Dart Impact Test Research Articles

Development and characterization of ester modified endospermic guar gum/polyvinyl alcohol (PVA) blown film: Approach towards greener packaging

With growing environmental concerns, the biopolymer-based film provides a suitable substitute for sustainable packaging applications. In this article, guar gum based bioplastic films were prepared by taking various ratios of Polyvinyl Alcohol with guar gum along with Octenyl succinic anhydride (OSA) and plasticizer followed by blown film extrusion process to encourage industrial-scale production. The films were prepared with the utilization of pre-treated guar gum powder, Polyvinyl alcohol and OSA at various weight ratios with the help of blown film extruder . The temperature zone of the extrusion machine was maintained from feeding zone to metering zone with optimized processing parameters. After the production of film, characterization studies such as mechanical, thermal and morphological properties were analyzed. The tensile strength of films was gradually improved in the machine direction due to modified OSA in GG/PVA having good tear resistance whereas, the percentage of failure is less during dart impact test. The thermal characterization reveals the transition temperature exceeding due to modification. The morphological analysis also supports better compatibility between GG with PVA with improved chemical interaction, as established by FTIR analysis. The contact angle test was carried out to measure the hydrophobicity, which suggest improved characteristics suitable for packaging application. • Esterified GG/PVA-based films were prepared with improved hydrophobicity. • Morphological analysis showed improved compatibility and interaction between PVA and guargum. • Film-forming of GG/PVA-based films provides suitability for various packaging applications. • Traditional extrusion process suit the market demand in the field of biopolymer .

Use of virgin/recycled polyethylene blends in rotational moulding

Abstract Aiming to further plastics recycling via rotational moulding plastics processing, blends of virgin and recycled polyethylene sourced from post-consumer plastics were developed. Three different kinds of recycled high density polyethylene – from bottles, pipes and mixed household waste – were compounded with virgin medium density polyethylene in an extruder. The ideal amount of recyclate was chosen based upon the impact resistance of different contents (25, 50 and 75%) of recycled plastic with the 50/50 blend found to have the best performance. Compression-moulded and rotationally-moulded samples were analysed through falling dart impact test, flexural test, melt flow rate and differential scanning calorimetry analysis. The impact results of the compression-moulded samples showed an increase in the impact resistance of the blends with a higher melt flow index and lower degree of crystallinity. The rotationally-moulded specimens displayed much lower impact resistance than the pure virgin plastic and a 20–30% reduction in the flexural moduli, which were ascribed to the crystalline structure of the part and issues in the blends’ rotomoulding process. It was concluded that blending virgin and recycled polyethylene for rotational moulding can be an effective way to further plastics recycling inside the Circular Economy context.

The effect of degree of curvature and fabric orientation on the impact properties of single and multilayer textile composites

The usage of textile composites as lightweight gadgets is increasing day by day. The application range varies from personal protective tools to aerospace vehicle parts. However, every specific application demands specific functionality. Anisotropic nature of textile materials makes it possible to design composites in structural as well as non-structural shapes. In this research, single and multilayered textile composites were fabricated by using cotton woven fabric as a reinforcement and unsaturated polyester resin as a polymer. The fabrication was done at different degrees of curvature with different fabric orientations (i.e. the positioning of second and third layer fabric was turned from warp to weft) in multilayered composites to analyze their effect on the impact property of the resultant composite. Falling dart impact test was performed, to measure the impact properties of the samples. The curved specimens had shown higher strength as compared to the flat specimens. Furthermore, the increment in the degree of curvature causes the rise in fractural energy value. The number of layers has a direct effect on impact property as the number increases, the strength also increases. Finally, there was no significant effect of fabric orientation observed in double and triple layered composites.

