Optimization of Lay-Up Stacking for a Loaded-Carrying Slender Composite Beam

Many aircraft composite structures experiencing the high operational loads must have the specified mechanical stiffness to prevent some structural failure due to the inadmissible deformations. Usually, such parts are manufactured using composites with orthotropic symmetry, which provides the best combination of structural rigidity, strength, and weight. In this chapter, we consider a cantilevered long tube-like composite structure with varied cross-section that is manufactured by winding of glass fiber unidirectional tape. The operational loads include the bending forces and the distributed torques. To reduce the total strain energy and peak von Mises stress, the search of the best lay-up scheme and its angles is performed. The wall thickness, lay-up scheme, and the total number of layers for each modeled design are assumed as unchanged along the tube, whereas its mechanical properties are considered as homogenized and dependent on the lamina properties and lay-up scheme only. The search of the pseudo-optimal design includes the analysis of all moduli angular distributions for each lay-up stacking. The better solutions are then studied by using the finite element model of the structure for three most critical load scenarios. The choice of the most preferred design is made by discarding the solutions with sharply degraded structural rigidity at least at one load scenario

Multi-agent Planning of the Network Traffic between Nanosatellites and Ground Stations

AbstractMulti-agent technologies application for adaptive planning of communication sessions establishment requests with nanosatellites in the ground stations network in response to the arising events, considering constraints, is considered. Mathematical problem statement of adaptive communication sessions scheduling is given. Method of coupled interactions extension based on the demand-resource networks model for operative requests allocation for communication sessions between ground stations and nanosatellites implementation is described

The water temperature characteristics of the Lena River at basin outlet in the summer period

The water temperature characteristics of the Lena River at basin outlet during the summer season (June–September) are considered. The analysis is based on long-term data series covering the period from the beginning of observation (1936) to the present time at Kusur (Kyusyur) station and complementary data at several stations downstream and one station upstream. These additional data are rarely used, but their analysis is important for understanding processes in the basin outlet area. The differences between the stream surface temperatures at Kusur station and 200 km downstream to the north at Habarova (Khabarova) station have almost always been an anomalously large and negative for the considered period since the beginning of observation during open water season from July to September. The description of this difference and its analysis are presented. To sort the problem out, we consider the observational data in terms of the hydrology and morphology of the Lena River delta and main channel area, apply statistical and deterministic modelling approaches

Features of the water temperature long-term observations on the Lena River at basin outlet

The goal of the current work is to analyze the available data on the water temperature of the Lena River at the basin outlet in the summer ice-free period (June–September). The analysis is based on a long-term data series covering the period from the beginning of observations to the present time at Kyusyur gauging station and complementary data at several stations downstream and one station upstream. These complementary data are rarely used, but their analysis is important for understanding processes in the basin outlet area. The differences between the stream surface temperatures at Kyusyur station and Yu. A Khabarova station 200 km downstream to the north have almost always been anomalously large and negative during open water season from July to September since the beginning of observations. The warming of the water downstream from Kyusyur raises questions because it cannot be explained by the heat exchange with the atmosphere. The analysis of factors that may be responsible for it is a major focus of this paper. We discuss whether the water temperature observations at Kyusyur station represent the mean stream temperature and show that they fail to represent the mean cross-sectional value but reflect thermal variability of the Lena River at this position. We carry out numerical experiments to verify this hypothesis and to explain the mentioned difference

Incremental Numerical Approach for Modeling the Macroscopic Viscoelastic Behavior of Fiber-Reinforced Composites Using a Representative Volume Element

The objective of this study is to describe the stress relaxation behavior of an epoxy-based fiber-reinforced material. An existing incremental formulation of an orthotropic linear viscoelastic material behavior was adapted to Voigt notation and to the special case of an isotropic material. Virtual relaxation tests on a representative volume element were performed, and the behavior of individual components of the relaxation tensor of the transversely isotropic composite material was determined. The study demonstrated that in the case of only one viscoelastic material, each component of the relaxation tensor can be described in terms of a scalar form factor and the behavior of the neat resin. The developed method was implemented in an incremental finite element model (FEM) analysis to calculate the stress relaxation on the macroscopic ply level. A validation of the approach has shown a promising agreement up to a limit below the glass transition temperature of 15 °C in longitudinal and 35 °C in transverse direction. This study therefore demonstrates a novel way to incrementally describe the macroscopic viscoelastic behavior of materials with a single viscoelastic component with good controllability for engineering purposes

Hybrid machine-learning and finite-element design for flexible metamaterial wings

