Pre-Cracking techniques of polymeric materials: an overview

Abstract

In fracture toughness tests, a number of notched specimens with identical artificial pre-cracks are essential to obtain accurate fracture parameters. The test results are critically depending on the initiation stage quality. Any slight variance in pre-cracks front shape, length and orientation could significantly affects the test results; therefore, producing identical pre-cracks is a critical issue to obtain accurate results. The pre-cracking technique should be selected carefully to fulfil controllably and repeatability requirements of the standard pre-cracks for a certain material while preserving the induced residual stresses at the crack tip at a minimal value. The notching and pre-cracking standards for metallic material have been well specified in ASTM E399. However, the case is more cumbersome for polymeric materials due their viscoelastic nature. ASTM D5045, ISO 13586:2000 and ASTM D6068 specified different procedures to prepare a sharp pre-crack for polymeric materials. Many pre-cracking techniques have been proposed in literature. The present work introduces an overview of the pre-cracking techniques for polymeric materials.

Failure characteristics of thick hard roof stratum under hydraulic pre-splitting and its application in a coal mine, Dongsheng mining area

“…Directional hydraulic fracturing for hard roofs in different simulation conditions had been discussed by XFEM (extended finite element method). Besides, the differences between conventional drill holes and directional drill holes, transverse perforation and axial perforation leading to the expected results of fracture propagation were analyzed (Kamal et al, 2020;Sun et al, 2021;Zhang et al, 2022). A multi-stage fracturing prevention method for the hard roof was proposed to weaken the strength of low-level roofs, reduce the potential occurrence of large-scale suspended layers, and alleviate energy accumulation in overlying hard strata .…”

The effect of rubber powder additives on mechanical properties of polypropylene glass-fiber-reinforced composite

“…These techniques help in improving adhesion between PP and fibers, which consequently enhances the mechanical strength of the produced composites. The interfacial adhesion between wood fibers (bleached kraft pulp of eucalyptus) and PP was enhanced by treating the PP using m-isopropenyl-α and α-dimethylbenzyl isocyanate grafted polypropylene (Karmarkar et al, 2007). Despite the hydrophilic nature of wood fibers and the hydrophobic nature of PP, the proposed preprocessing technique improved the interfacial adhesion between wood fibers and PP.…”

Rheological Properties of TiO2/POE Nanolubricant for Automotive Air-Conditioning System

“…Nano additives are nanoparticles, whereas chemical additives are antioxidants, AW, EP, PPD corrosion inhibitors, and others. Nanoparticle dispersion as nano additives has been widely used in a variety of industries including biomedical, health care, food agriculture, industrial, electronics, environment, renewable energy, and textile [2][3][4][5][6].…”