Dart Impact Research Articles

Impact behavior of aramid fiber/glass fiber hybrid composite: Evaluation of four-layer hybrid composites

Aramid fiber/glass fiber hybrid composites were fabricated to investigate the impact behavior of four-layer composites through the analysis of delamination area. The effect of position and content of aramid layer on the impact properties of hybrid composites was examined by using driven dart impact tester. The surface-treated composites were prepared by treating the surface of aramid fiber with oxygen plasma and silane coupling agent. The trend of total impact energy was correlated to that of delamination area in both untreated and treated composites. The impact energy and delamination area of hybrid composites depended on the position of aramid layer. When aramid layer was at back surface, the composite exhibited the higher impact energy and delamination area. In surface-treated composites, however, the position of aramid layer had a minor effect on the impact energy of hybrid composites. This was due to the restriction in deformation of aramid fiber. The impact behavior of four-layer hybrid composites was affected by the delamination area at each interface. The deformation at neighbored-aramid layers increased the deformation at adjacent interfaces.

Effects of Filler Content and Surface Treatment on Drop-Weight Dart Impact Fracture Behaviour of Glass Bead-Filled Polypropylene Binary Composites

The effects of A-glass bead content and its surface treatment on the drop-weight dart impact fracture behaviour of the filled polypropylene (PP) binary composites at room temperature have been investigated. For the uncoated filler filled system (PP/3000U), the maximum impact force (Fmax) and the crack propagation energy (Epc) vary gently with the volume fraction (of); while for the system filled with coated fillers with silane coupling agent (PP/3000), Fmax and EP, values reach minimum at around Of = 15%. The impact fracture energy (Ed C) and crack initiation energy (Eic) for both the composites increase with increasing Of when Of is greater than 15%. The influence of the filler surface treatment on Ed C and Ej, of the composites is irregular. Furthermore, the impact fracture morphology of the specimens has been observed and analyzed.

Effects of Filler Content and Size on Drop-Weight Dart Impact Fracture Behavior of Glass Bead-Filled Polypropylene Composites

Three sizes of A-glass beads, 6000 (4 [im), 3000 (35 prm), and 1922 (219 μm), were chosen in this work to identify the effects of filler content and size on the drop-weight dart impact fracture behavior of filled polypropylene (PP) composites at room temperature. At higher filler concentration, the values of the maximum impact load and the crack initiation energy for the PP filled with smaller glass beads were higher than those of the unfilled PP and the systems filled with larger glass beads. However, the crack propagation energy of the former was lower than that of the latter. The influence of the filler content and size on the impact fracture energy of these composites was insignificant. Comparatively, the drop-weight dart impact resistance of the systems filled with smaller glass beads was somewhat improved. Furthermore, the impact fracture morphology of the specimens was observed and analyzed. The results indicated that the smaller particles were more beneficial to initiate and increase microcracks in the PP matrix interlayer around them and thus to improve the impact resistance of the composites at high filler concentrations.

Effects of Filler Content and Size on Drop-Weight Dart Impact Fracture Behavior of Glass Bead-Filled Polypropylene Composites

Three sizes of A-glass beads, 6000 (4 [im), 3000 (35 prm), and 1922 (219 μm), were chosen in this work to identify the effects of filler content and size on the drop-weight dart impact fracture behavior of filled polypropylene (PP) composites at room temperature. At higher filler concentration, the values of the maximum impact load and the crack initiation energy for the PP filled with smaller glass beads were higher than those of the unfilled PP and the systems filled with larger glass beads. However, the crack propagation energy of the former was lower than that of the latter. The influence of the filler content and size on the impact fracture energy of these composites was insignificant. Comparatively, the drop-weight dart impact resistance of the systems filled with smaller glass beads was somewhat improved. Furthermore, the impact fracture morphology of the specimens was observed and analyzed. The results indicated that the smaller particles were more beneficial to initiate and increase microcracks in the PP matrix interlayer around them and thus to improve the impact resistance of the composites at high filler concentrations.

