Impact and Flexural Properties

Variation in tensile, impact, and flexural properties of thermoset composites, viz. sisal-polyester, sisal-epoxy, and sisal-phenol-formaldehyde is explained here, with the change in length of the fiber (5-30 mm), fiber volume, etc. 

Testing of mechanical properties such as tensile strength (ASTM-D-638), flexural strength (ASTM-D-790), and impact strength (ASTM-D-256) was done following standard methods. The water absorption of both untreated and treated composites was determined as per ASTM-D-570. The variation in tensile, impact, and flexural properties of thermoplastic composites, viz. sisal-polypropylene and sisal polystyrene, is explained here, and the change in fiber volume also given here. 

Following the trend of using PVC as matrix, research on the use of EFB as composite in PVC matrix was also reported. Bakar et at [37] used the EFB as filler in unplasticized poly(vinyl chloride) (PVC-U). They studied the effects of extracted EFB on the processability, impact and flexural properties of EFB/PVC-U composites. PVC-U resin, EFB and other additives were first dry-blended using a heavy-duty laboratory mixer and then milled into sheets on a two-roll mill before being hot-pressed and cut into impact and flexural test specimens. There were two kinds of EFB used in this experiment, which were extracted and xmextracted. The FTIR showed that the unextracted EFB contained oil residue, while the extracted one contained less oil residue. The results showed that both extracted and unextracted EFB decreased the fusion time and melt viscosity. However, the fusion time increased with the increase of extracted EFB content. Meanwhile, there was no significant difference in both the impact and flexural properties of extracted and xmextracted EFB. 

A. AbuBakar, A. Hassan, and A.FM. Yusof, The effect of oil extraction of the oil palm empty fruit bunch on the processabihty, impact, and flexural properties of PVC-U composites. Int. J. Polym. Mater. 55, 627-641 (2006). 

Tensile, impact, and flexural properties Tensile test is the most widely used method to evaluate the mechanical properties of the resultant nanocomposites, accordingly. Young s modulus, tensile strength, and elongation at break are the three main parameters obtained. These vary with the silica content, but the variation trends are different. Furthermore, the impact test is also widely used for mechanical property characterization. 

The properties of SAN resins depend on their acrylonittile content. Both melt viscosity and hardness increase with increasing acrylonittile level. Unnotched impact and flexural strengths depict dramatic maxima at ca 87.5 mol % (78 wt %) acrylonitrile (8). With increasing acrylonitrile content, copolymers show continuous improvements in barrier properties and chemical and uv resistance, but thermal stabiUty deteriorates (9). The glass-transition... 

Polycarbonates with superior notched impact strength, made by reacting bisphenol A, bis-phenol S and phosgene, were introduced in 1980 (Merlon T). These copolymers have a better impact strength at low temperatures than conventional polycarbonate, with little or no sacrifice in transparency. These co-carbonate polymers are also less notch sensitive and, unlike for the standard bis-phenol A polymer, the notched impact strength is almost independent of specimen thickness. Impact resistance increases with increase in the bis-phenol S component in the polymer feed. Whilst tensile and flexural properties are similar to those of the bis-phenol A polycarbonate, the polyco-carbonates have a slightly lower deflection temperature under load of about 126°C at 1.81 MPa loading. 

Tensile and flexural properties were studied with an Instron 4204 testing machine. Tensile tests were performed on the drawn strands at a test speed of 3 mm/ min, while three-point-bending tests (ISO 178) at a speed of 5 mm/min were applied to the injection molded specimens. Charpy impact strength was measured of the unnotched samples with a Zwick 5102 pendulum-type testing machine using a span of 70 mm. The specimens (4 X 10 X 112 mm) used for three-point-bending tests were also used for the impact tests. It should be noted that neither the tensile tests for the strands nor the impact tests were standard tests. The samples were conditioned for 88 h at 23°C (50% r.h,) before testing. 

Regarding the properties required of the solidified materials in 2D printing, the most important properties are generally related to thin material layers, such as color, adhesion to the substrate, hghtfastness, and scratch resistance, whereas in 3D printing, the most important properties are generally related to the bulk material mechanical and thermomechanical properties, for example tensile and flexural properties, impact resistance, and Glass Transition Temperature (Tg). 

The mechanical properties of rapidly polymerizing acrylic dispersions, in simulated bioconditions, were directly related to microstructural characteristics. The volume fraction of matrix, the crosslinker volume in the matrix, the particle size distribution of the dispersed phase, and polymeric additives in the matrix or dispersed phase were important microstructural factors. The mechanical properties were most sensitive to volume fraction of crosslinker. Ten percent (vol) of ethylene dimethacrylate produced a significant improvement in flexural strength and impact resistance. Qualitative dynamic impact studies provided some insight into the fracture mechanics of the system. A time scale for the elastic, plastic, and failure phenomena in Izod impact specimens was qualitatively established. The time scale and rate sensitivity of the phenomena were correlated with the fracture surface topography and fracture geometry in impact and flexural samples. 

Properties of a thermoset can be varied by using different formulations such as fiber content, filler content, etc. this uniqueness makes it difficult to generalize the definition of properties of the material. Its characteristics are used as guidelines in part design and material selection to understand the effect of the change in formulation on mechanical properties. Table 6 shows static and impact properties of SMC, BMC, LPMC, and ZMC. Tensile and flexural properties are routinely... 

Surface modifiers are used for a number of reasons, and these include reduction of dustiness and moisture content, improved processing, and enhanced composite properties. Table 11.1 shows that filling polypropylene with uncoated magnesium hydroxide results in a significant decrease in impact and flexural strength. However, surface treatment of the filler can counteract these effects to some degree. 

Many cardo polymers exhibit improved solubility in different solvents with little sacrifice in properties. A survey was made of the physical properties of different cardo copol mides with varying microstructures. As might be expected, copolyimides with increasing aliphatic fragment content were shown to exhibit the highest impact and flexural strength. 

It is worth noting that ISO/IEC and ASTM test methods for many properties, in principle, are similar and the differences between the specific test methods are rather minimal. Even so, differences in measured data between the two methods, depending on the type of material, are expected, particularly with thickness-dependent properties such as impact strength, DTUL, and flexural properties stemming from the variance in test specimen dimensions and its preparation. Thus, any correlation between two sets of data is dependent on the material type, implying that one should not assume that the property values generated by the ISO test methods would always be equivalent to the values obtained by using the ASTM method with simple conversion to appropriate units. 

Maleic anhydride modified polypropylene consistently decreased Izod impact but provided large increases in Gardner and unnotched Izod impact. Heat deflection temperature plus tensile and flexural properties were also increased substantially. 

Zhou and co-workers [27] studied the effects of surface treatment on the mechanical and thermal properties of composites comprising calcium carbonate particles with varying proportions of PEEK. Tensile impact and flexural testing were carried out and the effect of particle size, loading and surface treatment on deformation and crystallinity was investigated. 

The tensile and flexural properties can be enhanced by the addition of common fibrous reinforcing fillers such as chopped glass fiber or carbon fiber. Although these fillers offer an increase in strength and stiffness, such improvements can come with a reduction in impact resistance. Fortunately, glass-fiber-reinforced polysulfones still offer practical toughness. The ambient temperature mechanical properties for reinforced PSF, PES, and PPSF are presented in Table 13.5. 

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