Residual Internal Stresses Determined Experimentally in Hollow Composite Laminates

2007 ◽  
pp. 129-130
Author(s):  
Horatiu Teodorescu ◽  
Sorin Vlase ◽  
Dorin Rosu ◽  
Mihai Ulea
Keyword(s):  
Composite Laminates ◽  
Internal Stresses

Deformation and Failure Behavior of Woven Composite Laminates

1994 ◽  
Vol 116 (2) ◽  
pp. 222-232 ◽  
Author(s):  
M. Karayaka ◽  
P. Kurath
Keyword(s):  
Composite Laminates ◽  
Failure Mechanisms ◽  
Elastic Stiffness ◽  
Experimental Program ◽  
Internal Stresses ◽  
Failure Behavior ◽  
Deformation Model ◽  
Deformation And Failure ◽  
Linear Elastic ◽  
Proposed Model

Conceptually, fabric composites have some structural advantages over conventional laminates. However, deformation and failure analyses become more complex with the additional anisotropy introduced by the weaving geometry. A micromechanistic deformation model, that could realistically be incorporated into structural finite element codes, is proposed where loading direction and weave parameters are allowed to vary. Comparisons are made to previous models and experimental results for woven materials, indicating that the proposed model provides improved estimates for the linear elastic stiffness. The model further provides predictions for internal stresses in the longitudinal, transverse, and interlace regions of the woven laminate which qualitatively correspond to the experimentally observed failure mechanisms. The experimental program investigates deformations behavior and failure mechanisms of 5-harness 0/90 weave Graphite/Epoxy laminates under tension, compression, and 3-point and 4-point bending loading. Under these conditions the woven laminates exhibit orientation dependent mechanical properties and strength.

scholarly journals Internal Stresses in Composite Laminates Due to Cyclical Hygrothermal Loading

AIAA Journal ◽  
2004 ◽  
Vol 42 (12) ◽  
pp. 2600-2605 ◽  
Author(s):  
Marco Gigliotti ◽  
Alain Vautrin ◽  
Frédéric Jacquemin
Keyword(s):  
Composite Laminates ◽  
Internal Stresses

Analysis of Orthogonally Cracked Laminates Under Tension

1987 ◽  
Vol 54 (4) ◽  
pp. 872-879 ◽  
Author(s):  
Z. Hashin
Keyword(s):  
Lower Bound ◽  
Variational Method ◽  
Stress Analysis ◽  
Composite Laminates ◽  
Previous Analysis ◽  
Fiber Composite ◽  
Internal Stresses ◽  
Complementary Energy ◽  
Stiffness Reduction ◽  
True Value

The problems of stiffness reduction and stress analysis of cross-ply fiber composite laminates, where all plies are cracked in fiber directions, are treated by a variational method on the basis of the principle of minimum complementary energy. The Young’s modulus obtained is a strict lower bound but is expected to be close to the true value on the basis of experience with a previous analysis. Approximate values of Poisson’s ratio and internal stresses have been obtained. The latter reveal important tendencies of continued failure by delamination.

Measurement of Transverse Deflection for Composite Laminates Using Holographic Interferometry

2003 ◽  
Author(s):  
Jin-Chein Lin ◽  
T. Y. Yang ◽  
L. C. Chang
Keyword(s):  
Holographic Interferometry ◽  
Fiber Orientation ◽  
Thermal Effects ◽  
Composite Laminates ◽  
Composite Laminate ◽  
Internal Stresses ◽  
Fiber Types ◽  
Light Waves ◽  
Engineering Problems ◽  
Transverse Deflection

Holographic interferometry is an accurate and important technolngy. Through the application of recording and reconstructing light waves, one can solve a wide variety of mechanical or engineering problems caused by internal stresses, mechanical, electrical or thermal effects. The mechanical properties of composite materials, such as, deflection, strain and stress will be determined by the fiber types, the cross-section of specimens ans the fiber orientation of composite laminate. The purpose of this investigation will discuss the holographic technique and its application of measurement of transverse deflection for various composite laminates. The analysis for both theoretical and experimental results will be presented, and the effect of fiber orientation for composite laminate will be studied in this paper.

Failure of fiber-reinforced composite laminates under longitudinal compression

2019 ◽  
Vol 53 (24) ◽  
pp. 3395-3411 ◽  
Author(s):  
Yi Zhou ◽  
Zheng-Ming Huang
Keyword(s):  
Stress Concentration ◽  
Failure Criterion ◽  
Composite Laminates ◽  
Failure Surface ◽  
Kink Band ◽  
Unidirectional Composite ◽  
Internal Stresses ◽  
Longitudinal Compression ◽  
Concentration Factors ◽  
Stress Concentration Factors

A micro-mechanics approach is put forward to predict the fiber kink inclination angle and the strength of a unidirectional composite under longitudinal compression. Internal stresses of constituent materials in the kink-band are calculated through Bridging Model; thus, only the constituent fiber and matrix properties of the composite are needed. Considering the non-uniform stress distribution caused by the embedded fiber, the homogenized stresses of the matrix are converted into true values with stress concentration factors before being used for failure analysis. The definition and application of stress concentration factors are introduced. A failure criterion based on Mohr’s theory is established to determine the orientation of potential failure surface and the failure situation of matrix, whereas a maximum normal stress failure criterion is used to detect the fiber breakage. The longitudinal compressive strength of a laminate is defined as the applied load at the moment when a failure of whichever constituent materials occurs first. The practicability and accuracy of the theory have been verified with a comparison between the predictions and the measurements obtained from the worldwide failure exercises and some other literatures.

