Xujing Yang

Crashworthiness optimization of new thin-walled cellular configurations

Purpose – The purpose of this paper is to optimize a new thin-walled cellular configurations with crashworthiness criteria, so as to improve the crashworthiness of components of a vehicle body. Design/methodology/approach – ANSYS Parametric Design Language is used to create the parameterized models so that the design variables can be changed conveniently. Moreover, the surrogate technique, namely response surface method, is adopted for fitting objective and constraint functions. The factorial design and D-optimal criterion are employed to screen active parameters for constructing the response functions of the specific energy absorption and the peak crushing force. Finally, sequential quadratic programming-NLPQL is utilized to solve the design optimization problem of the new cellular configurations filled with multi-cell circular tubes under the axial crushing loading. Findings – Two kinds of distribution modes of the cellular configurations are first investigated, which are in an orthogonal way and in a d...

Experimental study on strain-rate-dependent behavior and failure modes of long glass fiber-reinforced polypropylene composite

Due to its good mechanical performances and design flexibility, long glass fiber-reinforced polypropylene (hereinafter referred to as LGFRP) composite has been increasingly used in the automotive industry, in which the LGFRP components are likely to sustain different strain rates loading during a crash event. The objectives of this study are to investigate the correlations between the LGFRP and strain rates 10−3 s−1 to 50 s−1, and the corresponding failure modes of LGFRP. Therefore, tensile and compression tests are conducted at different strain rates and the corresponding microstructures of the specimens are investigated with scanning electron microscope. The experimental results show that the failure strain and ultimate strength increase as increasing strain rate. The elastic modulus is sensitive to strain rate in tensile tests, but less sensitive to strain rate in compression tests. The main failure modes of the specimens are the matrix crack and fiber pull-out. The defects such as bubbles, shrinkage cavities, or dry fibers of the specimens play important roles in the initiation and propagation of cracks during the tensile and compression tests.

Experimental and numerical investigation of Long Glass Fiber Reinforced Polypropylene composite and application in automobile components

Due to the good mechanical performances and design flexibility of Long Glass Fiber Reinforced Polypropyl-ene (LGFRP) composite, it has been increasingly used in the automotive components, in which the LGFRP components are likely to sustain different strain rates loading during a crash event. This study aims to investigate the correlations between the LGFRP and strain rate, which will be applied to crash-worthiness and energy absorbing property analysis of a bumper beam under the longitudinal impact. Firstly, strain rate dependent material properties are determined, for which the experimental procedure is explained in detail on the tensile specimens of long glass fiber and polypropylene matrix based composite configurations. The gained experimental results provide the input parameters for a numerical analysis of specimens. The numerical results of properties are compared with those from tests. The constitutive model that fits for LGFRP is employed to crash-worthiness and energy absorbing property analysis of a bumper beam under the longitudinal impact. First Published Online: 17 May 2017

Characterization of nesting effects on compression processes for plain woven fabrics in composites manufacturing

Nesting and compression processes of plain woven fabrics are the most important features in the composites manufacture of fiber-reinforced composite components, while their relationships are still not reported. Here, in this work, we clearly reveal nesting and compression characteristics of typical fabrics through systematical compression experiments. We present the theoretical expression of the nesting effects on the initial thickness h and experimentally demonstrate its effectiveness. We find that nesting decreases the h and the minimum h appears in the maximum nesting condition. Meanwhile, we experimentally demonstrate that for plain woven fabrics, nesting has relationships with the thickness in compression t, while it has no effects on the thickness deformation Δ in the whole compression processes. Thus, we reveal the relationships between the nesting and h, t, Δ in the compression processes. Moreover, the applicability of these results for other types of fiber is also illustrated by comprehensive analysis. These obtained results provide the references for thickness evolution rules, volume fraction, and molding process of the fiber-reinforced composite components.

Evolutionary Topological Design of Frame for Impact Loads

Over the past decade remarkable progress has been made in the development of software used in crash simulation and analysis. A number of commercial codes have been available with accepted accuracy. However, there has been limited report in its inverse problem yet, i.e. topological and shape optimization for crashworthiness. The difficulty is primarily raised from two folders on (1) the nonlinear sensitivity analysis and computational cost, which become particularly challenging in various topological designs; (2) dynamic multi-modals and non-convex design space, which do not lend the crash problems themselves well to classical gradient techniques. This paper aims at developing an alternative approach to the crashworthiness design problems. The Evolutionary Structural Optimization (ESO) will be applied to reduce the dependence on the continuum sensitivities.

Computational Design of Beam Sections under Impact Loading

Computational crashworthiness design is of special interest in automotive engineering to ensure the vehicle structural integrity and more importantly the occupant safety in the even of the crash. Nevertheless, most of the collision energy is absorbed by various types of structural components during the impact. For this purpose, hollow thin-walled beam sections have been extensively adopted as an important element of energy absorption in various vehicles. It is highly desirable to have such beam structure to absorb as much energy as possible once impact occurs.