Alfa fibers for Cereplast bio-composites reinforcement: Effects of chemical and biological treatments on the mechanical properties

The present work is a comparative study of the impact of Alfa fiber modifications on the Cereplast composites mechanical behavior. Various treatments have been employed, including mechanical, soda, saltwater-retting, hot-water treatments and enzymatic treatment using xylanase. Chemical and morphological analyses were carried out in order to determine the changes of the biochemical composition and the dimensions of fibers. Cereplast composites reinforced with Alfa fibers were fabricated using a twin-screw extrusion followed by an injection molding technique with a fiber load of 20 wt. %. Resulting materials were assessed by means of tensile, flexural and Charpy impact testing. Scanning Electron Microscopy analysis was carried out to investigate the interfacial properties of the composites. The results have shown a significant enhancement of mechanical strengths and rigidities for the xylanase-treated fiber composites, owing to the increase of cellulose content, the enhancement of defibrillation level and the improvement of matrix-fiber adhesion. The data proved that the technology of enzymes can be used as a powerful and eco-friendly approach to modify fiber surfaces and to increase their potential of reinforcement.

INVESTIGATION OF THE PROPERTIES OF DIRECT ENERGY DEPOSITION ADDITIVE MANUFACTURED 304 STAINLESS STEEL

One of the main considerations in adopting the additive manufacturing (AM) technology is whether the material properties of the AM-produced part are comparable with the wrought material. This study compared the properties of AM-produced 304 stainless steel via the direct energy deposition (DED) AM process with wrought 304 stainless steel. The samples were studied in their as-built or as-received condition; and the characterisation analysis included micro-structural evaluation, hardness tests, Charpy impact testing, tensile testing, and X-ray diffraction. The results demonstrated that, in general, the strength characteristics of the AM sample exceeded those of the wrought material other than for toughness.

A Proposed Estimation of the Expanded Uncertainty of Charpy Impact Testers

Uncertainty estimation is one of the very delicate tasks in the field of measurements. For the purpose of calibration of Charpy impact testing machines, it is necessary to evaluate and identify the expanded uncertainty. Factors affecting the uncertainty estimations are; the uncertainty of reference force and length measuring devices and its long-term instability (drift), machine resolution, rated energy error, indicated energy error, losses due to the drag of the pointer, friction losses in the bearing and air resistance, and other geometric parameters. In this study, the uncertainty estimation of the Charpy impact machines is based on the direct verification used in the BS DIN ISO 148-2 standard.

Empirical estimation of uncertainties of Charpy impact testing transition temperatures for an RPV steel

The aim of the present work is to derive empirically a simple expression of the uncertainties on Charpy transition temperatures (TT), which depends only on the test temperatures and the number of tests at each of these temperatures. Calculations of the TT uncertainties of a RPV steel are performed based on an empirical representation of Charpy test results and a Monte Carlo procedure to generate large numbers of data sets for different test matrices. Applying usual procedures to determine the TT to the generated data sets gives access to the distributions of these quantities from which the uncertainties are calculated.An analytical expression for these uncertainties is proposed.

Fracture Toughness and Charpy Impact Test of MIM Steels and Correlation of Results by KIC- CVN Relationships

This paper presents results of fracture toughness and Charpy impact tests of 4 steels prepared by metal injection moulding (MIM) method: AISI 4140, 4605, 17-4 PH and SS 420W Grade. Charpy impact testing was performed on the series of machined specimens with sub-size cross-section to obtain values of CVN impact energy. Fracture toughness test method according to ASTM E1820 was performed on SENB specimens, fatigue pre-cracked, to obtain values of KIC. All tests were performed at the room temperature. After the material testing, next step was to evaluate the results and apply known correlation relationships between fracture toughness KIC and Charpy impact CVN energies. Many empirical relations exist and describe existence of such relationship. Procedure was used to correlate energies of sub-size Charpy specimens to full-size specimens. Several proposed correlation relationships from transition and upper shelf region of transition curve were used, where the best correlation was found to be Robert-Newtons with average deviation of 22% in comparison to tested values.