Control of cracks by interfaces in composites

1975 ◽  
Vol 341 (1627) ◽  
pp. 409-428 ◽  
Keyword(s):  
Composite Material ◽  
Elastic Properties ◽  
Adhesive Joint ◽  
Composite Structures ◽  
Crack Path ◽  
Brittle Materials ◽  
Novel Theory ◽  
The Individual ◽  
Model Crack

A novel theory is proposed to show how a crack may he accelerated or retarded when it meets an interface between two equally brittle materials of different elastic properties. Measurements of a model crack travelling through a brittle adhesive joint have substantially verified the theory. The results demonstrate that the toughness of a composite material, having a periodic stiffness change along the crack path, may be very much greater than the toughness of the individual components of the composite. The relevance of these ideas to the design of tough composite structures is discussed.

scholarly journals Numerical evaluation of the elastic properties of carbon fiber reinforced composite material at elevated and lowered temperatures

2021 ◽  
Vol 53 (1) ◽  
pp. 127-136
Author(s):  
Alteer Saleem ◽  
Veljko Petrovic ◽  
Aleksandar Grbovic ◽  
Jasmina Lozanovic-Sajic ◽  
Igor Balac
Keyword(s):  
Composite Material ◽  
Carbon Fiber ◽  
Elastic Properties ◽  
Composite Structures ◽  
Thermal Stresses ◽  
Epoxy Composite ◽  
Laminated Composite ◽  
Laminated Composite Structures ◽  
Multi Phase ◽  
Carbon Fiber Epoxy

The effect of elevated and lowered temperatures on the elastic properties of carbon fiber-epoxy composite material was studied using multi-phase unit cell (MPUC) numerical model. Evaluation of the elastic properties of carbon fiber-epoxy composite material is based on the finite element method. Obtained results confirmed that elevated and lowered temperature has noticeable influence on elastic properties of carbon fiber-epoxy composite material. As demonstrated, this fact has considerable influence on accurate evaluation of generated thermal stresses in real laminated composite structures, exposed to extremely high or low operating temperatures.

Advances in Tire Composite Theory

1973 ◽  
Vol 1 (2) ◽  
pp. 210-250 ◽  
Author(s):  
J. D. Walter ◽  
G. N. Avgeropoulos ◽  
M. L. Janssen ◽  
G. R. Potts
Keyword(s):  
Composite Material ◽  
Stress Analysis ◽  
Elastic Properties ◽  
Material Technology ◽  
Present Composite ◽  
Pneumatic Tires

Abstract Fundamentals of composite material technology are applied to the investigation of multi-ply cord-reinforced rubber systems as used in pneumatic tires. The stiffness parameters of such multi-ply systems are determined through the use of the elastic properties of the constituent cord and rubber components. The effects of coupling between the bending and stretching modes of deformation are discussed along with the limitations of present composite material technology as applied to soft rubbery systems. The predicted stiffness parameters are related to tread wear, obstacle envelopment, vibration, and stress analysis of tires.

scholarly journals Mechanics of tubular helical assemblies: ensemble response to axial compression and extension

2021 ◽  
Author(s):  
Jacopo Quaglierini ◽  
Alessandro Lucantonio ◽  
Antonio DeSimone
Keyword(s):  
Boundary Conditions ◽  
Elastic Properties ◽  
Central Region ◽  
Mechanical Response ◽  
Different Boundary Conditions ◽  
Kirchhoff Rods ◽  
Model Versus ◽  
The Individual ◽  
Opposite Chirality

