Stress Transfer in Single Fiber/ Resin Tensile Tests

SYNOPSISAdhesion between organic fibers and thermoplastics in a composite material is usually weak because of the lack of chemical and mechanical bonding. This study investigated the influence of plasma gas species in a novel technique to improve interfacial adhesion of Kevlar 49 fibers to polycarbonate. Single Kevlar fibers were exposed to radio-frequency plasma discharge in atmospheres of argon, oxygen, and ammonia. Plasma treatment has been shown to generate reactive free radicals on polymer surfaces. The fibers that were coated immediately with a polycarbonate melt while still in the vacuum environment of a plasma reactor showed an increase in interfacial shear strength that was maximum a t 4.1 s exposure and decreased at longer exposure times. At 4.1 s exposure, Ar and 0, plasma treatment increased shear strength by 20 and 18%, respectively. NH3 plasma treatment produced only a statistically insignificant increase at 4.1 s of exposure and a significant decrease in adhesion at 8.3 s of exposure. Fibers that were exposed to air for 1 h before coating showed no statistically significant increase or decrease in adhesion. The increase in adhesion of the directly coated fibers was attributed to free radical-initiated formation of covalent bonds between the Kevlar and the polycarbonate.

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“…21 However, no transverse breaks in the Kevlar filament were observed near the birefringence nodes or anywhere else in the fiber.…”

Section: Embedded Single-filament Testingmentioning

confidence: 98%

The influence of plasma gas species on the adhesion of thermoplastic to organic fibers

Pitt

Lakenan

Strong

1993

J of Applied Polymer Sci

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“…The distribution of overstress has been studied in both two dimensions [27,36,37,38] and three dirnensions [7]. We consider in this study that the stress concentration is maximum in the plane of the break, and that it decreases along the axis of the central über proportionally to the distance from this plane.…”

Section: Stress Concentra Tion Near Discontinuities Of Fibersmentioning

confidence: 99%

“…Encouraged by the correlation between our theoretical results and P. J. Sabat's experimental measurements, we use this test again, even if it has not been entirely satisfctory in the past [6,27].…”

Section: Critical Fiber Length Testmentioning

confidence: 99%

“…To do so, several übers have to be embedded parallel and close together in the same specimen. Bascom and Jensen [27] have been the pioneers in this domain, using specimens that contain two to üve über aligned in the same plane. In keeping with the study of übrous composites, a sample containing a three·dimensional array of übers is developed in this study.…”

Section: Matrixmentioning

confidence: 99%

“…A method largely used in the past to quantify the stress transfer between the matrix and the übers consists of embedding a single über in a thermoplastic or thermoset matrix and then submitting the matrix to a tensile load in the direction of the über [24][25][26][27][28][29]. If the über matrix bond is strong enough to transfer a load able to break the ülament, a rninirnum legnth of the über pieces will be reached, Figure 27.…”

Section: Matrixmentioning

confidence: 99%

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Matrix-fiber stress transfer in composite materials: Elasto-plastic model with an interphase layer

Lhotellier

Brinson

1988

Composite Structures

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The matrix-liber stress transfer in glass/epoxy composite materials was studied using analytical and experimental methods. The mathematical model that was developed calculates the stress fields in the liber, interphase, and neighboring matrix near a liber break. This scheme takes into account the elastic·plastic behavior of both the matrix and the interphase, and it includes the treatment of stress concentration near the discontinuities of the libers. The radius of the libers and the mechanical properties of the matrix were varied in order to validate the mathematical model. The computed values for the lengths of debonding, plastic deformation, and elastic deformation in the matrix near the liber tip were confirmed by measurements taken under polarized light on loaded and unloaded single liber samples. The liber-liber interaction was studied experimentally using dog-bone samples that contained seven libers forming an hexagonal pattem.

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Multiple fiber technique for the single fiber fragmentation test

Moon

McDonough

1998

J. Appl. Polym. Sci.

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ABSTRACT:The single fiber fragmentation test has been modified by embedding multiple fibers into matrix resin. During testing, we examined the interfacial shear strengths between the fibers and the matrix. In addition, the time-dependent nature of the fragmentation process was considered. In the fragmentation test, we examined the failure process of two fibers placed far from each other, and we found that the failure profile of the two fibers were similar to the failure profiles from tests done on single fibers. When we examined three fibers, we found that the measured interfacial shear strength values were much greater than the shear strength values from either the single or two fiber tests. However, when we used three fibers, we found it difficult to control the interfiber spacing. Consequently, whenever the interfiber spacing was too small, breaks in one fiber caused breaks in the adjacent fiber. In conclusion, using multiple fibers in a fragmentation test has many merits, such as saving time in testing, ease of comparing the effects of fiber surface treatment, and testing different fibers in the same matrix exposed to the same processing conditions.

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Stress Transfer in Single Fiber/ Resin Tensile Tests

Cited by 165 publications

References 7 publications

The influence of plasma gas species on the adhesion of thermoplastic to organic fibers

The influence of plasma gas species on the adhesion of thermoplastic to organic fibers

Matrix-fiber stress transfer in composite materials: Elasto-plastic model with an interphase layer

Multiple fiber technique for the single fiber fragmentation test

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