Improved Impact Properties Research Articles

Evaluation of Performance of Cotton Fiber Reinforced Epoxy Composites

This experimental study explored the impact of varying weight proportions (5%, 10%, 15%, and 20%) of cotton fiber reinforcement in epoxy composites on compressive strength, Charpy impact strength, and water absorption characteristics. Concurrently, the interfacial properties were examined using Scanning Electron Microscopy (SEM). The inclusion of 15 wt.% cotton fiber notably enhanced compressive strength, displaying consistent improvement as cotton content increased until reaching 15 wt.%. Beyond this point, further increases yielded diminishing enhancements in compressive properties. EC20 demonstrated superior impact strength and energy absorption. Increased cotton concentrations improved impact properties due to the fibrous nature of cotton, enhancing energy dissipation and crack resistance within the epoxy matrix. Higher cotton content correlated with increased water absorption, aligning with cotton’s hydrophilic properties. The EC20 composite exhibited heightened water uptake and permeability, indicating the influence of elevated cotton concentrations. SEM analysis of fracture surfaces identified crucial features such as fiber pull-out, matrix cracking, interfacial debonding, and surface irregularities. These findings contribute significantly to understanding the inherent failure mechanisms in these composite materials.

Fracture and mechanical properties of an impact toughened polypropylene composite: modification for automotive dashboard-airbag application.

Thermoplastic olefin (TPO) is the principal material for automotive instrument panels and is prone to fracture especially under heavy airbag deployment, which can prevent the airbag deploying properly. Thus, polyolefin elastomer (POE) was introduced to improve impact properties and fracture resistance. Fundamental methods to characterise TPO with the addition of POE are proposed. The influence of POE content on the mechanical properties was examined. With increasing POE content, the storage modulus and glass transition temperature values decreased, and the damping increased due to the POE increasing the polymer chain mobility. The tensile modulus, ultimate tensile strength and yield stress decreased with increasing POE content, while the ductility of the blends significantly increased. Furthermore, the POE reduced hardness and increased energy absorption during impact. In the fracture analysis, the addition of POE content increased the fracture resistance by increasing the crack energy and decreasing the resistance to crack initiation. Fractographic analysis showed how stretched microfibrils in the blends increase the fracture resistance. These results gave a significant indication of the utility of the elastomer in improving some mechanical properties and impact toughness of the interior automotive material to resist an undesired failure or over-fracture in airbag deployment.

Fibre–Wood Laminate Biocomposites: Seawater Immersion Effects on Flexural and Low Energy Impact Properties

The present paper explores a new concept of a hybrid eco-composite by substituting the natural fibre plies with thin wood veneers. The new composite, named Fibre–Wood Laminate (FWL), is inspired by fibre–metal laminate materials. The studied FWL configuration consisted of a single thin pinewood veneer at each of the outer layers of a flax woven fabric reinforced bio-epoxy composite manufactured by infusion. Three-point bending results showed that wood veneer gives a highly anisotropic nature to the FWL. In the best case, with the grain of the wood at 0°, the stiffness and the strength increased by 28 and 41%, respectively, but reduced the strain-at-break by 27% compared to the flax fibre reinforced bio-epoxy (FFRB). The penetration and perforation energy thresholds and the peak force of the FWL obtained by falling weight impact tests were 32, 29, and 31% lower than those of the FFRB, respectively. This weakening was due to using single wood veneers, so the challenge for improving impact properties will be to explore thicker FWLs with different stacking sequences and orientations. The effect of immersing the FWL in seawater also showed considerable differences. The epoxy matrix filled the cellular structure of the wood veneers, creating a barrier effect and reducing the amount of water absorbed by the flax fibres.

