Effect of Load Introduction in Compression Testing of Composite Laminates

Reiss, R.; Clark, R. K.; Yao, Tianlei

doi:10.1520/stp36205s

Cited by 7 publications

(1 citation statement)

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“…The contact cylinders were used to aid in the distribution of load to reduce detrimental end effects (ASTM, 2006). Although the probability of failure in other modes such as buckling is reduced by a shorter gage length, the complicated state of stress that exists at the extremities of the specimen due to the clamping forces that prevent lateral expansion can extend throughout the specimen because of a small aspect ratio (Reiss et al, 1983). This effect was first studied by Pagano & Halpin (1968) in tensile tests of anisotropic bodies where it was concluded that the aspect ratio of the specimen and gripping mechanism were the principal reasons for the non-existence of a uniform stress state.…”

Section: Specimen Aspect Ratiomentioning

confidence: 99%

High-resolution stress mapping of polycrystalline alumina compression using synchrotron X-ray diffraction

Raghavan

Imbrie

2011

J Synchrotron Radiat

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The ability to achieve uniform stress in uniaxial compression tests of polycrystalline alumina is of significance for the calibration of piezospectroscopic coefficients as well as strength studies in ceramics. In this study high-energy X-rays were used to capture powder diffraction profiles over a half-section of a polycrystalline alumina parallelepiped sample under an increasing uniaxial compressive load. The data were converted to strain and results were used for stress mapping of the sample. Stress maps from the study quantify the higher stresses at the sample-platen contact interface and reveal the evolution of the stress distribution in these specimens with load. For the geometry of the samples used, at the center section of the specimen the overall magnitudes of the compressive stresses were found to be 20% higher compared with the average expected theoretical stress based on the applied load and cross-sectional area. The observed compressive stresses at the corners of the parallelepiped specimen were 62% higher and shear stresses were observed at the specimen interface to the load mechanism. The effects, seen at the interface, can lead to premature failure at these locations and can affect the accuracy of calibration of spectral peaks with stress as well as compression strength measurements. The results provide important information that can be used to establish guidelines on material and geometry considerations in developing compression tests on high-strength ceramics.

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Section: Specimen Aspect Ratiomentioning

confidence: 99%

High-resolution stress mapping of polycrystalline alumina compression using synchrotron X-ray diffraction

Raghavan

Imbrie

2011

J Synchrotron Radiat

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Effects of specimen size and sample aspect ratio on the elastic stiffness of graphite/epoxy laminates

Potter

Gupta

Hauert

2000

Composites Science and Technology

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Effect of Loading Method on Compression Testing of Composite Materials

Xie

Adams

1995

Journal of Composite Materials

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Compression testing methods for composite materials usually employ either shear loading or end loading to apply the compressive load to the specimen. The effect of both loading methods on compression testing of unidirectional composite materials was studied. A combined loading scheme, i.e., the compression specimen was subjected to a combined end and shear loading, was also investigated. The stress distributions within a compression specimen subjected to each of these three different loadings were studied using a three-dimensional finite element analysis. It was found that the shear loading method yielded the most severe stress concentration at the tab tip of the specimen, while the end loading yielded a high shear stress concentration at the loading end of the specimen. The combined loading method was found to be a good compromise to reduce the stress concentration at both the tab tip and the loading end of the specimen, when compared to the shear loading and the end loading methods, respectively. The effect of loading method on a thick-section compression specimen was also analyzed. The end loading method was found to be superior to the shear loading method. The analytical results were also correlated with available experimental data. End crushing of the end-loaded specimen is often experimentally observed, due to the high stress concentration at the end of the specimen as predicted in the present study. However, if the end crushing problem can be overcome, available experimental results show that the end loading method generally yields slightly higher compressive strengths for unidirectional composites than the shear loading method. This agrees with the present analytical results, the end loading method yielding less stress concentration at the tab tip.

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Effect of Load Introduction in Compression Testing of Composite Laminates

Cited by 7 publications

References 0 publications

High-resolution stress mapping of polycrystalline alumina compression using synchrotron X-ray diffraction

High-resolution stress mapping of polycrystalline alumina compression using synchrotron X-ray diffraction

Effects of specimen size and sample aspect ratio on the elastic stiffness of graphite/epoxy laminates

Effect of Loading Method on Compression Testing of Composite Materials

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