Can the standard impact tests become a true materials evaluation tool?

Impact resistance constitutes one of the most popular quality control tools for polymeric materials and plastic finished parts. There are a number of standard impact test methods devoted to evaluate the impact response of polymeric materials (e.g., tensile-impact, Charpy and Izod tests, falling weight, Gardner, etc.). Nevertheless, to the questions: which test to use? how the different toughness measurements are related between each other? straightforward answers cannot be given. The shortcomings of standardized impact tests were recognized long ago: these tests are unable to generate an ‘actual material property’.Fil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Challenge with the scatter in ductile to brittle transition fracture transition of polymers

Fil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Depth sensing indentation of organic-inorganic hybrid coatings deposited onto a polymeric substrate

PEO-Si/SiO2 hybrid coatings deposited onto a PVC substrate were micromechanically characterized using depth sensing indentation. The effect of curing time and coating thickness was investigated. Elastic moduli of coated systems determined by the Oliver–Pharr approach displayed a continuous decreasing trend with increasing indentation depth, reflecting that the hybrids are stiffer than the substrate. Aiming to extract coating-only elastic modulus a simple method based on FE simulations was developed. The method was applied to evaluate the moduli of the hybrid coatings and the values were compared with those obtained by applying different approaches available in literature. The elastic modulus of PEO-Si/SiO2 hybrids was proven to be practically independent of curing time after 24 h. However, large curing times resulted in coatings being more prone to failure.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Seltzer, Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

El reto de fabricar piezas de nanocompuestos de organoarcilla y polipropileno a nivel industrial mediante moldeo por inyección

Nota EditorialFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentin

Fracture toughness determination of ABS polymers using the J-method

Abstract The suitability of J–R curve fitting methods proposed by ASTM E 813-81 and E 813-87 metal standards in fitting ABS J–R curves is discussed. Tests were carried out at room temperature on one commercial grade ABS resin in three-point bending. Specimens were precracked with a razor blade and tests were performed over a X20 range of crosshead rate in the quasistatic regime. Specimens of different geometric relationships (B/W, a/W, smooth specimens of different thickness, and side-grooved specimens) were assayed. The two ASTM fitting procedures were also checked against data reported by other authors for other ABS type resins. Model appropriateness was checked by statistical analysis. Results appeared to be geometrically independent for deeply notched specimens. No significant variation in the J–R curve was found for changes in the displacement rate. Both J–R curve fittings appeared to be adequate. The ASTM E 813-87 procedure led to less conservative critical initiation J IC values

Optimal ligament lengths in impact fracture toughness estimation by the essential work of fracture method

This work presents a statistical analysis of the confidence in fracture parameters of polymers estimated through the essential work of fracture (EWF) methodology under impact conditions. Fracture toughness parameters—essential, we, and non-essential work of fracture, wp—are obtained from the experimental relationship between specific total work of fracture wf and ligament length of the tested samples l: we is obtained from the y-intercept and wp from the slope of wf versus l in cases where a linear fit is suitable. The distribution of ligament lengths within a fixed number of samples to be tested under impact loading conditions is determined in order to minimize the uncertainty of the estimated parameters when linear reduction of the data is assumed. The statistical approach applied to two different polymeric materials shows that the uniform ligament length distribution along the ligament range is not the optimal one. We propose an optimal distribution of ligament lengths to be tested that depends on the distribution of error standard deviations of the measured work of fracture along the l-axis

A simple method for J-R curve determination in ABS polymers

Abstract The objective of this paper is to investigate the applicability of a very simple new method, based on load separation criterion, developed for evaluating J-R curves in steels, when applied to ABS polymers. This technique proposes the testing of a single precracked specimen and a single blunt notched specimen. The latter provides a method to detect the plastic displacement range during crack tip blunting in which the assumption of load separation criterion in the precracked specimen is valid, and also allows determination of J IC independently of J-R curve determination. The deformation material function is assumed to be a Ramberg-Osgood type law deformation function which leads to a very easy procedure to determine J-R curves. The J-R curve resulting from this new method is compared with one resulting from a traditional multiple specimen J-R curve determination method. Both results are in good agreement

Fiber Orientation Distribution Predictions for an Injection Molded Venturi-Shaped Part Validated Against Experimental Micro-Computed Tomography Characterization

