TY - GEN
T1 - DETERMINATION OF INTERRACIAL FRACTURE TOUGHNESS IN HIGH TEMPERATURE COMPOSITES
AU - Bechel, V.
AU - Sottos, N. R.
N1 - Funding Information:
The authors would like to acknowledge the support of the ONR and the AFOSR (Senior Knight Program). Also, we would like to thank Dr. N.J. Pagano from Wright Laboratory and Professor T.J. Mackin from the University of Illinois for the time, effort, and ideas they contributed to this project.
Publisher Copyright:
© 1996 American Society of Mechanical Engineers (ASME). All rights reserved.
PY - 1996
Y1 - 1996
N2 - Understanding the behavior of the fiber/matrix interface region over a range of temperatures is essential for designing composites that will have a high service temperature. In the current work, the interface failure sequence was observed during fiber pushout tests on two model composites (steel/epoxy and polyester/epoxy) with different Young's moduli ratio and residual stress values. Novel photoelastic experiments were conducted on the model composites to measure the interfacial crack length versus load during the fiber push-out test. The data were used to better understand the failure mechanisms during the test and to determine the range of applicability of analytical and computational models of the test. Debonding was observed to occur from either the top or the bottom of the sample depending on the ratio of the elastic moduli of the fiber and matrix and the residual stress state. The pushout data from a polyester/epoxy system which debonded from the top was fit to a shear lag solution to obtain the fiber-matrix interfacial toughness (Giic). The resulting interfacial toughness was then used to check the predicted debond length as a function of pushout force. The debond length calculated from the shear lag model was less than the measured debond length by a nearly constant 1.5 fiber radii which may correspond to the thickness of the surface effects region for polyester/epoxy. In the future, the results of the model experiments will be used to understand the interfacial properties of two representative high temperature composites, SiC/Ti-Al-V and AI2O3/TÌ-AI-V. A special high temperature apparatus was constructed for performing the push-out test at temperatures ranging from room temperature to 1000°C under vacuum. Performing interfacial measurements at elevated temperatures can be used to optimize interfacial performance at service temperatures and to better evaluate the effects of residual stresses and matrix ductility on fiber debonding and sliding.
AB - Understanding the behavior of the fiber/matrix interface region over a range of temperatures is essential for designing composites that will have a high service temperature. In the current work, the interface failure sequence was observed during fiber pushout tests on two model composites (steel/epoxy and polyester/epoxy) with different Young's moduli ratio and residual stress values. Novel photoelastic experiments were conducted on the model composites to measure the interfacial crack length versus load during the fiber push-out test. The data were used to better understand the failure mechanisms during the test and to determine the range of applicability of analytical and computational models of the test. Debonding was observed to occur from either the top or the bottom of the sample depending on the ratio of the elastic moduli of the fiber and matrix and the residual stress state. The pushout data from a polyester/epoxy system which debonded from the top was fit to a shear lag solution to obtain the fiber-matrix interfacial toughness (Giic). The resulting interfacial toughness was then used to check the predicted debond length as a function of pushout force. The debond length calculated from the shear lag model was less than the measured debond length by a nearly constant 1.5 fiber radii which may correspond to the thickness of the surface effects region for polyester/epoxy. In the future, the results of the model experiments will be used to understand the interfacial properties of two representative high temperature composites, SiC/Ti-Al-V and AI2O3/TÌ-AI-V. A special high temperature apparatus was constructed for performing the push-out test at temperatures ranging from room temperature to 1000°C under vacuum. Performing interfacial measurements at elevated temperatures can be used to optimize interfacial performance at service temperatures and to better evaluate the effects of residual stresses and matrix ductility on fiber debonding and sliding.
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U2 - 10.1115/IMECE1996-0475
DO - 10.1115/IMECE1996-0475
M3 - Conference contribution
AN - SCOPUS:85169162674
T3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
SP - 155
EP - 165
BT - Aerospace and Materials
PB - American Society of Mechanical Engineers (ASME)
T2 - ASME 1996 International Mechanical Engineering Congress and Exposition, IMECE 1996
Y2 - 17 November 1996 through 22 November 1996
ER -