December 1, 2024
(The November 4th version was proofread using ChatGPT)
The fracture of polymeric materials begins when stress concentration at defect sites exceeds the fracture strength of the network structure formed by molecular chains. When defects are present, strain is constrained, leading to volume changes. Due to the high bulk modulus, which is the resistance to volume deformation, the impact of stress concentration caused by defects becomes significant. By alleviating strain constraints and distributing the applied stress more evenly across the structure, the degree of stress concentration can be reduced. This allows for stable, large deformations while maintaining high strength. This mechanism forms the foundation of toughening in polymeric materials.
Introduction 1
1. Fundamentals of solid deformation and fracture
1.1 Deformation and strength of solids
1.2 Strain constraint and stress concentration
1.3 Effect of bulk modulus K on stress concentration
2. Micromechanics of polymeric material fracture
2.1 Shear deformation-dominated fracture
2.2 Fracture controlled by volumetric deformation
2.2.1 Void expansion due to nonlinear elastic deformation
2.2.2 Unstable expansion of voids by plastic deformation
2.2.3 Evaluation of crazing formation stress
2.3 Fracture and toughening of polymer materials
3. Toughening through microstructural adjustment
3.1 Effect of number-average molecular weight on crazing strength and yield stress
3.2 Effect of molecular weight distribution width on crazing strength and viscosity
3.3 Effect of stereoregularity of i-PP on crazing strength and yield stress
3.4 Effect of copolymerization on crazing strength and yield stress
4.Toughening by release of strain constraint
4.1 Release of strain constraint by voids and relaxation of bulk modulus
4.2 Factors influencing the efficiency of toughening by elastomer blending
4.2.1 Effect of the strength of dispersed phase on toughness
4.2.2 Orientation hardening and toughness of matrix resins
5.Strength design of plastic composites with high stiffness and toughness
5.1 Toughening by blending inorganic particles
5.1.1 Toughening of i-PP with CaCO3 Particles
5.1.2 Toughening by carbon black( CB) in rubbers
5.2 Efficiency of strength and toughness improvement
6.Conclusion