Search results

The mechanical properties of FRP composites have a remarkable scatter, even when the specimens are prepared and tested under identical conditions. Proposes a new computerized method for estimating accurately the parameters (X₀, α, β) of Weibull distribution function. Calculates the safe design of fatigue life data of glass fibre (ER 1150 F‐183) reinforced polyester (Q 8520 A) pultruded composite rods using the time to first failure (TTFF) concept. The shape parameter of a two‐parameter Weibull distribution function is the major limiting factor for the reliability analysis by this method. Shows that the penalty paid to gain a certain reliability and confidence level for static strength and fatigue life was decreased by increasing fibre volume fractions of GFRP composite rods. Indicates that the area under the curves of master diagrams were decreased by increasing the value of reliability (probability of survivability) of GFRP composite rods.

Damage due to delamination is an important issue during drilling in polymer-matrix composites (PMCs). It depends on thrust force and torque which are functions of feed rate. Transfer function of thrust force with feed rate and torque with feed rate is constructed through experiments. These transfer functions are then combined in state-space to formulate a sixth-order model. Then thrust force and torque are controlled by using optimal controller. The paper aims to discuss these issues.

A glass fiber reinforced plastic composite is drilled at constant feed rate during experimentation. The corresponding time response of thrust force and torque is recorded. Third-order transfer functions of thrust force with feed rate and torque with feed rate are identified using system identification toolbox of Matlab®. These transfer functions are then converted into sixth-order combined state-space model. Optimal controller is then designed to track given reference trajectories of thrust force/torque during drilling in composite laminate.

Optimal control is used to simultaneously control thrust force as well as torque during drilling. There is a critical thrust force during drilling below which no delamination occurs. Therefore, critical thrust force profile is used as reference for delamination free drilling. Present controller precisely tracks the critical thrust force profile. Using critical thrust force as reference, high-speed drilling can be done. The controller is capable of precisely tracking arbitrary thrust force and torque profile simultaneously. Findings suggest that the control mechanism is efficient and can be effective in minimizing drilling induced damage in composite laminates.

Simultaneous optimal control of thrust force and torque during drilling in composites is not available in literature. Feed rate corresponding to critical thrust force trajectory which can prevent delamination at fast speed also not available has been presented.

The purpose of this paper is to investigate the cutting mechanism of drilling printed circuit board (PCB) and to optimize the drilling parameters for decreasing burr size and thrust force.

An experimental study was carried out to investigate the effect of drilling parameters on thrust force and burr formation. The drilling process of PCB was divided by the variation of drilling force signals. Analysis of variance (ANVONA) was carried out for burr size and thrust force. Desirability function method was used in multiple response optimization, to find the best drilling parameters.

Enter burr and exit burr have different morphologies and types. The generation of enter burr is mainly caused by burr bending which can be observed in micrographs, whereas the generation of exit burr is more complicated than enter burr; both burr breakup and burr bending are observed in exit burrs. In the selected area, the optimized spindle speed and feed rate for drilling PCB is 12 krev/min and 6 mm/s, respectively.

In this paper, hole wall roughness and tool wear were not considered in the optimization of drilling parameters. The future research work should consider them.

This paper investigates the mechanism of burr formation and thrust force in drilling PCB and then optimizes the drilling parameters to decrease the burr formation and thrust force.

This paper aims to attempt to use grey relational analysis (GRA) coupled with Taguchi technique for the optimization of machining parameters (cutting speed, feed rate and drill bit type) with multiple performance characteristics of delamination factor, surface roughness and circularity in drilling of carbon fiber-reinforced polymer (CFRP) along the fiber direction.

Machining trials involved drilling of 6-mm diameter holes on 8-mm-thick CFRP plates was performed according to L27 (313) Taguchi’s orthogonal array technique using the drill material of high speed steel (HSS), Titanium Nitride (TiN) and Titanium Aluminium Nitride (TiAlN). Analysis of variance has been used find the effect, percentage contribution and significance of the process parameters, namely, cutting speed, feed rate and drill bit type.

The Taguchi technique is combined with the GRA to find the optimum process parameter which minimizes the delamination factor, surface roughness and circularity within the range of parameters investigated. The effective implementation of the hybrid approach helps to produce quality and defect free holes.

Experimental investigation on delamination factor, surface roughness and circularity in drilling of CFRP along the fiber direction using Taguchi-GRA was seldom reported.

Drilling holes in composite materials is a complex and challenging process because of their intrinsic anisotropic characteristics and unevenness compared to conventional metals. Hybridization of composites enhances the strength and hardness of the material but makes it more difficult to drill a hole in it. The purpose of this study is to optimize the drilling to minimize the delamination and taperness of hybrid glass fiber reinforced plastic (GFRP)/Al₂O₃ composites.

The present study investigates the impact of drilling parameters on delamination of the drilled hole and the taperness of the hole on hybrid GFRP/Al₂O₃. Optimum drilling conditions for minimizing delamination and taperness of the hole are determined to enhance the hole quality. Feed (f), speed (N) and drill diameter (D) are the parameters taken into consideration for drilling operation. By applying Taguchi’s signal-to-noise ratio analysis, process parameters have been optimized to reduce the delamination and taperness of holes on Hybrid GFRP/Al₂O₃ composites. The effect of process parameters was analyzed using the analysis of variance method.

The investigational results confirmed that the delamination is positively affected by speed, drill diameter and feed rate. Also, the taperness of the hole is positively affected by the drill diameter. Regression-based models were developed to predict the delamination and taperness of the hole matched with the experimental results, which are attained with an order of 95% and 97%.

