|
|
||
|
|
|
|
From:
[1] Yeh, H-Y and Chen, V., 1996. Experimental Study and Simple Failure Analysis of Stitched J-Stiffened Composite Shear Panels. Journal of Reinforced Plastics and Composites, Vol. 15, pp. 1070-1087.
[2] Minnetyan, L. and Huang, D., 2001. Progressive Fracture of Stitched Stiffened Composite Shear Panels in the Postbuckling Range. Journal of Reinforced Plastics and Composites, Vol. 20, pp. 1617-1632.
and from:
GENOA Engineering Newsletter, Issue 15, June 10, 2008
http://www.ascgenoa.com/newsletter/15/index.jsp
"Software Suite for Durability, Damage Tolerance, Reliability & Life Prediction
Enhances FEA Solvers MSC Nastran, ABAQUS, ANSYS, RADIOSS & LS-DYNA
Best Performance and Verified Solutions with MSC Nastran"
The anonymous blogger writes:
"Predicting Post-Buckling Response and
Ultimate Failure of Composite 2-Stringer Panels Subjected to Post-Buckling Analysis:
"Predicting the failure load of composite panels with post-buckled regions [this slide] is a complicated undertaking as it involves buckling and damage evolution. The difficulty is complicated further by the fact that the ultimate failure (structural collapse) is driven by localized failures produced by damage in fiber and matrix in the post-buckled area of the structure. Reliable assessment of these load limits requires the application of advanced computational simulation that integrates composite mechanics at the micro-scale of fiber and matrix with finite elements, buckling, damage tracking and fracture analysis. The technical approach must rely on physics-based composite failure criteria capable of detecting all types of damages including non-visible ones. If localized buckling takes place before damage, the buckling mode shape is superimposed on the structure's geometry. Inception of damage prior to buckling requires repeated buckling analysis with degraded stiffness to account for detected damage. This analysis capability, integrated in the GENOA Software, was applied successfully to a two-stiffener composite panel under shear loading. The test results were closely reproduced with the analysis simulation. Including post-buckling effect was instrumental to replicate the test, since otherwise we risk over-predicting the failure load. As shown next, this analytical approach can be very effective in guiding the design and in reducing the number of tests of post-buckled composite panels.
"Problem Description:
"The two-stringer J-stiffened composite panel evaluated for durability with post-buckling consideration is presented in [the blog]. It was made of AS-4/3501-6 carbon/epoxy unidirectional fabric. The fabric consisted of a wide sheet of unidirectional tows of fibers based together with polyester thread to keep it from unraveling. Twelve plies of the skin were laid up to form a 1.83 mm (0.072 in.) thick quasi-isotropic [0,90,45,0,-45,90]s laminate. The "J" shaped stiffeners were constructed with the same lay-up except for the flanges that were only half the thickness of the basic laminate. The skin panel and the stiffeners were stitched together with Kevlar and fiberglass threads [1,2]. The experimental results were adopted from the literature [1].
"The panel was modeled with Mindlin-Reissner thick shell elements and loaded in tension in the diagonal direction at one corner of the panel [in-plane shear buckling] while fixing the opposite corner [2]. Details of the technical approach are provided [in the blog] followed by [a ] discussion of [the]results."
Page 117 / 227