EFFECT OF CALCIUM CARBONATE PROPERTIES ON THE REINFORCEMENT OF HMW-HDPE FILM

Pelleted concentrates based on linear low density polyethylene (LLDPE) were used to add 0, 7.5% and 15 wt% of different fine-ground, surface-treated calcium carbonate (CaCO3) minerals to a high-molecular weight (HMW) high density polyethylene (HDPE) film resin. These dry blends were extruded into 13 μm thick film. Neck height and blow-up ratios (BUR) were varied to determine how the addition of CaCO3 affected film property response to variations in these process conditions. Mineral addition yielded output rate increases of 5% at 7.5% CaCO3 and 10% at 15% CaCO3 while simultaneously decreasing melt pressure and motor load (current). Depending upon calcium carbonate grade, mineral loading and processing conditions, increases in dart impact strength and/or tensile yield strength were achieved. Calcium carbonate mineral grades also exhibited differences in the level of extrusion and bubble stability. Mineral reinforcement of HMW-HDPE films increases film coefficient of friction, which improves stacking of line...

Butorphanol/xylazine/ketamine immobilization of free-ranging Baird's tapirs in Costa Rica.

Cardiopulmonary effects and the utility of a butorphanol/xylazine/ketamine combination were evaluated during twenty immobilizations of sixteen Baird's tapirs (Tapirus bairdii) between March 1996 and January of 1998 in Corcovado National Park (Costa Rica). The animals were attracted to a bait site and darted from tree platforms. The tapirs were estimated to weigh between 200 to 300 kg. Actual weights of three tapirs taken at later dates fell within the estimated range. A butorphanol, 48+/-1.84 (x +/- SE) mg/animal IM, and xylazine, 101+/-2.72 mg/animal IM, combination was used to immobilize the animals. In some instances, ketamine was used either IM or IV at 187+/-40.86 mg/animal to prolong the immobilization period in addition to the butorphanol/xylazine combination. Naltrexone was used IM to reverse butorphanol at 257+/-16.19 mg/animal. Either yohimbine, 34+/-0.61 or tolazoline at 12+/-10.27 mg/animal, was used to reverse xylazine. The mean time from dart impact to first visible effect was 4.63+/-0.50 min (x +/- SE). Mean time to sternal recumbency was 12.21+/-1.08 min. Mean time the tapirs were immobilized was 45.63+/-3.6 min. Mean time to return to sternal recumbency and standing in animals that received yohimbine and naltrexone was 3.16+/-1.06 and 5.33+/-1.45 min, respectively. Mean time to return to sternal recumbency and standing in animals that received tolazoline and naltrexone was 1.57+/-0.39 and 3.14+/-0.51 min, respectively. Cardiopulmonary parameters including heart rate, respiratory rate, body temperature, electrocardiogram, percent oxygen satoration, and indirect blood pressure were recorded. Arterial blood gas analysis was performed on four animals. A mild degree of hypoxemia was evidenced by low arterial oxygen saturations. Five of 14 (36%) animals measured had oxygen saturations below 90%. Bradycardia (heart rates <45 BPM) was an expected finding in 11 (55%) immobilizations. Induction, recovery and muscle relaxation of each immobilization was graded. Premature arousal, which occurred in six (30%) animals, was the only problem associated with the immobilizations. Butorphanol/xylazine is a recommended protocol for immobilization of calm, free-ranging tapirs lasting less than 30 min. Supplemental intravenous administration of ketamine is recommended for longer procedures. Nasal insufflation of oxygen is recommended.

Compatibilizing effect of styrene-maleic anhydride copolymer on the properties of polyamide-6/liquid crystalline copolyester composites