Energy absorption from composite reinforced with high performance auxetic textile structure

The objective of this study is to analyze the impact behavior on the basis of energy approach of weft knitted structures, namely a jersey composite and an auxetic composite using high performance yarns. Weft knitted fabrics were produced with the same structural and machine parameters, using 100% para-aramid and hybrid (47% para-aramid and 53% polyamide) structure. Composite fabrication was achieved through hand lay-up using epoxy resin. Negative Poisson ratio of the reinforcing auxetic fabric was transferred from the fabric to the composite developed. Results obtained by drop weight dart impact test show that the impact experiment with different impact loads confirmed the auxetic composites, regardless de material composition, have an increase in the total energy absorption compared to jersey reinforced composite, approximately 2.5 and 4 times more for para-aramid and hybrid composite, respectively. Auxetic composites developed within this work present great potential for applications in different areas, mainly where energy absorption is a key factor to be considered, such as in protection, sports among others.

Novel Hybrid Structural Biocomposites from Alkali Treated-Date Palm and Coir Fibers: Morphology, Thermal and Mechanical Properties

In this concern study, the surging demands for regulating the environmental aspects associated with controlling a massive generated synthetic wastes in the field of structural applications, has motivated researchers to synthesize green products using agricultural wastes. Therefore, in this work, a novel hybrid epoxy composites based on alkali treated-date palm fiber and native coir fiber at different weight fractions were prepared using hand layup technique and investigated the hybridization effect of the resultant composites. Hybrid composites were characterized using several analytical techniques i.e. X-ray diffraction analysis, thermogravimetric analysis, contact angle measurement, dart impact test and tensile test. Reported results explored that the alkali treatment on date palm fiber had a reliable impact on the experimentally evaluated mechanical, hydrophobic and thermal properties of the resultant hybrid composites. The required structural properties for 50 wt% coir fiber incorporated in 50 wt% treated-date palm fiber based epoxy composites are 76.51 MPa tensile strength, 2.77% elongation limit, 832.2 J/m impact strength, and 100.2° contact angle, respectively possess highest value as compared to all other hybrid composites. Hence, the incorporation of 50 wt% treated-date palm fiber in 50 wt% coir fiber based epoxy composite has the best structural properties in terms of mechanical, water resistant and thermal properties for green rigid applications.

Bio-based composite from poly(butylene succinate) and peanut shell waste adding maleinized linseed oil

Nowadays, the biobased plastic products have become one of the worldwide topics that people give the attention. Applications of bio-based poly (butylene succinate) (PBS) is interesting since it is fully biodegradable. However, the resin cost is expensive compared to olefins so that it is not widely used. This research attempted to produce cost-effective composite sheets from PBS and peanut shell powder (PSP) with particle size of 100 mesh in the weight ratio of 70/30, 60/40, and 50/50 wt% using a twin-screw extruder and then a compression molding. In addition, maleinized linseed oil (MLO) of 3 phr was used as a compatibilizer for the composites. It was found that the obtained composites had higher Young’s modulus and Shore D hardness with respect to the PSP content, but elongation at break was reduced. The impact resistance by means of the falling dart impact test also reduced with the higher PSP content. Adding MLO into the PBS/PSP composites increased elongation at break and impact resistance, but reduced the rigidity due to plasticizing effect. Due to lignocellulosic nature of PSP, the thermal stability of the composites was decreased and MLO did not have significant influence on it. After the weathering testing for 60 h, mechanical properties and thermal stability of the composites were reduced significantly implying that these bio-based composites could degrade faster compared to pure PBS sample.

A transparent three-layered laminate composed of poly(methyl methacrylate) and thermoplastic polyurethane subjected to low-velocity impact

Experimental and numerical results of a novel polymeric laminate consisting of poly(methyl methacrylate) (PMMA) and thermoplastic polyurethane (TPU) are presented. The laminate was subjected to low-velocity impact loadings using clamped three-point bending and dart impact tests at different temperatures and velocities in order to investigate the highly strain-rate and temperature dependent characteristics of a purely polymeric laminate. An investigation of the adiabatic heating of the highly strained interlayer in the post-breakage phase was performed with high-speed infrared thermography. A significant temperature rise of the interlayer in the impacted area and in the vicinity of cracks of the broken PMMA was observed, which facilitates temperature-based alteration of material properties during the test. Material and Finite Element modelling techniques are proposed and discussed, which are able to represent the mechanical and thermal behaviour of the laminate qualitatively and quantitatively.

