Multiscale Buckling Modes in the Mechanics of Fiber-Reinforced Plastics

This book is a useful source of knowledge for engineers and scientists in the field of mechanics of deformation and destruction of composite materials.

In Chapter 1 three-dimensional equations of elasticity theory composed for the case of finite displacements and deformations of solids have been analyzed. It is found that the generally accepted simplifications known in the literature and carried out for the case of small deformations result in equations that are considered to be absolutely correct and consistent in all scientific and educational literature on mechanics of deformable solid bodies. However, this conclusion is not sufficiently well-founded as confirmed by formulation and solution of problems on the basis of generally accepted equations for determining both the stress-strain state (SSS) and the critical loads and buckling modes. In Chapter 2 the theoretical and experimental methods for determining the mechanical characteristics of fiber-reinforced plastics (FRPs) based on tensile and compression tests of flat specimens with [0]_s, [ 90]_s, and [ 45]_2s lay-ups are analyzed. For FRPs with [ 45]_2s lay-ups, relations are derived for determining the components of lamina strains and stresses in the orthotropy axes of FRP monolayer in terms of axial strains and Poisson ratios of specimens measured in experiments. In Chapter 3 the structure of a unidirectional fibre composite of two types ELUR-P carbon fibre based on KhT-118 cold-curing binder and HSE 180 REM prepreg based on hot-curing binder has been studied. The diameters of fibres and fibre bundles (filaments) of both types of composites have been measured. Based on the results of the analysis of the composite material structure, a refined formulation of the linearised problems of a refined statement of linearized problems on flat internal multiscale buckling modes of a rigid lamina with either fibers or a fiber bundle is presented taking into account their interaction with an epoxy matrix. In Chapter 4 for shells of a layered structure based on the Timoshenko's model, taking into account the transverse compression used for each layer, two versions of two-dimensional equations are constructed that describe geometrically nonlinear deformation with arbitrary displacements and small deformations. The formulation of a linear problem on the initial (subcritical) stress-strain state of a test specimen from a unidirectional fibrous composite with the [90⁰]_s structure during tension-compression tests with shear is given. A numerical method for solving the formulated problem is developed, which is based on the reduction of the original problem to a system of integro-algebraic equations and the search for their numerical solution by the finite sum method. In Chapter 5 conclusions were done and directions for further research have been identified.