A common application of short fiber reinforced polymer composites (SFRPCs) is in the automotive industry. A high demand of these polymer composites is due to their low cost, ease of manufacturing in complex geometries, high production rate, and a low ratio of weight to strength. In structures such as automobile, components are typically subjected to fluctuating loads and generally prone to fatigue failure. Therefore, a profound understanding of fatigue prevents premature failures of structural components. This study investigates uniaxial fatigue behavior of two short glass fiber polymer composites including 30 wt% short glass fiber polybutylene terephthalate (PBT) and 35 wt% short glass fiber polyamide-6 (PA6) under a number of load and environmental conditions. The main objectives are to evaluate the behavior of these materials under monotonic and cyclic loadings and present fatigue life prediction methodologies to reduce their development expenses and time. The considered environmental effects include those of low and elevated temperatures as well as moisture (or water absorption) effect. Fatigue behavior is also explored under the action of nonzero mean stress (or R ratio) as well as various cyclic loading frequencies. Material anisotropy and geometrical discontinuity effects (i.e. stress concentration) are also considered in this study. Microscopic failure analysis is also performed, when necessary, to identify failure mechanisms. Tensile tests were performed in various mold flow directions and with two thicknesses at a range of temperatures and strain rates. A shell-core morphology resulting from orientation distribution of fibers influenced the degree of anisotropy. Tensile strength and elastic modulus nonlinearly decreased with specimen angle and Tsai-Hill criterion was found to correlate variation of these properties with the fiber orientation. Kinetics of water absorption was studied and found to follow the Fick's law. Tensile tests were performed at room temperature with specimens in the longitudinal and transverse directions and with various degrees of water absorption. Mathematical relations were developed to represent tensile properties as a function of water content. Mathematical relationships were developed to represent the stress-strain response, as well as tensile properties in terms of strain rate and temperature. Time-temperature superposition principle was also employed to superimpose the effect of temperature and strain rate on tensile strength. A temperature dependent shift factor of Arrhenius type is suggested, which is independent of the mold flow direction. Variation of tensile toughness with fiber orientation and strain rate was evaluated and mechanisms of failure were identified based on fracture surface microscopic analysis and crack propagation paths. Fiber length, diameter, and orientation distribution mathematical models were also used along with analytical approaches to predict tensile strength and elastic modulus form tensile properties of constituent materials. Laminate analogy and modified Tsai-Hill criteria provided satisfactory predictions of elastic modulus and tensile strength, respectively. Short-term creep experiments were performed at high temperatures and mathematical equations were developed to relate temperature, stress and rupture time. Effect of frequency on fatigue life was evaluated and incremental step frequency tests were performed at different stress ratios and stress levels. Surface temperature rise was found to be material, frequency and stress level dependent. Three energy-based models were applied to the incremental step frequency data and relationships were developed for each material to estimate surface temperature rise as a function of test frequency and stress level. Cyclic deformation tests were performed at different temperatures and in different directions of mold flow. Effect of mold flow direction on fatigue behavior was significant at all temperatures and stress ratios and the Tsai-Hill criterion was used to predict off-axis fatigue strengths. Fatigue behavior of PA6 was influenced by water absorption, while PBT indicated a high resistance against water. Temperature also greatly influenced fatigue strength and a shift factor of Arrhenius type was developed to correlate fatigue data at various temperatures, independent of the mold flow direction and stress ratio. Micromechanisms of fatigue failure at different temperatures and water absorption were also investigated. Good correlations between fatigue strength and tensile strength were obtained and a method for obtaining strain-life curves from load-controlled fatigue test data is presented. A fatigue life estimation model is also presented which correlates data for different temperatures, fiber orientations, and stress ratios. Effect of mean stress on fatigue life was found to be significant at all temperatures. Several mean stress parameters were evaluated for their ability to correlate mean stress data. Notched fatigue tests of an unreinforced polymer and a short glass fiber thermoplastic composite were also conducted using plate type specimens with a central circular hole. Effect of stress concentration was found to be considerable, with or without mean stress and in both the longitudinal and transverse directions. The commonly used Neuber's rule for metallic materials, nonlinear FEA, as well as critical distance approaches were utilized for notch deformation and fatigue life analyses.

This book covers several aspects of the fatigue behavior of textile and short fiber reinforced composites. The first part is dedicated to 2D and 3D reinforced textile composites and includes a systematic description of the damage evolution for quasi-static and tensile-tensile fatigue loadings. Acoustic emissions and digital image correlation are considered in order to detect the damage modes’ initiation and development. The acoustic emission thresholds of the quasi-static loading are connected to the “fatigue limit” of the materials with distinctions for glass and carbon reinforcements. The second part is devoted to the fatigue behavior of injection molded short fiber reinforced composites. Experimental evidence highlights the dependence of their fatigue response on various factors: fiber and matrix materials, fiber distribution, environmental and loading conditions are described. A hybrid (experimental/simulations) multi-scale method is presented, which drastically reduces the amount of experimental data necessary for reliable fatigue life predictions.