Nanostructure of semiconductor quantum dots in a borosilicate glass matrix by complementary use of HREM and AEM

1990 ◽  
Vol 48 (4) ◽  
pp. 728-729
Author(s):  
M.J. Kim ◽  
L.C. Liu ◽  
S.H. Risbud ◽  
R.W. Carpenter
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Glass Matrix ◽  
Optical Switching ◽  
Response Times ◽  
Fast Response ◽  
Processing Technique ◽  
Internal Stresses ◽  
Electron Hole ◽  
Spatial Dimensions

When the size of a semiconductor is reduced by an appropriate materials processing technique to a dimension less than about twice the radius of an exciton in the bulk crystal, the band like structure of the semiconductor gives way to discrete molecular orbital electronic states. Clusters of semiconductors in a size regime lower than 2R {where R is the exciton Bohr radius; e.g. 3 nm for CdS and 7.3 nm for CdTe) are called Quantum Dots (QD) because they confine optically excited electron- hole pairs (excitons) in all three spatial dimensions. Structures based on QD are of great interest because of fast response times and non-linearity in optical switching applications.In this paper we report the first HREM analysis of the size and structure of CdTe and CdS QD formed by precipitation from a modified borosilicate glass matrix. The glass melts were quenched by pouring on brass plates, and then annealed to relieve internal stresses. QD precipitate particles were formed during subsequent "striking" heat treatments above the glass crystallization temperature, which was determined by differential thermal analysis.

Internal stresses, dislocation mobility and ductility

1991 ◽  
Vol 1 (6) ◽  
pp. 945-956 ◽  
Author(s):  
G. Saada
Keyword(s):  
Internal Stresses ◽  
Dislocation Mobility

Theoretical study of the prestressing strand's stress by computer modeling methods

2020 ◽  
Vol 76 (11) ◽  
pp. 1139-1148
Author(s):  
A. G. Korchunov ◽  
E. M. Medvedeva ◽  
E. M. Golubchik
Keyword(s):  
Residual Stresses ◽  
High Strength ◽  
Pearlitic Steel ◽  
Internal Stresses ◽  
Steel Microstructure ◽  
Compressive Stresses ◽  
Wide Range ◽  
Prestressing Strands ◽  
Increasing Temperature ◽  
Wire Strand

The modern construction industry widely uses reinforced concrete structures, where high-strength prestressing strands are used. Key parameters determining strength and relaxation resistance are a steel microstructure and internal stresses. The aim of the work was a computer research of a stage-by-stage formation of internal stresses during production of prestressing strands of structure 1х7(1+6), 12.5 mm diameter, 1770 MPa strength grade, made of pearlitic steel, as well as study of various modes of mechanical and thermal treatment (MTT) influence on their distribution. To study the effect of every strand manufacturing operation on internal stresses of its wires, the authors developed three models: stranding and reducing a 7-wire strand; straightening of a laid strand, stranding and MTT of a 7-wire strand. It was shown that absolute values of residual stresses and their distribution in a wire used for strands of a specified structure significantly influence performance properties of strands. The use of MTT makes it possible to control in a wide range a redistribution of residual stresses in steel resulting from drawing and strand laying processes. It was established that during drawing of up to 80% degree, compressive stresses of 1100-1200 MPa degree are generated in the central layers of wire. The residual stresses on the wire surface accounted for 450-500 MPa and were tension in nature. The tension within a range of 70 kN to 82 kN combined with a temperature range of 360-380°С contributes to a two-fold decrease in residual stresses both in the central and surface layers of wire. When increasing temperature up to 400°С and maintaining the tension, it is possible to achieve maximum balance of residual stresses. Stranding stresses, whose high values entail failure of lay length and geometry of the studied strand may be fully eliminated only at tension of 82 kN and temperature of 400°С. Otherwise, stranding stresses result in opening of strands.

Reliable Bonding of Composite Laminates Using Reflowable Epoxy Resins

2019 ◽  
Author(s):  
Frank Palmieri ◽  
Tyler Hudson ◽  
Roberto Cano ◽  
Erik Tastepe ◽  
Dean Rufeisen ◽  
...  
Keyword(s):  
Composite Laminates ◽  
Epoxy Resins
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