ABSTRACT
I. Introduction ................................................................. 318 A. Toughening Mechanism ................................... 320 B. Modeling Strategy ............................................ 322
II. Soft Fillers: Can Local Anisotropy Induce Toughness?................................................................... 325 A. Constitutive Model of the Anisotropic
Bulk Polymer .................................................... 326
B. Micromechanical Models.................................. 328 1. The First Model: An Axisymmetric
RVE, the SA Model ............................. 328 2. The Second Model: A Multiparticle
Plane Strain RVE, the ID Model ....... 330 C. Results............................................................... 332 D. Failure Mechanisms ......................................... 334 E. Conclusions ....................................................... 337
III. Hard Particles: Can They Also Act as Toughness Modifiers?..................................................................... 339 A. Model Description............................................. 340 B. Results............................................................... 340 C. Conclusions ....................................................... 344
IV. Full Multiscale Modeling: What Did We Learn? ...... 345 A. Microscopic Scale: Material Models ................ 346
1. Crystalline Phase................................ 346 2. Amorphous Phase ............................... 347
B. Mesoscopic Scale: Composite Inclusion Model ................................................................. 348 1. Anisotropy of Preferentially
Oriented Material ............................... 349 C. Macroscopic Models .......................................... 352 D. Effect of Transcrystallized Anisotropy
on Toughness..................................................... 353 E. Influence of Processing Conditions ................. 361 F. Conclusions ....................................................... 366
V. Discussion .................................................................... 367 Acknowledgments................................................................. 371 References............................................................................. 372
I. INTRODUCTION
Semicrystalline polymeric materials are widely used in a range of engineering applications. Despite many advantages such as low cost and weight, their application is limited by some unfavorable mechanical properties, such as brittle response in plain or notched applications. Toughening can be enhanced by rubber blending, and a criterion proposed by Wu
[1] states that a sharp brittle-to-tough transition occurs for, e.g., nylon/rubber blends when the average interparticle matrix ligament thickness
Λ is reduced below the critical value
Λ
= 0
.