This work evaluates and compares the accuracy of different fiber orientation prediction models for a short fiber reinforced injection molded Venturi-shaped part which displays variable thickness. The experimental characterization of the specimen fiber orientation distribution (FOD) was carried out by the micro computed tomography technique (micro-CT). The computational study of fiber orientation predictions was performed using Moldex3D. All the possible combinations of the Folgar-Tucker (FT) and improved Anisotropic Rotary Diffusion (iARD) rotary diffusion models and the Hybrid (Hyb), Orthotropic (ORE), and Invariant Based Optimal Fitting (IBOF) closure approximations were considered. The relevance of the Retardant Principal Rate (RPR) model on predictions results was also evaluated. The values of the fiber-fiber (Ci), matrix-fiber (Cm) interaction coefficients and the alpha-RPR parameter were varied in a significant range in order to find the set of parameters that better fits the experimental fiber orientation data. The parameters' sensitivity effect over the second order orientation tensor components was quantified via the Analysis of Variance (ANOVA) statistical method. The experimental micro-CT results show an increase in the fiber orientation degree at the specimen constriction region due to the narrowed cavity and the Venturi effect. The comparison of the experimental and predicted orientation profiles demonstrates that the predictions of the iARD model, in combination with the IBOF closure approximation, are the most accurate for the case studied. However, simulations fail to estimate the change in orientation caused by variable thickness and section. ANOVA results prove that the orientation tensor component in the flow direction (a11) is more sensitive to changes in alpha-RPR and Ci coefficient, while the perpendicular components (a22, a33) are also significantly affected by Cm. From the predictive error analysis it is seen that the optimal parameters set to capture the orientation state of the specimen is: (i) for the FT model, Ci = 0.005, alpha-RPR = 0.7 and (ii) for the iARD model, Ci = 0.005, Cm = 0.2, and alpha-RPR = 0.7.Fil: Quintana, María Camila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Arriaga, Aitor. Johannes Kepler University Linz; AustriaFil: Plank, Bernhard. University of Applied Sciences Upper; AustriaFil: Major, Zoltan. Johannes Kepler University Linz; Austri

Poly(acrylic acid) surface grafted polypropylene films: Near surface and bulk mechanical response

Radical photo-grafting polymerization constitutes a promising technique for introducing functional groups onto surfaces of polypropylene films. According to their final use, surface grafting should be done without affecting overall mechanical properties. In this work the tensile drawing, fracture and biaxial impact response of biaxially oriented polypropylene commercial films grafted with poly(acrylic acid) (PAA) were investigated in terms of film orientation and surface modification. The variations of surface roughness, elastic modulus, hardness and resistance to permanent deformation induced by the chemical treatment were assessed by depth sensing indentation. As a consequence of chemical modification the optical, transport and wettability properties of the films were successfully varied. The introduced chains generated a PAA-grafted layer, which is stiffer and harder than the neat polypropylene surface. Regardless of the surface changes, it was proven that this kind of grafting procedure does not detriment bulk mechanical properties of the PP film.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Costamagna, Vanina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; ArgentinaFil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Strumia, Miriam Cristina. Universidad Nacional de Córdoba. Facultad de Cs.agropecuarias. Departamento de Fundamentación Biológica. Cátedra de Química Organica; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Efecto de las variables del proceso de inyección sobre la resistencia al impacto de PP

En este trabajo se estudió la influencia de las variables del proceso de inyección, sobre la respuesta en impacto biaxial de piezas de Polipropileno homopolímero (PPH). Con este fin, se fabricaron probetas con geometría de disco variando sistemáticamente las temperaturas de molde (Tm) y de inyección (Ti). Como resultado, se encontró que en las ventanas de procesamiento empleadas, a menores Tm y a mayores Ti las probetas muestran una mayor energía de perforación, y el tipo de fractura tiende a ser dúctil. Sin embargo, se observó que el PPH estudiado se encuentra en la zona de transición dúctil-frágil, por lo tanto, existe una dispersión asociada al porcentaje de ductilidad (energía absorbida) de una pieza dada.The present work studies the influence of injection molding process conditions over the impact response of Polypropylene Homopolymer (PPH) parts. For this, disc shaped samples were injection-molded for a wide range of mold (Tm) and injection (Ti) temperatures values. Impact response was assessed through the falling weight force-displacement curves. As a result, it was found that by decreasing Tm and increasing Ti , test samples show higher impact energies and ductile failure modes. However, it was observed that the studied PPH is under the ductile-fragile transition regime and therefore there is an associated statistical dispersion in the absorbed impact energy values obtained for a given set of processing parameters.Fil: Gonzalez, Daysi. Universidad Simon Bolivar; VenezuelaFil: Costantino, María Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Candal, María Virginia. Universidad Simon Bolivar; Venezuel