Interfacial stress transfer behavior in a specially-shaped fiber/matrix pullout test

Abstract

Specially designed fibers are widely used in engineering practice because the specially-designed shape can help to improve the bonding strength of the fiber and the interface. Studied in this paper is the interfacial shear stress transfer behavior on both sides of the specially designed fiber when it is being pulled out; in which automatic analysis of three-dimensional photoelasticity is employed and the finite element method is adopted. The results show that the stress transfer occurs mainly in the region near the fiber's embedded end where the stress reaches its critical point, leading to debonding of the interface. Before debonding, as the pullout loading increases, the peak value of shear stress transfers along the fiber from the embedded end to the interior of the matrix, and then stops at the hooked part of the fiber because of its impediment. When the interface begins to debond as the load increases, the shear stress can be transferred to the hooked part.

Modeling the Effect of Climate Change on the Potential Distribution of Qinghai Spruce (Picea crassifolia Kom.) in Qilian Mountains

“…Our results showed that the variables related to air temperature (Bio1, Bio8) and elevation were dominant variables in determining the suitable habitat for Qinghai spruce. Previous studies demonstrated that distribution of the species was affected by temperature in July, annual precipitation and aspect [44]. Xu et al [39] indicated mean temperature of the warmest quarter, precipitation of the wettest quarter, annual solar radiation, and topographic wetness index were important variables.…”

“…In our study area, realized distribution of the species had suffered from intensive deforestation. It was reported that some area of Qinghai spruce forest has been converted into grasslands [44] in the middle part of the study area and has been transformed to farmland in the east [39]. The comparative analysis of potential species distribution under current climate and the realized species distribution could identify human activities and provide information about prior areas to restore the species.…”

“…Vegetation types in the study area are displayed in spatial sequences (from low to high elevations): desert, desert steppe, steppe, steppe-forest, sub-alpine shrubby meadow and alpine frost-action barren zone. Qinghai spruce forests distributed from 2500 m to 3500 m are in the steppe-forest zone [44].…”

“…steppe-forest, sub-alpine shrubby meadow and alpine frost-action barren zone. Qinghai spruce forests distributed from 2500 m to 3500 m are in the steppe-forest zone [44].…”

Comparison of push-in and push-out tests for measuring interfacial shear strength in nano-reinforced composite materials

“…The single fiber test can be divided into two groups, depending on whether the test is carried out in single fiber composites prepared for this purpose or in actual composite samples. The fragmentation test, 8,15 the pull-out test 16,17 and the microdroplet test 13,[18][19][20] belong to the first category, while the pushout test 2,[21][22][23] and the push-in test [24][25][26][27][28] stand in the second one. It is nowadays accepted that the values of the IFSS obtained with these tests are good indicators of the interface strength from a comparative viewpoint but it is also recognized that the local environment in the single fiber composites is very different from the actual environment within the composite.…”