Noorfaizal Yidris

Tensile Properties of Woven Carbon/Kevlar Reinforced Epoxy Hybrid Composite

Carbon fibres and Kevlar fibres are among the commonly used fibres in the composite industry. As carbon fibres usually known for its superior strength, its low impact resistance limited its application in the industry. However, further research found that combining the high strength fibres with more ductile fibres like Kevlar could improve the material’s impact resistance. This hybrid effect was also found to be most effective by using intra-ply woven hybrid fibres in the composite. In this work, hybrid composite material was fabricated by using woven carbon-Kevlar cloths with epoxy matrix and the mechanical properties are determined at 0 ̊, 45 ̊ and 90 ̊. The hybrid composite material was found to have highest tensile strength at 0 ̊ (carbon) direction. As the material’s strength and tensile behaviour are different at every fibre types, the selection of fibre direction of the woven cloth in loading is an important criteria in any applications.

Quasi Static Analysis of a Biocomposite Aircraft Radome

This paper investigates the quasi static compression analysis behavior of a biocomposite radome using nonlinear static modeling. Bio-based fiber is proposed to be used in aircraft radome due to its low dielectric constant. In this instance, kenaf was being utilized as the natural fiber to form a hybrid combination of fiberglass/kenaf epoxy laminates. The quasi static behavior was modeled using MDNastran SOL106 Nonlinear Static. The radome was modeled as a hemispherical shell based on Beechcraft’s radome geometric configuration. The radome is designed as a four-layered laminates with randomly oriented fiberglass and kenaf. The nonlinear compression was performed in the range of 0.01 mm to 0.49 mm with a maximum reaction force of 189 N. The radome was not displaced equally or symmetrically as the translational load applied since the shape of radome is asymmetry and the surface at the top is uneven. The increment of the forces leads to elastic local flattening deformation at the apex of the radome. Its shape influences in determining the displacement and the stress to the radome.

The Effect of Layers and Bullet Type on Impact Properties of Glass Fibre Reinforced Polymer (GFRP) Using a Single Stage Gas Gun (SSGG)

The purpose of this work is to study the best number of layer with the higher impact energy using Glass Fibre Reinforced Polymer (GFRP). The number of layers used in this study was 25, 33, 41, and 49. The impact test was performed using Single Stage Gas Gun (SSGG) for each layers given above with different bullets such as blunt, hemispherical and conical bullets. The gas gun pressure was set to 5, 10, 15 and 20 bar. All of the signals captured from the impact test were recorded using a ballistic data acquisition system. The correlation between the impact energy in terms of number of layer and type of bullet from this test are presented and discussed. It can be summarise that as the number of layer increases, impact energy also increases. In addition, from the results, it was observed that by using different types of bullets (blunt, hemispherical, conical), there is only a slight difference in values of energy absorbed by the specimen.

Impact Damage Analysis for Glass Reinforced Epoxy Laminated Plates Using Single Stage Gas Gun

The overall purpose of the research is to investigate the effect of thickness on fiberglass reinforced epoxy laminates. In this study, simplified coupon specimens made from Epoxy/C-glass (200 g/m2) and Epoxy/C-glass (600 g/m2) with different thicknesses were used. To perform the high velocity impact tests (250 m/s), an instrumented single stage gas gun was used. The impacted specimens were examined to determine the extent of damages induced around the impacted point. For the projectiles velocity of 250 m/s, it was found that Epoxy/C-glass 200 g/m2 was able to absorb 21.5 J of energy at the thickness of 12 mm, while Epoxy/C-glass 600 g/m2 was able to absorb 96.1 J of energy at 10 mm thickness. Both the fibreglasses compute damage in terms of slight matrix breakage and cracking. A general trend was observed on the overall ballistic test results, which indicated that, as the plate thickness continue to increase, the damage at the lower skin decreases and could not be seen.

Vacuum infusion method for woven carbon/Kevlar reinforced hybrid composite

The vacuum assisted resin transfer moulding (VaRTM) or Vacuum Infusion (VI) is one of the fabrication methods used for composite materials. Compared to other methods, this process costs lower than using prepregs because it does not need to use the autoclave to cure. Moreover, composites fabricated using this VI method exhibit superior mechanical properties than those made through hand layup process. In this study, the VI method is used in fabricating woven carbon/Kevlar fibre cloth with epoxy matrix. This paper reports the detailed methods on fabricating the hybrid composite using VI process and several precautions that need to be taken to avoid any damage to the properties of the composite material. The result highlights that the successfully fabricated composite has approximately 60% of fibres weight fraction. Since the composites produced by the VI process have a higher fibre percentage, this process should be considered for composites used in applications that are susceptible to the conditions where the fibres need to be the dominant element such as in tension loading.