Liquid crystalline polymer–polyamide-6 (LCP/PA6) composites containing 20 wt % LCP content were compatibilized by a random styrene–maleic anhydride copolymer (RSMA). The blending was performed via extrusion followed by injection molding. The LCP employed was a commercial copolyester, Vectra A950. The dynamic mechanical (DMA), rheological, thermal, and mechanical properties as well as the morphology of the composites were studied. The DMA and rheological results showed that RSMA is an effective compatibilizer for LCP/PA6 blends. The mechanical measurements showed that the stiffness, tensile strength, and toughness of the in situ composites are generally improved with increasing RSMA content. However, these mechanical properties deteriorated considerably when RSMA content was above 10 wt %. The drop-weight dart impact test was also applied to analyze the toughening behavior of these composites. The results show that the maximum impact force (Fmax) and crack-initiation energy (Einit) tend to increase with increasing RSMA content. From these results, it appeared that RSMA prolongs the crack-initiation time and increases the energies for crack initiation and impact fracture, thereby leading to toughening of LCP/PA6 in situ composites. Finally, the correlation between the mechanical properties and morphology of the blends is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1964–1974, 2000

Morphology and mechanical property relationship in linear low-density polyethylene blown films

Linear low-density polyethylene (LLDPE) blown films fabricated under two different processing conditions, namely a non-stalk bubble configuration and a stalk bubble configuration, were investigated. Morphological characterization was performed using small-angle X-ray scattering, transmission electron microscopy, infrared dichroism, and differential scanning calorimetry. The findings on crystal orientation characteristics of the films suggest that modification on the widely accepted row orientation model of Keller and Machin may be needed. In comparison to the conventional non-stalk bubble geometry for LLDPE film blowing, the stalk bubble configuration can produce a more randomly orientated lamellar texture, resulting in less anisotropy in mechanical properties and a higher dart impact resistance. A good correlation between mechanical properties and morphological features was found.

Effects of Filler Content and Surface Treatment on Drop-Weight Dart Impact Fracture Behaviour of Glass Bead-Filled Polypropylene Binary Composites

Effects of Filler Content and Surface Treatment on Drop-Weight Dart Impact Fracture Behaviour of Glass Bead-Filled Polypropylene Binary Composites

Blown Film Extrusion of LLDPE/LDPE Blends

An experimental study was carried out to investigate the effect of LLDPE/LDPE blend compositions on the physical properties of blown films and processing properties during extrusion. Spiral mandrel die analysis was also performed by FAN method and its results were compared with measured die pressure. Positive synergy effects of LDPE addition into LLDPE could be seen except the dart impact and MD tear strength of the films.

Easy Processing Metallocene Polyethylene

A new family of metallocene polyethylene (mPE) has an outstanding combination of processability, toughness and stiffness. It provides an opportunity to downgauge and improve extrusion output in applications where blends of conventional Ziegler-Natta catalyzed linear low density polyethylene (ZN-LLDPE) and high pressure low density polyethylene (HP-LDPE) are currently used. The processability of this new product was found to be significantly better than that of ZN-LLDPE and comparable to that of ZN-LLDPE/HP-LDPE blends. Its film properties are substantially better than blends of ZN-LLDPE and HP-LDPE. Its dart impact strength is 60% better than that of a comparable ZN-LLDPE product.

Semi-IPNs formed from poly(ethylene glycol monomethyl ether acrylate) and an epoxy thermoset

Poly(ethylene glycol monomethyl ether acrylate) (PEGMEA) was synthesized from the reaction of poly(ethylene glycol monomethyl ether) (PEGME) with acryloyl chloride. Semi-IPNs based on various weight ratios of diglycidyl ether of bisphenol A (DGEBA)/PEGMEA were prepared, using isophronediamine (IPDA) and 2,2′-azo-bis(isobutyronitrile) (AIBN) as curing agents. The glass transition temperature and exothermic peak shifts were studied with differential scanning calorimetry (DSC). Viscosity changes during semi-IPN formation were measured with a Brookfield viscometer. Dynamic mechanical properties were investigated by rheometric dynamic spectroscopy (RDS). Stress–strain curves were obtained with an Instron tensile tester, while impact resistance was measured with a computer aided falling dart impact tester. Experimental results revealed retarded curing rates for all semi-IPNs, as evidenced from the shifts of curing exothermic peaks to higher temperatures, together with retarded viscosity increases during semi-IPN formation. These phenomena were interpreted in terms of chain entanglement between epoxy and PEGMEA. Nevertheless, the semi-IPNs indicated good compatibility as inferred from a single Tg in DSC and a single damping peak in RDS for each semi-IPN. Improved tensile stress and strain along with toughness improvements were noticed for this semi-IPN system. Shear band yielding was proposed to interpret this result. © 1999 Society of Chemical Industry

