چكيده به لاتين
Despite all advantages composite materials have in respect to conventional materials, they demonstrate more complicate mechanical behaviour and physical structure by far, which make them difficult and limited to wield. Also, these fragments should be designed timidly due to several mechanisms of damage in composites. Thus, in many cases, high reliability should be considered to compensate these shortages. Delamination phenomenon which occurs due to lack of reinforcement (fibre) in direction of thickness, is one of the most important mechanisms of damage in lamination of composites. In order to perfect exploitation of useful features of composites, it essential to peruse the delamination phenomenon scrutinizingly. The main goal in this research is checking loss and energy absorption mechanisms or hardening and softening mechanisms, such as zig-zag crack growth, fibre bridging, fibre and resin adhesion and …and also indagating effective factors on strain energy release rats perimeter temperature and samples’ cooking temperature. Researches are divided into some sections in this conference. In the first section, we survey impacts of different length primary cracks on strain energy release ratio and consider samples of glass/epoxy with 0//90 interface using DCB experiment for this section. In the next section, effect of sample cooking temperature on strain energy release ratio is observed and DCB glass/epoxy samples with 0//90 interface are considered. Third section is specified to perusing effects of different interfaces on strain energy release ratio with [05/θ/06] lay-up in which θ comprises 0,30,45 and 90 degree angles. In the fourth section, lay-up changes in a composite carbon/epoxy sample and its impression on strain energy release ratio is researched. Finally, we discuss different fabrication models of carbon sandwich panels with honeycomb core and indicate area of beginning of separation by tension and shear experiments in the last section. In every stages and researches, load-movement curve which is extracted from empirical experiments by software analysis is surveyed.
According to experimental tests in this research, it can be said that whatever fibre angles in interface increase, the interlayer strain energy release ratio increases as well. Generally, the [05/90/06] lay-up has more GIc than [012] due to zig-zag crack growth mechanism which is not occurred in zero-angle interface lay-up. Also it can be seen that bridging area length in zero-angle interface lay-up is greater than the others because same directional fibres have more interaction with each other. Also we understand that primary cracks length has no effect on strain energy release ratio and it means strain energy release ratio is a somatic parameter and it is independent from geometry, crack length and…. However crack length changes have a tremendous impact on load-movement curve. Based on obtained results from composite carbon/epoxy sample test, it is understood that lay-up changing in samples may have an influence on strain energy release rate and interface layer is not the only criterion but changes in farther layers in respect to interface can also affect strain energy release rate. It is observed in last section that one of the best ways to fabricate sandwich panels is using three stage method in which separation occurs in middle of core or honeycomb which is the best possible case.
