Fracture characterization of random short fiber reinforced thermoset resin composites

Mower, Todd M.; Li, Victor C.

doi:10.1016/0013-7944(87)90100-7

Cited by 25 publications

(16 citation statements)

References 10 publications

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“…These crack-like "crazes" are oriented such that the load-bearing fibrils contained within are parallel to the maximum principal stress. Fracture of crazable polymers may initiate by the nucleation of crazes at stress concentrators such as included dust particles, and proceeds by the necking and rupture of craze matter until the remaining crazes become unstable [72]. While the inadvertent generation of crazes is deleterious, the fostering of crazes in a controlled manner can, in fact, be employed to toughen brittle glassy polymers which are capable of crazing.…”

Section: Cavitationmentioning

confidence: 99%

Experimental investigations of crack trapping in brittle heterogeneous solids

Mower

Argon

1995

Mechanics of Materials

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Over the past two decades many mechanisms of toughening have been considered for brittle solids. Some of the most prominent ones applicable to either monolithic materials or fiberreinforced composites include deformation-induced local transformations, micro-cracking, crack trapping, crack bridging, and fiber pull-out. Few if any of these have been studied in the past in a manner which permitted evaluation of the effects of individual mechanisms in the absence of other interacting mechanisms. Here we present the development, analysis and results of an experimental study of toughening by the process of crack trapping by second-phase particles (spheres and fibers) of such toughness that make them impenetrable by probing cracks, forcing the cracks to bow around the obstacles with increasing applied load.The model fracture specimens employed here were wedge-loaded double cantilever beams cast of a brittle epoxy, containing macroscopic (3mm-diameter) inclusions of Nylon or polycarbonate having similar elastic properties to the matrix. The tests were performed at -60*C to achieve controlled, stable crack propagation. Images of the crack fronts advancing at velocities of about 10-4 M/s were recorded with good resolution, providing a continuous record of crack-front shapes during the evolution of the crack-trapping process from the initial pinning configuration through the transition to crack-flank bridging. Remarkable agreement between these images and crack-front shapes predicted by the numerical simulation of Bower & Ortiz is demonstrated. A parametric approach was adopted to study the influence of obstacle spacing, surface adhesion and thermally-induced residual stresses upon the observed crack-front behavior and enhanced stress intensity required to propagate the cracks past these obstacles. Analysis of the quantitative data has demonstrated that, in brittle matrices containing particle volume fractions of approximately 0.2, toughness enhancement by over a factor of two, relative to neat matrix values, may be achieved through the crack-trapping mechanism alone, provided that a high level of adhesion can be maintained between the matrix and the tough reinforcing particles.

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Section: Cavitationmentioning

confidence: 99%

Experimental investigations of crack trapping in brittle heterogeneous solids

Mower

Argon

1995

Mechanics of Materials

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“…The induced chemical and physical interaction between the polymeric chains of PBT and SGF will inhibit the crystalline phase formation in SGFR-PBT composites [34,35]. This would increase the tensile strength and Young's modulus by the stress transfer between the fiber and PBT matrix [29][30][31]. Similar types of results have reported for polyethylene oxide/starch blends and polyvinyl alcohol/Graphene oxide composite respectively [36,37].…”

Section: Correlation Between Mechanical Properties Crystallinity Anmentioning

confidence: 82%

“…This increased value of both tensile strength and Young's modulus with silane treated short glass fiber is due to the random distribution of fibers in the polymer matrix and the improved adhesion between the fiber and matrix by the induced chemical interactions [9,27,28]. The improved adhesion between the fiber and matrix transfers stress through fibers and thereby increases the tensile strength and Young's modulus of the composites [29][30][31]. Figure 5c shows the variation of elongation at break as a function of SGF concentration in SGFR-PBT composites.…”

Section: Mechanical Properties Resultsmentioning

confidence: 99%

“…In SGFR-PBT composites the chains of silane treated glass fiber are randomly distributed on PBT matrix [29][30][31]. The sites of interaction between the constituent polymeric chains are high.…”

