An evaluation of residual stresses in graphite/PMR-15 composites by X-ray diffraction

Benedikt, B.; Kumosa, M.; Predecki, Paul

doi:10.1016/j.actamat.2005.06.008

Cited by 14 publications

(15 citation statements)

References 32 publications

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“…The XRD strain measurements in the Al inclusions embedded in the graphite fiber/polyimide matrix composite were performed at the University of Denver. The most important findings from these experiments were already presented in a series of papers [1][2][3][4]. In this work, we re-examine some of the experimental results reported in [1][2][3][4] and compare the MRS strain measurements with the XRD technique.…”

Section: All Copyrights For the Document Are Retained By Icddmentioning

confidence: 78%

“…On the other hand, to extract the composite strains and stresses caused by the prescribed four-point bending moment did not require computing the visco-elastic close range stresses. Furthermore, it has been shown in [4] that the interactions between the embedded inclusions did not significantly change the average strains in the inclusions. Consequently, the effect of the interactions could be neglected in the numerical computations if only averaged strains in the inclusions were measured.…”

Section: Analytical Modelsmentioning

confidence: 98%

“…If both =0, and =90, vs. sin 2 ( ) form straight lines, then the intercepts and slopes of he sin 2 ( ) plots determine the principal strains. After the experiment had been performed, it turned out that the sin 2 ( ) plots were linear within experimental error [1][2][3][4]. The normal strain 33 was taken to be an average between =0, =0 and =90, =0 .…”

Section: Materials Tested and Experimental Proceduresmentioning

confidence: 99%

“…The method is based on strain measurements inside embedded sensors. The strain measurements in the sensors were done using either x-ray diffraction with embedded spherical aluminum inclusions as strain sensors [1][2][3][4] or micro Raman spectroscopy with Kevlar-49 fibers as strain sensors [5]. We show that the accuracy of the strain measurements depend not only on the experimental technique, but the geometry of the embedded sensors as well.…”

Section: Introductionmentioning

confidence: 99%

“…It was shown by Predecki and Barret [6] that the internal strains and stresses transferred to various crystalline inclusions embedded in epoxy matrix composites could be detected by XRD. Using a methodology developed by Benedikt et al [1][2][3][4] the method of Predecki and Barret was further developed to measure internal strains in spherical Al inclusions embedded in unidirectional and woven graphite/PMR-15 composites. In addition to these measurements, the residual interlaminar stresses in the investigated composites were determined from the inclusions strains using the model based on the Eshelby approach.…”

Section: Introductionmentioning

confidence: 99%

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D-11 Measurement and Modeling of Residual Stresses at Microscopic and Mesoscopic Levels Using Micro Raman Spectroscopy and X-ray Diffraction

Benedikt¹,

Lewis²,

Rangaswamy³

2004

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In this study, we use x-ray diffraction (XRD) and micro Raman spectroscopy (MRS) to measure internal strains in sensors embedded in polymer matrix composites. Two types of strain sensors embedded in either chopped graphite fiber/epoxy matrix composite (MRS) or unidirectional graphite fiber/polyimide matrix composite (XRD) were investigated. For XRD measurements, the sensors were in the form of spherical aluminum inclusions with diameters ranging from 1 to 20 m. Due to large cross section area of an incident x-ray beam, only average stresses are reported using the XRD approach. Complementary to XRD experiments, MRS was pursued to measure internal strains in Kevlar-49 fibers embedded in chopped graphite fiber/epoxy matrix composite. In recent years, MRS as an experimental tool for micro-strain measurements has drawn considerable attention mostly due to its excellent spatial resolution. The resolution of MRS typically ranges between 1 and 10 m, which means that strains can be measured in individual sensors. The principle of this method relies on a change of certain molecular vibration frequencies as a result of an applied stress. Several examples are presented and discussed to demonstrate the potential of combining micro and macro strain measurements and modeling to capture the stress distribution in heterogeneous materials.

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