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Byline: Naresh Bhatnagar, Mukesh Kumar Jalutharia, Inderdeep Singh Composite materials are finding substantial application in the automotive and the construction sector. The primary processing of these materials is quite developed whereas, the secondary processing, that is machining is still in the nascent stage. The cutting forces directly influence the machining induced damage. The forces can be measured and the resulting damage thereby can be controlled. The present research endeavour is an attempt to analyse the force signals during drilling of polymeric matrix composites and to propose models for predicting the cutting forces. A 10% variation was found in the predicted and experimental values.

Byline: G. Venu Gopala Rao, Puneet Mahajan, Naresh Bhatnagar Orthogonal machining of unidirectional carbon fibre reinforced plastic composites is simulated using finite element method based on experiments. The cutting forces during orthogonal machining were studied both experimentally and numerically for a range of fibre orientations, depths of cut and tool rake angles. The failure of fibre is found to be a combination of bending and crushing for higher fibre orientation, while the bending effect becomes more significant for lower fibre orientation. The cutting forces mainly varies with fibre orientation and depth of cut. The cutting and thrust forces predicted by FE simulations matched well with the experimental results.

We consider a host of regular lattice architectures and present analytical and computational approaches to derive the structure-property relationship for such structured material by exploiting the translational periodicity of infinite lattices. Two specific geometries - the so-called hexagonal honeycomb and the woodpile lattice - are studied analytically and computationally. The elasto-plastic response in the case of the first, and the bending response of lattice beams for the second, is considered. These specific problems have been motivated by biostructures relevant to medical implants and scaffolds. We also present novel methods to additively manufacture such lattices. When possible, the response is obtained as an analytical function of the microstructural parameters described by the geometry of the repetitive elements of the lattice, such as characteristic diameter, length, or thickness. Alternative methods of manufacturing materials with random internal architectures are also presented. The relative strengths and weaknesses of the two classes of materials with respect to analysis and manufacture are discussed. [ABSTRACT FROM AUTHOR]

This paper presented an experimental and numerical investigation on the low velocity impact response of thermoplastic hybrid composites reinforced with Kevlar/basalt fabrics. Two hybrid and one Kevlar homogeneous composite laminates were manufactured with polypropylene as a resin. In the hybrid composites, one hybrid composite (H-1) was manufactured with alternate stacking of four layers of basalt and four layers of Kevlar and the second hybrid composite (H-2) was manufactured with four Kevlar layers on front face and four basalt layers on back face. Low velocity impact tests were performed using a drop-weight impact equipment at three different energies (25J, 50J and 75J). Among the two hybrid composites H-1 hybrid composite exhibited 15.58-20.79% and 13.47-20.47% improvement in the peak force and energy absorption, respectively, than the H-2 hybrid composite. The peak force and energy absorption of Kevlar homogeneous composite was also improved by 10.07-14.37% and 5.38-11.29%, respectively, due to hybridization. A three dimensional (3D) dynamic finite element software, Abaqus/Explicit, was implemented to simulate the experimental results of low velocity impact tests. A user-defined material subroutine (VUMAT) based on Chang-Chang linear-orthotropic damage model was implemented into the finite element code. The predictions from numerical simulation were found to be in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

In this study, the influence of die opening gap on foam attributes during a microcellular extrusion foaming process was investigated. Lower die openings developed higher pressure drops on the foams, as a result of which greater thermodynamic instability was stimulated and, consequently, higher cell density foams along with enhanced expansion ratios were achieved. Further investigations were performed to study the synergistic influence of altering die opening with critical process parameters, namely, screw rotational speed and die temperature, on the foam expansion ratio and morphological transformations. Higher screw rotational speed induced shear nucleation phenomenon, which further enhanced the foaming process significantly. Also, an optimum die temperature was observed, which developed maximum expansion ratio at the lowest die opening gap. This study intends to enhance the understanding of extrusion foam processing among academia as well as among industries. [ABSTRACT FROM AUTHOR]

High impact polystyrene sheets (HIPS) of 1.5 mm and 2.5 mm thicknesses were thermoformed on moulds of different parameters at sheet heating temperatures of 130℃ and 140℃. Formability studies indicated no difference in wall thickness distribution at different sheet temperatures. Due to non-uniform stretching of the sheet, wall thickness distribution along the slant length was found to have three regions. In the regions near the mould corner and clamp point, wall thickness was found to decrease with increase in distance from the corner, in these zones. The decrease near the corner was much greater and sharper than that near the clamp point. The decrease in both regions was found to increase at higher depths of draw and decrease at higher draft angles. In the intermediate portion of the slant length, no significant variation in wall thickness was observed. [ABSTRACT FROM AUTHOR]