Finite Element Method Online Course
Section: FEM Analysis of Mechanical and Structural Properties of Long Fiber-Reinforced Composites
Lesson: FEM simulation of mechanical properties of long fiber-reinforced composite – PART 1
Finite Element Method.
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Studies and analyses of mechanical properties of long fiber-reinforced composites provide important information for future lightweight constructions. First of all, it is important to approach the issues and specifics of long fiber-reinforced composite structures to increase the strength and toughness of the resulting structure. The long fiber-reinforced composite structure is typically formed from two dominant components: carrier fiber reinforcement and a matrix. Ideal arrangement of the final composite (fiber-matrix connection), due to synergy, the high specific properties (high strength, stiffness, and toughness) can be achieved, where none of input components reached. It is that the optimal synergistic effect is characterized by a known “illogical” rule 2 + 3 = 7, which characterizes the sum of the properties of the individual input components (fibers + matrix) achieves a higher value of the specific properties of the newly created structure. In general, the highest specific properties can be achieved if the fibers are stressed up to the strength limit σMfF f→max with stress transferred with matrix. The matrix transforms the stress into the fibers, and it also has a significant effect on the bonding with the fibers. Thus, the matrix is the binder component of the composite, creating the final geometry of the composite and at the same time protecting the fibers from wear and damage, which would lead to loss of stability and strength of the resulting composite. The description of the properties of composite structures reinforced with long fibers due to their potential and specific characteristics was given by the authors namely Agarwal et al. , Guedes , Gay and Gambelin , Reifsnider , Teply and Reddy , Berthelot , Gibson , or Soden et al.. The authors agree that long fiber-reinforced composite structures are unique materials whose mechanical properties cannot be generally described in an analytical or experimental manner. Theories also differ in mathematical relationships derived for unidirectional composite structures, let alone complete synthesis of mechanical properties for geometrically complex structures of frames with multidirectional fibrous arrangement. This is due to the fact that their properties vary significantly with the type of fibers and a matrix (e.g., physical and mechanical properties, surface treatment, chemical compositions, binding agents, density, thermal expansion, etc.) because only a slight change forms various combinations with significantly different properties in mechanical behavior.1 Generally, long fiber-reinforced composite structures can be considered as inhomogeneous and heterogeneous structures with anisotropic properties in terms of physical and mechanical behavior. Their heterogeneity is manifested by a large number of combinations of different variants of the resulting structural materials suitable or unsuitable for the specific design requirements and load.2 If the strength of the composite has to be maximized, the specific surface of the fiber-matrix interface must be high and free of defects. The selection of fiber reinforcement is possible to use a wide range of fibers, whereas their offer is developed and expanded. For structural applications such as frames for machine parts and equipment may be used virtually any organic natural fibers (e.g., coconut, cotton, cellulose fibers, etc.) from a variety of polycrystalline ceramic materials, polymeric fibers, glass, or carbon fibers. The production technology of these fibers is well described by Bareš. Carbon fibers are industrially manufactured with a diameter of 5–12 μm by various methods such as carbonization of organic fibers or pyrolysis. It is generally known that carbon can exist in nature in three forms: diamond, graphite, and glassy (amorphous). Carbon fibers can be considered as fibers
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Finite Element Method Online Course