Determination of Coefficient for Transformation Plasticity in Terms of Three Point Bending System

The subject of the research was the production of silsesquioxane modified rigid polyurethane (PUR) foams (POSS-Cl) with chlorine functional groups (chlorobenzyl, chloropropyl, chlorobenzylethyl) characterized by reduced flammability. The foams were prepared in a one-step additive polymerization reaction of isocyanates with polyols, and the POSS modifier was added to the reaction system in an amount of 2 wt.% polyol. The influence of POSS was analyzed by performing a series of tests, such as determination of the kinetics of foam growth, determination of apparent density, and structure analysis. Compressive strength, three-point bending strength, hardness, and shape stability at reduced and elevated temperatures were tested, and the hydrophobicity of the surface was determined. The most important measurement was the determination of the thermal stability (TGA) and the flammability of the modified systems using a cone calorimeter. The obtained results, after comparing with the results for unmodified foam, showed a large influence of POSS modifiers on the functional properties, especially thermal and fire-retardant, of the obtained PUR-POSS-Cl systems.

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Fracture Resistance of AAAS Composites with Ceramic Precursor

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.322.54 ◽

2021 ◽

Vol 322 ◽

pp. 54-59

Author(s):

Iva Rozsypalová ◽

Petr Daněk ◽

Pavla Rovnaníková ◽

Zbyněk Keršner

Keyword(s):

Mouth Opening ◽

Crack Model ◽

Arithmetic Means ◽

Mechanical Fracture ◽

Three Point Bending ◽

Static Modulus ◽

Fracture Parameters ◽

Ceramic Precursors ◽

Static Modulus Of Elasticity

The paper deals with selected alkali-activated aluminosilicate (AAAS) composites based on ceramic precursors in terms of their characterization by mechanical fracture parameters. Composites made of brick dust as a precursor and an alkaline activator with a silicate modulus of Ms = 0.8, 1.0, 1.2, 1.4 and 1.6 were investigated. The filler employed with one set of composites was quartz sand, while for the other set it was crushed brick. The test specimens had nominal dimensions of 40 × 40 × 160 mm and were provided with notches at midspan of up to 1/3 of the height of the specimens after 28 days. 6 samples from each composite were tested. The specimens were subjected to three-point bending tests in which force vs. displacement (deflection at midspan) diagrams (F–d diagrams) and force vs. crack mouth opening (F–CMOD) diagrams were recorded. After the correction of these diagrams, static modulus of elasticity, effective fracture toughness, effective toughness and specific fracture energy values were determined using the Effective Crack Model and the Work-of-Fracture method. After the fracture experiments, informative compressive strength values were determined from one of the parts. All of the evaluations included the determination of arithmetic means and standard deviations. The silicate modulus values and type of filler of the AAAS composites significantly influenced their mechanical fracture parameters.

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Fracture Toughness and Cracking Behaviour of SCC Compared to VC

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.577-578.205 ◽

2013 ◽

Vol 577-578 ◽

pp. 205-208

Author(s):

Sara Korte ◽

Veerle Boel ◽

Wouter de Corte ◽

Geert de Schutter

Keyword(s):

Fracture Toughness ◽

Fracture Process ◽

Critical Value ◽

Fracture Parameter ◽

Self Compacting Concrete ◽

Bending Tests ◽

Three Point Bending ◽

Notched Specimens ◽

Subsequent Determination

Vibrated concrete (VC) and self-compacting concrete (SCC) have a substantially different composition, resulting in dissimilar mechanical properties regarding cracking behaviour. The critical value of the mode I stress-intensity factor KICis an appropriate fracture parameter for evaluating fracture toughness and can be obtained from three-point bending tests (3PBT) on small, notched specimens. Subsequent determination of the energy release rate thus allows to examine the crack propagation and fracture process of both concrete types. This paper describes the results of such 3PBTs on samples, made from VC and SCC. Evaluation of the cracking behaviour, derived from these results, reveals remarkable differences.

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Determination of transverse compressive strength of long fibre composites by three-point bending of [90m/0n] cross-ply laminated strips

Polymer Testing ◽

10.1016/j.polymertesting.2011.04.012 ◽

2011 ◽

Vol 30 (5) ◽

pp. 578-584 ◽

Cited By ~ 1

Author(s):

N. Carbajal ◽

F. Mujika

Keyword(s):

Compressive Strength ◽

Three Point Bending ◽

Fibre Composites

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Determination of Elastic Modulus in Mouse Bones Using a Nondestructive Micro-Indentation Technique Using Reference Point Indentation

Journal of Biomechanical Engineering ◽

10.1115/1.4039982 ◽

2018 ◽

Vol 140 (7) ◽

Author(s):

Ganesh Thiagarajan ◽

Mark T. Begonia ◽

Mark Dallas ◽

Nuria Lara-Castillo ◽

JoAnna M. Scott ◽

...

Keyword(s):

Elastic Modulus ◽

Reference Point ◽

Ex Vivo ◽

Numerical Procedure ◽

Indentation Modulus ◽

Three Point Bending ◽

Bending Modulus ◽

Reference Point Indentation

The determination of the elastic modulus of bone is important in studying the response of bone to loading and is determined using a destructive three-point bending method. Reference point indentation (RPI), with one cycle of indentation, offers a nondestructive alternative to determine the elastic modulus. While the elastic modulus could be determined using a nondestructive procedure for ex vivo experiments, for in vivo testing, the three-point bending technique may not be practical and hence RPI is viewed as a potential alternative and explored in this study. Using the RPI measurements, total indentation distance (TID), creep indentation distance, indentation force, and the unloading slope, we have developed a numerical analysis procedure using the Oliver–Pharr (O/P) method to estimate the indentation elastic modulus. Two methods were used to determine the area function: (1) Oliver–Pharr (O/P—based on a numerical procedure) and (2) geometric (based on the calculation of the projected area of indentation). The indentation moduli of polymethyl methacrylate (PMMA) calculated by the O/P (3.49–3.68 GPa) and geometric (3.33–3.49 GPa) methods were similar to values in literature (3.5–4 GPa). In a study using femurs from C57Bl/6 mice of different ages and genders, the three-point bending modulus was lower than the indentation modulus. In femurs from 4 to 5 months old TOPGAL mice, we found that the indentation modulus from the geometric (5.61 ± 1.25 GPa) and O/P (5.53 ± 1.27 GPa) methods was higher than the three-point bending modulus (5.28 ± 0.34 GPa). In females, the indentation modulus from the geometric (7.45 ± 0.86 GPa) and O/P (7.46 ± 0.92 GPa) methods was also higher than the three-point bending modulus (7.33 ± 1.13 GPa). We can conclude from this study that the RPI determined values are relatively close to three-point bending values.

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