Details

Autor(en) / Beteiligte

• Kausch, Hans-Henning
• Michler, Goerg H.

Titel

The Effect of Time on Crazing and Fracture

Ist Teil von

• Intrinsic Molecular Mobility and Toughness of Polymers I, 2005, p.1-33

Ort / Verlag

Berlin, Heidelberg: Springer Berlin Heidelberg

Erscheinungsjahr

2005

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• By way of introduction to the subject of this Volume1 this contribution reviews the effects of the most prominent properties of macromolecules (their enormous length, strong elastic anisotropy in axial and lateral directions and high segmental mobility) and of their characteristic dimensions on the elementary molecular deformation mechanisms of thermoplastic polymers. The competition between these mechanisms has a determinant influence on the different failure modes (crazing, creep, yielding and flow, fracture through crack propagation). The main part is devoted to an analysis of failure in creep. The micro-morphological approach is further developed and compared to criteria derived from visco-elastic theory with representative equations. Small angle X-ray analysis of the formation of fibrillar structures in amorphous polymers SAN and PC identifies three distinct regimes associated to fluid-like behaviour and disentanglement by forced reptation at low and moderate stresses (or high temperatures) and chain-scission dominated craze initiation (at low temperatures and high stresses), respectively. In semi-crystalline polymers similar differences are found: homogeneous creep at high stresses mostly involving the plastic deformation and break-up of crystal lamellae as opposed to the formation of craze-like structures due to the disentanglement of chains at low stresses. This review focuses on the important dual role of molecular mobility, to be at the origin of time-dependent properties of polymer materials, especially of their toughness, and to influence without exception all damage mechanisms which limit the strength and durability of polymer components.