Preface The experimental characterization of composite materials has been an elusive topic,because it has been a continually evolving one.As new types of com- posites have been developed and new applications found,new testing chal- lenges have continually evolved.For example,in the 1960s the primary structural composite material available to compete with metals consisted of carbon fiber in a brittle epoxy matrix,a material of relatively low toughness. Thus,toughness as a property was de-emphasized by the composite materials community.However,by the beginning of the 1980s,many new matrix mate- rials,e.g.,toughened epoxies and high-temperature thermoplastics,were being incorporated to produce toughened composites.Obviously,the need quickly arose to develop test methods for ranking the relative toughness of composite materials.But there are multiple definitions of toughness,damage tolerance,and the effect of defects.Soon many test methods not previously applied to composites were being proposed,including Mode I,II,and mixed- mode fracture mechanics,beam and plate impact,compression after plate impact,and open-hole tension and compression. This evolution of test methods to meet new demands has continued over the years as additional aspects have risen in importance;e.g.,influences of temperature,moisture,solvents,and other factors affecting durability. Improvements in fiber-matrix interfacial bonding,the introduction of organic fibers such as aramid,polyethylene,liquid crystal polymer,and natural forms such as hemp and jute,and ultrahigh modulus inorganic fibers,particularly carbon,also have occurred.Likewise,new classes of matrix materials such as bismalimides,polyimides,and many others have necessitated still more test methods,or revisions of existing ones. As we now enter the 21st century,applications of all types of composite materials to commercial products are being emphasized.In anticipation of this development,the 1990s were a period of consolidation of test methods, and attempts to better understand those methods being used.Thus,the present text comes at an opportune time,i.e.,when the evolution of test methods is in a relatively stable period and definitive recommendations can be made.The goal of this text is to present primarily only those mechanical test methods that have achieved some consensus as being the best presently available,recognizing that "best"is often subjective. The primary audience for this text will be university,junior college,and technical school undergraduate students,and beginning university graduate students,taking a course in experimental mechanics of composite materials. However,this text also addresses a much larger audience.Quite frequently, engineers and technicians in industry and government laboratories are ©2003 by CRC Press LLCPreface The experimental characterization of composite materials has been an elusive topic, because it has been a continually evolving one. As new types of com￾posites have been developed and new applications found, new testing chal￾lenges have continually evolved. For example, in the 1960s the primary structural composite material available to compete with metals consisted of carbon fiber in a brittle epoxy matrix, a material of relatively low toughness. Thus, toughness as a property was de-emphasized by the composite materials community. However, by the beginning of the 1980s, many new matrix mate￾rials, e.g., toughened epoxies and high-temperature thermoplastics, were being incorporated to produce toughened composites. Obviously, the need quickly arose to develop test methods for ranking the relative toughness of composite materials. But there are multiple definitions of toughness, damage tolerance, and the effect of defects. Soon many test methods not previously applied to composites were being proposed, including Mode I, II, and mixed￾mode fracture mechanics, beam and plate impact, compression after plate impact, and open-hole tension and compression. This evolution of test methods to meet new demands has continued over the years as additional aspects have risen in importance; e.g., influences of temperature, moisture, solvents, and other factors affecting durability. Improvements in fiber–matrix interfacial bonding, the introduction of organic fibers such as aramid, polyethylene, liquid crystal polymer, and natural forms such as hemp and jute, and ultrahigh modulus inorganic fibers, particularly carbon, also have occurred. Likewise, new classes of matrix materials such as bismalimides, polyimides, and many others have necessitated still more test methods, or revisions of existing ones. As we now enter the 21st century, applications of all types of composite materials to commercial products are being emphasized. In anticipation of this development, the 1990s were a period of consolidation of test methods, and attempts to better understand those methods being used. Thus, the present text comes at an opportune time, i.e., when the evolution of test methods is in a relatively stable period and definitive recommendations can be made. The goal of this text is to present primarily only those mechanical test methods that have achieved some consensus as being the best presently available, recognizing that “best” is often subjective. The primary audience for this text will be university, junior college, and technical school undergraduate students, and beginning university graduate students, taking a course in experimental mechanics of composite materials. However, this text also addresses a much larger audience. Quite frequently, engineers and technicians in industry and government laboratories are TX001_FM_Frame Page 7 Saturday, September 21, 2002 4:46 AM © 2003 by CRC Press LLC