scholarly journals Methodologies for the optimization of fibre-reinforced composite structures with manufacturing uncertainties

2006 ◽  
Author(s):  
◽  
Ryan Jason Hamilton
Keyword(s):  
Composite Structures ◽  
Design Space ◽  
Laminated Composite ◽  
Full Potential ◽  
Rectangular Plates ◽  
Case Scenario ◽  
Worst Case ◽  
Reinforced Plastics ◽  
Design Variables ◽  
Structural Applications

Fibre Reinforced Plastics (FRPs) have been used in many practical structural applications due to their excellent strength and weight characteristics as well as the ability for their properties to be tailored to the requirements of a given application. Thus, designing with FRPs can be extremely challenging, particularly when the number of design variables contained in the design space is large. For example, to determine the ply orientations and the material properties optimally is typically difficult without a considered approach. Optimization of composite structures with respect to the ply angles is necessary to realize the full potential of fibre-reinforced materials. Evaluating the fitness of each candidate in the design space, and selecting the most efficient can be very time consuming and costly. Structures composed of composite materials often contain components which may be modelled as rectangular plates or cylindrical shells, for example. Modelling of components such as plates can be useful as it is a means of simplifying elements of structures, and this can save time and thus cost. Variations in manufacturing processes and user environment may affect the quality and performance of a product. It is usually beneficial to account for such variances or tolerances in the design process, and in fact, sometimes it may be crucial, particularly when the effect is of consequence. The work conducted within this project focused on methodologies for optimally designing fibre-reinforced laminated composite structures with the effects of manufacturing tolerances included. For this study it is assumed that the probability of any tolerance value occurring within the tolerance band, compared with any other, is equal, and thus the techniques are aimed at designing for the worst-case scenario. This thesis thus discusses four new procedures for the optimization of composite structures with the effects of manufacturing uncertainties included.

Beyond the Known: Detecting Novel Feasible Domains Over an Unbounded Design Space

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Wei Chen ◽  
Mark Fuge
Keyword(s):  
Real World ◽  
Adaptive Sampling ◽  
Design Space ◽  
Fundamental Problem ◽  
Domain Boundary ◽  
Sampling Technique ◽  
Standard Test ◽  
Worst Case ◽  
Trade Offs ◽  
Design Variables

To solve a design problem, sometimes it is necessary to identify the feasible design space. For design spaces with implicit constraints, sampling methods are usually used. These methods typically bound the design space; that is, limit the range of design variables. But bounds that are too small will fail to cover all possible designs, while bounds that are too large will waste sampling budget. This paper tries to solve the problem of efficiently discovering (possibly disconnected) feasible domains in an unbounded design space. We propose a data-driven adaptive sampling technique—ε-margin sampling, which learns the domain boundary of feasible designs and also expands our knowledge on the design space as available budget increases. This technique is data-efficient, in that it makes principled probabilistic trade-offs between refining existing domain boundaries versus expanding the design space. We demonstrate that this method can better identify feasible domains on standard test functions compared to both random and active sampling (via uncertainty sampling). However, a fundamental problem when applying adaptive sampling to real world designs is that designs often have high dimensionality and thus require (in the worst case) exponentially more samples per dimension. We show how coupling design manifolds with ε-margin sampling allows us to actively expand high-dimensional design spaces without incurring this exponential penalty. We demonstrate this on real-world examples of glassware and bottle design, where our method discovers designs that have different appearance and functionality from its initial design set.

An Experimental Study of Continuous and Discrete Visualization Paradigms for Interactive Trade Space Exploration

2013 ◽  
Vol 13 (2) ◽  
Author(s):  
Brian J. German ◽  
Karen M. Feigh ◽  
Matthew J. Daskilewicz
Keyword(s):  
Design Space ◽  
Human Subjects ◽  
Optimal Designs ◽  
Full Potential ◽  
Design Metrics ◽  
Functional Relationships ◽  
Design Variables ◽  
Visualization Tools ◽  
Interactive Data ◽  
Trade Space Exploration