On the Effect of Hot Rolling on Inclusion Size and Distribution in a Cast AISI 1070 Steel Railroad Wheel

The goal of this work is to examine the effect of hot deformation on shrinkage porosity and nonmetallic inclusions in an AISI 1070 grade steel industrially produced wheel casting. Steel cleanliness is an important consideration as it influences the mechanical properties of the final product. A high density of porosity and inclusions have been shown to be detrimental for mechanical properties, especially during hot rolling. Using a laboratory-scale rolling mill, cast preforms were subjected to a 66% cumulative reduction to determine the effect of thermomechanical processing on void closure and inclusions that may produce anisotropy in mechanical properties. Quantitative automated feature analysis, AFA, of inclusion type, size, morphology, and distribution was conducted utilizing an Aspex PICA 1020 scanning electron microscope to determine differences in inclusions and shrinkage porosity in the as-cast and as-rolled conditions. The results were compared with previously reported impact toughness values which indicated a trend with MnS projected length and average impact toughness in the T-L orientation. Reduction in shrinkage porosity was also verified utilizing 3D micro-X-ray CT scans. The AFA results showed a decrease in shrinkage porosity from 177 ppm in the as-cast condition to less than 35 ppm after rolling. Pores were in general much smaller and widely distributed after hot rolling and this would suggest improved impact properties. Analysis of nonmetallic inclusions revealed three primary categories of inclusions that included MnS, Al2O3, and complex inclusions that mainly consisted of MnS with an Al2O3 core, with small quantities of mixed silicates of Mn and Al and calcium aluminates (CaAl2O4).

Sensitivity of the impact performance of nano reinforced sandwich structures to the material and geometrical variations

The low-velocity impact response of sandwich structures with aluminum face sheets and neat or nano-reinforced polypropylene core was studied. A strain-rate dependent micromechanics model (SRDM) was presented in the literature for predicting the dynamic behavior of nano-reinforced polymers. In the present study, the dynamic behavior of nano-reinforced polypropylene was simulated based on SRDM results. The finite element model was validated against the experimental results. It was shown that the results of the simulation performed by the SRDM model were in very good agreement with the experimental data. Then, the proposed finite element model was used for checking the sensitivity of the impact performance of nano-reinforced sandwich structures to the material and geometrical variations. A special sandwich structure with a core of 1 mm thickness and a face thickness of 1 mm was considered as the base structure. Different material and geometrical variations including doubling the thickness of the core or face sheets, a different weight ratio of graphene, and increasing material parameters of the face sheets up to 90%, were undertaken on the base structure. The results of the present study imply that the optimal amount of graphene should not exceed 0.5 wt.% to improve impact properties. The impact response of nano-reinforced sandwich structures was more sensitive to the variations of the face thickness in comparison to the variations of the core thickness. Moreover, the impact outputs were more sensitive to changes in the yield stress of faces compared to changes in Young’s modulus of faces.

To Explore the Effect of Injection Molding Processing Parameters on Crazing in Acrylic Polymers

Plastic manufacturing industry is the fastest growing industry as the demand for plastic products is exponentially growing worldwide. Poly (methyl methacrylate) (PMMA), also known as acrylic glass, is a transparent and rigid thermoplastic. PMMA is highly resistant to UV light. Weathering has an excellent light transmission and unlimited coloring options compared to other transparent plastic and has been used in wide applications such as architecture, automotive and transportation, lighting (LED lights), medical and healthcare, and furniture. Injection molding is the widely used plastic manufacturing process to produce plastic products for various applications. The quality of the plastic products depends on the injection molding parameters, viz. melting temperature, injection speed, and pressure, holding and cooling time, and holding pressure. Therefore, it is important to control injection molding parameters to reduce injection molding defects or parts. Hence, the main objective of this research is to optimize the injection molding parameters, including the amount of mold releasing agent, to avoid the crazing marks in PMMA which is a long-standing problem in the production of PMMA products or parts such as motorbike headlight lenses. Three different holding pressures (65, 75, and 85 kg/cm2) were varied against three different injection pressures (70, 80, and 90 kg/cm2). The injection speed (60 %), cooling time (4 s), and barrel zones temperature (185-205: 185-205: 190-210: 195-215) were kept constant not to disturb the production cycle, a constraint from the production industry. The minimum criteria required for the motorbike headlight lens selection was based on the LUX intensity test, density, and crazing demanded by the Japanese standard throughout this research. The optimized injection molding parameters and amount of mold releasing agent (Nabakem mold release R2) were 70 kg/cm2 (injection pressure), 65 kg/cm2 (holding pressure), and 1.18 g, respectively. The motorbike headlight lens produced with optimized injection molding parameters showed no crazing. In addition to the desired LUX intensity, density, and no crazing criteria, the motorbike headlight lens also showed improved impact properties and no substantial changes in mechanical properties when compared to virgin PMMA or literature. Hence, it is concluded that the optimized injection molding parameters (thermo-mechanical history) did not much affect the molecular weight and morphology of the PMMA.

