Mostafa A. Hamed

Design, Manufacture and Analysis of Composite Epoxy Material with Embedded MWCNT Fibers

Abstract The weight and fuel savings offered by composite materials make them attractive not only to the military, but also to the civilian aircraft, space, and automobile industries. In these industries, bolted and riveted joints are extensively used as a primary method for structural joining. Bolted joints in composite materials have complex failure modes, and hence the demand for improving their performance exists. The main objective of this work is to improve the performance of bolted joints in composite structures by introducing nanoparticles/fibers around the expected failure zone. The literature on this issue showed shortcomings in the investigations of such materials. Most of the investigations in this field aimed to enhance the mechanical properties of epoxy materials, which cannot be used alone for high performance structural applications due to their low mechanical properties. In the present work, epoxy resin was modified with different types of nanofillers including multi walled carbon nanotubes (MWCNT). Nano-phased epoxy was used to fabricate different types of nanocomposites as well as nano-hybridized glass fiber reinforced composite laminates. Therefore, six different advanced materials were fabricated including a nanocomposite material (MWCNT/E), a quasi-isotropic nano-hybridized composite laminate (QI-GFR/MWCNT/E), a unidirectional nano-hybridized composite laminate (UD-GFR/MWCNT/E) and a control panel manufactured without nano-fillers (neat epoxy, QI-GFR/E, UD-GFR/E). The materials were characterized by tension and compression tests. The obtained properties are essential for the validation of respective finite element analysis. The results showed improvements in the tensile and compressive properties (strength and modulus) of the fabricated nanocomposites (MWCNT/E) compared with neat epoxy. The hybridized composite laminate with MWCNT showed high improvements in their mechanical properties compared to the composite laminates without nanofillers.

Design, manufacture and analysis of composite epoxy material with embedded silicon carbide (SiC) and alumina (Al2O3) nanoparticles/fibers

Abstract The main objective of the presented study is to improve the performance of composite structures by introducing nanoparticles/fibers in the epoxy resin. The literature on this issue showed shortcomings in the investigations of such materials. Most of the investigations in this field are to enhance the mechanical properties of epoxy materials, which cannot be used alone for high performance structural applications due to their low mechanical properties. In the present work, the epoxy resin was modified with these different types of nanofillers such as silicon carbide (SiC) and alumina (Al2O3) nanoparticles. The nanophased epoxy was used to fabricate different types of nanocomposites as well as nano-hybridized glass fiber reinforced composite laminates. Therefore, nine different advanced materials have been fabricated including two nanocomposite materials (SiC/E and Al2O3/E), two quasi-isotropic nano-hybridized composite laminates (QI-GFR/SiC/E and QI-GFR/Al2O3/E), two unidirectional nano-hybridized composite laminates (UD-GFR/SiC/E and UD-GFR/Al2O3/E), and three control panels manufactured without nanofillers (neat epoxy, QI-GFR/E, UD-GFR/E). The materials were characterized under tension and compression. The results showed improvements in the tensile and compressive properties (strength and modulus) of the fabricated nanocomposites (SiC/E, and Al2O3/E) compared with neat epoxy. The hybridized composite laminate with Al2O3 showed high improvements in its mechanical properties compared to the composite laminates without nanofillers. In contrast, discouraging mechanical properties were observed for SiC hybridized composite laminate. Due to the many variables studied in the present work, the literature list will be long. The investigated parameters include nanofillers, nanocomposites, nano-hybridized advanced composite laminates, mechanical properties, glass transition temperature (Tg), bolted joint parameters and sonication parameters.

Displacement Measurements Around Crack Tips by Digital and Conventional Laser Speckle

The use of optical experimental methods in fracture mechanics has become of greatiimportance since they are easily applied and give a more accurate result than conventional experimental methods. As one of these methods, Laser Speckle Photography was used to determine the displacement field around the crack-tip in a tensile C-specimen. An analytical data analysis was applied including an investigation of rigid body motion. The results were compared with the Westergaard solution and a discussion about this comparison is given. The application of digital image processing and digital data Analysis to the crack-tip problem is also discussed.

Crack problems in plane and antiplane elasticity using a singular integral equation

A numerical integration formula for the investigation of the singular integral of loakimidis for classical crack problems in plane and antiplane elasticity is developed. The method is based on a modification of the Gauss-Chebyshev quadrature and the definition of finite part integral having an algebraic sigularity of (−3/2) at the limits of integration. Once developed the procedure is applied to the determination of finite part integrals which have analytical solutions and the results are compared. Finally the integration for mula is applied to an actual crack problem and the stress intonsity factors are computed and presented.