Semi‐IPNs formed from poly(ethylene glycol monomethyl ether acrylate) and an epoxy thermoset

Poly(ethylene glycol monomethyl ether acrylate) (PEGMEA) was synthesized from the reaction of poly(ethylene glycol monomethyl ether) (PEGME) with acryloyl chloride. Semi-IPNs based on various weight ratios of diglycidyl ether of bisphenol A (DGEBA)/PEGMEA were prepared, using isophronediamine (IPDA) and 2,2′-azo-bis(isobutyronitrile) (AIBN) as curing agents. The glass transition temperature and exothermic peak shifts were studied with differential scanning calorimetry (DSC). Viscosity changes during semi-IPN formation were measured with a Brookfield viscometer. Dynamic mechanical properties were investigated by rheometric dynamic spectroscopy (RDS). Stress–strain curves were obtained with an Instron tensile tester, while impact resistance was measured with a computer aided falling dart impact tester. Experimental results revealed retarded curing rates for all semi-IPNs, as evidenced from the shifts of curing exothermic peaks to higher temperatures, together with retarded viscosity increases during semi-IPN formation. These phenomena were interpreted in terms of chain entanglement between epoxy and PEGMEA. Nevertheless, the semi-IPNs indicated good compatibility as inferred from a single Tg in DSC and a single damping peak in RDS for each semi-IPN. Improved tensile stress and strain along with toughness improvements were noticed for this semi-IPN system. Shear band yielding was proposed to interpret this result. © 1999 Society of Chemical Industry

Application of instrumented falling dart impact to the mechanical characterization of thermoplastic foams

The applicability of instrumented falling weight impact techniques in characterizing mechanically thermoplastic foams at relatively high strain rates is presented in this paper. In order to try simulating impact loading of foams against sharp elements, an instrumented dart having a hemispherical headstock was employed in the tests. Failure strength and toughness values were obtained from high-energy impact experiments, and the elastic modulus could be measured from both flexed plate and indentation low-energy impact tests. The results indicate a dependence of the failure strength, toughness, and the elastic modulus on the foam density, the foaming process, and the chemical composition. This influence was found to be similar to that of pure nonfoamed materials and also to that observed from low-rate compression tests. The results also indicate that the indentation low-energy impact tests were more accurate in obtaining right values of the elastic modulus than the flexed plate low-energy impact tests usually used to characterize rigid plastics. The foam indentation observed with this test configuration contributes to obtaining erroneous values of the elastic modulus if only a simple flexural analysis of plates is applied.

The Effect of Thickness on the Tensile and Impact Properties of Reinforced Thermoplastics

The properties of reinforced thermoplastics are affected by the amount of skin and core developed within a part during the injection molding process. Since the thickness of a part greatly influences the amount of skin and core developed within a molded part, thickness also affects the properties of reinforced thermoplastics. This study compares the tensile strength and modulus of several short and long fiber reinforced thermoplastics at 2.0, 3.2, 4.4, and 6.4 mm wall thicknesses. Falling dart impact properties of the short and long fiber reinforced materials are also examined at 3.2 and 6.4 mm wall sections. The results indicate that the tensile properties of the reinforced crystalline resins are more affected by thickness than the reinforced amorphous resins. The study also shows that increasing wall thickness from 3.2 to 6.4 mm will significantly increase the impact energy absorption characteristics of several reinforced thermoplastic materials.

Dynamic Calibration of Impact Test Instruments

Abstract This paper proposes a new dynamic calibration procedure of the force measuring system used in instrumented impact test apparatus. The method involves calculation of the force calibration factor on the basis of energy values obtained executing the Charpy or Izod test for a pendulum device and on the basis of velocity measurements in a rebound test for the falling dart impact apparatus. The procedure is simple, quick, and has the advantage that calibration is performed under the same dynamic conditions as in a test itself. Moreover, it does not require any additional equipment other than that used for conventional impact test execution: an impact device, an instrumented tup, and a data acquisition system.

