scholarly journals Method of Equivalent Strength Conditions in Composite Structures Evaluations

2021 ◽  
pp. 106-115
Author(s):  
A.D. Matveev
Keyword(s):  
Composite Structures ◽  
High Efficiency ◽  
Approximation Error ◽  
Regular Structure ◽  
Approximate Solutions ◽  
Discrete Models ◽  
The Finite Element Method ◽  
Elastic Bodies ◽  
Equivalent Strength ◽  
Computer Resources

It is important to know the error or the approximate solution when calculating the strength of elastic composite structures (bodies) using the finite element method (FEM). To construct a sequence of solutions according to the FEM is necessary for the evaluation of the approximation error. It involves the grinding procedure for discrete models. The implementation of the grinding procedure for basic models that take into account the inhomogeneous, micro-homogeneous structures of bodies within the microapproach requires ample computer resources. This paper proposes a method of equivalent strength conditions (MESC) to calculate the static strength of elastic bodies with a non-uniform, microuniform regular structure. The calculation of composite bodies strength according to the MESC is reduced to the calculation of isotropic homogeneous bodies strength using equivalent strength conditions. Adjusted equivalent strength conditions are used in the numerical implementation of the MESC. They take into account the error of the approximate solutions. If a set of loads is specified for a composite body, then generalized equivalent strength conditions are applied. The FEM-based calculation of composite bodies strength that follows the MESC using multigrid finite elements requires 103 ÷ 105 times less computer memory than a similar calculation using ground basic models of composite bodies. The provided example of strength calculation for a beam with an inhomogeneous regular fiber structure using the MESC shows its high efficiency. The main MESC implementation procedures are outlined.

scholarly journals Research on the Manufacturing Quality of Co-Cured Hat-Stiffened Composite Structure

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2747
Author(s):  
Xiangwen Ju ◽  
Jun Xiao ◽  
Dongli Wang ◽  
Cong Zhao ◽  
Xianfeng Wang
Keyword(s):  
Composite Structures ◽  
Sound Pressure ◽  
Integration Method ◽  
Complex Geometry ◽  
Sound Field ◽  
Thickness Measurement ◽  
Curing Process ◽  
The Finite Element Method ◽  
Manufacturing Quality

The stringer-stiffened structure is widely used due to its excellent mechanical properties. Improving the manufacturing quality of stringer-stiffened structure which have complex geometry is important to ensure the bearing capacity of aviation components. Herein, composite hat-stiffened composite structures were manufactured by different filling forms and bladders with various properties, the deformation of silicone rubber bladder in co-curing process was studied by using the finite element method. The thickness measurement at different positions of the hat-stiffened structure was performed to determine the best filling form and bladder property. Moreover, in view of the detection difficulties in R-zone of stringer, numerical simulation was performed to get the sound pressure and impulse response of at the R-zone of stringer by Rayleigh integration method, and an effective equipment which could stably detect the manufacturing quality of R-zone was designed to verify the correctness of sound field simulation and realize the detection of stringer. With the optimum filling form and bladder properties, hat-stiffened composites can be manufactured integrally with improved surface quality and geometric accuracy, based on co-curing process.

Energy absorption structures design of civil aircraft to improve crashworthiness

2014 ◽  
Vol 118 (1202) ◽  
pp. 383-398 ◽  
Author(s):  
Y. Ren ◽  
J. Xiang
Keyword(s):  
Finite Element Method ◽  
Energy Absorption ◽  
High Efficiency ◽  
Wave Beam ◽  
Sine Wave ◽  
Structure Design ◽  
Failure Model ◽  
The Finite Element Method ◽  
Civil Aircraft ◽  
Aircraft Crashworthiness

AbstractTo improve the crashworthiness of civil aircraft, the design concept of energy absorption structure for civil aircraft is investigated. Two typical different design principles could be identified. The first category includes Helicopter and Light fixed-wing Aircraft (HLA), and Transport, Mid-size and Commuter type Aircraft (TMCA) are classified into the second group. Frame, strut and bottom structure are the three kinds of energy absorption structure for TMCA. The strut layout of conventional civil aircraft is studied and some energy absorption devices are adopted. High efficiency energy absorption structures such as the foam and sine-wave beam are employed as the bottom structure for both of HLA and LMCA. The finite element method is used to analyse and design energy absorption structure in aircraft crashworthiness problem. Results show that the crashworthiness of civil aircraft could be largely improved by using proper strut layout and excellent energy absorption device. The stiffness combination of frame and strut should be considered to get better global aircraft deformation. Supporting platform and failure model are the two core problems of bottom energy absorption structure design. Foam and sine-wave beam under the lifted frame could improve the crashworthiness of civil aircraft.

Tunable Band Gaps of Acoustic Waves in Two-Dimensional Phononic Crystals With Reticular Band Structures

2009 ◽  
Author(s):  
Zi-Gui Huang ◽  
Yunn-Lin Hwang ◽  
Pei-Yu Wang ◽  
Yen-Chieh Mao
Keyword(s):  
Acoustic Waves ◽  
Composite Structures ◽  
Phononic Crystals ◽  
Band Gaps ◽  
Sound Insulation ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Elastic Band ◽  
Band Structures ◽  
Elastic Band Gaps

The excellent applications and researches of so-called photonic crystals raise the exciting researches of phononic crystals. By the analogy between photon and phonon, repetitive composite structures that are made up of different elastic materials can also prevent elastic waves of some certain frequencies from passing by, i.e., the frequency band gap features also exist in acoustic waves. In this paper, we present the results of the tunable band gaps of acoustic waves in two-dimensional phononic crystals with reticular band structures using the finite element method. Band gaps variations of the bulk modes due to different thickness and angles of reticular band structures are calculated and discussed. The results show that the total elastic band gaps for mixed polarization modes can be enlarged or reduced by adjusting the orientation of the reticular band structures. The phenomena of band gaps of elastic or acoustic waves can potentially be utilized for vibration-free, high-precision mechanical systems, and sound insulation.

scholarly journals Multiple shooting method in stability analysis of non-prismatic multi-segment columns

2013 ◽  
Vol 12 (4) ◽  
pp. 225-232
Author(s):  
Ryszard Hołubowski ◽  
Andrzej Merena
Keyword(s):  
Finite Element Method ◽  
Stability Analysis ◽  
Shooting Method ◽  
High Efficiency ◽  
Variable Coefficients ◽  
Multiple Shooting ◽  
System Of Differential Equations ◽  
The Finite Element Method ◽  
Concentrated Force ◽  
Multiple Shooting Method

The application of multiple shooting method in stability analysis of non-prismatic multi-segment columns with pinned ends loaded with a concentrated force applied to the upper node has been presented. Numerical analyses were carried out for an exemplary three-segment column by solving the system of differential equations with variable coefficients and parameter. The results were compared with the solution obtained by using SOFiSTiK software based on the finite element method. The analyses show that considering the stiffness changes along the length can have a significant influence on the values of critical loads and thus change the resistance of the column. The advantage of the proposed method is its high efficiency and easy description of stiffness changes.

scholarly journals Broad-band and high-efficiency polarization converters around 1550 nm based on composite structures

2017 ◽  
Vol 25 (13) ◽  
pp. 14406 ◽  
Author(s):  
Xiong-Jun Shang ◽  
Xiang Zhai ◽  
Jing Yue ◽  
Xin Luo ◽  
Jian-Ping Liu ◽  
...  
Keyword(s):  
Composite Structures ◽  
High Efficiency ◽  
Broad Band ◽  
Polarization Converters
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