TY - JOUR
T1 - Evaluation of the Effect of Thermal Oxidation and Moisture on the Interfacial Shear Strength of Unidirectional IM7/BMI Composite by Fiber Push-in Nanoindentation
AU - Xu, T.
AU - Luo, H.
AU - Xu, Z.
AU - Hu, Z.
AU - Minary-Jolandan, M.
AU - Roy, S.
AU - Lu, H.
N1 - Funding Information:
Acknowledgements The support by AFOSR FA9550-14-1-0227, NSF ECCS-1307997 and CMMI-1636306 is acknowledged. Lu also thanks the Louis A. Beecherl Jr., Chair for additional support. We thank Dr. Gregory A. Schoeppner at Air Force Research Lab for providing composites used in this work, and Dr. Dani Fadda for editing the manuscript.
Publisher Copyright:
© 2017, Society for Experimental Mechanics.
PY - 2018/1/1
Y1 - 2018/1/1
N2 - Fiber push-in nanoindentation is conducted on a unidirectional carbon fiber reinforced bismaleimide resin composite (IM7/BMI) after thermal oxidation to determine the interfacial shear strength. A unidirectional IM7/BMI laminated plate is isothermally oxidized under various conditions: in air for 2 months at 195 °C and 245 °C, and immersed in water for 2 years at room temperature to reach a moisture-saturated state. The water-immersed specimens are subsequently placed in a preheated environment at 260 °C to receive sudden heating, or are gradually heated at a rate of approximately 6 °C/min. A flat punch tip of 3 μm in diameter is used to push the fiber into the matrix while the resulting load-displacement data is recorded. From the load-displacement data, the interfacial shear strength is determined using a shear-lag model, which is verified by finite element method simulations. It is found that thermal oxidation at 245 °C in air leads to a significant reduction in interfacial shear strength of the IM7/BMI unidirectional composite, while thermal oxidation at 195 °C and moisture concentration have a negligible effect on the interfacial shear strength. For moisture-saturated specimens under a slow heating rate, there is no detectable reduction in the interfacial shear strength. In contrast, the moisture-saturated specimens under sudden heating show a significant reduction in interfacial shear strength. Scanning electron micrographs of IM7/BMI composite reveal that both thermal oxidation at 245 °C in air and sudden heating induced microcracks and debonding along the fiber/matrix interface, thereby weakening the interface, which is the origin of failure mechanism.
AB - Fiber push-in nanoindentation is conducted on a unidirectional carbon fiber reinforced bismaleimide resin composite (IM7/BMI) after thermal oxidation to determine the interfacial shear strength. A unidirectional IM7/BMI laminated plate is isothermally oxidized under various conditions: in air for 2 months at 195 °C and 245 °C, and immersed in water for 2 years at room temperature to reach a moisture-saturated state. The water-immersed specimens are subsequently placed in a preheated environment at 260 °C to receive sudden heating, or are gradually heated at a rate of approximately 6 °C/min. A flat punch tip of 3 μm in diameter is used to push the fiber into the matrix while the resulting load-displacement data is recorded. From the load-displacement data, the interfacial shear strength is determined using a shear-lag model, which is verified by finite element method simulations. It is found that thermal oxidation at 245 °C in air leads to a significant reduction in interfacial shear strength of the IM7/BMI unidirectional composite, while thermal oxidation at 195 °C and moisture concentration have a negligible effect on the interfacial shear strength. For moisture-saturated specimens under a slow heating rate, there is no detectable reduction in the interfacial shear strength. In contrast, the moisture-saturated specimens under sudden heating show a significant reduction in interfacial shear strength. Scanning electron micrographs of IM7/BMI composite reveal that both thermal oxidation at 245 °C in air and sudden heating induced microcracks and debonding along the fiber/matrix interface, thereby weakening the interface, which is the origin of failure mechanism.
KW - Carbon fibers
KW - Cohesive shear traction separation law
KW - Environmental degradation
KW - Finite element analysis
KW - Interfacial strength
KW - Polymer-matrix composites
UR - http://www.scopus.com/inward/record.url?scp=85028742513&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85028742513&partnerID=8YFLogxK
U2 - 10.1007/s11340-017-0335-6
DO - 10.1007/s11340-017-0335-6
M3 - Article
AN - SCOPUS:85028742513
VL - 58
SP - 111
EP - 123
JO - Experimental Mechanics
JF - Experimental Mechanics
SN - 0014-4851
IS - 1
ER -