Effects of oxygen content on Charpy impact properties and crack resistance of α titanium alloys

Charpy impact properties and crack resistance of commercial pure (CP) Ti and Ti–6Al alloy with different oxygen contents were systematically investigated by using the instrumented Charpy impact testing machine. The scanning electron microscope (SEM) equipped with electron backscatter diffraction (EBSD) detector and transmission electron microscope were employed to detect the deformation mechanisms. The experimental results showed that decreasing the oxygen content significantly improved the impact toughness of CP Ti and Ti–6Al alloy. Furthermore, decreasing the oxygen content simultaneously strengthened the resistance to crack initiation and propagation of CP Ti while only improved the resistance to crack propagation of Ti–6Al alloy. EBSD analysis demonstrated the significant effects of oxygen content on dislocation activities and deformation twinning behaviors in CP Ti and Ti–6Al. Decreasing the oxygen content significantly increased the dislocation activities and deformation twinning behaviors in CP Ti and Ti–6Al alloy which were mainly responsible for the improved impact properties and the strong crack resistance of CP Ti and Ti–6Al alloy. A mathematical model was introduced for the first time to uncover the interactions between oxygen atoms and dislocation as well as the deformation twinning on the view of valence electron by employing the Yu Rui-huang electron theory. By conducting the systematically experimental and theoretical investigations, we are aiming to provide deep insights into the relationships between interstitial oxygen and impact toughness as well as the crack resistance of titanium alloys and promote the production of titanium alloys with excellent impact properties.

Enhanced Impact Strength of Recycled PET/Glass Fiber Composites.

In this paper, we report a study on the effects of different ethylene copolymers in improving the impact strength of a fiber-reinforced composite based on a recycled poly(ethylene terephthalate) (rPET) from post-consumer bottles. Different ethylene copolymers have been selected in order to evaluate the effects of the polar co-monomer chemical structure and content. The composite mixtures were prepared via melt extrusion, and the samples were manufactured by injection molding. Impact strength was evaluated using Izod tests, and a morphological study (FESEM) was performed. As a result, a composite with substantially improved impact properties was designed. This study demonstrates that a post-consumer PET from the municipal waste collection of plastic bottles can be successfully used as a matrix of high-performance, injection-molded composites, suitable for use in the automotive sector, among others, with no compromise in terms of mechanical requirements or thermal stability.

Cover Image, Volume 138, Issue 25

This cover designed by Muhammad Irfan and colleagues shows how High Performance Polyethylene (HPPE) fibers are relatively tougher than carbon fibers and can be used to improve impact tolerance of carbon epoxy composite laminates. Composite laminates containing carbon fibers suffer from delamination upon impact. An interleave of a tough material like HPPE fibers inserted between these carbon fiber plies can reduce the damage due to impact. HPPE fibers do not undergo brittle fracture, rather ductile fracture is observed along with fibrillation. Nonwoven interleaves comprising HPPE fibers can be used to improve impact properties of carbon-epoxy composite laminates for various applications. DOI:10.1002/app.50683

Parameter optimization via the Taguchi method to improve the mechanical properties of bamboo particle reinforced polylactic acid composites

