Page 350 - Engineered Interfaces in Fiber Reinforced Composites

Chapter 8. Improvement of interlaminar ,fracture toughness with interface control 33 1

several references (Kinloch and Young, 1986; Kinloch, 1986, 1987; Garg and Mai,
1988a, b; Low and Mai, 1990).
The fracture behavior of toughened polymers, containing rubber or inorganic
fillers, may involve several mechanisms, as schematically illustrated in Fig. 8.1 (Garg
and Mai, 1988a). These include:
(1) shear band formation near rubber particle,
(2) fracture of rubber particle,
(3) stretching,
(4) debonding,
(5) tearing of rubber particles,
(6) transparticle fracture,
(7) debonding of hard particle,
(8) crack deflection by hard particle,
(9) cavitated or voided rubber particle,
( 10) crazing,
(1 1) plastic zone at crack tip,
(12) diffuse shear yielding,
(1 3) shear bandicraze interaction.
Several such failure mechanisms may take place simultaneously in a toughened
resin, depending on the type of particles, whether liquid rubber or rigid particles,
and the matrix material. Each of these mechanisms contributes to the energy
absorption of the whole structure.

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Fig. 8.1. Toughening mechanisms in rubber-modified polymers: (I) shear band formation near rubber
particles; (2) fracture of rubber particles after cavitation; (3) stretching, (4) debonding and (5) tearing of
rubber particles; (6) transparticle fracture; (7) debonding of hard particles; (8) crack deflection by hard
particles; (9) voided/cavitated rubber particles; (IO) crazing; (1 1) plastic zone at craze tip; (12) diffuse
shear yielding; (13) shear band/craze interaction. After Garg and Mai (1988a).