[en] Transcendental equations are given for calculating the dispersion curves of the longitudinal and flexural waves in orthotropic plates. An experimental method is shown how to get the elastic constants of the generalized Hookes law of an unidirectionally fiber-strengthened composite laminate by measuring the fastest velocities of the longitudinal, transverse, flexural waves in an impacted orthotropic plate. An unidirectionally strengthened carbon/epoxy composite plate is used for the experimental verification of the contact law and of the impact theory. (orig./DG)

[en] Short communication

[en] Prosthesis is a process of creating artificial human body part. The primary function of below-knee prosthesis is controlling the leg during static and dynamic conditions. The aim of this study is to develop a prosthetic socket made from kenaf-glass fiber composite. The development of prosthetic socket with kenaf-glass fiber was carried out as an attempt to substitute prosthetic socket made from fiberglass polyester composites. Lamination method was adopted to fabricate the prosthetic socket. The laminates contain woven kenaf, glass silk knitted fabric and nylon knitted fabric. The effect of kenaf fabric layering sequence on the volumetric and mechanical properties were evaluated. The flexural and impact strength of 2 layers of kenaf fiber-based laminates are 7.11 MPa and 16.7 kJ/m² respectively which is higher than the single layer kenaf fabric-based composites. From the results woven kenaf fabric composites has the potential to replace the existing glass fabric-based polymer composites. It is a great initiative to fabricate a prosthetic socket which biodegradable, environmental friendly, locally available, lightweight, comfortable and psychosocially acceptable. (paper)

[en] This work demonstrates possibilities of development of a heterogeneous hardened structure with alternating hard and plastic areas using impact deformation waves. There is a possibility of preserving impact strength of the metal material during formation process of heterogeneous hardened structure. (paper)

[en] Theoretical work is reported on the determination of the stresses produced by a single impact load in rod specimens of polycrystalline graphites, typically 0.1 m long and 0.015 m diameter, simply supported at the ends. The impact force function was calculated from the theory of Timoshenko, the effects of a finite area between rod and impactor being included by varying the radius of curvature of the impactor. Results have been obtained for the maximum tensile stress as a function of time produced by an impactor of mass 0.29 kg striking with a velocity of 1.3 ms^-1. Compared with some previous calculations for a point impact force, the effect of a larger contact area was found to reduce the contributions of the higher order vibrational modes. However, even for the largest radius of curvature of the impactor studied, 1 m, the net effect on the predicted stresses was to reduce their values by only a few percentage from those obtained for a point contact force. (author)

[en] The HDR plant has been out of service for several years and is now a test facility for full scale blowdown experiments. The first experimental program was concerned with valves and their dynamic behaviour under blowdown conditions. The pressure waves and the loading of the discharge pipe influenced by the blowdown and the quick closing valves were also observed. A steam isolation valve and a feed water check valve have been tested in this program. The correct operation of these valves is essential in blowdown. For the first tests an original isolation valve which is installed in the steam line of PWR's or BWR's was used. The HDR pressure vessel has a volume of about 66 m³. On the top of this vessel a test blowdown tube with a length of 20 m and an I.D. of 450 mm was constructed. With this facility several tests were conducted with various discharge rates (from nominal rate up to strong blowdown conditions) in the blowdown tube and with a delayed closure so that closing behaviour during two phase flow could also be investigated. In the second part of the valve experiments a quick closing feed water check valve (I.D. 200 mm) was tested with a variation of the damping in order to study the influence on the closing time and on the pressure waves. The pressure amplitudes observed after the valve was closed reached 300 bars in some tests which indicates that it is necessary to consider these severe problems very carefully. (orig.)

[en] Closed form solutions have been obtained using Fourier transform method for the deflection, curvature and particle velocity of a long elastic beam when it is subjected to a concentrated transverse force which is varying with time. These solutions have been illustrated with the help of two force histories, i.e. a half-sine pulse and a rectangular pulse. Dimensionless parameters representing deflection, curvature and particle velocity have been plotted as functions of dimensionless distance and dimensionless time. Furthermore, the particular case of constant velocity impact which has been studied by other authors using different techniques has also been considered in the present paper and the results compare within numerical errors involved in the evaluation of integrals. (orig.)

[en] The main critical factors, which have direct influence on the fracture toughness and imapct strength properties of natural fibers composites, are reviewed in details in this paper. Considering the vast body of literature on the aforementioned subject, there are six main factors controlling these properties: (i) Intrinsic properties of the constituents related to packing arrangements, length, loading and orientation of the fibers; (ii) Type of physical and chemical treatment on natural fibers; (iii) Environmental conditions such as temperature and moisture; (iv) Material properties of reinforcing fiber and hosting resin, which constitute the natural composites; (v) The type of hybridization of natural composites such as self-hybridization based on same natural fiber and hybridization of natural fiber with another natural or synthetic fibers; (vi) Type of nano reinforcements, which is used to improve the fracture toughness of natural composites at nano and micro scale levels. Among the aforementioned factors, it is found out that the most critical factors affecting the fracture toughness and impact strength of natural composites are the type of physical and chemical treatments used to improve interfacial adhesion at fiber-matrix interface and the type of hybridization process. (topical review)

[en] This report describes the results of 43 impact tests on 152 mm (6 in) nominal bore steel pipes. The missiles included solid steel billets and sections of steel pipe with impact velocities in the range 46 to 325 ms^-1. The tests showed that, for the solid billets, the impact resistances of the pipes were greater than expected from previous tests on flat plates. The perforation energies have been correlated against normalised target wall thickness and relative diameter of missile and target. The results of non-circular section missiles can be predicted using an equivalent circular missile based on the length of the perimeter. The correlation provides satisfactory indications of the results obtained with axially-impacting pipe sections with outer diameters equal to the target pipe diameter. Laterally-impacting pipe missiles were unable to cause perforation of the target or initiate fracture in the target pipe wall even when the target-pipe section collapsed completely. However, these tests indicated that the global response of the impacted pipe could transmit very large forces to the supporting structure. (author)

[en] The objective of the present research work is to investigate the Charpy impact behavior of intraply hybrid carbon/aramid fabric layers with S-glass fabric layers composite laminates for asymmetric and symmetric arrangements. The hybridization effects on Charpy impact characteristics for carbon/aramid with S-glass hybrid composite laminates were compared with those of carbon/aramid/epoxy composite laminates and S-glass/epoxy composite laminates. Deformation degree, impact energy and impact strength were strongly affected by the position and number of carbon/aramid layers in addition to the impact side direction due to variation of impact properties between carbon/aramid fibers and S-glass fibers. Using S-glass layers instead of carbon/aramid layers exhibited decreasing in the deformation level particularly for carbon/aramid side impact in addition to improve the impact strength of the hybrid composite. (paper)