Fracture and Fatigue of a Self-Healing Polymer Composite Material - PowerPoint PPT Presentation

Fracture and Fatigue of a Self-Healing Polymer Composite Material Eric N. Brown Advised by Nancy R. Sottos en_brown@illinoisalumni.org www.autonomic.uiuc.edu E.N. Brown, Fracture & Fatigue of Self-Healing Polymer Composites

Motivation and Concept Grubbs Ru Microencapsulated • Thermosetting polymers are used Catalyst Healing Agent, in a wide range of applications, but Dicyclopentadiene are susceptible to damage in the (DCPD) form of cracking • Cracks are often deep in a structure where detection is costly and difficult Epoxy Matrix, • Repair of cracks by external EPON 828/ intervention is often impossible DETA White et al Nature 2001 Crosslinked Cracking in cross-ply laminate Jennings (1990) polymer network E.N. Brown, Fracture & Fatigue of Self-Healing Polymer Composites

TDCB Load -Displacement Data 60 � = 90.3% 50 40 Stick-Slip Failure Load (N) 30 Healed 20 Virgin 10 0 0 250 500 750 1000 1250 1500 Displacement (µm) Brown et al Experimental Mechanics 2002 E.N. Brown, Fracture & Fatigue of Self-Healing Polymer Composites

Fracture Mechanism of Neat Epoxy Plastic Zone Size: • Measured plastic zone size ~ 37 µ m • Theoretical plastic zone size = 39 µ m � 2 � 2 � � r y = 1 K Ic = 1 0.55 MPa m � � � � � � � � 2 � � ys 2 � 35 MPa Brown et al Journal of Materials Science 2004 E.N. Brown, Fracture & Fatigue of Self-Healing Polymer Composites

Low-Cycle In Situ Healing Healed in situ with rest period under K max loading 50 Control Self-healing Crack length, a (mm) 45 40 35 Rest 30 1 10 4 2 10 4 3 10 4 4 10 4 5 10 4 0 Cycles, N � � = � 118% � K I � = � 0.405 � MPa � m 1/2 , K max � = � 0.450 � MPa � m 1/2 , K min � = � 0.045 � MPa � m 1/2 , R � = � 0.1, and f � = � 5 � Hz E.N. Brown, Fracture & Fatigue of Self-Healing Polymer Composites

Conclusions • Recover over 90% of virgin fracture toughness • Addition of microcapsules significantly toughens the epoxy • In situ healing while under constant load provides crack tip shielding that retards or completely arrests fatigue crack growth • ………the introduction of smart materials with autonomic functionality enables a paradigm shift in how we design for material failure E.N. Brown, Fracture & Fatigue of Self-Healing Polymer Composites