Insect wings are formed by intricate combinations of flexible membranes and rigid veins; such a structure enables excellent flight performance, adaptability to aerodynamic forces, and biological functions. Comprehensive understanding of the interplay between wing patterning and flight dynamics has however not been achieved yet due to enormous variability of natural patterns and the extreme complexity of the modeling wing-air interactions. Therefore, the design of a pattern for artificial flexible wings is challenging. In contrast to other studies mimicking biological patterns of insect wings, we propose usage of metamaterials principles to enable controllable dynamics, and machine-learning techniques to solve a related multi-parameter design optimization problem. We demonstrate the advantages of this hybrid approach by finding practical patterns with improved target property – enhanced lift. The obtained designs were manufactured by means of a low-cost fused deposition modeling (FDM) 3D-printer from a single commercially available thermoplastic polyurethane (TPU) and revealed the required balance between the rigidity of metamaterial “veins” and the flexibility of the wing base. Extensions of our approach to other designs or analyses of other moving structures offer straightforward benefits in tackling a wide range of computationally complex aerodynamic and vibroacoustic problems

ANN-Based Estimation of the Defect Severity in the Drilling of GFRP/Ti Multilayered Composite Structure

The main purpose of this study was to develop a model for predicting the quality of holes drilled in the root part of the spar of helicopter main rotor blades made of glass fiber-reinforced plastic (GFRP)-Ti multilayer polymer composite. As the main quality criterion, delaminations at the entry and exit of the drill from the hole were taken. In the experimental study, a conventional drill and two modified geometry drills, a double-point angle drill and a dagger drill, were used. Preliminary experiments showed the best hole quality when using modified drills, which allowed further detailed study only with both modified drills at different drilling speeds and feed rates. Its results in the form of training sets were used to build artificial neural networks (ANNs) to predict delamination at the entry and exit of the drilled holes. An analysis of the fitted response functions presented as 3D surface plots and contour plots led to the selection of the best tool, a double-point angle drill, which demonstrated the lowest achievable delamination both at the entry and at the exit of the holes approximately 1.5 times less (0.45/0.48 mm) compared to dagger drills (0.68/0.7 mm) and determined the ~5 times larger optimal area for the drilling speed and feed rate. The results obtained confirm the possibility of effective prediction of the quality and productivity of mechanically processed composites of complex reinforcement using ANN to quantify the quality criteria and search for the optimal modes of such technologies

Numerical Study of Thin-Walled Polymer Composite Part Quality When Manufactured Using Vacuum Infusion with Various External Pressure Controls

The article presents the results of modeling various modes of vacuum infusion molding of thin-walled polymer-composite structures of arbitrary geometry. The small thickness of the manufactured structures and the fixation of their back surface on the rigid surface of the mold made it possible to significantly simplify the process model, which takes into account the propagation of a thermosetting resin with changing rheology in a compressible porous preform of complex 3D geometry, as well as changes in boundary conditions at the injection and vacuum ports during the post-infusion molding stage. In the four modes of vacuum-infusion molding studied at the post-infusion stage, the start time, duration and magnitude of additional pressure on the open surface of the preform and in its vacuum port, as well as the state of the injection gates, were controlled (open–closed). The target parameters of the processes were the magnitude and uniformity of the distribution of the fiber volume fraction, wall thickness, filling of the preform with resin and the duration of the process. A comparative analysis of the results obtained made it possible to identify the most promising process modes and determine ways to eliminate undesirable situations that worsen the quality of manufactured composite structures. The abilities of the developed simulation tool, demonstrated by its application to the molding process of a thin-walled aircraft structure, allow one to reasonably select a process control strategy to obtain the best achievable quality objectives

Multi-Criteria Decision Approach to Design a Vacuum Infusion Process Layout Providing the Polymeric Composite Part Quality

The increasingly widespread use of vacuum assisted technologies in the manufacture of polymer-composite structures does not always provide the required product quality and repeatability. Deterioration of quality most often appears itself in the form of incomplete filling of the preform with resin as a result of the inner and outer dry spot formation, as well as due to premature gelation of the resin and blockage of the vacuum port. As experience shows, these undesirable phenomena are significantly dependent on the location of the resin and vacuum ports. This article presents a method for making a decision on the rational design of a process layout. It is based on early forecasting of its objectives in terms of quality and reliability when simulating its finite element model, on the correlation analysis of the preliminary and final quality assessments, as well as on the study of the cross-correlation of a group of early calculated sub-criteria. The effectiveness of the proposed method is demonstrated by the example of vacuum infusion of a 3D thin-walled structure of complex geometry