Load Transfer Index for Composite Materials

2015 ◽  
Author(s):  
Qingguo Wang ◽  
Khashayar Pejhan ◽  
Christine Q. Wu ◽  
Igor Telichev
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Load Transfer ◽  
External Loading ◽  
Load Path ◽  
New Paradigm ◽  
Linear Elastic ◽  
Transfer Index ◽  
Fundamental Equations ◽  
Load Transfer Analysis

Load transfer analysis is a new paradigm for lightweight vehicle design. U* index has been proved to be an effective indicator for the load path. The U* theory indicates that the external loading mainly transfers through the parts with higher U* values in the structure. However, the fundamental equations of the theory are based on isotropic, homogenous, and linear elastic assumptions for the materials. Consequently, U* index is inadequate for composite materials which are increasingly used in automotive structures. In this study, a new load transfer index for composite structures, U*O, is proposed for the first time inspired by the basic U* theory. The U*O index considers the composite material as orthotropic instead of isotropic and eliminates the limitation of the basic U*. The effectiveness of the new U*O index on load path prediction is demonstrated by a case study for a general Graphite-epoxy lamina. The U*O index is capable to evaluate the accurate load path for the composite specimen. By contrast, the basic U* analysis shows the incorrect results.

Application of Load Transfer Index (U*) in Structural Analysis in Comparison With Conventional Stress Analysis

2014 ◽  
Author(s):  
Khashayar Pejhan ◽  
Christine Q. Wu ◽  
Igor Telichev
Keyword(s):  
Stress Analysis ◽  
Load Transfer ◽  
Structure Design ◽  
Stress Distributions ◽  
Load Path ◽  
Additional Information ◽  
Path Index ◽  
Comprehensive Information ◽  
Transfer Index ◽  
Load Transfer Analysis

The U* index has been used for load transfer analysis to show its capability in giving general awareness regarding performance of structure. Although U* index and stress values have been proven to be useful indexes as structure design criteria, a thorough comparison between conventional stress analysis and loads transfer analysis (based on U* index) is lacking. In this study, we evaluate load transfer behaviors of a parcel rack of multiple passenger vehicles under different loading conditions using the U* index. Then by demonstrating the unique capabilities of U* as an index for stiffness, it is shown that the load path concept can be combined with the stress analysis results to provide comprehensive information about the structure responses to loading. In addition to the agreement between stress analysis and the U* analysis, it is shown that U* can provide additional information about the structure response that stress analysis fails. Such information includes: interpreting high and complicated stress distributions in structure and detection of questionable stiffness in certain parts of structure. More importantly, the load path index U* can detect the area where significant changes in the structure stiffness occurs. Such information can be used as a guideline for structure design with the goal to reduce the weight while still keeping the structure integrity.

Extension of U* Index Theory to Nonlinear Case of Load Transfer Analysis

2015 ◽  
Author(s):  
Khashayar Pejhan ◽  
Qingguo Wang ◽  
Christine Q. Wu ◽  
Igor Telichev
Keyword(s):  
Load Transfer ◽  
Index Theory ◽  
Design Tool ◽  
Load Path ◽  
Nonlinear Load ◽  
Index Value ◽  
Transfer Index ◽  
Static Conditions ◽  
Nonlinear Elastic ◽  
Load Transfer Analysis

Load transfer analysis has been proved to be an effective approach for designing light weight vehicle structures in last two decades. There are two main procedures for predicting the load path in a vehicle: The stress trajectory method and the U* index theory. The first approach has shown some shortcomings in dealing with geometrical irregularities. As a result, automotive industries have mainly applied the U* index as a design tool to study the load transfer behavior in the vehicle structure. The U* index, is an indicator for the load transfer in the structure, i.e. higher U* index value indicates more significant role in the load transfer process. So, the distribution of the U* index in the structure can be used to predict the main load path in the structure. Nevertheless, this foundation of this theory is based upon the linear elasticity equations and consequently, it has always been limited to linear elastic problems in static or quasi static conditions. Eradicating this limitation and extending the U* Index theory to nonlinear elastic problems is the main objective of this study. An extension to nonlinear criteria for U* index theory is proposed in this paper. It is shown, for the very first time, that the extended nonlinear load transfer index (U*NL) is a true measure for the load transfer in the structure in a nonlinear elastic problem.

