of GFRP Laminates Exposed to Harsh Environment

The present study indicates the importance of using glass fiber reinforced polymer (GFRP) laminates with appropriate thickness and fibers orientation when exposed to harsh environmental conditions. The effect of different environmental conditions on tensile properties of different GFRP laminates is investigated. Laminates were exposed to three environmental conditions: (1) Freeze/thaw cycles without the presence of moisture, (2) freeze/thaw cycles with the presence of moisture and (3) UV radiation and water vapor condensation cycles. The effect of fiber configuration and laminate thickness were investigated by considering three types of fiber arrangement: (1) Continuous unidirectional, (2) continuous woven and (3) chopped strand mat and two thicknesses (2 and 5 mm). Microstructure and tensile properties of the laminates after exposure to different periods of conditioning (0, 750, 1250 and 2000 h) were studied using SEM and tensile tests. Statistical analyses were used to quantify the obtained results and propose prediction models. The results showed that the condition comprising UV radiation and moisture condition was the most aggressive, while dry freeze/thaw environment was the least. Furthermore, the laminates with chopped strand mat and continuous unidirectional fibers respectively experienced the highest and the lowest reductions properties in all environmental conditions. The maximum reductions in tensile strength for chopped strand mat laminates were about 7%, 32%, and 42% in the dry freeze/thaw, wet freeze/thaw and UV with moisture environments, respectively. The corresponding decreases in the tensile strength for unidirectional laminates were negligible, 17% and 23%, whereas those for the woven laminates were and 7%, 24%, and 34%.