On the determination of the point of fracture initiation by the load separation criterion in J-testing of ductile polymers
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Introduction structure of the spectral collection the decimal classification spectra hydrocarbons CHal polymers CHHal polymers CHN polymers CHO polymers CHS polymers CHaIX polymers CNO polymers CNS polymers CHHall-lal polymers CHHaIN polymers CHHaIO polymers CHHaIS polymers CHNO polymers CHNS polymers CHOS polymers CHaINO polymers CHaINS polymers CHHalHal'O polymers CHHalNO polymers CHHaIOS polymers CHNOS polymers polymers made up of 6 and more elements deuterated polymers boron compounds silicon compounds germanium compounds phosphorus compounds polymers with boron and Si, Ge or P polymers with Si and Ge or P polymers with a heteroelement (B,Si, Ge,P) and a metal organometallic polymers.
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Experiments were conducted to establish a correlation between the weight loss of a polyimide (PMR- 15) matrix and graphite fibers and the in-plane shear properties of their unidirectional composites subjected to different isothermal aging times up to 1000 hr at 316 C. The role of fiber surface treatment on the composite degradation during the thermo-oxidative aging was investigated by using A4 graphite fibers with three surface modifications: untreated (AU-4), surface treated (AS-4), and surface treated and sized with an epoxy-compatible sizing (AS-4G). The weight loss of the matrix fibers, and composites was determined during the aging. The effect of thermal aging was seen in all the fiber samples in terms of weight loss and reduction in fiber diameter. Calculated values of weight loss fluxes for different surfaces of rectangular unidirectional composite plates showed that the largest weight loss occurred at those cut surfaces where fibers were perpendicular to the surface. Consequently, the largest amount of damage was also noted on these cut surfaces. Optical observation of the neat matrix and composite plates subjected to different aging times revealed that the degradation (such as matrix microcracking and void growth) occurred in a thin surface layer near the specimen edges. The in-plane shear modulus of the composites was unaffected by the fiber surface treatment and the thermal aging. The shear strength of the composites with the untreated fibers was the lowest and it decreased with aging. A fracture surface examination of the composites with untreated fibers suggested that the weak interface allowed the oxidation reaction to proceed along the interface and thus expose the inner material to further oxidation. The results indicated that the fiber-matrix interface affected the composite degradation process during its thermal aging and that the the weak interface accelerated the composite degradation.
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Arrangement of Spectra The Decimal Classification System Spectra Hydrocarbons CHal Polymers CHHal Polymers CHN Polymers CHO Polymers CHS Polymers (x?'/CNO Polymers CNS Polymers CHHalHal' Polymers CHHalN Polymers CHHalO Polymers CHHalS Polymers CHNO Polymers CHNS Polymers CHOS Polymer CHalNO Polymers CHalNS Polymers CHHallial'O Polymers CHHalNO Polymers CHHalOS Polymers CHNOS Polymers Polymers Made Up of 6 Elements Deuterated Polymers Boron Compounds Silicon Compounds Germanium Compounds Phosphorus Compounds Polymers with Boron and Si. Ge or P Polymers with Si and Ge or P Polymers with a Heteroelement (B, Si, Ge, P) and a Metal Organometallic Polymer Spectral Appendix Index Alphabetic Index of Compounds and Spectra of Monomeric Units in Polymers and Copolymers Formula Index of Monomeric Units in Polymers and Copolymers Author Index.
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Experiments were conducted to study the effects of thermo-oxidative stability (weight loss) and fiber surface modification on the inplane shear properties of graphite/PMR-15 unidirectional composites. The isothermal aging was conducted at 316°C and up to 1000 hours of aging times. The role of fiber surface treatment on the composite degradation during the thermo-oxidative aging was investigated by using A-4 graphite fibers having three different surface modifications, namely untreated (AU-4), surface treated (AS-4), and surface treated and sized with epoxy-compatible sizing (AS-4G). Weight loss of matrix, fibers, and composites was determined during the aging. The effect of thermal aging was seen in all the fiber samples in terms of their weight loss and reduction in fiber diameter. Calculated values of weight loss fluxes for different surfaces of rectangular unidirectional composite plates showed that the largest weight loss occurs at those cut surfaces where fibers are perpendicular to the surface. Consequently, the largest amount of damage was also noted on these cut surfaces. Optical observation of neat matrix and composites plates subjected to the different aging times revealed that the degradation (such as matrix microcracking, void growth, etc.) occurred within a thin surface layer near specimen edges. The inplane shear modulus of the composites was unaffected by the fiber surface treatment and the thermal aging. The shear strength of the composites having the untreated fibers was the lowest and it decreased with aging. Fracture surface examination of the composites having untreated fibers suggests that the weak interface allows the oxidation reaction to proceed along the interface and thus expose the inner material to further oxidation. The results indicate that fiber-matrix interface affects the composite degradation process during its thermal aging and that the weak interface accelerates the composite degradation.
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Abstract The intensity of light scattered from dilute solutions of mixtures of two nonidentical polymers in a single solvent was measured. The parameter A 24 characterising the thermo‐dynamic interaction of two nonidentical polymer molecules in solution was calculated for several systems polymer 2 ‐ polymer 4 ‐ solvent. For chemically strongly different polymers, A 24 is independent of molecular weights of the polymers and probably also of solvent. A 24 is related to the compatibility of both polymers and decreases contrary to expectation with increasing chemical difference between polymers 2 and 4.
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Polymers have become essential part of life. One can’t think of life without polymers, reason being their innumerable physical and engineering characteristics. Most prominent quality of polymers is their low cost and durability.However, seize to strength ratio of polymers is large as compared to metals. Heat capacity of polymers is also less. Structural strength of polymers is also poor which make them unsuitable for heavy structures. Above all polymer are non biodegradables they may persist in environment for centuries. Due to this disability many countries have imposed restrictions on their use. Low price, long life and readiness to adopt any shape has made polymers invulnerable. Non bio degradability of synthetic polymers shifted the quilt towards the invention of biopolymers. Scientists found the solution in biopolymers. They can be biosynthesized by living organisms or chemically synthesized from biological matter. The biopolymers are natural polymers formed by living organisms. Biopolymers are monomeric units which are bound covalently to form large molecules. Unlike polymers the biopolymers are biodegradable which decompose in bio-products with time after the expiry of intended purpose. Mainly there are three classes of biodegradable polymers namely polysaccharides, polypeptides and poly nucleotides Biopolymers mostly find applications in manufacturing, packaging, biomedical engineering and food industry. Difference between natural and synthetic polymers is discussed. Advantages of biopolymers over polymers are compared. Present study enlists brief overview of biopolymers. Keywords: Polymers, Biopolymers, Biodegradable Abbreviations: PVC, PVDF, Tg, DNA, RNA
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