Abstract Nature and technology often adopt structures that can be described as tubular helical assemblies. However, the role and mechanisms of these structures remain elusive. In this paper, we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchhoff rods, arranged in pairs with opposite chirality and connected by pin joints, both analytically and numerically. We first focus on compression and find that, whereas a single helical rod would buckle, the rods of the assembly deform coherently as stable helical shapes wound around a common axis. Moreover, we investigate the response of the assembly under different boundary conditions, highlighting the emergence of a central region where rods remain circular helices. Secondly, we study the effects of different hypotheses on the elastic properties of rods, i.e., stress-free rods when straight versus when circular helices, Kirchhoff’s rod model versus Sadowsky’s ribbon model. Summing up, our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods, as well as some interesting features, and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology. Graphic Abstract We study the mechanical response under compression/extension of an assembly composed of 8 helical rods, pin-jointed and arranged in pairs with opposite chirality. In compression we find that, whereas a single rod buckles (a), the rods of the assembly deform as stable helical shapes (b). We investigate the effect of different boundary conditions and elastic properties on the mechanical response, and find that the deformed geometries exhibit a common central region where rods remain circular helices. Our findings highlight the key role of mutual interactions in the ensemble response and shed some light on the reasons why tubular helical assemblies are so common and persistent.

Numerical Simulation of Thermoplastic Composite Material by ANSYS

2011 ◽  
Vol 279 ◽  
pp. 181-185 ◽  
Author(s):  
Guo Hua Zhao ◽  
Qing Lian Shu ◽  
Bo Sheng Huang
Keyword(s):  
Numerical Simulation ◽  
Composite Material ◽  
Composite Structures ◽  
Material Model ◽  
General Purpose ◽  
Thermoplastic Composite ◽  
Finite Element Code ◽  
Peek Composite ◽  
Test Result ◽  
Good Agreement

This paper proposes a material model of AS4/PEEK, a typical thermoplastic composite material, for the general purpose finite element code—ANSYS, which can be used to predict the mechanical behavior of AS4/PEEK composite structures. The computational result using this model has a good agreement with the test result. This investigation can lay the foundation for the numerical simulation of thermoplastic composite structures.

Industrial Constraints Handling With a GA Approach in Multiobjective Optimization of a Composite Material

2008 ◽  
Author(s):  
David H. Bassir ◽  
WeiHong Zhang ◽  
Jose´ L. Zapico
Keyword(s):  
Genetic Algorithms ◽  
Composite Material ◽  
Multiobjective Optimization ◽  
Composite Structures ◽  
Laminated Composite ◽  
Constraints Handling ◽  
Laminated Composite Structures ◽  
Technological Constraints

In this article, complexities related to the multicriteria (multiobjective) optimization of laminated composite structures subjected to technological constraints we will be presented. So, various technological constraints will be presented and a strategy of handling each constraint (in order to use the multiobjective optimization tools based on genetic algorithms) will be also introduced.

scholarly journals Numerical Analysis of the Effect of Microscale Components Interaction on Measurements of Fiber Optic Strain Sensors Used in Composite Structures

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Mikhail Tashkinov ◽  
Igor Shardakov
Keyword(s):  
Composite Material ◽  
Numerical Analysis ◽  
Optical Fiber ◽  
Composite Structures ◽  
Fiber Optic ◽  
Strain Tensor ◽  
Strain Sensors ◽  
Numerical Estimation ◽  
Structural Components ◽  
Fiber Optic Strain Sensors

The paper investigates the influence of structural components of a composite material on the strain values measured by using an embedded optical fiber with Bragg gratings. The effect of composite plies and intermediate epoxy layers on the transfer of deformations from the measured object to the optical fiber was studied taking into account various methods of the fiber attachment and surrounding media configurations. A numerical estimation of the effect of the longitudinal and transverse components of the strain tensor on the wavelength of the reflected spectrum is performed.

