Mohamed S. Aly-Hassan

Mechanical Properties of Natural Jute Fabric/Jute Mat Fiber Reinforced Polymer Matrix Hybrid Composites

Recycled needle punched jute fiber mats as a first natural fiber reinforcement system and these jute mats used as a core needle punched with recycled jute fabric cloths as skin layers as a second natural fiber reinforcement system were used for unsaturated polyester matrix composites via modifying the hand lay-up technique with resin preimpregnation into the jute fiber in vacuum. The effect of skin jute fabric on the tensile and bending properties of jute mat composites was investigated for different fiber weight contents. Moreover, the notch sensitivity of these composites was also compared by using the characteristic distance d o calculated by Finite Element Method (FEM). The results showed that the tensile and flexural properties of jute mat composites increased by increasing the fiber weight content and by adding the jute fabric as skin layers. On the other hand, by adding the skins, the characteristic distance decreased and, therefore, the notch sensitivity of the composites increased. The fracture behavior investigated by SEM showed that extensive fiber pull-out mechanism was revealed at the tension side of jute mat composites under the bending load and by adding the jute cloth, the failure mode of jute mat was changed to fiber bridge mechanism.

Natural Fiber Composites

1 Department of Advanced Fibro-Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-Ku, Kyoto 606-8585, Japan 2 Industrial Materials Institute, National Research Council of Canada, 75 de Mortagne Boulevard Boucherville, QC, Canada J4B 6Y4 3Department of Plant Agriculture, University of Guelph, 50 Stone Road. E., Guelph, ON, Canada N1G 2W1 4 School of Aerospace Engineering and Applied Mechanics, Tongji University, 1239 Siping Road, Shanghai, China

SQUID NDE on Braided Carbon Fiber Reinforced Polymers With Middle-End Fibers Under Step-by-Step Tensile Loading

Three braided carbon fiber reinforced polymer (CFRP) samples with different middle-end fibers were fabricated. Damage mechanisms of the samples under step-by-step tensile loading were investigated using a nondestructive evaluation (NDE) method utilizing a high-temperature superconducting SQUID gradiometer. Commercial carbon fibers UTS50 were used for base braided fabrics, while UTS50, XN05 with higher electric resistivity, and XN60 with lower resistivity were used for the middle-end fibers. In the step-by-step tensile tests, observation of surfaces and measurements of stress-strain curves of the samples were carried out. At certain damage stages, the SQUID NDE method, which visualizes flowing currents in the samples, were applied to detect damage and assess the integrity of the carbon fiber yarns in the samples after removal of the loading. As a result, different damage mechanisms and stress-strain curves were observed and measured. From the results using the SQUID NDE method, it was shown that the current distributions in the samples were determined by the middle-end fibers at respective virgin stages, and the middle-end fibers XN60 were broken in some parts of the sample at its final fracture.

Jute Fiber Reinforced Polymeric Composites With Flexible Interphase

In this research, the flexible interphase concept was introduced to enhance the poor mechanical properties of jute fiber reinforced unsaturated polyester matrix composites. The jute cloth reinforcement was obtained from recycled coffee bags. These jute cloths after washing by water and drying were soaked in mixture of Polybutadiene Epoxydied as flexible resin and acetone for 10 seconds. Several mixtures consist of 0, 2, 3.5, 5 and 8 wt% of Polybutadiene Epoxydied and 100, 98, 96.5, 95 and 92 wt% of acetone, respectively, to form flexible interface around the jute fibers. Jute cloth reinforced unsaturated polyester matrix composites with different flexible interphase incremental weight ((Wa-Wb)/Wb) ratios were fabricated by hand lay-up method and examined by a series of mechanical tests. The mechanical testing including tensile, bending, Izod strength impact and drop impact was carried out for these composites to evaluate the effect of the flexible interphase and acetone on the jute cloth composites. The flexible interphase succeed to control the mechanical properties of jute fiber reinforced unsaturated polyester matrix composites. Inserting flexible interphase between unsaturated polyester matrix and jute fibers leads to smooth fluctuation, less matrix cracking, in the second part after the knee point of each stress-strain curve as exhibited in composites with higher flexible interphase incremental weight ratio. This means not only the brittle matrix but also interface/interphase dominates the multiple matrix cracking behavior in jute cloth reinforced unsaturated polyester matrix composites. Inserting flexible interphase between unsaturated polyester matrix and jute fibers leads to less number of multiple cracking as shown in the second portion of flexural stress-displacement curve. This means the number of multiple cracking are dominated by flexible interphase. The impact strength of jute cloth reinforced unsaturated polyester matrix composites with flexible interphase incremental weight ratio of 1.2% is higher than that of jute cloth reinforced unsaturated polyester matrix composites without flexible interphase by about 45%. The impact energy after maximum load has increased significantly with all flexible interphase incremental weight ratios.Copyright

