Introduction
Currently we are standing on the edge of a fourth industrial revolution; one which,
while enabling us to mate the worlds of production and the “Internet of Things”, is making “Industry 4.0” a reality that could connect embedded system production technologies and smart production processes.
The development of the new technological age of the “Smart factory” will radically transform the industrial production value chains and business models. “Smart production” is then becoming the standard in a world where ICT intelligent machines, networks and systems are capable of independently exchange and respond to information to manage an industrial production processes (Hwang et al., 2016).
The present paper presents an experimental verification of the application of an intelligent process strategy choice and control for the fabrication of Glass Reinforced Polymeric (GRP) centrifuged pipes.
Flexible GRP pipes are designed to act as soil-pipe interaction system and, as such, the external loadings resulting from the soil pressure, assembly, accidental loads and impacts must be evaluated for this type of design system to perform properly.
The manufactured product must maintain, from a quality control and design point of view, a constant and adequate smooth wall thickness and profile. Any variance from the theoretical thickness or not homogeneous profile alters the pipe stiffness values leading to:
- Increased deflection
- Increased dependence on soil to carry the load and minimize deflection
- Decreased resistance to buckling
- Increased distortion of the pipe profile
- Increased strain in pipe wall
- Joint leaks
- Reduced hydraulic capacity
- Ground surface settlement
- Increased aging by stress corrosion
The factors that affect GRP pipe stiffness are:
- Stress and Strain distribution
- Ratio External Temperature/Glass transition of the polymerized resin
- Creep characteristics (viscoelasticity)
- Manufacturing flaws and tolerances
- Use of fillers and their positioning in the pipe wall
- Type of thermosetting resins
During the processing of thermosetting-based composites, shaping operations are accompanied by polymerization reactions and rheological changes that, altering some of the feature of the previous list, may strongly influence the quality and the final mechanical properties of the composite structure.
Pioneering studies of the chemo-rheological behavior prediction has been done in the 80’s (Apicella et al., 1983; 1984; Nicolais and Apicella, 1985; Kenny et al., 1989; Aversa et al., 2016 a-o, 2017 a-e; Mirsayar et al., 2016-2017).
In these studies by Apicella et al. (1983; 1984) it has been mathematically described and links together the chemical and physical phenomena occurring during polymerization of thermosetting resins. The initial stages of the polymerization process of a composite pipe are associated with a significant increase of the material viscosity (molecular weight increase) that is combined with a heat generation due to the exothermic nature of the polymerization reactions. The relative rates of heat generation and heat transmission govern the temperature through the pipe wall and therefore, the reaction conversion and the resin viscosity through the thickness of a composite part.
An uncontrolled polymerization may cause excessive un
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desired variations of the temperature that could induce inhomogeneity in the polymer network and macroscopic defects in the composite (voids, bubbles and debonded and broken fibers (Halpin et al., 1983; Kenny et al., 1989; Stevenson, 1980; 1986). Processing of polymeric composites based on thermosetting matrices needs, therefore, optimization of the cure cycle parameters as well as adequate formulation of the reacting system as a function of the geometry of the part (Bamford et al., 1958; Beisemberg and Sebastian, 1983; Odian, 1970; Huang, 1976; Han et al., 1983; 1987; Petrescu and Calautit, 2016 a-b).
Polymeric composite pipes that are used in water and sewage transport are made of glass reinforced unsaturated polyester (GRP). The final properties of such pipes depend on the manufacturing method. Low pressure applications pipes could be made by centrifugal casting, a technique in which chopped fibres and liquid resin are pored together inside of a rotating steel cylindrical mold by centrifugal force until the resin has set. For high-pressure applications, conversely, the use of continuous glass fibers by filament winding these fibers onto a rotating mandrel could attain high mechanical strength and rigidities.