THE PROBLEM OF USING COMPOSITE MATERIALS REINFORCED WITH GLASS FIBRES TO MANUFACTURE SOME COMPONENTS OF GARDEN CHAIRS

Camelia CERBU
Conf.dr.ing. - Universitatea Transilvania din Brasov - Facultatea de Inginerie Mecanica
Address: B-dul Eroilor 29, 500036 Brasov
Tel.: +40 268 412921 / int.171.
E-mail: cerbu@unitbv.ro

Calin ITU
Asist.ing. - Universitatea Transilvania din Brasov - Facultatea de Inginerie Mecanica
Address: B-dul Eroilor 29, 500036 Brasov
E-mail: calinitu@yahoo.com

Ioan CURTU
Prof.dr.ing. - Universitatea Transilvania din Brasov - Facultatea de Inginerie Mecanica
Address: B-dul Eroilor 29, 500036 Brasov
E-mail: curtui@unitbv.ro

Abstract: In this work, one analysis the effects of the moisture on some components made of composite materials based on glass fibres and synthetic resins, from the structure of a chair for garden or terrace. Composite materials involved in study does not contain wood flour. With this purpose in view, experimental data previously determinate, that refers to the effects of the moisture on the degradation of the mechanical characteristics (modulus E, normal stress se at the elastic limit) in case of two composite materials: E-glass / polyester Heliopol 8431 ATX; E-glass / epoxy LY 554. One proposes a numerical model of structure of the garden chair for the analysis of the both stress state and strain state that develop during the mechanical loading. Two cases of loading are considered: 1) the entire weight of the human body is uniformly distributed on the seat plate of the chair; 2) 75% of the weight of the body is uniformly distributed on the seat plate while 25% of weight is distributed on the seat-back of the chair. One comparatively analyses the results concerning the deflections, both in case of undamaged composite materials and damaged composite materials after long-time exposure in environment with high humidity. One may remark that the decreasing of the Young's modulus E due to the moisture absorption, leads to the increasing of the deflections in components of the chair made of composite materials. Finally, the paper recommends the using of the composite materials based on polyester resin Heliopol 8431 ATX because the mechanical characteristics of such as material change a little after long-time soaking in humid environment.

Key words: composite material, humidity, stiffness, finite element method.

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