There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Investigation of failure modes and influence on ballistic performance of Ultra-High Molecular Weight Polyethylene (UHMWPE) uni-directional laminate for hybrid design

https://www.research.manchester.ac.uk/portal/files/50244711/1_s2_0_S026382231632030X_main.pdf

Investigation on energy absorption efficiency of each layer in ballistic armour panel for applications in hybrid design

This study investigated the effect of graphene nanoplatelets (GnPs) on the ballistic performance of Kevlar/Cocos nucifera sheath-reinforced epoxy composites. GnPs with different wt. % (0%, 0.25%, 0...

Effect of graphene nanoplatelets on the ballistic performance of hybrid Kevlar/Cocos nucifera sheath-reinforced epoxy composites:

Body armor is a material to protect body from injury of various kind of high speed projectile impact velocity in combat or other dangerous situation. Researchers were found to actively research and exploring new body armor technology due to the invention of new firearms. Furthermore, they were also competing in developing ballistic panel which is lighter in weight, more flexible and comfort in use, cheaper in cost and manufacturability. This paper reviews the body armor commercial and current development materials, structure and construction techniques involved and related works on enhancing ballistic energy absorption.

Body Armor Technology: A Review of Materials, Construction Techniques and Enhancement of Ballistic Energy Absorption

This research work was concerned with the evaluation of mechanical properties; flexural strength and impact strength of coconut coir textile composites. The coir fabric reinforcement was in a form of woven and cross ply structure. The two types of laminates orientations for cross-ply structures were 0/90 degrees and 45/-45 degrees. Composites with fibre weight fraction of 30% were prepared by hand lay-up and vacuum bagging technique. Mechanisms of composites failure were examined using scanning electron microscopy (SEM). Results have shown that the woven coir reinforced composites exhibited higher impact resistance and flexural strength (warp woven) compare to cross-ply composites. Moreover, 0/90 degrees orientations demonstrated better strength performance compare to 45/-45 degrees. However, damage propagation on woven composites was found to be larger than cross-ply composites. Normality test of data distribution were evaluated using Minitab software and it was proven that all samples were in a very stable behaviour (p > 0.05). Experimental results were also validated using one way analysis of variance technique (one way-ANOVA) and it revealed there was statistically significant difference (p < 0.05) between all different fabric structures of coir fabric as reinforcement in composite.

Influence of Woven and Cross-ply Laminates on Mechanical Properties of Coir Epoxy Composite

The effects of different laminated hybrid composites stacking configuration subjected to ballistic impact were investigated. The hybrid composites consist of woven coir (C) and woven Kevlar (K) layers laminated together. The samples of woven coir were prepared using handloom device. The composites were produced by stacking the laminated woven coir and Kevlar alternately with the presence of the binder. The samples were tested under ballistic impact with different stacking configuration. The results obtained had successfully achieved the National Institute of Justice (NIJ) standard level IIA with energy absorption of 435.6 kJ and 412.2 kJ under the projectile speed of between 330 m/s and 321 m/s respectively. Samples that having Kevlar layer at the front face and woven coir layer as back face achieved partial penetration during projectile impact. This orientation is proven to have good impact energy absorption and able to stop projectile at the second panel of the composites.

/pdf/ballistic-impact-response-of-woven-hybrid-coir-kevlar-19t5zrty6g.pdf

Ballistic Impact Response of Woven Hybrid Coir/Kevlar Laminated Composites

Several approaches have been implemented to enhance the impact performance of natural fibre-reinforced composite
structures. The control of reinforcement structure and fibre modification through treatment are among the approaches.
The objective of this study was to evaluate the impact behaviour of woven coir-epoxy composite as a function of fabric
density and fabric modification using alkalisation treatment. Samples were subjected to low-velocity impact penetration
tests and image analysis technique was used to measure the area and perimeter of the damaged samples under impact.
A multi-level full factorial design was implemented in this study as a systematic and efficient way to distinguish the
interactions of more than one factor. Two levels of woven density (Type 1 and Type 2) were investigated and four levels
of treatment percentage (0%, 6%, 9% and 12%) were examined. Moreover, analysis of variance (ANOVA) was employed
to determine the significant factors that predominantly influence the impact behaviour of woven composites. It was found
that the differences in woven density and woven treatment significantly affect the maximum impact load and deflection of
woven coir-epoxy composites. Impact energy absorption, however, was only affected by woven treatment. Factor
interactions were also apparent for maximum impact load, initiation energy and deflection. The results showed that
woven reinforcement with denser structure was less stiff in nature. The deformability of the composites was also found
to reduce with the increase of treatment percentage. Furthermore, poor damage resistance was observed in denser
woven structure.

Impact behaviour of woven coir-epoxy composite: Effects of woven density and woven fabric treatment:

The hybrid of natural and synthetic fibres in a composite system has gained interest in research field due to the environmental consciousness. Coir natural fibre has been found to have a high potential as impact resistance, in which brittle fibre helps to spread the impact energy over a wider area. The focus of the study is to determine if any improvement in impact response exists as a result of combining high performance Kevlar synthetic fibre and coir natural fibre in a specified laminated stacking sequence. In this research, quasi-static experiments were conducted at the speed of 1.25 mm/s, and low velocity impact tests were conducted using a 12.7 mm hemispherical impactor at the speed varying from 5 m/s to 17 m/s. Matlab software was used for curve fitting of the raw data, whereas ANOVA and DOE via Minitab software were employed for statistical examination to support the results. The area of the damaged composite was evaluated using the image analysis technique by Matlab image processing tool. The morphology analysis of the impact fractured surfaces was also observed by SEM. At the beginning stage, the optimum impact responses of coir epoxy composites subjected to different reinforcement architecture, composite manufacturing method, fabric modification and fabric density were determined. The findings showed that the impact responses could be effectively controlled by varying material parameters. Coir fibre in the form of woven structure with dense structure, treated using 6% of NaOH solution and
xx
manufactured by compression moulding method was found to be effective in absorbing and propagating impact energy. The respective coir was then used in hybrid laminates. Coir/Kevlar epoxy hybrid composites consisted of three interply laminates layers at six different stacking configurations were developed. It was observed that the hybrid composite (two coir layers and one Kevlar layer) had equivalent specific total energy absorption as 100% Kevlar laminate (at three layers). It can be concluded that the hybrid of coir/Kevlar-epoxy laminated composites had shown an improved in impact response. It also provides cost-effective materials and contributes towards green technology which will be of great benefit to the industry and community.

A.R. Azrin Hani

Papers

Body Armor Technology: A Review of Materials, Construction Techniques and Enhancement of Ballistic Energy Absorption

Influence of Woven and Cross-ply Laminates on Mechanical Properties of Coir Epoxy Composite

Ballistic Impact Response of Woven Hybrid Coir/Kevlar Laminated Composites

Impact behaviour of woven coir-epoxy composite: Effects of woven density and woven fabric treatment:

Low velocity impact response of laminated textile coir-aramids/epoxy hybrid composites subjected to transverse penetration loading