Reinforcement with natural fibres is a common method to improve impact properties of poly(lactic acid) (PLA). In this study, composites made from PLA and bamboo particles were melt-compounded in a twin-screw extruder and formed by compression moulding. Tensile, flexural, and impact tests were conducted. Particle size (A), particle loading (B), screw speed (C), and die temperature (D) were varied at three levels. Tensile strength and modulus, flexural strength and modulus, and impact strength were the response variables. The experiment design was based on Taguchi’s (L9) orthogonal array. Through variance analysis, the particle loading was found to be the dominant factor influencing the mechanical properties, followed by die temperature. The optimum parameters were validated with a confirmation test. The results showed a noticeable improvement of impact properties compared to neat PLA by 55%, without compromising tensile and flexural properties. Flexural strength, flexural modulus, and tensile modulus of the composites were greater than that of pure PLA. However, only tensile strength was reduced by about 28% compared to pure PLA. Importantly, the DOE method with maximizing the desirability properties was found to be an effective systematic approach to identify an optimal parameter setting of the extrusion moulding process.

Thermal, Mechanical and Micromechanical Analysis of PLA/PBAT/POE-g-GMA Extruded Ternary Blends

In order to toughen Poly(lactic) acid and binary blends with low PBAT content while maintaining a high biodegradability of the final material, poly(lactic) acid (PLA)/poly(butylene-adipate-co-terephthalate) (PBAT)/ polyolefin elastomer grafted with glycidyl methacrylate (POE-g-GMA) extruded ternary blends have been investigated in this work from a thermal, mechanical and rheological point of view. The two elastomers have been added in different amounts as dispersed phases into the PLA matrix, paying attention to the final objective: the design of a 90 % biodegradable formulation according to EN 13432. These ternary blends exhibited improved impact properties but still low elongation at break. Consequently, to the ternary composition with the best compromise of PLA quantity, biodegradability and thermo-mechanical properties (81 wt.% PLA, 9 wt.% PBAT and 10wt.% POE-g-GMA) a small quantity (10 wt.%) of a biobased plasticizer was added in order to further increase the impact properties in parallel with the tensile flexibility. Two types of plasticizers were investigated, one not reactive (Acetyl Tributyl Citrate (ATBC)), and one reactive (Glycidyl ether (EJ-400)). A micromechanical study, in order to investigate the toughening mechanism of these systems, was carried out on the final formulations. They were also examined by dilatometric tests and elasto-plastic fracture mechanics correlating the data obtained to the morphology and to the rheological properties. In conclusion, the best compromise between impact, tensile properties and biodegradability content was achieved using the reactive plasticizer (EJ-400) whose interaction with the matrix is confirmed by the FT-IR analysis.

Effect of SEBS and OBC on the Impact Strength of Recycled Polypropylene/Talc Composites

In this paper, we report a study on the use of a linear triblock copolymer based on styrene and ethylene/butylene (SEBS) and a polypropylene (PP)-based olefin block copolymer (OBC) for improving the impact strength of a recycled polypropylene (PP) from packaging waste. Talc was used as a reinforcing filler in order to prepare a material suitable for being used in the automotive sector. The composite mixtures were prepared by melt extrusion, and the samples were manufactured by injection molding. Impact strength was evaluated by Izod tests, and a morphological study of the produced fractures was performed. As a result, a composite with substantially improved impact properties was prepared, with a two-fold increase of the impact strength in the case of unnotched specimens, while only a limited positive effect was produced on notched specimens. Since talc-filled PP is a typical material used in the automotive sector, the obtained results demonstrate that post-consumer PP coming from the municipal waste collection of plastic packaging can be successfully used in car components with no compromise in terms of mechanical requirements.

Sustainable Alternative Composites Using Waste Vegetable Oil Based Resins

Laminates were produced with epoxy resins from waste vegetable oil (WVO) intended for the manufacturing of environmentally-friendly alternatives for the composites industry. Post-use cooking oil appears a promising source of triglycerides for polymer manufacturing. Matrices cured with methylhexahydrophthalic anhydride (MHHPA) were reinforced with glass and flax fibres, creating a library of composites that were compared to analogues from virgin oil and benchmarked against commercial diglycidyl ether of bisphenol A (DGEBA). Glass fibre-reinforced composites presented Young’s moduli similar to the benchmark but reduced tensile strength. Chemical pre-treatment of the flax fibre (NaOH and stearic acid) countered the limited tensile performance observed for materials with untreated flax; improvements were evidenced by DMA and SEM. Moreover, WVO-based resins greatly improved impact properties and reduced density with no effect on thermal stability. Therefore, WVO-based composites appear as more sustainable alternatives in applications demanding toughness, stiffness and lightweight over strength.