Thermal and Mechanical Analysis of Polyethylene Homo-Composites Processed by Rotational Molding.

This work is aimed at studying the suitability of ultra-high molecular weight polyethylene (UHMWPE) fibers for the production of polyethylene homo-composites processed by rotational molding. Initially pre-impregnated bars were produced by co-extrusion and compression molding of UHMWPE fibers and linear low-density polyethylene (LLDPE). A preliminary screening of different processing routes for the production of homo-composite reinforcing bars was performed, highlighting the relevance of fiber impregnation and crystalline structure on the mechanical properties. A combination of co-extrusion and compression molding was found to optimize the mechanical properties of the reinforcing bars, which were incorporated in the LLDPE matrix during a standard rotational molding process. Apart from fiber placement and an increase in processing time, processing of homo-composites did not require any modification of the existing production procedures. Plate bending tests performed on rotational molded homo-composites showed a modulus increase to a value three times higher than that of neat LLDPE. This increase was obtained by the addition of 4% of UHWMPE fibers and a negligible increase of the weight of the component. Dart impact tests also showed an increased toughness compared to neat LLPDE.

Comparison of falling dart and Charpy impacts performances of compatibilized and not compatibilized polypropylene/woven glass fibres composites

The effect of the matrix/fibre interface strength on the in-plane and out-of-plane impact performances of glass woven fabric/polypropylene laminates, prepared by means of film stacking technique, was investigated. The interface strength between polymer and fibres was varied by means of a coupling agent added to two different polypropylene grades in order to evaluate its contribution to the impact resistance of the laminates. The static characterization showed that the flexural strength of compatibilized laminates was higher with respect to that of composites based on neat matrices. On the contrary, composites with low interface strength between fibres and polymer showed a strong improvement in impact resistance, in both Charpy and falling dart impact tests. This was related to the possibility of fibres to slip into the matrix and dissipate energy through friction, and to the improved capability to bear load before fibre failure, allowed by the limited propagation of cracks through the laminate. The damage after impact was assessed by means of micro-computed tomography, which elucidated the role of the weak matrix/fibre interface in improving the impact resistance.

Study of plant fibre composites with damage induced by laser and mechanical impacts

Abstract Polymer composite materials provide good strength to weight ratio and tailored mechanical properties thanks to the reinforcing fibres. Until recently, the need for taking into account the whole life cycle of a composite structure was neglected and only the service aspects were important. Today, the designers of a new composite structure have to take into account the environmental aspects from the sustainability of raw materials to the management of end life products. There are recycling issues related to the most popular composites. A solution for the recycling issue can be sought in green composites with reinforcing fibre originating from plants. The behaviour of eco-composites, when subjected to laser or mechanical impact loadings, is not well known yet. Short fibre composites were made with spruce fibres. Another set of samples was made of flax fibres. Also a woven hemp fabric-based eco-composite was investigated. A fully synthetic woven composite was used for comparison with green composites. Mechanical impacts were performed by means of a falling dart impact testing machine. Laser impacts were made with high power laser source. Four assessment techniques were employed in order to analyse and compare impact damage. Damage detection thresholds for each material and technique were obtained.

Development of polyhydroxyalkanoates/poly(lactic acid) composites reinforced with cellulosic fibers

In this work, the mechanical behavior of [30:70] (wf) PHA/PLA blend matrix reinforced with cellulosic fibers is investigated in the range of fiber incorporation of 10%, 20% and 30% wf.The mechanical properties of the composites can be optimized through the variation of the fiber content on the composite. It is possible to predict the tensile properties recurring to modified Halpin–Tsai equation, Ishai and Cohen Model and Rule-of-Mixtures Models.Analyzing the data from the dart impact test, the irregular fiber distribution for fiber ratio over than 20% is confirmed. The highest synergetic effect is found for fiber ratio of 20%.The incorporation of fiber improves the Heat Deflection Temperature (HDT) of the matrix when the fiber presents a homogeneous distribution through the matrix.The microscopic analysis allows identifying the good dispersion of the fiber through the matrix and a lower interfacial adhesion.The incorporation of 20% wf of fibers drives to an increasing of the tensile, flexural and impact behavior and also to a superior HDT.