Software tools that enable interactive data visualization are now commonly available for engineering design. These tools allow engineers to inspect, filter, and select promising alternatives from large multivariate design spaces based upon an examination of the tradeoffs between multiple objectives. There are two general approaches for visually representing data: (1) discretely, by plotting a sample of designs as distinct points; and (2) continuously, by plotting the functional relationships between design variables and design metrics as curves or surfaces. In this paper, we examine these two approaches through a human subjects experiment. Participants were asked to complete two design tasks with an interactive visualization tool: one by using a sample of discrete designs and one by using a continuous representation of the design space. Metrics describing the optimality of the design outcomes, the usage of different graphics, and the task workload were quantified by mouse tracking, user process descriptions, and analysis of the selected designs. The results indicate that users had more difficultly in selecting multiobjective optimal designs with common continuous graphics than with discrete graphics. The findings suggest that innovative features and additional usability studies are required in order for continuous trade space visualization tools to achieve their full potential.

Modelling the Effect of Microstructural Randomness on the Fracture of Composite Laminates with Stochastic Cohesive Zone Elements

2009 ◽  
Vol 417-418 ◽  
pp. 13-16
Author(s):  
Zahid R. Khokhar ◽  
Ian A. Ashcroft ◽  
Vadim V. Silberschmidt
Keyword(s):  
Cohesive Zone ◽  
Composite Laminates ◽  
Composite Structures ◽  
Laminated Composite ◽  
Specific Strength ◽  
Laminated Composite Structures ◽  
Structural Applications ◽  
Fibre Reinforced Polymer ◽  
Strength And Stiffness ◽  
Cohesive Zone Elements

Fibre reinforced polymer composites (FRPCs) are being increasingly used in structural applications where high specific strength and stiffness are required. The performance of FRPCs is affected by multi-mechanism damage evolution under loading which in turn is affected by microstructural stochasticity in the material. This means that the fracture of a FRPC is a stochastic process. However, to date most analyses of these materials have treated them in a deterministic way. In this paper the effect of stochasticity in FRPCs is investigated through the application of cohesive zone elements in which random properties are introduced. These may be termed ‘stochastic cohesive zone elements’ and are used in this paper to investigate the effect of microstructural randomness on the fracture behaviour of cross-ply laminate specimens loaded in tension. It is seen from this investigation that microstructure can significantly affect the macroscopic response of FRPC’s, emphasizing the need to account for microstructural randomness in order to make accurate prediction of the performance of laminated composite structures.

Multidisciplinary Design Optimization of Actuator Arrangements, Lay-Up Configurations and Control Systems for Smart Laminated Composite Structures

2010 ◽  
Author(s):  
Shinya Honda ◽  
Itsuro Kajiwara ◽  
Yoshihiro Narita
Keyword(s):  
Design Optimization ◽  
Control Systems ◽  
Multidisciplinary Design Optimization ◽  
Composite Structures ◽  
Vibration Suppression ◽  
Laminated Composite ◽  
Piezoelectric Actuators ◽  
Multidisciplinary Design ◽  
Design Variables ◽  
And Control

Structures and control systems of smart laminated composites consisting of graphite-epoxy composites and piezoelectric actuators are designed optimally for the vibration suppression. Placements of piezoelectric actuators, lay-up configurations of laminated composite plates and the H2 control system are employed as design variables and are optimized simultaneously by a simple genetic algorithm (SGA). An objective function is H2 performance with assuming that the state feedback is available. A multidisciplinary design optimization is performed with above three design variables and then the output feedback system is reconstructed with the dynamic compensator based on the linear matrix inequality (LMI) approach. Optimization results show that the optimized smart composite successfully realizes vibration suppression of the system and it is confirmed that the present multidisciplinary design optimization technique is quite efficient to the smart composites.

scholarly journals Structural Integrity Assessment of Composites Plates with Embedded PZT Transducers for Structural Health Monitoring

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6148
Author(s):  
Tianyi Feng ◽  
M.H. Ferri Aliabadi
Keyword(s):  
Elastic Modulus ◽  
Lead Zirconate Titanate ◽  
Composite Structures ◽  
Structural Integrity ◽  
Fatigue Loading ◽  
Active Sensing ◽  
Case Scenario ◽  
Worst Case ◽  
Integrity Assessment ◽  
Compressive Tests

