A Numerical Approach to the Classical Laminate Theory of Composite Materials

This book is intended as a study aid for the finite element method. Based on the free computer algebra system Maxima, we offer routines to symbolically or numerically solve problems from the context of two-dimensional problems. For this rather advanced topic, classical 'hand calculations' are difficult to perform and the incorporation of a computer algebra system is a convenient approach to handle, for example, larger matrix operations. The mechanical theories focus on the classical two-dimensional structural elements, i.e., plane elements, thin or classical plates, and thick or shear deformable plate elements. The use of a computer algebra system and the incorporated functions, e.g., for matrix operations, allows to focus more on the methodology of the finite element method and not on standard procedures. Furthermore, we offer a graphical user interface (GUI) to facilitate the model definition. Thus, the user may enter the required definitions in a source code manner directly in wxMaxima or use the GUI which is able to execute wxMaxime to perform the calculations.

A typical approach to treat composite materials, which are composed of layered unidirectional lamina, is the so-called classical laminate theory (CLT). This theory is based on the theory for plane elasticity elements and classical (shear-rigid) plate elements under the assumption of orthotropic constitutive equations. The solution of the fundamental equations of the classical laminate theory is connected with extensive matrix operations and many problems require in addition iteration loops.This two-dimensional approach and the underlying advanced continuum mechanical modeling might be very challenging for some students, particularly at universities of applied sciences. Thus, a reduced approach, the so-called simplified classical laminate theory (SCLT), has been recently proposed. The idea was to use solely isotropic one-dimensional elements, i.e., a superposition of bar and beam elements, to introduce the major calculation steps of the classical laminate theory. Understandingthis simplified theory is much easier and the final step it to highlight the differences when moving to the general two-dimensional case.This monograph first provides a systematic and thorough introduction to the simplified laminate theory based on the theory for bars and classical beam plate elements. The focus is on stacking of isotropic layers to simplified laminates. In addition to the elastic behavior, failure is investigated based on the maximum stress, maximum strain, Tsai-Hill, and the Tsai-Wu criteria. We provide a Python-based computational tool, the so-called Composite Laminate Analysis Tool (CLAT 1D) to easily solve some standard questions from the context of fiber reinforced composites. The tool runs in any standard web browser and offers a user-friendly interface with many post-processing options. The functionality comprises stress and strain analysis of simplified lamina and laminates and the failure analysis based on different criteria.

A typical approach to treat composite materials, which are composed of layered unidirectional lamina, is the so-called classical laminate theory (CLT). This theory is based on the theory for plane elasticity elements and classical (shear-rigid) plate elements under the assumption of orthotropic constitutive equations. The solution of the fundamental equations of the classical laminate theory is connected with extensive matrix operations and many problems require in addition iteration loops.This two-dimensional approach and the underlying advanced continuum mechanical modeling might be very challenging for some students, particularly at universities of applied sciences. Thus, a reduced approach, the so-called simplified classical laminate theory (SCLT), has been recently proposed. The idea was to use solely isotropic one-dimensional elements, i.e., a superposition of bar and beam elements, to introduce the major calculation steps of the classical laminate theory. Understandingthis simplified theory is much easier and the final step it to highlight the differences when moving to the general two-dimensional case.This monograph first provides a systematic and thorough introduction to the simplified laminate theory based on the theory for bars and classical beam plate elements. The focus is on stacking of isotropic layers to simplified laminates. In addition to the elastic behavior, failure is investigated based on the maximum stress, maximum strain, Tsai-Hill, and the Tsai-Wu criteria. We provide a Python-based computational tool, the so-called Composite Laminate Analysis Tool (CLAT 1D) to easily solve some standard questions from the context of fiber reinforced composites. The tool runs in any standard web browser and offers a user-friendly interface with many post-processing options. The functionality comprises stress and strain analysis of simplified lamina and laminates and the failure analysis based on different criteria.

Diese Studienhilfe zu numerischen Optimierungsverfahren richtet sich an Studierende des Maschinenbaus im Grundstudium und im Hauptstudium. Optimierungsverfahren gewinnen zunehmend an Bedeutung für den Leichtbau, wo eine Gewichtsreduzierung z.B. im Automobilbau oder in der Luft- und Raumfahrtindustrie zu einem geringeren Kraftstoffverbrauch und einer entsprechenden Senkung der Betriebskosten sowie zu positiven Auswirkungen auf die Umwelt führen kann. Basierend auf dem freien Computeralgebrasystem Maxima stellen die Autoren Verfahren zur numerischen Lösung ingenieurmathematischer Probleme sowie Anwendungen aus traditionellen Lehrveranstaltungen zur Festigkeit von Werkstoffen vor. Die mechanischen Theorien konzentrieren sich auf die typischen eindimensionalen Strukturelemente, d.h. Federn, Stäbe und Euler-Bernoulli-Balken, um die Komplexität des numerischen Rahmens zu reduzieren und den resultierenden Entwurf auf eine geringe Anzahl von Variablen zu beschränken. Die Verwendung eines Computeralgebrasystems und der darin enthaltenen Funktionen, z. B. für Ableitungen oder Gleichungslösungen, ermöglicht eine stärkere Konzentration auf die Methodik der Optimierungsverfahren und nicht auf Standardverfahren.Das Buch enthält auch zahlreiche Beispiele, darunter einige, die mit Hilfe eines grafischen Ansatzes gelöst werden können, um dem Leser ein besseres Verständnis der Computerimplementierung zu vermitteln.