Experimental investigation of cooling conditions, MWCNTs and mandrel diameter effects on the thermal residual stresses of multi-layered filament-wound composite pipes

This study employs numerical and experimental approaches to analyze effects of various filament-winding parameters, including mandrel diameter and cooling conditions, on the process-induced thermal residual stresses of composite and nanocomposite pipes. Simultaneous effects of the addition of multi-walled carbon nanotubes (MWCNTs) and the cooling conditions were also analyzed in detail. To accomplish this aim, a few composite and nanocomposite cylinders with various diameters in different cooling conditions were produced using filament-winding process and experimented. The incremental hole-drilling method using an integral inverse solution was employed for measuring the curing-induced residual stresses. The experimental findings confirm that using MWCNTs for reinforcing the matrix, choosing a slow cooling condition, and increasing the diameter generate less residual stresses during the process. Moreover, this study clearly showed that the addition of MWCNTs decreases the sensitivity of the structure to the effects of cooling conditions during the curing process. Therefore, finding optimum amounts of MWCNTs and cooling rate leads to the minimum cost of fabrication.

Optimizing Mandrel Dimensions for a Fixture Hardening Process of High-Strength Steel Aerospace Parts by Finite Element Simulation

A fixture hardening process for aerospace gear box components of alloy S156 (16NiCrMo16-5, 1.6722) is investigated by thermomechanical metallurgical 2D axisymmetric Finite Element simulations. Material parameters are experimentally determined. Contact and transformation plasticity effects among others are implemented in Abaqus® with user subroutines. The study aims to optimize the mandrel diameter of a fixture hardening tool for processing of planet gears. Plasticity, transformation plasticity, arising contact forces, and pressure depending on different mandrel sizes are investigated in depth. Distortion is evaluated and an optimal setting is derived from the calculations. Results show that cylindricity, defined here as the difference between maximum and minimum radius of the part, and maximum contact pressure, both can be reduced by increasing the mandrel radius. Physical effects and distortion evolve strongly nonlinear. Analysis methods highlighting cylindricity depending on the different mandrel diameters are developed to illustrate this nonlinear behavior and to enhance knowledge about the process.

Functional Failure in Filament-Wound Composite Pipe: A Parametric Sensitivity Analysis Approach

The performance of filament-wound FRP composite is dependent on the properties of constituent materials (i.e. fiber, matrix and fiber-matrix interface) as well as on the manufacturing and design parameters (e.g. fiber lay-up, laminate stacking sequence, mandrel diameter, winding tension, winding time, fiber wet-out, etc.). In the first part of this work, we present a sensitivity analysis approach to ascertain the degree of influence of various mechanical and material design parameters on the structural failure of the composite laminated pipes. In the second part, sensitivity analysis results were used to design pipes with improved mechanical strength.

Circular Braiding Process Simulation for a Pressure Vessel

Pressure vessel manufacturing is currently dominated by the filament winding process. When higher production rates are required, circular braiding can be considered as an alternative because hundreds of yarns are deposited simultaneously from interlacing spools. The process has a high repeatability and is suited for automated series production, as is currently shown with the production of a-pillars and rockers in the automotive industry. Important manufacturing constraints related to the overbraiding of cylindrical pressure vessels are to avoid excessive jamming of the braid, typically occurring at a small mandrel radius, and to achieve a 100% cover factor at the largest mandrel diameter. In this paper, design guidelines for braiding of cylindrical pressure vessels are proposed. It is shown that a proper choice of the yarn cross-sectional area size and of yarn width-to-thickness aspect ratio can improve the design feasibility, but an adjustment of the braid angle can be required as well.

Preparation of Small-Diameter Silk Fibroin Tubular Scaffolds with Electrospinning Method

In recent years, electrospinning has received much attention to prepare porous tubular scaffold due to electrospun nanofibers mat, which can mimic the structure characteristics of the extracellular matrix (ECM). In the present paper, silk fibroin (SF) tubular scaffolds with small-diameter were prepared by electrospinning from regenerated silk fibroin (RSF) aqueous solutions with rotating mandrel collector. The morphology and fiber diameter distribution of SF tubular scaffolds were influenced much by the concentration of regenerated silk fibroin (RSF) solution, collecting distance and mandrel diameter. The results showed that SF tubular scaffold, which was in flat surface with smaller fiber diameter and uniform distributed, could be obtained at the concentration of 22%, collection distance of 10 cm and mandrel diameter of 4 mm. The structure of SF tubular scaffolds before and after ethanol treatment was characterized by FTIR and XRD. After ethanol treatment, the SF tubular scaffolds had a conformation transition from random-coil conformation to Silk II conformation.

The Simulation Spreading Process of Steel Tubes Hollow

The paper presents finite element analysis of spreading process of hollow steel tubes implemented within commercial software MES FORGE2-V3.0. To this purpose, rigid-plastic model of deformed material was assumed. The analysis was realised for hollow tube made from steel C45 with external diameter D0 = 50 mm and internal one d0 = 40 mm. Distributions of temperature, stress and deformation for different values of gradient radius of mandrel  (1535) and different friction conditions on the area of metal-tool were determined. With the piercing press the billet is introduced into a vertical or horizontal die, subsequently to be pierced by mandrel. Afterwards pipe is elongated in Diescher’s mill. Hollow steel tubes undergo hot deformation spreading process in two-roll press by mandrel. Process stability depends on dimensions of the hollow tube and mandrel: tube external diameter, tube internal diameter, mandrel diameter and inclination angle of mandrel. Increase of external diameter of hollow tube occurs in the course of spreading process by mandrel. Process parameters depend on chemical composition and type of material. In this paper the contact problem in metal – tool interface is considered. Burnishing implies the sizing of a hollow tube by its plastic spreading.