Interlaminar Fracture Toughness of a Graphite/Epoxy Multidirectional Composite1

2000 ◽  
Vol 122 (4) ◽  
pp. 428-433 ◽  
Author(s):  
Z. Yang ◽  
C. T. Sun
Keyword(s):  
Fracture Toughness ◽  
Data Reduction ◽  
Crack Extension ◽  
Plate Theory ◽  
Interlaminar Fracture Toughness ◽  
Element Analysis ◽  
Unstable Crack ◽  
Interlaminar Fracture ◽  
Reduction Methods ◽  
Data Reduction Method

In this paper, an experimental investigation on interlaminar fracture behavior and fracture toughness of a graphite/epoxy multidirectional composite laminate is presented using end-notched flexure specimens. The 0/θ interfaces are considered. The interlaminar fracture toughness is obtained and compared using three data reduction methods, i.e., the area method, classical laminated plate theory, and finite element analysis. Results show that the toughness value depends on the data reduction method used. Two different crack-length-to-span ratios are chosen to study how the stable or unstable crack extension influences the toughness measurement. It is observed that the toughness obtained from the tests of stable crack extension is appreciably higher than that from the tests of unstable crack extension. It is also seen that friction resulting from contact of crack surfaces greatly affects the measured toughness in the case of stable crack extension. In addition, effects of the specimen geometry and fiber orientation on the interlaminar fracture toughness are also evaluated. [S0094-4289(00)02804-8]

Double Cantilever Beam Measurement and Finite Element Analysis of Cryogenic Mode I Interlaminar Fracture Toughness of Glass-Cloth/Epoxy Laminates

2000 ◽  
Vol 123 (2) ◽  
pp. 191-197 ◽  
Author(s):  
Y. Shindo ◽  
K. Horiguchi ◽  
R. Wang ◽  
H. Kudo
Keyword(s):  
Fracture Toughness ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Cantilever Beam ◽  
Double Cantilever Beam ◽  
Mode I ◽  
Interlaminar Fracture Toughness ◽  
Element Analysis ◽  
Interlaminar Fracture ◽  
Delamination Crack

An experimental and analytical investigation in cryogenic Mode I interlaminar fracture behavior and toughness of SL-E woven glass-epoxy laminates was conducted. Double cantilever beam (DCB) tests were performed at room temperature (R.T.), liquid nitrogen temperature (77 K), and liquid helium temperature (4 K) to evaluate the effect of temperature and geometrical variations on the interlaminar fracture toughness. The fracture surfaces were examined by scanning electron microscopy to verify the fracture mechanisms. A finite element model was used to perform the delamination crack analysis. Critical load levels and the geometric and material properties of the test specimens were input data for the analysis which evaluated the Mode I energy release rate at the onset of delamination crack propagation. The results of the finite element analysis are utilized to supplement the experimental data.

Finite Element Simulation of the Sachs Boring Method of Measuring Residual Stresses in Thick-Walled Cylinders

2003 ◽  
Vol 125 (3) ◽  
pp. 274-276 ◽  
Author(s):  
R. R. de Swardt
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Data Reduction ◽  
High Speed ◽  
High Strength ◽  
Residual Stress Field ◽  
Element Analysis ◽  
Element Mesh ◽  
Reduction Methods ◽  
Data Reduction Method

During a recent study the residual strain/stress states through the walls of autofrettaged thick-walled high-strength steel cylinders were measured with neutron diffraction, Sachs boring and the compliance methods (Venter et al., 2000, J. Strain Anal. Eng. Des., 35, pp. 459–469). The Sachs boring method was developed prior to the advent of high speed computers. A new method for the data reduction was proposed. In order to verify the proposed procedure, the Sachs boring experimental method was simulated using finite element modeling. A residual stress field was introduced in the finite element method by elasto-plastic finite element analysis. The physical process of material removal by means of boring was simulated by step-by-step removal of elements from the finite element mesh. Both the traditional and newly proposed data reduction methods were used to calculate the residual stresses. The new data reduction method compares favorably with the traditional method.

Influence of Fiber Orientation on Interlaminar Fracture Toughness of Composites

1999 ◽  
Author(s):  
Z. Yang ◽  
C. T. Sun
Keyword(s):  
Fracture Toughness ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Fracture Mode ◽  
Fiber Orientation ◽  
Composite Laminates ◽  
Three Dimensional ◽  
Interlaminar Fracture Toughness ◽  
Element Analysis ◽  
Interlaminar Fracture

Abstract In this paper, an experimental investigation and a finite element analysis on interlaminar fracture behavior and fracture toughness of multidirectional composite laminates are presented using end-notch flexure specimens. The (0 / θ) interfaces are considered. The fracture toughness of the interfaces is obtained from the experimental records of load and displacement histories, which is then calibrated by a finite element analysis based on the pseudo three-dimensional assumption. The fracture modes are separated and represented by fracture mode phase angles. Finally, the interlaminar fracture toughness and fracture mode mixities as functions of fiber orientation θ are established.

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