Experimental Study of U* Index Response to Structural and Loading Variations

2015 ◽  
Author(s):  
Khashayar Pejhan ◽  
Qingguo Wang ◽  
Igor Telichev
Keyword(s):  
Load Transfer ◽  
Experimental Testing ◽  
Minimum Weight ◽  
Index Theory ◽  
Load Path ◽  
Stress Concentrations ◽  
Structural Variations ◽  
Design Modification ◽  
Testing Procedures ◽  
Load Transfer Analysis

Load transfer analysis tracks the path, on which the imposed load is being carried through the structure. Recently, vehicle structure designers have paid growing attention to this aspect of structural analysis for designing lighter vehicle structures that can efficiently carry the imposed loads with minimum weight. There are two main procedures for load transfer analysis in automotive engineering: 1) Stress trajectory method and 2) U* index theory. The former method faces some difficulties in following load path in structures with stress concentrations made by geometrical irregularities. As a result the U* index theory has been utilized more frequently in this area. This theory has shown exceptional capacities in following load transfer in the structure and has provided innovative tools for design modification in automotive industry. Although it can be shown mathematically that U* index quantifies the internal stiffness of the structure there has not been an experimental validation for that. Moreover, the term internal stiffness itself is not an easy concept to follow and it can be easily mistaken for the structural stiffness of the structure. As a result in the current paper two experimental testing procedures are presented to distinguish the internal stiffness, that can be quantified with U* index and the structural (conventional) stiffness of the structure. Through these experiments, for the first time, physical evaluation of U* index response to loading and structural variations can be performed.

Behavior of Composite Materials Under Impact: Strain Rate Effects, Damage, and Plasticity

2001 ◽  
Author(s):  
Serge Abrate
Keyword(s):  
Composite Materials ◽  
Strain Rate ◽  
Composite Structures ◽  
Current Knowledge ◽  
Matrix Material ◽  
Material Behavior ◽  
Elastic Behavior ◽  
Linear Elastic ◽  
Matrix Cracks ◽  
Different Types

Abstract Composite materials are often subjected to low velocity impacts, ballistic impacts, or crash impacts. In order to analyze such events, realistic model of the material behavior must be used to capture phenomena no included in linear elastic models. Nonlinear behavior occurs when a unidirectional lamina is loaded in the transverse direction or in shear when the matrix material deforms plastically. The stiffness and strength of composite materials at high strain rates is often very different from what is measured in quasi-static tests. In addition, different types of damage are introduced during impart: matrix cracks, delaminations, fiber failures, fiber-matrix debonding. The introduction of this damage will affect the subsequent behavior of the material. Many different approaches have been taken to account for the effects of strain rate, plasticity and damage on the mechanical behavior of composite materials. The objective of this paper is to assess current knowledge in this area, review and compare models used to describe the stress-strain behavior and predict failure of such materials. Continuum mechanics approaches are used to describe the behavior of laminas with different types of damage, and to model the behavior of interfaces between plies. Phenomenological plasticity models account for the nonlinear effects under transverse and shear loads. Some of these models are shown to be similar even though they were derived by very different approaches. Many accurate analyses of composite structures under impact assume linear elastic behavior and do not considered the complicating effects discussed here. The applicability of the different models for material behavior is also discussed in terms of selecting an appropriate model for analyzing a particular impact.

scholarly journals Defects and uncertainties of adhesively bonded composite joints

2021 ◽  
Vol 3 (9) ◽  
Author(s):  
Sadik Omairey ◽  
Nithin Jayasree ◽  
Mihalis Kazilas
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Production Efficiency ◽  
Adhesive Bonding ◽  
Detection Methods ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Wide Range ◽  
Bonded Composite