Local-Overall Flexural Interaction of Pinned-Ended Thin-Walled I-Section Columns

The structural performance of thin-walled compression members are subject to the effects of local buckling, interaction between buckling modes, loading end conditions and material yielding and that due to these effects the compressive carrying capability of thin-walled members can be significantly diminished. This paper employs the finite element simulation to examine the local-overall flexural interaction response of pinned-ended thin-walled I-section columns that covers the complete compressed loading history from the onset of elastic local buckling through the nonlinear elastic and elasto-plastic post-buckling interactive phases of behaviour to final collapse and unloading. A detailed account of the growth and redistribution of stresses on the surfaces is given in the paper. Pinned-ended conditions means, of course, simply supported conditions at the column ends with respect to global rotations and the ends of the constituent plates of the cross-section can be treated as either locally rotationally constrained or locally rotationally free. The numerical simulations take into account the influence of material nonlinearity and geometrical imperfections on the compressive ultimate failures of the sections, however, the study is limited to the interaction of local buckling with overall flexural bending as well as locally rotationally constrained condition. This paper shows that the ultimate failure of the columns is related with yielding on the compression sides of the outer surfaces of the section walls at the web, flanges and section junctions mostly located along the length of the columns.

High Velocity Impact Test on Glass Fibre Reinforced Polymer (GFRP) Using a Single Stage Gas Gun (SSGG) - An Experimental Based Approach

The aim of this work is to study the effect of thickness and type of bullet in impact test on structures made from a composite material. The composite material used in this study was Glass Fibre Reinforced Polymer (GFRP). This material was fabricated to produce laminated plate specimens with dimension of 100 mm × 100 mm and 6, 8, 10, and 12 mm thickness. The impact test was performed using a Single Stage Gas Gun (SSGG) with blunt, hemispherical, and conical types of bullets. The gas gun pressure was set to 5, 10, 15 and 20 bar. In the tests, gas gun pressure, bullet type and specimen thickness were varied to ascertain the influence of these parameters on the materials response. The relation between impact force with gas pressure, type of bullets and specimens thickness are presented and discussed. The best thickness for GFRP was identified according to the impact results. From the impact tests conducted, it was found that at the same amount of pressure, the higher the thickness, the bigger the impact force because as the specimen thickness increases, the amount of impact force absorbed by the specimen is higher.

Damage Identification and Classification in CFRP Laminates – A SEM Based Study

There are two main factors that need to be considered as important parameters that affect the response of a structure: kinetic energy (E=1/2mv^2 ) and potential energy (E=mgh). For instance, if one has a large mass but with lower height, the amount of damage produced on the structure may not be the same as if one has a smaller mass with a higher dropping height although the potential energies will be the same. Therefore, before performing tests on the structures, the selection for the appropriate test apparatus and test procedures must be made carefully to ensure that the test conditions are similar to the actual impact conditions. In this present work, a study was conducted to fully understand the damage progression and growth, not only should the impacted surface be evaluated, but also the cross sectional defects on the impacted area must be accurately identified and examined. In this current work, the impacted test specimens will be observed at different magnifications to distinguish the types of failure mechanisms using Scanning Electron Microscopy (SEM). To perform this, the impacted specimens will be examined by two different approaches: surface defects and cross-sectional defects. This allows the failure mechanism to be observed more precisely.

Damage Classification in CFRP Laminates Using Principal Component Analysis (PCA) Approach

Signal processing is an important element used for identifying damage in any SHM-related application. The method here is used to extract features from the use of different types of sensors, of which there are many. The responses from the sensors are also interpreted to classify the location and severity of the damage. This paper describes the signal processing approaches used for detecting the impact locations and monitoring the responses of impact damage. Further explanations are also given on the most widely-used software tools for damage detection and identification implemented throughout this research work. A brief introduction to these signal processing tools, together with some previous work related to impact damage detection, are presented and discussed in this paper.

Failure Mechanics of Uniformly Compressed Thin-Walled Box-Section Struts

It is well known that the structural performance of thin-walled compression members is subject to the effects of local buckling and material yielding. Due to these effects, the compressive carrying capability of short strut members can be significantly reduced. This paper employs finite element simulation to examine the post-buckled response of thin-walled box-sections that covers complete loading history of the compression struts from the onset of elastic local buckling through the nonlinear elastic and elasto-plastic post-buckling phases of behaviour up to final collapse and unloading. A detailed account of the growth and redistribution of stresses on the surfaces is given in the paper. The results from finite element simulations are shown to compare well with the analytical method of analysis.