Journal of Engineering Materials and Book Review Technology

Introduction to Plastics Engineering, by Vijay K. Stokes, viscoelasticity in Part II, a dedicated chapter on evaluating viscoe- Downloaded from http://asmedigitalcollection.asme.org/materialstechnology/article-pdf/143/3/036501/6700693/mats_143_3_036501.pdf by guest on 02 October 2021 Wiley-ASME Press Series, Wiley. ISBN: 978-1-119-53657-4. lastic properties of plastics using techniques such as DMA and responses of several candidate materials is included next in this part. The description of the time–temperature superposition princi- REVIEWED BY HAREESH TIPPUR, Department of ple in sufficient detail is quite valuable to the reader as well. The Mechanical Engineering, Auburn University, AL 36830. chapter on the mechanical behavior of different plastics, to which the author has personally contributed a great deal during his Industrial and consumer products made of plastics are ubiquitous long career, provides a phenomenological perspective and links in our daily lives. Converting raw plastics into useful parts is a between materials and mechanics aspects of plastics. This fairly scientific and technological challenge that has been progressively elaborate chapter includes a great deal of useful data that elucidates overcome in the past several decades. This expansive monograph distinguishing aspects of mechanical failure behavior of plastics in authored by one of the leading experts with vast experience as an terms of necking and thermomechanical response which are often academic at IIT-Kanpur and a practitioner while at GE Corporate mistakenly assumed to be similar to that of metals. R&D tackles this huge subject by expounding aspects of transform- The flexibility of plastics to be designed and made into intricate ing modern plastics into useful day-to-day items based on principles parts with different sizes, shapes, colors, and finishes via low-cost of mechanical engineering and engineering mechanics. It weaves manufacturing processes make them highly competitive relative together complex issues related to the mechanics, mechanical to metals. Accordingly, the book emphasizes in the next part, Part design, fabrication, and assembly of engineered plastics. In doing IV, shaping of different types of unfilled and filled plastics—ther- so, the book distinguishes itself from others by emphasizing not moplastics, thermosets, and elastomers—into complex parts. A just the material science and “build-and-test” approach embraced chapter that describes large-scale manufacturing of resins and its by the plastics industry but by adopting approaches from engineer- conversion into products is described via flowcharts in this part of ing science and materials science synergistically to address practical the book. Subtle issues such as the wall thickness of the part that issues of part design, size, cost, development cycle, and assembly, can be achieved from the perspective of thermal conductivity, among others. thermal diffusivity, and viscous flow characteristics of plastics are The author demonstrates this distinct approach of integrating also discussed. A rather expansive chapter on processing thermo- materials and engineering aspects of plastics by dividing the mono- plastics using injection molding and its variants follows. It deals graph into five distinct parts. In Part I, an overview of plastics engi- with all the process-related intricacies in terms of the design of neering is offered by describing what plastics are, why they have the molding machines, fabrication of molds and simulation tools become important in the last half-a-century or so, how engineering used for designing flow paths, prediction of residual stresses, and materials have and can influence the product design, the role of shrinkage and warpage of molded parts. This chapter also illustrates engineering science on processing, design, and assembly of parts, the complexity of heat transfer and flow paths around obstructions and how innovative designs can overcome the complexity and eco- such as pins, inserts, dimensionally disparate parts, among others. nomics associated with plastic products. To drive these ideas home, The author underscores the importance of computer-aided process for example, the author elegantly demonstrates the historical evolu- control and computer simulations alongside measurements to tion of structural designs and constructions based on stone, iron, and tackle the complexities intrinsic to the molding process. The next steel over the eons. Part II of the book lays out the fundamentals of chapter in this part is dedicated to shrinkage, dimensional stability, continuum mechanics to plastics engineers. It includes concepts of and residual stresses in plastic parts from shaping processes such as stress, strain, and constitutive relations along with analyses used for injection molding. The author recognizes that although these factors axial, flexural, and torsional members. In this part, separate chapters are easy to conceive, tackling them practically is far more challeng- dealing with the fluid mechanics and viscous behaviors of plastics ing, often requiring a trial-and-error approach. Again, by tapping address many important foundational components. Infilling of plas- into his own research on the subject, the author considers the tics with other functional phases is a common strategy used to example of injection molding of a simple thin rectangular part for enhance the mechanical performance such as stiffness, strength, monitoring the pressure histories in the mold as well as shrinkage coefficient of thermal expansion, and susceptibility to ultraviolet at various spatial locations as a function of different hold pressures. radiation. This category of plastics being a major segment of the The importance of pressure–temperature-specific volume data, modern plastics industry, micromechanics of filled plastics is introduced in Part II of the book, is revisited again in the context described in a separate chapter in this part of the book. Part III of part shrinkage. The presentation on the evolution of residual deals with the classification and chemical structure of plastics in stresses and warpage is also highly informative for practicing engi- general. The associated concepts are introduced to the beginners neers. The processing methods other than injection molding— in sufficient detail by considering simple polymer systems such as extrusion, injection molding, blow molding, thermoforming, and polyethylene and polypropylene. Modification of polymers using three-dimensional (3D) printing—are all described in sufficient various additives and blending of different plastics to achieve detail and with good illustrations in a follow-on chapter. Processing desired mechanical behavior is also described in this part of the of parts using thermoset resins and elastomers is addressed in a book. A history of developments of various plastics over the 20th separate chapter. It includes details on processing advanced com- century adds a nice perspective to the rapid evolution of the posites and rubber parts including reinforced rubber such as auto- modern plastics industry. Building on the foundational aspects of motive tires. Pultrusion, filament winding, and laminated

