Testing And Simulation Of Industrial CompositeStructures For Optimizing Customer Satisfaction

Abstract

A large industrial composite vessel is designed optimally. Its shell is made of glass fiber reinforced plastic stiffened with steel beams. The goal is to maximize customer satisfaction on the cost and stress level of the beams and shells. The goal is formulated in a fuzzy way using combinations of individual satisfaction functions. FE method is used to check the stress levels of the analytical models. Micromechanical models are used to simulate tensile test behaviour of fiber reinforced materials. Introduction The aim of this work was to design optimally a large GRP composite vessel structure using customer satisfaction goal and relevant technical and economical constraints. The manufacturer wants to satisfy the needs of the end user customer and also to minimize own total costs, like cost of materials, manufacturing, transportation, assembly and guaranty costs. Design for manufacturing and optimum design principles can be embodied in the two principles of the axiomatic design as proposed by Suh [1]. These recommend independence of the functional requirements and minimization of the information content. These were achieved by assembling the vessel of identical segments. The goal was to maximize customer satisfaction on the technology and economy of the product. First the initial concept was optimized globally and then the critical details were checked using FEM. Micromechanical models were used to simulate tensile test curves and strength behaviour of fiber reinforced materials. Transactions on Engineering Sciences vol 10, © 1996 WIT Press, www.witpress.com, ISSN 1743-3533 50 Composite Material Technology V Computational models and calculations Geometry, materials and loads The studied structure is shown schematically in Fig. 1. [2]. Figure 1: The structure, a) Side view of the cylinder and cone, b) segments and the RHS beams supporting it. The critical areas are shown shaded. Geometry Diameter of the cylinder is D = 13 m and height H* = 2.5 m. The wall thickness is determined using the strength constraints [2]. Materials Material of the walls is GRP laminate with 30...35 wt % glass fiber chopped strand and woven roving.The material is nearly isotropic in the plane directions. The tensile strengths in the main strength directions are the same ^mx = Rmy = m = 140 MPa The bending strength is R b* = Rmby = 140 MPa [2]. The required factor of safety is SA = 7.5. The elastic moduli are E* = Ey = 8000 MPa. The density of the acidic fluid is p = 1400 kg/m Function and loadings The function of the structure is to contain the liquid reliably for several years by withstanding the planned loads. Loading is hydrostatic pressure and temperature load of 50...80°C and the chemical load. Wall thickness of the cylinder The wall thickness s of the cylinder is determined using the membrane theory. The allowed stress is UTS divided by the safety factor a^ R^ I SA = 140/7.5 =18.7 MPa Application of the constraint R(\) on the circumferential stress gave s = 0.012 m. SA SA >0 (1) Transactions on Engineering Sciences vol 10, © 1996 WIT Press, www.witpress.com, ISSN 1743-3533 Composite Material Technology V 51 Joints of the segments at the wall The tangential forces are transmitted through a glue joint, Fig 2.