Finite Element Modeling and Experimental Characterization of Enhanced Hybrid Composite Structures for Improved Crashworthiness

2013 ◽  
Vol 80 (5) ◽  
Author(s):  
Luciana Arronche ◽  
Israel Martínez ◽  
Valeria La Saponara ◽  
Elias Ledesma
Keyword(s):  
Finite Element ◽  
Composite Material ◽  
Hybrid Composite ◽  
Composite Structures ◽  
Testing Machine ◽  
Strain Curve ◽  
Qualitative Behavior ◽  
Fe Model ◽  
Impact Tests ◽  
Highly Nonlinear

In this work, two hybrid composite structures were designed, modeled, and tested for improved resistance to impact. They were inspired by bistable composite structures, which are structures composed of two parts: a so-called “main link” and a so-called “waiting link.” These links work together as a mechanism that will provide enhanced damage tolerance, and the structure exhibits a bistable stress/strain curve under static tension. The function of the main link is to break early, at which point the waiting link becomes active and provides a redundant load path. The goal of the current study was to design, manufacture, and test a similar concept for impact loading and achieve greatly improved impact resistance per unit weight. In the current project, the main link was designed to be a brittle composite material (in this case, woven carbon/epoxy) exposed to impact, while the waiting link was chosen to be made with a highly nonlinear and strong composite material (in this case, polyethylene/epoxy), on the opposite surface. Hence, the structure, if proven successful, can be considered an enhanced hybrid concept. An explicit finite element (FE) commercial code, LS-DYNA, was used to design and analyze the baseline as well as two proposed designs. The simulations' methodology was validated with results published in the literature, which reported tests from linear fiber-reinforced composites. The plots were obtained via the ASCII files generated from the FE code, processed using matlab®, and compared to experimental impact tests. An instrumented drop-weight testing machine performed impact tests, and a high-speed camera validated the specimens' displacement under impact. It is shown that the FE model provided qualitative behavior very consistent with the experiments but requires further improvements. Experimentally, it is shown that one of the two enhanced hybrid models leads to up to a 30% increase of returned energy/weight when compared to its baseline and, therefore, is worthy of further investigations.

Improved elliptical triangulation method for damage detection in composite material structures

2016 ◽  
Vol 231 (16) ◽  
pp. 3011-3023 ◽  
Author(s):  
Assunta Sorrentino ◽  
Angelo De Fenza
Keyword(s):  
Composite Material ◽  
Damage Detection ◽  
Composite Structures ◽  
Lamb Waves ◽  
Propagation Speed ◽  
Main Research ◽  
Detection Techniques ◽  
Triangulation Method ◽  
Wave Propagation Speed ◽  
Main Research Topic

In this paper, an improvement of the elliptical triangulation method for damage detection using Lamb waves is presented. The damage is the main cause of structural failure and often occurs on structures. In order to avoid sudden failure, a special attention was given in the past decades to the damage detection in structures. In order to obtain efficient damage detection techniques, the structural health monitoring has been the main research topic of many scientists worldwide. The elliptical triangulation method, proposed in this paper, is a non-destructive method based on measurement of Lamb waves. This method, through the calculation of the time of flight of the signals and the actuator-sensor positioning, allows to identify position and dimension of the damage. The application of the method to the metallic structures and to the composite material structures is presented in this paper. The complexity connected with the uncertainty of the waves’ propagation speed due to the anisotropy of the composite materials has been explored through an iterative approach. The initialization of the wave propagation speed at first tentative iteration is the key issue for the convergence of the method. Seven different conditions were used to validate the method on both metallic and composite structures combining two damage shapes, two damage dimensions (effective damaged area), and three different positions. Upon evaluating the effectiveness, the method has been applied at two composite panels in order to detect by test the post-impact damages. Tests results have been compared with the numerical ones. The feasibility of the elliptical triangulation method to detect the damage (evaluating the damage position and area) has been proved using the ultrasonic C-Scan.

scholarly journals On the effective elastic properties of a layered composite material made using 3-D technology

2021 ◽  
Vol 22 (3) ◽  
pp. 438-442
Author(s):  
Igor Konstantinovich Arkhipov ◽  
Vlada Igorevna Abramova ◽  
Olga Vladimirovna Kuzovleva ◽  
Alexander Evgenievich Gvozdev
Keyword(s):  
Composite Material ◽  
Elastic Properties ◽  
Layered Composite ◽  
Effective Elastic Properties ◽  
Layered Composite Material
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