Mode II Delamination Toughness in Glass Fiber-Reinforced Polymers with Bridging Fibers and Stitching Threads

Abstract

This article presents results for mode II delamination resistance of fiber-reinforced polymers (FRP) using a recently developed internal notched flexure (INF) test. The study showed that the decrease of the compliance with the growth of delamination in the INF test was much less than that predicted by analytical or finite element analyses of the same configuration. The difference was mainly due to pronounced shear force interaction generated by bridging fibers and stitching threads between fracture surfaces. A new data-deducing method, named direct method with correction (DMC), was developed for establishing a delamination resistance curve (R-curve), which can take into account the effects of shear force interaction but does not require in situ measurement of crack growth length. The DMC was further examined using results from a series of INF tests with variation in test set-up configurations and types of glass fiber preform.

Keywords

delamination mode II fracture FRP INF.

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References

ASTM D5528-01. Standard Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites. Annual Book of ASTM Standards 2000; 15.03.

Russell, A.J. and Street, K.N. (1985). Moisture and Temperature Effects on the Mixed-Mode Delamination Fracture of Unidirectional Graphite/Epoxy. In: Delamination and Debonding of Materials, pp. 349-370, Pittsburgh, PA, USA: ASTM, Philadelphia, PA, USA.

Blackman, B.R.K. , Brunner, A.J. and Williams, J.G. (2006). Mode II Fracture Testing of Composites: A New Look at an Old Problem, Eng . Fract. Mech. , 73(16): 2443-2455.

Martin, R.H. and Davidson, B.D. (1999). Mode II Fracture Toughness Evaluation using Four Point Bend, End Notched Flexure Test, Plastics, Rubber and Composites, 28(8): 401-406.

Vinciquerra, A.J. and Davidson, B.D. (2004). Effect of Crack Length Measurement Technique and Data Reduction Procedures on the Perceived Toughness from Four-Point Bend End-Notched Flexure Tests, J. Reinf. Plast. Compos., 23(10): 1051-1062.

Zile, E. and Tamuzs, V. (2005). Mode II Delamination of a Unidirectional Carbon Fiber/Epoxy Composite in Four-Point Bend End-Notched Flexure Tests, Mechanics of Composite Materials, 41(5): 383-390.

Davidson, B.D. and Sun, X. (2005). Effects of Friction, Geometry, and Fixture Compliance on the Perceived Toughness from Three- and Four-Point Bend End-Notched Flexure Tests, J. Reinf. Plast. Compos., 24(15): 1611-1628.

Fan, C. , Jar, P.-B. and Cheng, J.J.R. Internal-Notched Flexure Test for Measurement of Mode II Delamination Resistance of Fiber-Reinforced Polymers, J. Composite. Mater. (in press).

Anderson, T.L. (1995). Fracture Mechanics, 2nd edn, CRC Press LLC, Florida.

10.

Choi, H.Y. , Downs, R.J. and Chang, F. (1991). New Approach Toward Understanding Damage Mechanisms and Mechanics of Laminated Composites Due to Low-Velocity Impact. Part I. Experiments, J. Composite. Mater., 25(8): 992-1011.

11.

Schuecker, C. and Davidson, B.D. (2000). Evaluation of the Accuracy of the Four-point Bend End-Notched Flexure Test for Mode II Delamination Toughness Determination, Composites Sci. Technol. , 60(11): 2137-2146.

12.

Fan, C. , Jar, P.-Y.B. and Cheng, J.J.R. (2006). Energy-Based Analysis of Delamination Development on Fiber-Reinforced Polymers (FRP) Under Three-Point Bending Test, Composites Sci. Technol., 66: 2143-2155.

13.

Davies, P. , Casari, P. and Carlsson, L.A. (2005). Influence of Fiber Volume Fraction on Mode II Interlaminar Fracture Toughness of Glass/Epoxy using the 4ENF Specimen, Composites Sci. Technol., 65(2): 295-300.