Effects of pressure, boundary conditions, and cutting reliefs on thermo-hydroforming of fiber-reinforced thermoplastic composite helmet based on numerical optimization

2019 ◽  
pp. 089270571984263
Author(s):  
Hyunchul Ahn ◽  
Nicholas Eric Kuuttila ◽  
Farhang Pourboghrat
2008 ◽  
Vol 76 (1) ◽  
Author(s):  
E. Shmoylova ◽  
A. Dorfmann

In this paper we investigate the response of fiber-reinforced cylindrical membranes subject to axisymmetric deformations. The membrane is considered as an incompressible material, and the phenomenon of wrinkling is taken into account by means of the relaxed energy function. Two cases are considered: transversely isotropic membranes, characterized by one family of fibers oriented in one direction, and orthotropic membranes, characterized by two family of fibers oriented in orthogonal directions. The strain-energy function is considered as the sum of two terms: The first term is associated with the isotropic properties of the base material, and the second term is used to introduce transverse isotropy or orthotropy in the mechanical response. We determine the mechanical response of the membrane as a function of fiber orientations for given boundary conditions. The objective is to find possible fiber orientations that make the membrane as stiff as possible for the given boundary conditions. Specifically, it is shown that for transversely isotropic membranes a unique fiber orientation exists, which does not affect the mechanical response, i.e., the overall behavior is identical to a nonreinforced membrane.


1995 ◽  
Vol 117 (2) ◽  
pp. 228-234 ◽  
Author(s):  
Byung S. Kim ◽  
Terry F. Lehnhoff

An orthotropic hygrothermal stress solution has been formulated for an infinitely long fiber-reinforced tube of any number of plies of any material, with arbitrary orientation of each of the plies. The solution allows the determination of stresses when the tube is subjected to changes in temperature and moisture content. In the formulation, a temperature gradient through the thickness has been taken into account such that the formulation can be applied when the temperature inside the tube is not the same as that outside. This set of equations, together with the prescribed boundary conditions, has been solved numerically. It is shown that the stresses induced due to moisture absorbed from the environment are significant.


2020 ◽  
Vol 10 (16) ◽  
pp. 5499
Author(s):  
Abera Tullu ◽  
Bong-Sul Lee ◽  
Ho-Yon Hwang

The anisotropic nature of fiber reinforced composite materials causes great challenges in predicting the inter-ply shear stress during forming. The complexity of understanding the functional dependency of inter-ply shear stress on multiple forming parameters such as blank temperature, pressure load, inter-ply slippage, and the relative fiber orientation angle of adjacent plies further limits the effort to produce a defect-free composite structure. Performing real experiments for various combinations of the mentioned parameters is both time consuming and economically costly. To overcome these difficulties, a surrogate-based analysis of inter-ply shear stress is proposed in this study. Based on the ranges of the forming parameters, computer experiments were performed. Using these experimental data, a radial basis function (RBF) based surrogate model that mimics inter-ply shear stress during composite press forming was developed. The fidelity of this model was checked with test data and found to be over 98% efficient.


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