Large deformations of cordreinforced multilayered shells

of ferrocement in flexure is presented. The effects of cyclic creep of mortar, steel relaxation, and bond deterioration under cyclic loads are addressed. An analytical model is proposed; it predicts, from the fatigue properties of the constituent materials, the increases in crack widths and deflections and the deterioration of flexural rigidity due to repeated loads. The validity of the model is checked by comparing predicted results with experimental observations on ferrocement beams. A generally good agreement is found. It is hoped that the analytical procedure can be successfully modified to become applicable to reinforced concrete structural elements. (Authors' abstract )

Sulphur-impregnated concrete materials Hope, B.B. and Nashid, M.S. The

International Journal o f Cement Composites Vol 1 No 1 (May 1979) pp 29-36 Various types of hardened cement paste, mortar, and plain and reinforced concrete specimens were impregnated with elemental sulphur. The physical and mechanical properties of each type of specimen were extensively examined. The elastic modulus and the stress/strain characteristics of the impregnated materials reflected a significant improvement in behaviour and emphasized the important role of the final porosity. The mechanical properties of the impregnated cement paste and mortar composites were determined from the properties of the constituent materials by means of an analytical finite element technique. (Authors' abstract)

in the direction which is in the plane of both the crack and the laminate (along the coupon width). A finite difference solution scheme is used to obtain stress distributions for various combinations of cracked plies. The solution scheme is unique in its treatment of boundary operators tridiagonal algorithm is generated and applied. Comparisons with established data are made and example distributions of stress are presented. (Authors' abstract)

Large d e f o r m a t i o n s of cordreinforced muitUayered shells Tabaddor, F. Fibre Science and

Technology Vo112 No 4 (July 1979) pp 253-267 The problem of general deformations of cord-reinforced multilayered shells is formulated through the principle of virtual work, in the undeformed coordinate system. The shell is assumed to be made of N thin layers, each being reinforced with two families of cords symmetrically located with respect to meridians, bonded by (N-l)interlayers. By applying variati.onal calculus to the present evergy formulation, one can obtain the system of governing partial differential equations. The energy formulation also provides a convenient form for numerical analysis by the Ritz type of approximation. To illustrate the application of the theory, the case of a two-ply cord-reinforced rubber shell, subjected to internal pressure, is numerically analysed. The governing equations are non-linear ordinary differential equations. These equations were solved by the quasilinearization technique. Some results are presented and discussed. (Author's abstract)

GENERAL

Analysis of stress fields in composite laminates with interior cracks Talug, A. and Reifsnider, K.L. Fibre

Science and Technology Vo112 No 3 (May 1979) pp 201-215 The complete stress field in composite laminates having one or more cracked plies is determined by an approximate solution of the threedimensional equilibrium equations under the assumption that the components of the stress tensor are independent of co-ordinate position

52

A technique for evaluating a unique set of three weibull parameters considering composite materials Schneider, D. and Palazotto, A.N.

Fibre Science and Technology Vol 12 No 4 (July 1979) pp 269-281 The paper presents a method for finding three material parameters incorporated into the Weibull distribution function as pertaining to the probability of fracture for composite material. Basic theory

derived from homogeneous, isotropic beam analysis is applied to 0 ° and 90 ° undirectional laminated graphite/epoxy in order to demonstrate the application. (Authors' abstract )

METAL MA TRICES

Composites for electrical contact applications St6ckel, D.Zeitschrij~ fur Werkstoff-

technik Vol 10 No 7 (July 1979) pp 230-242 Metallic composites, such as laminates, particulate-reinforced, infiltrated and fibre-reinforced, have been used for the production of electrical contacts for several years. The paper reviews the various types of materials available, with particlular attention being given to silver/nickel, copper/nickel and copper/palladium fibre composites.

Initial tests with a directionally solidified eutectic super-alloy Sahm, P.R. and Hildebrandt, U.W.

Zeitschrifi fur Werkstoffiechnik Vol 10 No 8 (August 1979) pp 257-292 Several blades made with the directionally-solidified eutectic superalloy Co/CrTC a were tested in a stationary gas turbine plant over a period of 18 000 h. The average operating temperatures was 700°C. The blades were removed after 9000 operational cycles and inspected metallographically. It was observed that the purely eutectic microstructure, in the root section of the blades, survived the 18 000 h test, whilst the outer portions, having a matrix-rich non-eutectic structure showed carbide transitions (CrTC3~Cr2aC6) which induced coagulation of the carbide fibres.

RESIN MA TRICES

The impact resistance of unidirectional cfrp under tensile stress Butcher, B.R. Fibre Science and

Technology Vo112 No 4 (July 1979) pp 295-326 Two unidirectional carbon fibrereinforced plastic composites were used to study the experimental variables when specimens under tensile stress were subjected to impact. Two

COMPOSITES. JANUARY 1980