Work Of Fracture Parameters Research Articles

Polymer pre-notched small punch specimens to evaluate the essential work of fracture (EWF) parameters

Abstract Standardized deeply double edge notched tensile specimens (DDEN-T) have been usually used to assess fracture properties in thin polymer plates under plane stress conditions. The methodology is based on a multi specimen technique and is well known as the essential work of fracture (EWF) method. In some special circumstances these standard specimens cannot be machined as could be the case if the material is limited. A possible solution proposed in this paper could be the use of pre-notched small punch test specimens, in which the aim is to establish the feasibility of using pre-notched SPT specimens for evaluating the essential work of fracture parameters. The results obtained with these miniature specimens have been compared with those obtained from standard DDEN-T specimens.

Grafted Polyolefin-Coated Synthetic Mica-Filled Polypropylene-co-ethylene Composites: A Study on the Interfacial Morphology and Properties

Purified maleic anhydride grafted isotactic polypropylene (iPP-MA) and maleic anhydride grafted polyolefin elastomer (POE-MA) were used to coat synthetic mica, which was added to block polypropylene-co-ethylene (cPP) to prepare composites with 10 wt% mica content. The effect of the kinds of grafted polyolefin, their contents and composition ratios on the interfacial morphology, mechanical properties, crystallization behavior, and essential work of fracture parameters for the composites were studied. The results showed that the coating of synthetic mica with grafted polyolefin could effectively lower the surface polarity of the mica and improve the interfacial adhesion between mica and cPP. The sedimentation volume of mica reached a minimum, and the interface adhesion of the composites was comparatively good when the grafted polyolefin was 3 wt% of the weight of the mica. When the content of grafted polyolefin was fixed at 3–5 wt% of the weight of the mica, the sedimentation volume of mica decreased and the interface adhesion of the composites improved with increasing POE-MA content. The coating with grafted polyolefin and the composition change of the grafted polyolefin had little effect on the mechanical properties and crystallization behavior of the mica-filled composites. However, the coating with grafted polyolefin increased the special essential work of fracture (we ) of the composites significantly, whereas the special non-essential work of fracture (βwp ) showed a slight decrease. When the total grafted polyolefin was fixed, the we decreased and the βwp increased a little as the POE-MA content was increased.

Structures and properties of blown moulding LLDPE films

The crystalline structures, mechanical properties, transparence and fracture behaviours of linear low density polyethylene blown moulding films with nucleating agents incorporated in were investigated. The results indicated that with the nucleating agents used, the melting temperature Tm, crystalline structures, general profile of the stress–strain curves, tensile yield strength σy and essential work of fracture parameters before yield of the films, were almost unchanged, while the strain hardening phenomenon, tensile fracture strength σb, elongation at break &epsib, transparence and fracture parameters we and βwp were enhanced greatly. As the loading content of nucleating agent increasing, the crystallinity first decreased and then increased rapidly; the strain hardening phenomenon ϵb and σb increased to a maximum and then decrease to a stable value, while the Tm and σy were also unchanged; the haze decreased first and then reached a stable value; the we and we,y decreased remarkably first and then rapidly increased, even enormously exceeding the we of pure linear low density polyethylene, while βwp and βywp,y increased to a quite high value first and then dropped to a lower level.

Determination of the fracture toughness of polybutylene terephthalate (PBT) film by the essential work method: Effect of specimen size and geometry

AbstractThe fracture behavior of PBT films of thicknesses 0.125, 0.175, 0.275, 0.375 and 0.5 mm was investigated according to Essential Work of Fracture (EWF) method. Single edge and double edge notched specimens of varying ligament lengths were tested in tension producing load‐displacement traces that were typical of ductile failure. A linear relationship was obtained between the total specific work of fracture (Wf) and ligament length (L). This linearity was maintained as ligament length exceeded the plastic zone size or one third of sample width. It was found that while the specific essential work of fracture (We) was independent of thickness, the specific non‐essential work of fracture (βWp) decreased with increasing thickness. It was found also, that work of fracture parameters were independent of the specimen width for the range of thicknesses used in the present study. Nevertheless, for a sample width of 20 mm, a lower we and a higher βwp value was obtained. Good agreement was found between values of We obtained from SENT and those obtained from DENT specimens; the value of βwp was consistently higher for SENT specimens.