Reduction of KI and KII by the shape-memory effect in a TiNi shape-memory fiber-reinforced epoxy matrix composite

• Published in: Experimental mechanics Vol. 43; no. 1; pp. 77 - 82
• Main Authors: SHIMAMOTO, Akira, AZAKAMI, Takeshi, OGUCHI, Toshihiro
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.03.2003
• Subjects: Applied sciences; Composites; Exact sciences and technology; Forms of application and semi-finished materials; Fracture mechanics (crack, fatigue, damage...); Fracture mechanics, fatigue and cracks; Fundamental areas of phenomenology (including applications); Mechanical properties; Physical properties; Physics; Polymer industry, paints, wood; Properties and testing; Solid mechanics; Structural and continuum mechanics; Technology of polymers; Titanium alloy; photoelastic method; Notched test piece; Stress strain relation; Fiber reinforced material; Rupture; Epoxy resin; Photoelasticity; crack closure; Experimental study; Tension test; Composite material; Fracture toughness; Optical measurement; smart composite; Stress intensity factor; Shape memory alloy; Prestrained material; mixed-mode and phase transformation; Crack length; Crack tip; Nickel alloy; Shape-memory alloy; Stress measurement
• ISSN: 0014-4851; 1741-2765
• DOI: 10.1177/0014485103043001010

Shape-memory TiNi fiber-reinforced/epoxy matrix composites have been fabricated, and the suppression of crack-tip stress intensity and the change in fracture toughness have been systematically investigated. Stress-strain data for these composite specimens with notches at various angles and different crack lengths in the transverse direction have been measured in tensile tests. The stress intensity factor at the crack tip is experimentally determined from photoelastic fringe patterns. The decreases in K values are attributed to the compressive stress field in the matrix induced when the pre-strains of the TiNi fiber contract to their initial length upon heating above the austenitic final temperature. We present the influences of the pre-strain of TiNi fibers and the compressive domain size between a crack tip and fiber on the K value.