Active sensing using ultrasonic guided waves (UGW) is widely investigated for monitoring possible damages in composite structures. Recently, a novel diagnosed film based on a circuit-printed technique with piezoelectric lead zirconate titanate (PZT) transducers has been developed. The diagnostic film is a replacement for the traditional cable connection to PZT sensors and has been shown to significantly reduce the weight of the host structure. In this work, the diagnosed films were embedded into composite structures during manufacturing using a novel edge cut-out method during lay-up, which allowed for edge trimming after curing. In this paper, the effect of fatigue loading on the integrity of PZT transducers is initially investigated. The electro-mechanical impedance (EMI) properties at different fatigue loading cycles were used as the diagnostic measure for the performance of the sensors. At the same time, the behaviours of UGW were investigated at different fatigue loading cycles. It was found that the EMI properties and active sensing behaviours remained stable up to 1 million cycles for the force ranges of 0.5~5 kN and 1~10 kN. Next, the effect of embedding the diagnosed film on the mechanical properties of the host composite structure was investigated. Tensile and compressive tests were conducted and the elastic modulus of composite coupons with and without embedded PZT diagnosed films were compared. The elastic modulus of composite coupons with PZT diagnosed films embedded across the entire coupon reduced by as much as 20% for tensile tests and just over 10% for compressive tests compared to the coupons without embedded sensors. These reductions are considered the worst-case scenario, as in real structures the film would only be embedded in a relatively small area of the structure.

Genetic Algorithm Approach for Optimization of FRP Laminated Cylindrical Shells Under Constraint

1999 ◽  
Author(s):  
Yoshiki Ohta
Keyword(s):  
Genetic Algorithm ◽  
Cylindrical Shells ◽  
Laminated Composite ◽  
Frequency Equation ◽  
Genetic Operators ◽  
Fundamental Frequencies ◽  
Design Variables ◽  
Structural Applications ◽  
Genetic Algorithm Approach ◽  
Laminated Cylindrical Shells

Abstract Fiber Reinforced Plastic (FRP) materials have been increasingly used in many structural applications of space shuttles, airplanes and automobiles, and the structural optimization of FRP laminated composite shells has been studied for stiffer structural design by many researchers. This paper studies the maximization of fundamental frequencies of FRP laminated cylindrical shells under stiffness constraint by using Genetic Algorithm (GA). For this purpose, the frequency equation for simply-supported shells with symmetrically balanced stacking sequence is derived analytically based on Classical Lamination Theory. In optimization the fiber angles and the thickness ratio of each FRP ply, which have continuous real values, are taken as design variables, and fundamental frequency of the shell is maximized under in-plane stiffness constraints. In numerical experiments, extensive numerical calculations are carried out to determine better genetic operators that would be suitable for FRP laminates design, and genetic parameters are tuned for better reliabilities and lower computational costs in the present GA. Optimal design solutions for various laminated cylindrical shells are obtained and then the applicability of the GA to the maximization of frequencies of the shells is studied from numerical results obtained.

scholarly journals Antioptimisation of Trusses Using Two-Level Population-Based Incremental Learning

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Phinit Tontragunrat ◽  
Sujin Bureerat
Keyword(s):  
Optimum Design ◽  
Incremental Learning ◽  
Population Based ◽  
Numerical Results ◽  
Level Population ◽  
Case Scenario ◽  
Worst Case ◽  
Worst Case Scenario ◽  
Design Variables ◽  
Optimum Solution

Practical optimum design of structures often involves parameters with uncertainties. There have been several ways to deal with such optimisation problems, and one of the approaches is an antioptimisation process. The task is to find the optimum solution of common design variables while simultaneously searching for the worst case scenario of those parameters with uncertainties. This paper proposed a metaheuristic based on population-based incremental learning (PBIL) for solving antioptimisation of trusses. The new algorithm is called two-level PBIL which consists of outer and inner loops. Five antioptimisation problems are posed to test the optimiser performance. The numerical results show that the concept of using PBIL probability vectors for handling the antioptimisation of truss is powerful and effective. The two-level PBIL can be considered a powerful optimiser for antioptimisation of trusses.

