Acoustic emission during irreversible deformation in short fiber reinforced poly(vinyl chloride) composites

Yuan, Jie; Hiltner, A.; Baer, E.

doi:10.1002/pc.750070107

Cited by 20 publications

(15 citation statements)

References 13 publications

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“…Pioneered by Kaiser,16) acoustic emission AE has been a common tool in investigating damage processes in a wide variety of materials including metals 17,18) and composites. 5,19) From the tables reported in Faudree et al Figure 8(a) shows AE events during the tensile tests in the low amplitude (25-60 dB) range, which have been correlated with small-scale damage such as microcracking and fiber end debonding. 5,13,19) For example, fiber reinforced composites used in dentistry under flexural loading emitted low amplitude AE 25-60 dB events corresponding to polymer matrix cracking, 19) while Yuan et al reported E-glass reinforced PVC undergoing tension emitted AE in the same range, between about 25-60 dB corresponding to fiber-matrix debonding.…”

Section: Volume Fraction and Fiber End Effectsmentioning

confidence: 99%

“…[3][4][5][6] Tyson and Davies found by photoelastic experiments that interfacial shear stresses were higher than theories predict, most notably at the fiber ends.…”

Section: Volume Fraction and Fiber End Effectsmentioning

confidence: 99%

“…4,5) Since matrix damage at fiber ends appears to be a dominant fracture mechanism in toughening the BMC, fiber end density, E (mm À3 ) was calculated to quantify its effects on normalized tensile fracture strain, " f =" f,6.4 and tensile strength, f = f,6.4 normalized to show improvement over commercial 6.4 mm samples.…”

Section: Volume Fraction and Fiber End Effectsmentioning

confidence: 99%

“…7) This is also true for injection molded composites where microcracks and the main crack tend to form perpendicular to the loading direction, 11 . 4,5) Based on the fracture toughness and tensile strength of the matrix, the critical crack size of the matrix is estimated using Mode I loading in eq. (1):…”

Section: Introductionmentioning

confidence: 99%

“…Tyson and Davies found interfacial shear stresses have been exceptionally high at fiber ends, 3) while in injection molded short 6.4 mm, 20 and 30 mass% Eglass fiber reinforced polyvinyl chloride (PVC), cracks have been found to initiate at fiber ends. [4][5][6] By shortening the fiber to sub-millimeter length, the resulting higher fiber end density may act to increase relaxation sites impeding crack growth above the critical length, 2a c .…”

Section: Introductionmentioning

confidence: 99%

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Tensile Strength Enhancement by Shortening Glass Fibers with Sub-Millimeter Length in Bulk Molding Polymer Compound

Faudree

Nishi

2010

Mater. Trans.

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Effects of short fiber with sub-millimeter length on tensile strain, " f and tensile strength, f were investigated for a bulk molding compound (BMC) glass fiber reinforced polymer (GFRP) composite with 20 mass% E-short glass fibers. The " f and f values of BMC-GFRP samples with 0.44 mm short fibers were almost 40 and 60% higher than that of BMC-GFRP samples with long fibers (3.2 and 6.4 mm in length), as well as more than 65 and 110% higher than that of the filled fiber free resin, respectively. The reduced fracture strain (" f =" f,6.4 ) and reduced tensile strength ( f = f,6.4 ) as a function of the fiber end density, E (cm À3 ) were expressed by the following equations with linear regression as (" f =" f,6.4 ¼ 1:21 Â 10 À7 E þ 0:965) and ( f = f,6.4 ¼ 1:51 Â 10 À7 E þ 0:998). Acoustic emission (AE) analysis detected microcracking was increased threefold by shortening the mean fiber length from 6.4 to 0.44 mm. Scanning electron microscopy (SEM) results showed increased fiber/matrix debonding at fiber ends and along fiber lengths in the 0.44 mm samples compared with that reported for 6.4 mm samples. The fiber debonding is thought to impart an internal strain field in the matrix surrounding each fiber resulting in volume expansion sites, hence compressive stress sites which absorb energy from an approaching crack tip front in the nearby vicinity halting the crack's advance. Therefore, more microcracks can be tolerated increasing fracture strain. Moreover, the critical crack length range for thermoset polymers was calculated to be approximately 0:50 < 2a c < 5:0 mm from reported K IC results in the literature, and is greater than the 0.44 mm mean fiber length. The probability of a microcrack propagating above 0.44 mm before it encounters a matrix compressive site, therefore is reduced. Furthermore, increased microcracking in the vicinity of the main crack tip acts to reduce the main crack tip stress concentration. All of these serve to prevent crack propagation resulting in enhancement of fracture strain in the

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Section: Volume Fraction and Fiber End Effectsmentioning

confidence: 99%

“…[3][4][5][6] Tyson and Davies found by photoelastic experiments that interfacial shear stresses were higher than theories predict, most notably at the fiber ends.…”

Section: Volume Fraction and Fiber End Effectsmentioning

confidence: 99%

Section: Volume Fraction and Fiber End Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tensile Strength Enhancement by Shortening Glass Fibers with Sub-Millimeter Length in Bulk Molding Polymer Compound

Faudree

Nishi

2010

Mater. Trans.