Tensile and Bending Properties of Jute Fiber Mat Reinforced Unsaturated Polyester Matrix Composites

Jute fiber mat reinforced unsaturated polyester matrix composites having different fiber weight contents (11, 22, 32 wt%) were fabricated by modifying the hand lay-up technique with resin pre-impregnation into the jute mats in the vacuum. Tension and three-point bending tests were carried out to evaluate the effect of fiber contents on these mechanical properties of above-mentioned composites. The results showed that as the fiber weight content increases, tensile strength and modulus increase and the improvement had occurred at 22 wt% of fiber weight content with respect to that of neat resin. As the fiber weight content increases, flexural strength and modulus increase and the improvement had occurred at 11 and 32 wt% fiber contents for the flexural modulus and strength respectively compared to those of neat resin. Fiber pull out mechanism is the failure mode revealed at the fracture surfaces under tensile loading as well as at tension side of composites under bending loading.Copyright

A new perspective in multifunctional composite materials

In this chapter, two examples of our innovative multifunctional composites will be briefly introduced. These innovative composites can contribute toward advancing some new applications of composites through saving energy, efficient management of the thermal energy, and the mitigation of CO2 emissions due to the multifunctionality. The first example is by adding a novel property to composites for developing advanced energy composite materials entitled “Innovative Multifunctional Carbon/Carbon Composites.” This new generation of materials has a unique ability to direct or guide most of the transferred heat by conduction to the desired direction or area of the thermal structure via changing the in-plane thermal conductivity of the material functionally. The second example of our innovative multifunctional composites is for developing smart sandwich composite structures entitled “Innovative Multifunctional Sandwich Composite Structure as Roofs in Snowfall Regions.” These smart lightweight roofs will be able to remove automatically the dropped snow/rain on the roof. Those two innovative multifunctional composites are expected to have a serious impact on the development of new applications of composites where low weight, small size, and high performance are required.

Visualization of flowing current in braided carbon fiber reinforced plastics using SQUID gradiometer for nondestructive evaluation

In this paper, visualization of flowing current in various braided carbon fiber reinforced plastics (CFRPs) was demonstrated using high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) gradiometer, in order to study electrical properties and integrity of the braided CFRP samples. Step-by-step tensile loading was also applied to the samples, in order to study their mechanical properties and destructive mechanism. Experimental results indicated that the addition of carbon nano fibers and middle-end carbon fiber bundles attributed to modify not only the mechanical properties, but also the electrical properties of the samples. Combining the results by the both methods, a scenario of the destructive mechanism of one sample was estimated.

Assessment of Fracture Behavior of Flat Braided CFRP Composites Under Tensile Loading With Assistance of SQUID Technique

The goal of this research is to provide a sufficient understanding for the damage mechanism of ±45° flat braided CFRP composites under tensile loading based on in-situ macroscopic observations of surface cracking and off-line measurements for the state-of-fibers by Superconducting Quantum Interference Device (SQUID) technique to analyze the effect of the continuously oriented of all braided fiber bundles on the tensile and in-plane shear properties. SQUID technique displays an effective capability in inspection the state-of-fiber failure, whereas the in-situ surface macroscopic observation technique is very useful in observing the surface matrix cracking at different stages of damage. The damage mechanism of uncut-edges and cut-edges of ±45° flat braided CFRP composites are identified adequately by the above-mentioned experimental procedure. The cut-edges ±45° flat braided CFRP composites exhibit a pure shear damage mechanism associated with large shear deformation and no significant fiber failure, while the uncut-edges ±45° flat braided CFRP composites exhibit a slight fiber scissoring mechanism followed by a partially fiber failure. The enhancement of the tensile and in-plane strengths of the uncut-edges ±45° flat braided CFRP composites by about 60% higher than those of the cut-edges ±45° flat braided CFRP composites achieves not only by the effect of the continuously oriented carbon fibers at the edges but also by the effect of re-orientation of braiding fiber bundles with smaller angle than the original ±45° braiding angle of the fabricated composites, or so called fiber scissoring mechanism in composites.Copyright