On feasible regions of lamination parameters for lay-up optimization of laminated composites

2008 ◽  
Vol 465 (2104) ◽  
pp. 1123-1143 ◽  
Author(s):  
M.W Bloomfield ◽  
C.G Diaconu ◽  
P.M Weaver
Keyword(s):  
Composite Structures ◽  
Laminated Composite ◽  
Feasible Region ◽  
Lamination Parameters ◽  
Design Variables ◽  
Laminated Composite Structures ◽  
Out Of Plane ◽  
Finite Set ◽  
Convexity Properties ◽  
Independent Design

The stiffness tensors of a laminated composite may be expressed as a linear function of material invariants and lamination parameters. Owing to the nature of orienting unidirectional laminae ply by ply, lamination parameters, which are trigonometric functions of the ply orientation, are interrelated. In optimization studies, lamination parameters are often treated as independent design variables constrained by inequality relationships to feasible regions that depend on their values. The relationships between parameters enclose a convex feasible region of lamination parameters which is generally unknown. The convexity properties allow the efficient optimization of laminated composite structures where lamination parameters are used as design variables. Herein, a two-level method is presented to determine the feasible regions of lamination parameters where potential ply orientations are a predefined finite set. At the first level, the feasible region of the in-plane, coupling and out-of-plane lamination parameters is determined separately using convex hulls. At the second level, a nonlinear algebraic identity is used to relate the in-plane, coupling and out-of-plane lamination parameters to each other. This general approach yields all constraints on the feasible regions of lamination parameters for a predefined set of ply orientations.

Damage Detection in Laminated Composite Beams, Plates and Shells Using Dynamic Analysis

2015 ◽  
Vol 787 ◽  
pp. 901-906 ◽  
Author(s):  
G. Mahendran ◽  
Chandrasekaran Kesavan ◽  
S.K. Malhotra
Keyword(s):  
Numerical Analysis ◽  
Composite Structures ◽  
Laminated Composite ◽  
Composite Beams ◽  
Modal Testing ◽  
Mode Shapes ◽  
Rectangular Plates ◽  
Displacement Mode ◽  
Damage Indicator ◽  
Laminated Composite Beams

Vibration-based technique to detect damage in laminated composite beams, rectangular plates and cylindrical shells is presented in this paper.A parameter called damage indicator calculated based on mode shape curvature isused in this studyto detect the location and size of small damages accurately in laminated composite structures. Through numerical analysis of laminated compositecantilevered beam, plate and cylindrical shell models with edge crack as damage, the absolute change inthe damage indicator is localized in the region of damage. Thechange in damage indicatorincreases withincreasing size of damage. Thisinformationis obtained by considering two cases of damage sizes (case-1 and case-2)in the structures. Finite element methodbased commercial analysis package ANSYSis used to obtain thenormalized displacement mode shapesof the three models both for intact and damaged states and then the damage indicator is calculated from the mode shapes data.The numerical analysis to detect damage is followed by validation by experimental modal testing.

A comparative analysis of evolutionary algorithms in the design of laminated composite structures

2017 ◽  
Vol 24 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Pavel Y. Tabakov ◽  
Sibusiso Moyo
Keyword(s):  
Evolutionary Algorithms ◽  
Design Optimization ◽  
Composite Structures ◽  
Optimization Problems ◽  
Laminated Composite ◽  
Design Sensitivity ◽  
Optimization Techniques ◽  
Full Potential ◽  
Analysis And Design ◽  
Laminated Composite Structures

AbstractThe increased use of composite materials and structures in many engineering applications led to the need for a more accurate analysis and design optimization. While methods of stress-strain analysis developed faster, optimization techniques have been lagging behind. As a result, many designed structures do not fulfill their full potential. The present study demonstrates the major achievements in recent years in an application of evolutionary algorithms to the design optimization of fiber-reinforced laminated composite structures. Such structures are of much interest due to high structural design sensitivity to fiber orientations as well as complex multidimensional discrete optimization problems. Using an anisotropic multilayered cylindrical pressure vessel and an exact elasticity solution as an example, we show how the optimum, or near–optimum, solution can be found in a more efficient way.

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