Improved Impact Properties in Poly(lactic acid) (PLA) Blends Containing Cellulose Acetate (CA) Prepared by Reactive Extrusion.

Poly(lactic acid)/triacetine plasticized cellulose acetate (PLA/pCA) blends were prepared by extrusion at two different temperatures and tetrabutylammonium tetraphenyl borate (TBATPB) was added as a transesterification catalyst to reactively promote the formation of PLA-CA copolymer during the reactive extrusion. The occurrence of chain scission in the PLA phase and branching/crosslinking in the CA phase in the presence of TBATPB, resulting also in a darkening of the material, were demonstrated by studying torque measurements and by performing proper thermogravimetric tests on CA with the different additives. Tensile and impact tests onto the blends prepared at the lower temperature showed better properties than the ones obtained at a higher temperature. Then, the mechanical properties of PLA/plasticized cellulose acetate (pCA) blends prepared at the lower temperature were investigated as a function of the content of plasticized CA in the blend. A range of compositions was observed where blends exhibited improved impact properties with respect to pure PLA without a significant decrease in their elastic modulus. The study of the phase morphology of the blends revealed that the occurrence of reactive compatibilization did not significantly affect the phase distribution. In general, fibrillar CA particles were formed in the PLA matrix during extrusion, thus allowing the preparation of CA fibre reinforced composites. The trend of morphology as a function of the composition and processing conditions was then discussed by considering the evolution of phase morphology in immiscible polymer blends.

High toughness poly(lactic acid) (PLA) formulations obtained by ternary blends with poly(3-hydroxybutyrate) (PHB) and flexible polyesters from succinic acid

This work reports the development of poly(lactic acid) (PLA) formulations with improved toughness by ternary blends with poly(3-hydroxybutyrate) (PHB) and two different flexible polyesters derived from succinic acid, namely poly(butylene succinate) (PBS) and a copolymer, poly(butylene succinate-co-adipate) (PBSA). The main aim of this work is to increase the low intrinsic toughness of PLA without compromising the thermal properties by manufacturing ternary blends using epoxidized vegetable oils as compatibilizer agents. The ternary blends were manufactured by reactive extrusion in a co-rotating extruder and were subjected to mechanical, thermal, thermos-mechanical and morphology characterization. The obtained results confirm that these two succinic acid-derived polymers, i.e., PBS and PBSA, positively contribute to increase ductile properties in ternary blends with PLA and PHB with a subsequent improvement on impact toughness. In addition, both epoxidized vegetable oils, ELO and ESBO, are responsible for somewhat compatibilization between all three polyesters in blends which gives improved ductile properties with regard to uncompatibilized ternary blends. In addition, the temperature range in which these materials can be used is broader than ternary blends with other flexible polyester such as poly(e-caprolactone), as both PBS and PBSA melt at about 100 °C. These PLA-based materials with improved impact properties offer interesting applications in the packaging industry.

Processing and characterization of binary poly(hydroxybutyrate) (PHB) and poly(caprolactone) (PCL) blends with improved impact properties

The present work is focused on the development of binary blends from poly(hydroxybutyrate) (PHB) and poly(caprolactone) (PCL). Miscibility, mechanical and thermal properties as well as blends morphology are evaluated in terms of the blend composition. Binary PHB–PCL blends were manufactured by melt compounding in a twin screw co-rotating extruder and injection molded. The composition of PHB–PCL covered the full range between individual polymers at 25 wt% increments. The obtained results show that PCL acts as an impact modifier, thus leading to an increase in flexibility and ductility as the PCL content in the PHB–PCL blends increases with a noticeable increase in elongation at break and on the energy absorption in impact conditions. The tensile strength and the elastic modulus decrease with increasing PCL content in the PHB–PCL blends; nevertheless, the flexural strength and the flexural modulus reach the highest values for the PHB–PCL blends containing 25 wt% PCL, with a remarkable decrease over this composition. The analysis of fractured surfaces by field emission scanning electron microscopy and thermal properties obtained by differential scanning calorimetry (DSC) and TGA give clear evidences of the immiscibility of these two biodegradable polymers. Additionally, DSC results showed an increase in crystallinity of both PHB and PCL with regard to individual polymers for PHB–PCL blends containing 25 wt% PCL. Furthermore, an increase in the degradation onset (T 0) of about 30 °C higher was detected for the same blends. Dynamic mechanical thermal analysis showed slightly shifted glass transition temperatures of each individual polymer, thus indicating that although both PHB and PCL are not fully miscible, some interactions between them occur.