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Prefailure damage processes in highly filled glass/mica/epoxy composites

Regola

Baer

Hiltner

1991

J of Applied Polymer Sci

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SYNOPSISIn the present study, the prefailure damage processes of a series of short glass fiber/mica/ epoxy composites under three-point bending were elucidated using acoustic emission ( AE) coupled with in situ scanning electron microscopy ( SEM) observations. This study consisted of a detailed investigation of the damage tolerance of composite systems that had constant inorganic content of 75% by weight with a varying ratio of glass fibers to mica. The flexural strength was found to increase from 11 to 21 ksi as the glass fiber content increased (mica content decreased), while the flexural modulus decreased from 5.0 to 2.5 Msi. By monitoring the AE during flexural deformation of the glass fiber-to-mica ratio composites, it was determined that low amplitude (0-42 db) AE events, which occurred throughout the deformation process, were caused by matrix cracking, whereas the high-amplitude (43-100 db) AE events, which occurred just prior to failure, were caused by a fiber-related mechanism. In situ SEM observations of the composites during flexural deformation allowed a correlation between the AE and the damage mechanisms as a function of strain. In the all-mica composite, microcracking initiated in the linear region a t preexisting flaws, on the order of 10 pm, located at the mica interface. These microcracks grew along the mica contours over the majority of the deformation process, emitting low-amplitude events, until final fracture occurred at relatively low strains. In the glass fiber-containing composites, microcracking initiated in the linear region a t preexisting flaws and voids, on the order of 10 pm. These microcracks grew slowly, emitting low-amplitude events, as the strain increased, but were prevented from causing failure at low strains because of the toughening effect of the glass fibers. At sufficiently high strains, however, fiber breakage and fiber pull-out occurred that corresponded to the high-amplitude events detected by the AE. At strains just prior to failure, catastrophic crack growth occurred, producing a rapid increase in both low-and high-amplitude events, causing ultimate failure. INTRODUCTIONComposites are finding increased usage as structural components, oftentimes replacing materials in which the damage and failure mechanisms are well understood. Since damage accumulation in composites is closely related to the actual strength, stiffness, and life of the materials, understanding of the failure mechanisms and damage accumulation are of utmost importance.' This, however, has proved difficult To whom correspondence should be addressed. Continuous fiber-epoxy composites have received an immense amount of attention in the literature because of their structural uses. These structural uses are, in part, due to the varied processing techniques, such as hand lay-up, filament winding, and pultrusion, which are available. Although the optimum processing technique is imperative to the successful use of these materials, even more critical is an understanding of their failure mechanisms. The evaluatio...

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Preparation and characterization of poly(vinyl chloride)–continuous carbon fiber composites

Ráthy

Kuki

Borda

et al. 2011

J of Applied Polymer Sci

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In this article, we report on the preparation and characterization of novel poly(vinyl chloride) (PVC)-carbon fiber (CF) composites. We achieved the reinforcement of PVC matrices with different plasticizer contents using unidirectional continuous CFs by applying a warm press and a cylinder press for the preparation of the PVC-CF composites. We achieved considerable reinforcement of PVC even at a relatively low CF content; for example, the maximum stress (r max ) of the PVC-CF composite at a 3% CF content was found to be 1.5-2 times higher than that of the PVC matrix. There were great differences among the Young's modulus values of the pure PVC and PVC-CF composites matrices. The absolute Young's modulus values were in the range 1100-1300 MPa at a 3% CF content; these values were almost independent of the plasticizer content. In addition, we found a linear relationship between r max and the CF content and also recognized a linear variation of the Young's modulus with the CF content. The adhesion of CF to the PVC matrix was strong in each case, as concluded from the strain-stress curves and the light microscopy and scanning electron microscopy investigations. The mechanical properties of the PVC-CF composites with randomly oriented short (10 mm) fibers were also investigated. At low deformations, the stiffness of the composites improved with increasing CF content. Dynamic mechanical analysis (DMA) was used to determine the glass-transition temperature (T g ) of the PVC-CF composites. The high increase in the Young's modulus entailed only a mild T g increase. V C 2011 Wiley Periodicals,

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Acoustic emission during irreversible deformation in short fiber reinforced poly(vinyl chloride) composites

Cited by 20 publications

References 13 publications

Tensile Strength Enhancement by Shortening Glass Fibers with Sub-Millimeter Length in Bulk Molding Polymer Compound

Tensile Strength Enhancement by Shortening Glass Fibers with Sub-Millimeter Length in Bulk Molding Polymer Compound

Prefailure damage processes in highly filled glass/mica/epoxy composites

Preparation and characterization of poly(vinyl chloride)–continuous carbon fiber composites

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