Papers by Author: Bo Ming Zhang

Abstract: Shape memory alloy (SMA) is a type of smart material with huge driving force, and large driven displacement. Using SMA as the structure driver may force a bi-directional deformation structure that can achieve high efficiency and compact driving structure. SMA, together with elastic component, forms the two-way driving structure; however the two, if respectively serving as the driver, can enable the occurrence of the simplest bi-directional drivable structure. The offset structure constituted by SMA, not only can achieve two-way drive, and does not require continuous input of energy during the shape-stabilizing period. This paper studies the design methods of these two structures, gives the typical formulas, which makes possible efficient and compact bi-directional drivable structures.

Abstract: It is widely acknowledged that decisions made in the early design stages have a greater influence on the final product than those made in the later stages. In the early stages of a conventional design process, composite structures are designed without sufficient consideration being given to limitations of composite manufacturing process. Quite often some of composite designs cannot be produced with special performance requirement or cannot be produced at a reasonable cost. To resolve this drawback and achieve the manufacturable designs for composite product, a knowledge-based decision-making tool was introduced and applied to support the composite design optimization. Firstly, the current development of DFM techniques in composite domain, as well as the main problems in performing DFM for composites is analyzed. Secondly, some of key issues in the composite manufacturing process that should be considered during the composite design process are presented. And then, a knowledge-based DFM system for composite manufacturing process is proposed, focusing on the system decision task, the system framework and the flowchart. Finally, the system is illustrated with a case in autoclave process.

Abstract: A progressive damage and failure model for fiber reinforced laminated composites is developed in combination of finite element procedure and micromechanical model based on a unit cell. The micromechanical model can be used to evaluate failure criteria at the micro-level with fiber and matrix material properties. Once either of the constituents has damaged, the corresponding material properties are degraded by the damage factor. The micromechanical model and the damage theory are implemented in the finite software ABAQUS by using the user material subroutine UMAT and VUMAT, to model the damage progression and compute the ultimate strength of the composite laminates containing a hole. The predicted strengths for this model is compared with the experimental results, and a well agreement in the simulation and experimental resulted is revealed.

Abstract: For the sake of the carbon filaments’ fracture toughness, using the focused ion beam (FIB) to etch the carbon fibers and got different tensile strength, and all specimens were stretched on an Instron-type filaments testing machine and got the samples’ tensile strength, The crack-to-mirror size ratio was assumed as a constant, In virtue of Griffith fracture theory, Fracture toughness (KΙC) of representative high-strength type PAN (polyacrylonitrile)-based carbon fibers, Torayca T300 and T800, were estimated to be 1MPam1/2 from the tensile strength vs. fracture mirror size relation.

Abstract: Framed curing mold is subjected to an uneven thermal load, gravity force and the pressures from composite parts and auxiliary tools during autoclave processing of thermosetting composite structures. And those loads induce the warpage of framed-mold. The warpage of framed-mold during autoclave processing influences dimensional precision of composite parts. In the present work, a three-dimensional finite element model for prediction of the warpage of framed-mold during autoclave processing has been developed. This model solved the coupling problem between the deformation and the temperature distribution of framed-mold and allows analysis of all major identified deformation influencing factors. And numerical predictions compare quite well with experimental measurements. A parametric study was performed using FEM program to examine the effect of varying the thickness of framed-mold, the shape and the dimension of mold vents.

Abstract: An analytical model was established by means of Ritz method to calculate the cured shape of cross-ply unsymmetric composite laminates. A number of experiments of Carbon/Epoxy laminates were conducted. It was found in the experiment that the warped surface could be a multiple-value function, which should be studied further. The result of calculation correlates well with the experimental result except the regions very near the laminate edge. The conclusion is instructive to manufacture of composite laminates.