This article studies the effects of manufacturing defects of laminate composite materials on the first ply failure load and ultimate strength of the laminate, which are calculated using finite element modelling with Zinoviev’s damage model. The following types of defects are considered for cross-ply and quasi-isotropic layups: in-plane misalignement and out-of-plane waviness of fibres, misorientation of the layers and void content. The list of laminates studied in this article includes cross-ply and quasi-isotropic layups, loaded in tension and compression in 0°, 90°, 45° and 5° directions. The limits of the first ply failure load and strength degradation for a realistic range of the defect intensities are estimated.

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The paper describes a model for simulation of residual stresses and process-induced cracks in thermoplastic fibre-reinforced composites. The main aspect of the research is the modeling of phase transitions in thermoplastic matrix, taking into account changes in the matrix mechanical properties and shrinkage. An experimental comparison of modeling results for all mechanical characteristics at all stages of material phase transformation is provided. Equations for modeling of all key processes related to temperature cycle of a thermoplastic matrix solidification are provided together with corresponding material constants, using polyetheretherketone (PEEK) as an example. Approach to modeling of process-induced defects in thermoplastic matrix in dependence of crystallinity degree and different temperature conditions is proposed. Russian Federation compliances J and J .where subscript am denotes amorphous state and subscript cr denotes fully crystallized state. Then, the following relationships are introduced:And the assumption is made that J cr J uc J cr 0 ψ arctg(ωτ ),

In the presented study, LPBF 316L stainless steel tensile specimens were manufactured in three different orientations for the analysis of anisotropy. The first set of specimens was built vertically on the build platform, and two other sets were oriented horizontally perpendicular to each other. Tensile test results show that mean Young’s modulus of vertically built specimens is significantly less then horizontal ones (158.7 GPa versus 198 GPa), as well as yield strength and elongation. A role of residual stress in a deviation of tensile loading diagrams is investigated as a possible explanation. Simulation of the build process on the basis of ABAQUS FEA software was used to predict residual stress in 316L cylindrical specimens. Virtual tensile test results show that residual stress affects the initial stage of the loading curve with a tendency to reduce apparent Young’s modulus, measured according to standard mechanical test methods.

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