Evaluation of the causes of fracture in selected ply laminates as based on a structural criterion
Henryk Dąbrowski Politechnika Wrocławska, Wydział Mechaniczny, Wydziałowy Zakład Wytrzymałości Materiałów, ul. Smoluchowskiego 25, 50-370 Wrocław
Quarterly No. 4, 2006 pages 71-74
DOI:
keywords: nickel layers, nanocrystalline composite layers, structure, abrasion wear properties
abstract Phenomenological criterions, which are applied for estimation of the uniaxial strengthened layers oriented, require of strength tests of the layers. It makes difficult to use the laminates design and optimization processes of their structure elements. Additional defect of these applied criterions, which are used in method of elimination of layers is lack of information, which of them are the weakest elements and then undergo the decohesion process as the first links. It makes impossible to elaborate the method of the laminate strength properties improving the weakest element of its structure. It should be done during laminate structure design when structure elements are selected (fibers, warp and their chemical treatment). The causes of fracture were identified in cross-reinforced (±30, ±45, 0/90) ply laminates using a structural criterion. The model takes account of all the three material elements: fibres, matrix and phase interface, so strength characteristics and their changes for all the three constituents were used in the analysis. Laminates with differing strengths of the matrix and the interface were considered. The structural model yielded critical stresses for each element. The analysis involved loading paths from the 0÷360° range at the σx – σ y plane. It was assumed that attaining a critical condition by the fibres, the matrix or the interface is equivalent to attaining the critical condition by the whole laminate. The computed critical stresses served as a basis for determining plots of limit curves in the σx – σ y coordinates. In the plots the areas are marked that contain those loading paths which are responsible for damaging a particular structural element. It was found therefore that fracture in laminates is affected not only by their structure and strength of individual structural elements, but also by a loading path applied. Example plots show how the ply configuration and strength of individual structural elements determine types of fracture.