Fatigue has long been recognized as a mechanism that can provoke catastrophic material failure in structural applications and researchers are now turning to the development of prediction tools in order to reduce the cost of determining design criteria for any new material. Fatigue of Fiber-reinforced Composites explains these highly scientific subjects in a simple yet thorough way. Fatigue behavior of fiber-reinforced composite materials and structural components is described through the presentation of numerous experimental results. Many examples help the reader to visualize the failure modes of laminated composite materials and structural adhesively bonded joints. Theoretical models, based on these experimental data, are demonstrated and their capacity for fatigue life modeling and prediction is thoroughly assessed. Fatigue of Fiber-reinforced Composites gives the reader the opportunity to learn about methods for modeling the fatigue behavior of fiber-reinforced composites, about statistical analysis of experimental data, and about theories for life prediction under loading patterns that produce multiaxial fatigue stress states. The authors combine these theories to establish a complete design process that is able to predict fatigue life of fiber-reinforced composites under multiaxial, variable amplitude stress states. A classic design methodology is presented for demonstration and theoretical predictions are compared to experimental data from typical material systems used in the wind turbine rotor blade industry. Fatigue of Fiber-reinforced Composites also presents novel computational methods for modeling fatigue behavior of composite materials, such as artificial neural networks and genetic programming, as a promising alternative to the conventional methods. It is an ideal source of information for researchers and graduate students in mechanical engineering, civil engineering and materials science.

Science and Engineering of Short Fibre Reinforced Polymer Composites, Second Edition, provides the latest information on the 'short fiber reinforced composites' (SFRP) that have found extensive applications in automobiles, business machines, durable consumer items, sporting goods and electrical industries due to their low cost, easy processing and superior mechanical properties over parent polymers. This updated edition presents new developments in this field of research and includes new chapters on electrical conductivity, structural monitoring, functional properties, self-healing, finite element method techniques, multi-scale SFRCs, and both modern computational and process engineering methods. - Reviews the mechanical properties and functions of short fiber reinforced polymer composites (SFRP) - Examines recent developments in the fundamental mechanisms of SFRP's - Assesses major factors affecting mechanical performance, such as stress transfer and strength - Includes new chapters on electrical conductivity, structural monitoring, functional properties, self-healing, finite element method techniques, multi-scale SFRCs, modern computational methods, and process engineering methods

This book provides the first comprehensive review of its kind on the long-term behaviour of composite materials and structures subjected to time variable mechanical, thermal, and chemical influences, a subject of critical importance to the design, development, and certification of high performance engineering structures. Specific topics examined include damage, damage characterization, and damage mechanics; fatigue testing and evaluation; fatigue behaviour of short and long fibre reinforced polymer and metal matrix materials; viscoelastic and moisture effects; delamination; statistical considerations; the modeling of cumulative damage development; and life prediction. The volume provides an extensive presentation of data, discussions, and comparisons on the behaviour of the major types of material systems in current use, as well as extensive analysis and modeling (including the first presentation of work not found elsewhere). The book will be of special interest to engineers concerned with reliability, maintainability, safety, certification, and damage tolerance; to materials developers concerned with making materials for long-term service, especially under severe loads and environments, and to lecturers, students, and researchers involved in material system design, performance, solid mechanics, fatigue, durability, and composite materials. The scope of the work extends from entry level material to the frontiers of the subject.

Excerpt from A Fatigue Model for Fiber-Reinforced Polymeric Composites for Offshore Applications Over the last three decades, fiber-reinforced polymer (f rp) composites have been used extensively in a wide range of aerospace and military applications. There is a growing interest in extending the use of these materials into civil engineering structures such as offshore platforms An urgent need exists to develop quantitative analysis and methodology for assessing the safety and reliability of using polymer composites in these applications. One particularly critical issue in regard to using polymer composites in structural applications is their fatigue reliability in different environments and loading conditions. Fatigue damage in polymer composites for non civil engineering applications has been extensively investigated [3 Studies of the effects of water or salt water on the fatigue behavior of polymer composites have also been widely reported [8 However, there is little quantitative research on the effects of civil engineering environments, namely water, sea water, concrete pore solution, temperature, ultraviolet radiation. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

This text, now in its second edition, offers an up-to-date, expanded treatment of the behaviour of polymers with regard to material variables and test and use conditions. It highlights general principles, useful empirical rules and practical equations.;Detailing the specific behaviour of many common polymers, the text: places emphasis on time and frequency dependence over temperature dependence; uses contemporary molecular mechanisms to explain creep, stress relaxation, constant strain rate responses and crazing; provides explicit equations to predict responses; supplies a discussion of large deformation multiaxial responses; compares statistical and continuum theories on the same data set; and updates stress-strain behaviour and particulate filled systems.