Starch/polyester films: simultaneous optimisation of the properties for the production of biodegradable plastic bags

Blends of starch/polyester have been of great interest in the development of biodegradable packaging. A method based on multiple responses optimisation (Desirability) was used to evaluate the properties of tensile strength, perforation force, elongation and seal strength of cassava starch/poly(butylene adipate-co-terephthalate) (PBAT) blown films produced via a one-step reactive extrusion using tartaric acid (TA) as a compatibiliser. Maximum results for all the properties were set as more desirable, with an optimal formulation being obtained which contained (55:45) starch/PBAT (88.2 wt. (%)), glycerol (11.0 wt. (%)) and TA (0.8 wt. (%)). Biodegradable plastic bags were produced using the film with this formulation, and analysed according to the standard method of the Associação Brasileira de Normas Técnicas (ABNT). The bags exhibited a 45% failure rate in free-falling dart impact tests, a 10% of failure rate in dynamic load tests and no failure in static load tests. These results meet the specifications set by the standard. Thus, the biodegradable plastic bags fabricated with an optimised formulation could be useful as an alternative to those made from non-biodegradable materials if the nominal capacity declared for this material is considered.

Effect of process conditions on the dart impact properties of thin‐wall injection‐molded polycarbonate plates

AbstractMultifunctional mobile products, such as cellular phones, laptop computers, personal media players, etc., have become smaller and lighter; so the technology of thin‐wall injection molding (TWIM) has been highlighted for making lightweight and compact mobile electronic products. Regarding mechanical properties, many portable electronic products should pass the so‐called “drop test”; therefore, the evaluation of the dart (or impact) property of the housing that is made by the TWIM process is crucial for commercializing a product. However, extant research on the effect of injection molding process parameters on the physical properties of TWIM plates is insufficient as yet. Therefore, in this study, the pressure and temperature inside the cavity during the injection molding process are monitored by varying the injection molding process parameters, i.e., the gate size, injection speed, and melt temperature, and the effect of the average flow rate of the molten resin inside the cavity on the dart property of thin‐wall injection‐molded plates is examined. The dart property of thin‐wall injection‐molded plates is evaluated by the instrumented dart impact test to differentiate various responses of the load‐displacement data during dart tests. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci., 2013

Impact properties and microhardness of double‐gated glass‐reinforced polypropylene injection moldings

AbstractInjection moldings with weld lines were produced in glass reinforced polypropylene grades differing in filler content using a two‐gated hot runner injection mold. The skin‐core microstructure developed during injection molding was qualitatively analyzed by means of optical and scanning electronic microscopy techniques. The load bearing capacity of the moldings was assessed by uniaxial tensile‐impact and biaxial instrumented falling dart impact tests. Microhardness was also used to ascertain the possibility of using it as a simple nondestructive technique for characterizing glass fiber‐reinforced injection moldings. The properties were monitored at various points to evaluate their variation at the bulk and the knit region. The biaxial impact test highlights the 10‐fold reduction of the impact strength caused by the weld line. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Dart Impact Testing of Polyethylene Film: Mechanical Interpretation and Model

A physical model of dart impact tests of film manufactured from semi-crystalline polyethylene resins is developed. The models treat the dart impact tests as a special case of the standard high-speed stress/strain measurement performed on a polymer sample with a linearly changing cross section. They describe the dart impact strength as a complex function of the parameters that characterize the stress-strain curve of the resin: stresses and strains at the yield, necking and breaking points. The models correctly predict the range of the dart impact strength (ASTM D1709, ISO 7765) and are suitable for semi-quantitative characterization and ranking of linear low density polyethylene resins for film applications.