AbstractThe increasing use of fibre reinforced polymer composite materials in a wide range of applications increases the use of similar and dissimilar joints. Traditional joining methods such as welding, mechanical fastening and riveting are challenging in composites due to their material properties, heterogeneous nature, and layup configuration. Adhesive bonding allows flexibility in materials selection and offers improved production efficiency from product design and manufacture to final assembly, enabling cost reduction. However, the performance of adhesively bonded composite structures cannot be fully verified by inspection and testing due to the unforeseen nature of defects and manufacturing uncertainties presented in this joining method. These uncertainties can manifest as kissing bonds, porosity and voids in the adhesive. As a result, the use of adhesively bonded joints is often constrained by conservative certification requirements, limiting the potential of composite materials in weight reduction, cost-saving, and performance. There is a need to identify these uncertainties and understand their effect when designing these adhesively bonded joints. This article aims to report and categorise these uncertainties, offering the reader a reliable and inclusive source to conduct further research, such as the development of probabilistic reliability-based design optimisation, sensitivity analysis, defect detection methods and process development.

scholarly journals Introduction to Macroscopic Optimal Design in the Mechanics of Composite Materials and Structures

2021 ◽  
Vol 5 (2) ◽  
pp. 36
Author(s):  
Aleksander Muc
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Constitutive Relations ◽  
A Priori ◽  
Chemical Properties ◽  
Composite Plates ◽  
Failure Criteria ◽  
Lagrange Equations ◽  
Homogenization Methods ◽  
Mechanics Of Composite Materials

The main goal of building composite materials and structures is to provide appropriate a priori controlled physico-chemical properties. For this purpose, a strengthening is introduced that can bear loads higher than those borne by isotropic materials, improve creep resistance, etc. Composite materials can be designed in a different fashion to meet specific properties requirements.Nevertheless, it is necessary to be careful about the orientation, placement and sizes of different types of reinforcement. These issues should be solved by optimization, which, however, requires the construction of appropriate models. In the present paper we intend to discuss formulations of kinematic and constitutive relations and the possible application of homogenization methods. Then, 2D relations for multilayered composite plates and cylindrical shells are derived with the use of the Euler–Lagrange equations, through the application of the symbolic package Mathematica. The introduced form of the First-Ply-Failure criteria demonstrates the non-uniqueness in solutions and complications in searching for the global macroscopic optimal solutions. The information presented to readers is enriched by adding selected review papers, surveys and monographs in the area of composite structures.

The effect of nanoparticle additive on surface milling in glass fiber reinforced composite structures

2021 ◽  
pp. 096739112110141
Author(s):  
Ferhat Ceritbinmez ◽  
Ahmet Yapici ◽  
Erdoğan Kanca
Keyword(s):  
Composite Materials ◽  
Glass Fiber ◽  
Composite Structures ◽  
Fiber Composite ◽  
Cutting Speed ◽  
Fiber Reinforced ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite ◽  
Glass Fiber Reinforced ◽  
Composite Layers

In this study, the effect of adding nanosize additive to glass fiber reinforced composite plates on mechanical properties and surface milling was investigated. In the light of the investigations, with the addition of MWCNTs additive in the composite production, the strength of the material has been changed and the more durable composite materials have been obtained. Slots were opened with different cutting speed and feed rate parameters to the composite layers. Surface roughness of the composite layers and slot size were examined and also abrasions of cutting tools used in cutting process were determined. It was observed that the addition of nanoparticles to the laminated glass fiber composite materials played an effective role in the strength of the material and caused cutting tool wear.

Stress analysis of finite orthotropic composite containing an elliptical hole

2021 ◽  
pp. 002199832110507
Author(s):  
Narin S. Fatima ◽  
Robert E. Rowlands
Keyword(s):  
Composite Structures ◽  
Elliptical Hole ◽  
External Loading ◽  
Finite Geometries ◽  
Orthotropic Composites ◽  
Numerical Tools ◽  
Design Type ◽  
Measured Displacement ◽  
Type Information ◽  
Important Design

Although the mechanical integrity of a member can be highly influenced by associated stresses, determining the latter can be very challenging for finite orthotropic composites containing cutouts. This is particularly so if the external loading is not well known, a common situation in practical situations. Acknowledging the above, a finite elliptically-perforated orthotropic tensile laminate is stress analyzed by combining measured displacement data with relevant analytical and numerical tools. Knowledge of the external loading is unnecessary. Results are verified independently and the concepts are applicable to other situations. The developed technology can provide important design-type information for orthotropic composites. In particular, the ability to apply analyses for perforated composite structures which assume infinite geometry to finite geometries is demonstrated.

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