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Investigation of influence of fibres layout in composite specimens on their strength with cellular automata method
Abstract
Our goal is construction of suitable model to examine the fibre structure in composite specimens to achieve weight efficient structures with high strength. In this paper model of fibre breaking based on cellular automata technique was presented and applied in NOL composite specimens. Acoustic emission was used to verify results.
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Preface; 1. Introduction; 2. Cellular automata modeling; 3. Statistical
mechanics of lattice gas; 4. Diffusion phenomena; 5. Reaction-diffusion
processes; 6. Non-equilibrium phase transitions; 7. Other models and
applications; Bibliography; Glossary; Index.
The most important issues for the design of composite pressure vessels reflect on the selection of the most suitable rovings (in terms of strength and thickness) and the distribution of the intended number of circuits around the vessel periphery. In this paper we show that dimensioning a pressure vessel and selecting a roving without the simultaneous creation of winding patterns will definitely lead to a less optimal design. The designer should simultaneously ensure tangential pole passage for the rovings, homogenous coverage (by using roving widths according to a predetermined range), and, at the same time, minimise the excess of overwound circuits as compared to the number of rovings dictated by structural analysis. In this paper we provide a methodology for dealing with this contradicting set of demands.
The projective dimensional analysis based on the projective extension of scaling group and projective dimensional function is presented. We study the notion of self-similarity based on the physical quantities and not on topology. The projective analog of the classical theorem-π has been formulated in terms of (projective) numerical invariants. The additivity dimensions replacing fractal dimension are briefly discussed. Intuitive examples illustrate presented ideas.
Experimental data are presented to show the effects of winding angle on the strength of 100 mm diameter, 1 mm thick, filament wound E-glass fibre reinforced epoxy resin tubes tested under various combinations of internal pressure and axial tension or compression. Leakage and fracture strength envelopes are presented for winding angle tubes subjected to a wide range of different biaxial membrane stress states. Strengths range from 30 to 1250 MPa. Axial compression test results for tubes with wall thicknesses ranging from 1 to 3·6 mm establish the influence of shell buckling. Stress/strain curves up to fracture under three different types of loading show the effects of the winding angle on elastic constants and on nonlinear stress strain behaviour.
With appropriate numerical methods of composites modelling we can observe defects growth without using invasive experimental methods. In this paper we present results of simulation of quasi-static process of fracture in composite using cellular automata and fractal characteristics of defects growth based on box-counting method. Defects evolution in composite are treated as a dynamical system depending on external and internal conditions and properties of fibres.
A computer-integrated environment has been created around the filament winding process, including design, production and quality control. In the design phase, computer-aided design, finite element analysis and fibre path calculation techniques are integrated. Two filament winding machines have been developed for production: a two-axis filament winding machine and a robotic tape winding machine. The collision-free robot program is generated completely off-line. For quality control, a robotic ultrasonic C-scanning cell has been developed.
The projective dimensional analysis based on the projective extension of scaling group and projective dimensional function is studied. The differential calculus corresponding to geometry of dimensional spaces is constructed and examined. At the next step we explore the projective extension of dimensional derivatives. Simple fractal models of various processes with changing fractal dimension illustrate the proposed methods.
The influence of winding pattern on the mechanical response of filament wound glass/epoxy cylinders exposed to external pressure is studied by testing cylindrical specimens having stacked layers with coincident patterns in a hyperbaric testing chamber. Different analytical models are evaluated to predict buckling pressure and modes of thin wall cylinders (diameter to thickness ratio d/h of 25) and satisfactory predictions are obtained which are in the same order of magnitude that those obtained in experimental results. Test results show no evident pattern influence on either strength (implosion pressure) or buckling behavior (buckling modes) of thin wall or thick wall (d/h of 10) cylinders.
Influence of the winding fibers structures on mechanical strength of composite cylinder elements made up from epoxy-glass, 17th Danubia-Adria Symposium on Experimental Method in Solid Mechanics
- W Blazejewski
Procesing-structure relationships for filament-wound composite shells
- S J Claus
- H T Hahn