Polymerization of Formaldehyde Using Tetravalent Organo-Tin Compounds as an Initiator

Polymerization of gaseous formaldehyde in hexane using various initiators including tetravalent organo-tin compounds was investigated. The end group of the obtained polymer was examined and it was concluded that the chain-transfer agents (such as methanol, etc.) were almost completely consumed during the polymerization of gaseous formaldehyde. Only two series of initiators, quaternary ammonium salt and dialkyltin dimethoxide compounds, produced a polymer with a narrow-molecular-weight distribution (Mw/Mn = 2). The polymer with the narrow-molecular-weight distribution (Mw/Mn = 2) produced a product with high Dart impact strength. The polymer with the broad-molecular-weight distribution (Mw/Mn > 2.9) gave the product with low Dart impact strength.

Blends and interpenetrating polymer networks of polypropylene and polystyrene-block-poly(ethylene-stat-butylene)-block-polystyrene. 2: Melt flow and injection molding properties

Injection molding and melt flow properties of a set of blends prepared by mixing the triblock thermoplastic elastomer polystyrene-block-poly(ethylene-stat-buty-lene)-block-polystyrene with polypropylene and a processing oil are reported. Despite the high viscosity of the thermoplastic elastomer, the melt viscosity of the blends was similar to or lower than that of the pure polypropylene. The rheological behavior of the molten blends seems to be dominated by a low-viscosity melt phase containing mainly polypropylene and oil. The surface of solidified extrudates from the capillary rheometer was rich in polypropylene and free from large domains of the thermoplastic elastomer. Injection molded plates had a similar surface morphology, although in this case, larger domains of the elastomeric phase were found in narrow, band-shaped surface regions. These local surface heterogeneities were probably caused by flow-induced phase segregation during mold filling. Weld lines in injection molded test pieces prepared from blends within the composition range giving interpenetrating network structures had no noticeable effect on either stress-strain behavior or falling dart impact strength.

Behavioural Responses of Agile Wallabies (Macropus agilis) to Darting and lmmobilisation with Tiletamine Hydrochloride and Zolazepam Hydrochloride

A total of 28 free-ranging agile wallabies (Macropus agilis) was immobilised with a combination of tiletamine hydrochloride and zolazepam hydrochloride. The drug was administered by projectile syringe fired from a gas-powered pistol. A dose of approximately 10 mg per kg body mass produced ataxia in 3.8 ± 0.4 min (mean ± s.e.), initial recumbency in 4.9 ± 0.5 min, and lateral recumbency in 7.9 ± 0.7 min after dart impact. Wallabies were calm throughout handling, showed good muscle relaxation and started to regain consciousness after 53 ± 3 min. Recovery of mobility took more than 240 min and appeared uneventful. Wallabies moved 41 ± 5 m after dart impact, after which they either groomed or fed until the drug took effect. Five wallabies sought shelter in nearby forest after darting and these were found 11 ± 3 m inside the forest boundary.

Morphology-property relationships in ABS/PET blends. I. Compositional effects

Novel blends of PET and ABS were prepared by extrusion and injection molding. DSC and DMTA studies show that PET and ABS are immiscible and that the blends consist of four phases : SAN, grafted polybutadiene, amorphous PET, and minor amounts of crystalline PET. The morphology was investigated by transmission electron microscopy on OsO 4 -stained and unstained sections and by scanning electron microscopy of alkali- and solvent-etched surfaces. These techniques reveal that the two major domains, SAN and amorphous PET, interpenetrate and are cocontinuous over the compositional range of 30-70 wt % PET. The yield stress and flexural modulus increase in an almost linear fashion as the weight fraction of PET in the blend is increased. In contrast, the notched Izod impact energy passes through a maximum and the Dart impact energy shows a step transition at 50 wt % PET. SEM studies of the Izod fracture surfaces exhibit considerable plastic deformation in both domains when the specimens are tough, indicating that both phases participate in the toughening process.