Modeling and Simulation of Impact Failure Characteristic of Polypropylene by Elastoviscoplastic Constitutive Law

For simulating the final failure of glassy polymers under impact loading, Shizawa's constitutive model was modified by introducing the craze density based softening law in which the phenomenological softening law using the craze density is employed. The material parameter identification procedure in the constitutive law was developed based on the sensitivity analysis. All parameters were identified with the measurement data which were obtained by both the dumbbell-shape tensile test specimen and the notched tensile test specimen. The dart impact test was also conducted. The load displacement curve and damage zone development were compared with those obtained by the finite element analysis using proposed constitutive equations. Both results were in good agreement and the usefulness of the constitutive equations was validated.

Fracture simulation of elastomer blended polypropylene based on elastoviscoplastic constitutive equation with craze and tensile softening law

The strong strain-rate dependence, neck propagation and craze evolution characterize the large plastic deformation and fracture behavior of polymer. In the latest study, Kobayashi, Tomii and Shizawa suggested the elastoviscoplastic constitutive equation based on craze evolution and annihilation and then applied it to the plane strain issue of polymer. In the previous study, the author applied their suggested elastoviscoplastic constitutive equation with craze effect to the three dimensional shell and then showed that the load displacement history was in good agreement with the experimental result including only microscopic crack such as crazes. For the future industrial applications, the macroscopic crack has to be taken into account. Thus, the main objective of this study is to propose the tensile softening equation and then add it to the elastoviscoplastic constitutive equation with craze effect so that the load displacement history can be roughly simulated during the macroscopic crack propagation. The tested material in this study is the elastomer blended polypropylene used in the interior and exterior of automobiles. First, the material properties are obtained based on the tensile test results at wide range of strain rates: 10 -4 -10 2 (1/sec). Next, the compact tension test is conducted and then the tensile softening parameters are fixed. Then, the dart impact test is carried out in order to obtain the load displacement history and also observe the macroscopic crack propagation at high strain rate. Finally, the fracture behavior is simulated and then compared with the experimental results. It is shown that the predictions of the constitutive equation with the proposed tensile softening equation are in good agreement with the experimental results for the future industrial applications.

Effect of thermotropic copolyesteramide on the properties of polyamide‐66/liquid crystalline copolyester composites

AbstractLiquid crystalline copolyester‐polyamide 66 (LCPES/PA66) composites compatibilized by liquid crystalline copolyesteramide (LCPEA) were prepared by injection molding. The LCPES employed was a commercial copolyester, Vectra A950, and the LCPES was a semiflexible thermotropic copolyesteramides based on 30 mol% of p‐amino benzoic acid (ABA) and 70 mol% of poly(ethylene terephthalate) (PET). Thermal analysis, mechanical characterization, and morphological investigations were conducted on the blends. The dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) tests showed that LCPEA is an effective compatibilizer for the LCPES/PA66 composites. The mechanical measurements showed that the stiffness, tensile strength and Izod impact strength of the in‐situ composites are improved by adding LCPEA because of the compatibilization and reinforcement to LCPES/PA66 composites. However, the properties improvement vanished when LCP content reached 10 wt%. The drop weight dart impact test was also applied to analyze the impact fracture characteristics of these composites. The results showed that the maximum impact force (Fmax), crack initiation and propagation energy all improved with the addition of a small percent of LCPEA. From these results, it appeared that LCPEA prolongs the time for crack initiation and propagation. It also increases the energies for crack initiation and propagation, thereby leading to toughening of the LCPES/PA66 in‐situ composites. Finally, the correlation between the mechanical properties and morphology of the composites is discussed.

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

The Impact Behavior of Thermoplastic Sheet Composites

Polypropylene sheet composites were produced by both the melt consoli dation and slurry deposition processes. The resulting composites had comparable flexural properties, based on the efficiency of the glass fiber reinforcement, but dissimilar impact strengths. The impact strength of the composites was found to be related to a number of factors, including the degree of adhesion between the polymer and reinforcing glass fibers, the concentration of glass fibers, and the length of the fibers. The impact properties of the melt impregnated composites were quite high. Melt impregnated polypropylene compos ites absorbed up to 257 J/cm during an instrumented falling dart impact test. The impact properties of the slurry formed composites were much less, only 62 J/cm.