Section: Hydrodynamic Interaction Parameter Resultsmentioning

confidence: 99%

“…PBT and E-glass fiber were dried at 1308C for 4 h and at 1208C for 2 h, respectively. PBT granules and 3 mm short glass fibers (SGF) of various loading (10,20,30, and 40 wt%) were mixed in a Haake co rotating twin screw extruder (diameter 5 40 mm, L/D 5 16) operating at a barrel temperature profile ranging from 2608C to 2308C at the feed rate of 1 kg/h and a screw speed of 230 rpm. The extruded composites were subsequently pelletized by a granulator.…”

Section: Preparation Of Compositesmentioning

confidence: 99%

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Effect of hydrodynamic interaction on free volume changes and the mechanical properties of SGFR‐PBT composites

Munirathnamma

Ravikumar

2016

Polymer Composites

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In order to explore the effect of short glass fiber reinforcement (SGFR) on the mechanical properties of polybutylene terephthalate (PBT), 10–40 wt% of short glass fibers (SGF) are reinforced into PBT matrix. Microstructural characterization has been performed by positron lifetime technique. The fractional free volume obtained experimentally show negative deviation at 20, 30, and 40 wt% of SGF from the linear additivity relation. This indicates the improved adhesion between the short glass fiber and PBT matrix at 20, 30, and 40 wt% of SGF. The evaluated hydrodynamic interaction parameter (h) suggests the generation of excess friction at the interface of SGFR‐PBT composites. The positron lifetime parameters of SGFR‐PBT composites are correlated with the mechanical properties viz., tensile strength (TS), Young's modulus (YM), and elongation at break (EB). The decrease of crystallinity and average crystallite size of SGFR‐PBT composites evaluated by X‐ray diffraction results indicate the induced chemical interaction between PBT side chain and SGF due to the silane treatment of E‐glass fibers. The decreased positron lifetime parameters, reduced crystallinity, and crystallite size and improved mechanical properties are attributed to the improved chemical and physical interaction between the functional groups of SGF and PBT matrix. This is also evident from Fourier transform infrared spectrometry (FTIR) studies. POLYM. COMPOS., 39:1878–1886, 2018. © 2016 Society of Plastics Engineers

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Durability of alkali and heat‐treated kenaf fiber/unsaturated polyester composite fabricated by resin transfer molding under natural weathering exposure

et al. 2017

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Nonwoven kenaf fiber (KF) mat-reinforced unsaturated polyester resin composites were exposed to a natural weathering environment for 12 months. The composites were prepared using vacuum-assisted resin transfer molding (RTM). Prior to molding, the KF mat was treated by immersing it in 6% NaOH solution for 3 hrs and by heating it at 140°C for 10 hrs, respectively. The influences of weathering exposure on the composites with respect to the different treatments were investigated using flexural properties, fracture toughness, Fourier transform infrared, thermal stability, color and scanning electron microscopy analyses. Natural weathering reduced the flexural and fracture toughness due to damage to composite structures, the formation of microcracks on the sample surface, discoloration, and chemical content alteration.A relatively better durability in terms of flexural properties was exhibited by alkalitreated KF composites, although poor durability in fracture toughness was observed due to the improved fiber-matrix adhesion. K E Y W O R D Salkali treatment, heat treatment, natural weathering, nonwoven kenaf fiber, resin transfer molding

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Fracture characterization of random short fiber reinforced thermoset resin composites

Cited by 25 publications

References 10 publications

Experimental investigations of crack trapping in brittle heterogeneous solids

Experimental investigations of crack trapping in brittle heterogeneous solids

Effect of hydrodynamic interaction on free volume changes and the mechanical properties of SGFR‐PBT composites

Durability of alkali and heat‐treated kenaf fiber/unsaturated polyester composite fabricated by resin transfer molding under natural weathering exposure

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