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This work examines the experimental and analytical investigation of impact on the carbon/epoxy laminates of various stacking sequence. The impact tests were carried out by using gas gun equipped with high-speed camera. Projectile velocities selected were 80 m/s and 30 m/s where 80 m/s was above ballistic limit velocity and 30 m/s was below ballistic limit velocity. The impact process was recorded with high-speed camera which facilitated to identify different energy absorbing mechanisms. High-speed images were also used to measure pre-impact and post-impact velocities of the projectile accompanied by photo diode and aluminum foil method. Total energy absorbed by the laminates, which is the difference between pre-impact and post-impact kinetic energy of the projectile, was calculated for the laminates with different stacking sequences. Damage extent in the laminates of different stacking sequences were also assessed by C-Scan of the laminates. Then effect of stacking sequences on damage extent and energy absorbing capacity was established. An analytical model was proposed to predict the residual velocity of the projectile at above ballistic limit velocity, which was based on the total energy absorbed by different energy absorption mechanisms. The analytical model was validated with experimental results for different stacking sequences. Additionally, effect of fiber orientation on damage shape at below ballistic limit velocity was also studied. © The Author(s) 2019.

Department of Design and Automation

School of Mechanical Engineering

Vellore Campus

World University root node

Journal of Composite Materials

Impact damage assessment of carbon fiber reinforced composite with different stacking sequence

Drilling is a secondary manufacturing process used for the finishing of the parts done in the primary manufacturing. For drilling of traditional materials, there are several techniques available to attain the objective of good circularity of the hole without any damage. Drilling of the CFRP material is difficult, because of its anisotropic and non-homogeneous in nature. Carbon fibre reinforced materials extensively used in the aerospace industries, because of its specific properties in strength and stiffness. Hence, the drilling of CFRP requires a lot of research for using in the aerospace industry. The principal aim of this paper is to present an extensive literature report in the drilling of CFRP and that includes the studies on different input variables such as machining parameters (speed, feed and drill point angle) and drill biton the drilling induced damages. Also, the study focuses effects of input variables on delamination and hole circularity and induced thrust force and torque. © 2018, Transstellar Journal Publications and Research Consultancy Private Limited (TJPRC). All rights reserved.

International Journal of Mechanical and Production Engineering Research and Development

Drilling of Carbon Fibre Reinforced Polymer Materials - A Review

In the present work, an analytical model is proposed to obtain the damage area of the composite laminates at below ballistic limit velocities. The model is based on the fact that total kinetic energy of the projectile is absorbed by different energy absorbing mechanisms taking place in laminates during impact. Depending upon the projectile velocity, some or all energy absorbing mechanisms observed are; fibre breakage, deformation of fibres, delamination, matrix cracking and cone formation on the back face of the laminates. The accuracy of the model is then assessed by comparing its predictions for damage area and specific energy absorption with the experimental values for two different types of fibres (glass and kevlar) as well as glass/kevlar hybrid combinations. Experimental results are also used to quantify and compare the specific energy absorption capacity of the glass/epoxy, kevlar/epoxy and glass/kevlar/epoxy laminates. It is observed that the glass/kevlar/epoxy laminates in which kevlar percentage is 27.5% w/w showed 20% improvement in specific energy absorption as compared to the glass/epoxy laminates. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

International Journal of Crashworthiness

Effect of velocity and fibres on impact performance of composite laminates–Analytical and experimental approach

Kevlar/epoxy composite laminates are subjected to impact loading and the energy absorbing capacity of the laminates is studied. In the present study, laminates with four different orientations and thickness values are considered. It is found that cross-ply laminates are most efficient in ballistic resistance when compared with the laminates of other orientations. It is also noticed that the energy absorbing capacity is decreasing with increase in velocity of the projectile for a given lay-up and thickness value. © 2017 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

FE Analysis of Impact on Kevlar/Epoxy Laminates with Different Orientations and Thicknesses

Improvement of stability of thin isotropic shell in the presence of soft elastic filler has been investigated. Critical buckling loads for empty and filled cylinder have been studied both experimentally and theoretically using FE analysis. Various percentage of cross sectional filling are examined as a parametric variation. Nonlinear analysis with proper geometric imperfection modeling is carried out to represent correct behavior of soft elastic filler. The experimental results and FE analysis corroborate well to establish this improvement in buckling strength. It is observed that critical buckling load of the cylinder subjected to external pressure improves upto an extent of five times depending upon percentage of filling. It is concluded that improved strength can be utilized for more efficient design of thin tubular shells. © 2015 Elsevier Ltd.

Thin-Walled Structures

Stability improvement of thin isotropic cylindrical shells with partially filled soft elastic core subjected to external pressure

Composite laminates, made of glass/epoxy using compression molding technique, were subjected to impact loading. The ballistic limit and energy absorption capacity of the laminates were obtained. Experiments were carried out to study the effect of fiber orientation and thicknesses on ballistic limit and energy absorption of the laminates, by using a rigid conical bullet having 9.5 mm diameter and mass of 7.5 g in an air gun. Analytical expressions were obtained to find the ballistic limit, residual velocity and energy absorption capacity of the laminates. The expressions obtained by considering the various damage modes, which were involved in penetration, when laminates subjected to impact loading. The values obtained from analysis were compared with experimental results and good agreement was found. The strain rate sensitivity of the glass/epoxy composites was considered for analysis. © 2013 Elsevier Ltd. All rights reserved.

Composites Part B: Engineering

Influence of fiber orientation and thickness on the response of glass/epoxy composites subjected to impact loading

Glass/epoxy composite laminates are subjected to impact loading and the energy absorbing capacity of the laminates is studied. In the present study, laminates with four different orientations and thickness values are considered. Analytical study is carried out based on energy method and results are compared with FE results obtained from Abaqus/Explicit software. Results obtained from the analytical methods are showing good agreement with the FE results. It is found that cross-ply laminates are most efficient in ballistic resistance when compared with the laminates of other orientations. It is also noticed that the energy absorbing capacity is decreasing with increase in velocity of the projectile for a given lay-up and thickness value. © 2014, DESIDOC.

Defence Science Journal

Ballistic impact on glass/epoxy composite laminates

In the present study, impact behavior of Kevlar/Epoxy composite plates has been carried out experimentally by considering different thicknesses and lay-up sequences and compared with analytical results. The effect of thickness, lay-up sequence on energy absorbing capacity has been studied for high velocity impact. Four lay-up sequences and four thickness values have been considered. Initial velocities and residual velocities are measured experimentally to calculate the energy absorbing capacity of laminates. Residual velocity of projectile and energy absorbed by laminates are calculated analytically. The results obtained from analytical study are found to be in good agreement with experimental results. It is observed from the study that 0/90 lay-up sequence is most effective for impact resistance. Delamination area is maximum on the back side of the plate for all thickness values and lay-up sequences. The delamination area on the back is maximum for 0/90/45/-45 laminates compared to other lay-up sequences. © Versita sp. z o.o.