Journal of Engineering Materials and Technology JULY 2021, Vol. 143 / 036501-1 Copyright © 2021 by ASME composites are among the other topics described regarding the empirical data on different elastic moduli, ultimate stress and former. The last chapter of Part IV of the book presents various strain as a function of the density of modified PPO, and gas-filled joining methods—both temporary and permanent joints—used for PC structural foams useful to practicing engineers. The next plastics as they meet engineering design requirements and are fre- chapter deals with processing and mechanical properties of quently used alongside other engineering materials including random mat composites made of non-woven glass fiber mats as metals. The description includes sections ranging from traditional reinforcement in thermoplastics ideal for making large, low-cost, mechanical fastening and unique adaptations to adhesive bonding, stiff, and tough parts. As in the previous two chapters, the focus thermal bonding, friction welding, and electromagnetic bonding. of this chapter is on quantifying the elastic modulus and tensile In each of these categories, nicely illustrated sub-sections on differ- strength of these highly nonhomogeneous plastics. The empirical ent variants of each method, the resulting joint morphology, attain- data connecting the tensile modulus with the local material able strength, process complexities are all described in sufficient density and then tensile strength with modulus for glass mat- detail along with a good bit of tabulated data. polypropylene composite are valuable to practicing engineers. A The last part of this book, Part V, is dedicated to filled plastics, a great deal of insight into determining the effective elastic major segment of the modern plastics industry, that offer enhanced modulus of these complex materials, which often vary substantially mechanical and other functional attributes. It starts with a chapter on over short distances by as much as a factor of two over half an inch, Downloaded from http://asmedigitalcollection.asme.org/materialstechnology/article-pdf/143/3/036501/6700693/mats_143_3_036501.pdf by guest on 02 October 2021 state-of-the-art material processing concepts as well as elastic and is described using mechanics-based models coupled with idealized failure characteristics of discrete fiber-filled plastics comprising of sinusoidal or rectangular spatial variations. The larger questions of short and long fibers separately. A good bit of this chapter draws understanding properties—modulus and strength—of such complex from author’s own empirical and phenomenological research on materials and structural parts in general using statistical approaches the subject. It is sufficiently detailed and informative with a great are also considered in this chapter. The last chapter of this part, and deal of useful data on injection-molded glass fiber reinforced PS, the book, is on continuous fiber composites made of thermosets, PE, PBT, and others. Many not so well-known aspects of filled plas- originally developed as high-performance lightweight materials tics, namely, inhomogeneities due to the spatial variation of fiber for the aerospace industry. The coverage in this chapter is essen- orientation caused by flow patterns, process parameters, fiber tially qualitative and seems to have been included more for com- aspect ratio, and thickness of the part, to name a few, are all dis- pleteness than technical depth. Descriptive sections on filament cussed. The chapter includes a detailed section that outlines the wound, pultruded, sandwich, and resin transfer molded composites complexity of modeling discrete fiber-filled composites by consid- are also part of this chapter. Tires, reinforced hoses, and conveyer ering fiber orientation tensors in both 3D and 2D. The second belts which are rubber-based composites are described in this chapter of this part deals with lightweight rigid structural foams chapter as well. made of gas-charged and injection-molded thermoplastics In conclusion, this expansive 1000-page book authored by Pro- originally developed to avoid sink marks in the molded parts. The fessor Stokes is certainly a great addition to the bookshelves of resulting cross-sectional complexities associated with the nonho- both practicing plastics engineers and academics. Apart from a mogeneous distribution of millimeter size pores of different sizes few instances of repetitiveness and a few typographical errors are elaborated in this chapter. Understanding the mechanical char- (e.g., GPa instead of MPa for ultimate stress), each chapter of acteristics—elastic modulus, ultimate stress, and failure strain— the book has been put together meticulously and thoughtfully being rather challenging for such morphologies, the author again with informative illustrations, mechanics-based models, and adopts and demonstrates mechanics-based approaches to estimate empirical data. With many chapters of the book containing effective elastic moduli in the axial loading and bending configura- author’s own works besides others, the monograph is very tions. Many of the results reported in this chapter are again derived authentic and I strongly recommend it as a textbook and research from author’s own research on the topic. It contains a lot of monograph.

036501-2 / Vol. 143, JULY 2021 Transactions of the ASME