Minimum delamination was found at the optimum condition of drill diameter 10 mm, feed at 0.225 mm/rev and the speed at 151 rpm and minimum taperness were found at the optimum condition of drill diameter 10 mm, feed at level 0.3 mm/rev and speed at 86 rpm for hybrid laminate composite (S-glass+ GFRP/Al₂O₃) were evaluated.

The purpose of this paper is to investigate the concept of new drill bit geometry adjusted to a given composite type. This paper explores the possibility of drilling in composites without negative effects such as: delamination, rapid tool wear, matrix burns, pulling out of fibers, etc.

Appropriate modification of drill bit geometries applied to composite materials include, among other things: modifications of point angles, reduction of chisel edge width, modification of drill margins and proper preparation of drill bit corners.

Description of tool geometry for drilling of different types of composites, in particular drilling in parts included free grain surfaces but also drilling at a different angle than 90°.

Geometrical details of the tool for drilling are depended on the type of composite.

Making of montage holes in parts made of composites without negative effects during drilling.

Analysis of the current state of knowledge shows that there are insufficient solutions in terms of new drill geometry for drilling of composites. Existing solutions do not guarantee adequate stability and repeatability of the cutting process. It is necessary to create new geometry drills permit the elimination of negative phenomena during drilling.

The purpose of this paper is to develop a mathematical model for delamination during drilling by using a response surface methodology (RSM) and also to determine how the input parameters (tool diameter, spindle speed and feed rate) influence the output response (delamination) in machining of fiber metal laminates.

Three factors and a three-level central composite design in RSM are used to carry out the experimental investigation. A video measuring system is used to measure the width of maximum damage of the machined FML composite. The “Design Expert 7.0” is used to analyze the data collected graphically. Analysis of variance is carried out to validate the model and for determining the most significant parameter.

The response surface model is used to predict the input factors influencing the delamination on the machined surfaces of the ARALL composite at different cutting conditions with the chosen range of 95 percent confidence intervals. Analysis of the influences of entire individual input machining parameters on the delamination has been carried out using RSM.

The effect of delamination on drilling of ARALL composites with solid carbide tools of various diameters has not been analyzed yet using RSM.

This study aims to develop a bimodal nano-silver paste with improved mechanical property and reliability. Silicon carbide (SiC) particles coated with Ag were introduced in nano-silver paste to improve bonding strength between SiC and Ag particles and enhance high-temperature stability of bimodal nano-silver paste. The effect of sintering parameters such as sintering temperature, sintering time and the proportion of SiC particles on mechanical property and reliability of sintered bimodal nano-silver structure were investigated.

Sandwich structures consist of dummy chips and copper substrates with nickel and silver coating bonded by nano-silver paste were designed for shear testing. Shear strength testing was conducted to study the influence of SiC particles proportions on the mechanical property of sintered nano-silver joints. The reliability of the bimodal nano-silver paste was evaluated experimentally by means of shear test for samples subjected to thermal aging test at 150°C and humidity and temperature testing at 85°C and 85 per cent RH, respectively.

Shear strength was enhanced obviously with the increase of sintering temperature and sintering time. The maximum shear strength was achieved for nano-silver paste sintered at 260°C for 10 min. There was a negative correlation between the proportion of SiC particles and shear strength. After thermal aging testing and humidity and temperature testing for 240 h, the shear strength decreased a little. High-temperature stability and high-hydrothermal stability were improved by the addition of SiC particles.

Submicron-scale SiC particles coated with Ag were used as alternative materials to replace part of nano-silver particles to prepare bimodal nano-silver paste due to its high thermal conductivity and excellent mechanical property.

The purpose of this study is to check the reliability of a multi-pin joint to be a fail-safe joint by considering different geometric and material parameters. The pin joints are made of uni-directional fiberglass that has been impregnated with epoxy composites incorporating 3% nano-clay.

This study incorporates the analysis of multi-pin joints experimentally, numerically and statistically using the Weibull approach. During analyses, geometrical parameters edge to diameter (E:D), longitudinal pitch to diameter (F:D), side edge to diameter (S:D) and transverse pitch to diameter (P:D) were analyzed using the Taguchi method with a higher-the-better L16 orthogonal array.

This study aims to develop multi-pin laminated joints to attain higher reliability, which have been designated as fail-safe joints for the intended application and which have higher joint strength. The study reveals that to achieve 99% reliability or 1% probability of failure using the Weibull approach, 24.4% load decrement from the experimental result recorded for three-pin joint configuration at E:D = 4, F:D = 5, S:D = 4 and P:D = 5. Similarly, for the four-pin configuration at E:D = 4, F:D = 4, S:D = 4 and P:D = 5, 23.07% of load decrement observed from the experimental result implies that the expected load with a 99% reliability offers a safe load.

A reliability analysis on multi-pin joints was not conducted in structural application. Composite materials are used because of high reliability and high strength-to-weight ratio. So, in the present work, reliability of the multi-pin joint is analyzed using Weibull distribution.

The purpose of this paper is to optimise the process parameters, namely, point angle, spindle speed and feed rate in the drilling of glass-reinforced stainless steel mesh polymer (GRSSMP) composites using grey relational fuzzy logic.

Based on the full factorial design, the experiments were conducted. The output responses considered are thrust force, torque, delamination and diameter deviation. Based on responses, the optimised process parameter was selected using grey-fuzzy reasoning analysis (GFRA).

The percentage contribution of the drilling parameters is analysed using analysis of variance (ANOVA), and the result shows that feed rate is the most influential factor in the drilling of GRSSMP composites.

The optimised drilling parameters have been used for drilling of polymer composites in the production industry.

Optimisation of process parameters during the drilling of GRSSMP composites using GFRA has not been performed previously.