Functionalized Distiller's Dried Grains with Solubles for Improving Impact Properties of Polylactic Acid

Functionalized Distiller's Dried Grains with Solubles for Improving Impact Properties of Polylactic Acid

Design of composite materials with improved impact properties

Composites have been widely used in applications where there is a risk of impact, due to the excellent properties these materials display for absorbing impact energy. However, composites during impact situations typically generate an enormous number of small pieces, due to the energy absorption mechanism of these materials, a mechanism which does not include plastic deformation. This can prove dangerous in sports competitions, where the small fragments of the original structure may harm competitors.This study was designed to explore the possibility of incorporating a material which, whilst maintaining a high level of energy absorption without any plastic deformation mechanism, was able to maintain its original form, or at least significantly reduce the number of pieces generated after impact.The addition of a polyamide layer, NOMEX®, to a monolithic fabric laminate was investigated in this paper. The process of fabrication is described and the different properties of the material under consideration: interlaminar fracture toughness energy (GIC), indentation (id) and delamination after impact (Ai) and compression after impact (σCAI), were measured and compared with those of the original monolithic fabric.

Mechanical properties of compatibilized nylon 6/polypropylene blends; studies of the interfacial behavior through an emulsion model

ABSTRACTThe high interfacial tension between two immiscible phases in a polymer blend often prevents a homogenous stress distribution. Therefore, blends of Nylon 6 (Ny6) and polypropylene (PP) were compatibilized using two commercially available types of PP grafted with maleic anhydride (MAPP) with a low (∼2 %) and a high (∼7%) grade of maleation. The interfacial tension of compatibilized and non‐compatibilized blends of PA6/PP was calculated from the recoded data of oscillatory rheological measurements using an emulsion model. Both compatibilizers showed similar improvements in tensile strength of up to 25%, but the one low maleation grade compatibilizer showed improved impact properties (>200%). It could be shown that, despite, being more effective in reducing the interfacial tension, using a high grade of maleation in the compatibilizer causes no additional improvement in tensile strength over a low grade of maleation and even has a negative effect on the PA6/PP blend impact strength. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40792.

Effect of resin modification on the impact strength of glass-polyester composites

Summary — Fiber-reinforced plastics (FRP) are nowadays used commonly for constructions subjected to impacts of different energies and velocities, therefore the problem of their impact resistance is very important. One of the methods to improve impact properties of the composites is resin modification with elastomeric phase. In this study the effect of resins addition on properties of composites of unsaturated polyester (UP) resins with glass fibers was investigated. At the first stage, the properties of Polimal 109-32K UP resin modified by the addition of reactive liquid rubbers were tested. The wettability of glass fibers by resin compositions was also tested. Composites were then prepared with the addition of 2 and 6 phr of epoxy or vinyl terminated butadiene-acrylonitrile rubbers (ETBN or VTBN, respectively), as well as 5 and 15 wt. % of Polimal 150 elastic UP resin. These composites were subjected to mechanical tests. Impact properties were tested using Charpy method, as well as by a ballistic impact using a gas gun. After the ballistic impact, damage extent and residual strength as well as water leakage through the composites were evaluated. The damage was also investigated under a microscope. The damage extent was confirmed to be linearly dependent on the impact energy. The addition of rubber was found to decrease the damage extent and increase post-impact residual strength, as well as decrease water leakage rate.