Recently, alminum sheet is used for automobile body. In this short paper, TRIP steel sheet is discussed in compared with alminum sheet, and proposed to use for same purpose.

View full abstract

Fiber reinforced plastics are the most popular composite materials to be design for need orientation. But as the studies on the field of composite materials are very large and the member of researchers to study in many different technical fields are trying to promote the composite production separately. Then it is difficult to consider both design and production of composites totally. So this paper examined the composite properties of anisotropy and the design synthesis of composite structure, molding method and constitution of materials etc.. Then new materials have developed many applications in organic, inorganic and metals in these days but processing method and structural design of composites have not been investigated so actively. So this paper gave the synthesis considesation of these problems and promotion of molding method developing and structural design consideration are expected to expand in the many applications and these consideration will be develop in the production method of composites materials.

View full abstract

The unloaded photoplasticity technique can be employed in a large variety of applications, such as plane stress, plane strain, axisymmetric and general three-dimensional problems. Depending on the type of application, different sets of results may be obtaind. As a three-dimensional unloaded photoplasticity, photoplastic strain freezing method has been proposed by authors according to photoelastic stress freezing method. Several basic experiments were curried out to investigate the mechanical and optical properties of polycarbonate material, which is believed suitable to use as photoplastic model material. But because the polycarbonate material like other polymers has obvious viscosity, it should be clear that how the mechanical and optical properties are affected by temperature, deformation speed, and time etc. In this paper, some results of further studies on the photoplastic strain freezing method, which include a) the dependence of stress-strain curve, tensile yield stress, strain-fringe order and stress-fringe order relation on temperature and tensile speed, b) the behaviors of polycarbonate in creep at strain freezing temperature, and c) an analysis of uniaxially compressed short cylinder, are reported.

View full abstract

Various approaches have been attempted in order to solve fracture and toughness problems of metals. These approaches could be classified into three fields: physical, metallurgical, and fracture mechanical aspects. In the present paper, these investigations are briefly reviewed and the correlations among them are discussed. Although these have different purposes originally, it is stressed that the plastic deformation at the crack tip is important essentially for all. In order to clarify the fracture and toughness mechanism of metals further, fine experimental works concerning it are expected.

View full abstract

A stochastic material design method for fibrous reinforced composite material are reviewed. One of the major objectives of the method is to show a practical method of constructing the reliability-oriented material design. Some formulation for the reliability model of fibrous reinforced composite laminate is represented. A procedure of evaluating failure path of multiple layer composite laminates under the offaxial load condition is also presented. An extended study is suggested in order to calculate the failure probability of multiple layer laminates from effective failure path. In addition to the above, a relationship between stochastic material design method and some optimization techniques is discussed from the viewpoint of optimum material design and optimum reliability-based design for composite laminates.

View full abstract

Development of factual database for advanced materials is of current interest. On the other hand, the database systems for these advanced materials are not well established. For the case of advanced composite materials, the structure of data model is very complicated. Thus, it is very difficult for users without the knowledge of anisotropic mechanics, fibers, matrix etc. to retrieve design data from composite material factual database. In the present study, the concept of Intellectual Database Access Manager (IDAM) for composite materials is proposed. In this system, design of laminates layup and selection of materials can be done automatically by using artificial intelligence method. This paper describes the concept of artificial intelligence method used in this system.

View full abstract

Thermo-mechanical properties of three-dimensional (3D) fabric composites have been studied systematically. The fiber orientation distribution and the maximum volume fraction of various 3D-microtextures were at first examined. The fiber structures which could be fabricated are shown to be derived from the polyhedra which completely fill up the three dimensional space. Then, analytical studies for the elastic moduli and thermal expansion coefficients were carried out to clarify the relationship between the fiber textures and the thermo-mechanical properties. Although the complete isotropy of the moduli was obtainable theoretically by adequately placing reinforcing fibers in 6 directions, it was difficult to fabricate the preform with high fiber volume fraction. Among practical preforms, those with 3, 4, and 7 reinforcing axes are suggested to be useful for tailoring the thermomechanical properties. Next, the strength and fracture toughness were examined mainly for the tri-axial 3D composites. It was shown that the strength of the tri-axial 3D composites could be predicted by the rule of mixture but the fracture toughness was extraordinarily high compared with the laminate composite. The reason for this high toughness was suggested to be weak interface between the fiber and matrix caused by thermal mismatch between the constituents and 3D constraint by reinforcements. Finally, the effectiveness of the use of 3D composites in an actual applications are exemplified by picking up a 3D-reinforced truss joint frequently used in space structures as an example.

View full abstract

The SAICAS method was developed for measurement of adhesive strength and shear strength of coating materials. It is also suited to continuous measurement of strength of materials from outer layer to the inside, that is, the depth profiling. In other words, it means that the strength of a very small area at an optional depth can be measured. This paper relates to results of depth profiling of ABS resin deteriorated by weathermeter. It was confirmed that the hardening layer thickness of the surface irradiated with light tends to increase with the passing of the time, while it was also disclosed that the hardening layer thickness increases not only on the irradiated side but also on the back side. At the same time it was learned that the increasing tendency of the hardening layer thickness varies with the type of the accelerating aging testing machines.

View full abstract

As common feature of composite materials, prominent anisotropy in mechanical properties is observed fiber reinforced plastics FRP, which has higher fracture strength and stiffness along the fiber strengthening component. Since it is well known that a resin matrix exhibits characteristic time and temperature dependence on mechanical behavior, that is, viscoelastic behavior, the FRP is naturally expected to exhibit similar behavior. Based on the above mentioned hypothesis, the stress-strain relation and the fracture strength of advanced FRP were investigated over wide ranges of time and temperature, in conjunction with similar investigations on the epoxy resin matrix. Furthermore, the role of matrix resin on stress-strain relations and fracture strengths of advanced FRP is discussed.

View full abstract

In this paper, the growth mechanism of residual stress in crystalline polymer under the process of extrusion molding is cleared. A high density polyethylene (HDPE) is selected as the specimen, which is one of crystalline polymers. First, the thermoviscoelastic behavior and thermal expansion of HDPE which have direct effects upon residual stress are investigated carefully. Second, the residual stress in HDPE plate as mold, annealed plate and rapidly cooled plate are measured accurately by use of layer removal method. These residual stresses are discussed in relation to thermoviscoelastic behavior and thermal expansion of HDPE. Final, the growth mechanism of residual stress under extrusion molding is explained by using the viscoelastic model with thermal expansion based on experimental results.

View full abstract

On April 4, 1991 the author gave a seminar on Object-Oriented Approach to the Analysis and Optimization of Truss Structures at Interdisciplinary Reserch Office (IRO) of NASA Langley Reserch Center. This paper is the record of the seminar. The seminar was planned by Dr. Sobieski, who is the Head of Interdisciplinary Research Office. The figures in this paper are the same as the transparencies used in the seminar. Object-oriented approach is one of the methods for representing knowledge and has a paradigm in which the fundamental processing is to send a message to an object rather than a more traditional approach of calling a procedure to operate on some data. In this paper a concept of object-oriented approach to the analysis and optimization of truss structures is presented. Much attention is focused on the development of a knowledgebase for structural engineering and such knowledgebase is very useful for the conceptual design stage of structures.

View full abstract