Interfacial interactions and interphases play a key role in all fiber reinforced composites. However, a clear distinction must be made between interface and interphase. Interphase becomes interface if its thickness decreases to zero. In most of the available micromechanical models the interface is considered perfect (no interphase). However, such a condition is hardly fulfilled in real composites. It is possible to find the volume of interphase by using DSC or identification of interphase region using SEM or some other sophisticated instrument techniques as it is a region created between the two main phase of a composite. All these techniques require special technical skill. In the present study attempt is made to identify the existence of the interphase region in fiber matrix composites using SEM. It was also decided to develop an equation for volume fraction and thickness of interphase by considering the composite as three-phase RVE. Developed equations of interphase volume fraction was used by considering the soft and stiff interphase parameters. Comparisons were made to study elastic behavior of fiber reinforced composites in longitudinal and transverse directions with available experimental data and published model in the literature and they are in good agreement.

The present study is aimed to investigate micromilling performance of thermoplastics with different parameters, namely laser beam absorptivity, latent heat of vaporization, laser power and cutting speed. The 25-W CO 2 (CW) laser engraving machine is used for the investigation. In total 50 different combinations of laser power and cutting speed with four categories of thermoplastics, namely poly-methyl-methacrylate, poly-propylene, acrylonitrile butadiene styrene and nylon 6, are used in this study. Experimental results suggest that laser beam absorptivity, cutting power and cutting speed are the major influencing parameters on depth of cut. Theoretical model for the prediction of depth of cut in terms of material properties, cutting power and cutting speed has been proposed. Two correction parameters have been introduced in this analysis using non-linear regression method to improve the theoretical model. Comparison has been made between prediction capabilities of theoretical model, model based on multigene genetic programming and artificial neural network. The comparison clearly indicates that all the three models provide accurate prediction of depth of cut. The details of experimentation, model development, testing and the performance comparison are presented in this paper.

Composite materials have become a necessity in recent times due to their attractive properties. The use of natural fibers is also having enough potential in the formation of feasible composites. The use of such composites in structural application as a low cost material has created a new horizon for investigation. Jute is a stiff fiber and its application in the packaging industry as a load-bearing fiber is quite common. The structure of jute is porous and it has a tendency to absorb moisture from the atmosphere, which results in its deterioration at the interface. The theoretical model for prediction of strength for such composites having porous reinforcement is developed in the present work, by considering a hexagonal fiber packing. The area occupied by voids is considered as a region of ineffectiveness for load transfer to the fibers through the matrix. The region of interphase between fiber and matrix is introduced to represent impurities in the composite. The interphase volume and property are evaluated using a modified rule of mixture (ROM). The results are also compared with FEM results obtained using licensed package ANSYS and IDEAS, with interphase properties obtained from a theoretical model. The experiments are carried out for jute— polyester composite with variation in volume fraction from 4 to 36%. The specimens are prepared at a constant pressure of 3.43 104 N/m2 by the compression molding method and special care is taken to maintain a long continuous aligned reinforcement. The strengths of the specimen are measured as per ASTM D 3039-76. The results obtained by experiments are observed to be between 0.307 and 2.41% with the theoretical model and simulated FEM results, while it is deviating 25.87% with ROM.

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Composites are becoming essential part of today’s material because they offer advantages such as low weight, corrosion resistance, high fatigue strength; faster assembly etc. composites are generating curiosity and interest all over the worlds. The attempts can be found in literature for composite materials high strength fiber and also natural fiber like jute, flax and sisal natural fibers provides data but there is need of experimental data availability for unidirectional natural fiber composite with seldom natural fiber like cotton, palm leaf etc., it can provide a feasible range of alternative materials to suitable conventional material. It was decided to carry out the systematic experimental study for the effect of volume fraction of reinforcement on longitudinal strength as well as Modulus of Elasticity (MOE) using developed mould-punch set up and testing aids. The testing is carried out as per ASTM D3039/3039M-08. The comparative assessment of obtained experimental results with literature is also carried out, which forms an important constituent of present work. It is also observed through SEM images and theoretical investigations that interface/interphase plays and important role in natural fiber composite.