Round-robin programme for longitudinal tensile testing of unidirectional composites: results, conclusions, and recommendations

Abstract. Bonding characteristics, composition, and internal structure have a strong effect on the behavior of materials under mechanical loading. The paper explores the mechanical characteristics of dog-bone shape Carbon Fiber Reinforced Composite (CFRC) specimens with longitudinal tensile test. The first tests were done on an isotropic material i.e. Mild Steel, Brass, Aluminum, Acrylic and Poly Lactic Acid (PLA) under typical tensile testing conditions. These samples deformed in a homogeneous manner and broke in the gauge length without any supplement, and this was in line with the direction-independent mechanical properties of isotropic materials. Unlike this, CFRC specimens exhibited uncharacteristic failure, that is, they fractured at the gripping areas instead of the gauge section when put to the same test. This was due to the anisotropic nature of CFRC, which provided variations in mechanical properties with fiber orientation and loading direction, which were determined by detailed analysis as the cause of this anomaly. The low transverse constraint in gripping resulted in concentration of the stress and early failures in the holding portions. In order to integrate this problem, tensile testing fixture was adjusted to apply the right transverse clamping force, whereby the specimen remains stable with an even distribution of load. Further tests on the modified design brought about consistent failure in the gauge length and repeatability in tensile response. This research displays the need to deal adjustment in testing the approach to anisotropic composite materials and the practicality of testing on the correct mechanical identification of CFRC samples. Keywords: Carbon Fiber Composites, Tensile Test, UTM, Transverse Force, Water Jet Machine

The effect of hydrostatic pressure on the mechanical properties of glass fibre/epoxy unidirectional composites

No. 225 Venous large animal model for stenosis, thrombosis, and chronic occlusion: short-term results, with biomechanical analysis

The analysis of strain parameters at rolling of aluminum composite with wire-reinforcement was carried out in the present experimental work. The roll bonding of two strips of EN AW-5083 alloy with and without diagonal stainless-steel net-reinforcement between them was experimentally proceeded with different reductions. It is analyzed the influence of the rolling reduction in the range from 25% to 55% on the straining of the wires and composite bonding mechanisms. The present experimental work is established and used the set of describing parameters of the net behavior in the composite such as net cell elongation, wire elongation and wire ovalisation. The means of longitudinal and transversal tensile testing, impact testing and microscopic analysis determine the properties of the rolled composite. The analysis of the rolling reduction influence on the mechanisms of bonding formation in the composite its properties and fracture behavior are carried out. Based on the conducted tests, it was established the optimum range of rolling reductions.

This paper shows the capability of friction-assisted tube straining (FATS) method to fabricate high-strength long tubes. For this reason, copper tubes were successfully processed via 1–7 passes of the FATS. Mechanical properties of the processed tubes were investigated via longitudinal and peripheral tensile tests. Polarize microscopy and scanning electron microscopy were executed to study microstructure evolutions. Finite element analysis was used to determine strain and temperature fields. Results show significant improvement in mechanical properties where flow stress, ultimate tensile stress, and microhardness increased 9.3, 1.8, and 2 times more than the initial values. Average grain size of the FATSed tube was significantly decreased to 1.4 μm from an initial value 30 μm after 7 passes. Investigation of the tensile properties of the longitudinal and the peripheral samples resulted in a maximum 19% anisotropy which was considerably improved comparison with the same SPD methods.

Animals differ in the biochemical composition, attachments, and mechanical properties of tracheal cartilage. This study examined the biomechanical properties and morphological structure of the trachea of pigs, and rabbits as preclinical models. The trachea in pigs and rabbits can be divided into four regions, cranial cervical, middle cervical, thoracic inlet, and intra-thoracic parts. The total number of tracheal rings in pigs and rabbits was 32-35 and 34-38 rings, respectively. The pig bronchus first branches from the trachea, reaching the cranial lobe of the lungs before branching to the main bronchus, while the rabbit bronchus branched after the main bronchus. A comparison of the posterior region of the crosssectional trachea shows that the rabbit has a C-shape with cartilage connected to the tracheal muscle, and the pig has the tracheal muscle covered with cartilage. The trachea of pigs and rabbits decreased in tracheal thickness and size from the thoracic inlet toward the lungs. The stress-strain in the longitudinal and transverse tensile test was higher in rabbits than in pigs. The tensile stress of the four regions was significantly different in the transverse tensile test (p<0.001). In the bending test, more force was required to bend pig than rabbit tracheas. Microscopic and scanning electron microscopy showed no structural differences in tracheal cartilage between the two species. These results suggest that there is great variation in morphology and physical properties of the trachea in pigs and rabbits. We found porcine tracheas have similar biomechanical properties to those of humans.

The strain capacity of pipes under combined loading is an important research topic within strain-based design. While strain capacity equations assume homogeneous pipe material properties, a realistic pipeline shows scatter in mechanical properties. Test and simulation programs have indicated that this “pipe heterogeneity” may reduce the tensile strain capacity under uniaxial loading by a factor up to two. To date, its effect in other scenarios (compressive; combined internal pressure and axial plastic deformation) has received little attention. To investigate these scenarios and compare them with uniaxial tensile loading, Europipe, Salzgitter Mannesmann Forschung (SZMF) and Soete Laboratory, UGent have set up a large-scale test program on UOE pipe X70 (OD = 1219 mm, WT = 17.5 mm), comprising a full-scale pressurized bend test and curved wide plate tension tests. All tested welds joined pipes with nominally equal pipe grade from the same pipeline project, with strongly different actual properties. Optical full field strain measurements by means of digital image correlation reveal local effects of pipe heterogeneity on the strain distribution in the vicinity of the girth weld. All tests showed pronounced degrees of non-uniformity in strain development, in some cases even inhibiting plastic deformation in the stronger material as its weaker counterpart collapses. Implications of the observations with respect to strain-based design are discussed.

The mechanical behavior of carbon-fiber-reinforced polymer (CFRP) laminates manufactured using plasma-assisted solvolysis recycled fibers was evaluated experimentally through a comprehensive mechanical testing campaign. The plasma-assisted solvolysis parameters were selected based on an earlier sensitivity analysis. Prepregs made from both virgin and recycled carbon fibers were fabricated via a hand lay-up process and manually stacked to produce unidirectional laminates. Longitudinal tension tests, longitudinal compression tests, and interlaminar shear strength (ILSS) tests were performed to assess the fundamental mechanical response of the recycled laminates and quantify the retention of mechanical properties relative to the virgin-reference material. Prior to mechanical testing, all laminates underwent ultrasonic C-scan inspection to assess manufacturing quality. While both laminate types exhibited generally satisfactory quality, the recycled-fiber laminates showed a higher density of defects. The recycled laminates preserved around 80% of their original tensile strength and maintained an essentially unchanged elastic modulus. Compressive strength was more susceptible to imperfections introduced during remanufacturing, with the recycled laminates exhibiting roughly a 14% decrease compared with the virgin material. On the contrary, the compressive modulus was largely retained. The most substantial reduction occurred in ILSS, which dropped by 58%. Overall, the results demonstrate that plasma-assisted solvolysis enables the recovery of carbon fibers suitable for remanufacturing CFRP laminates, while the observed reduction in mechanical properties of recycled CFRPs is mainly attributed to defects in manufacturing quality rather than to intrinsic degradation of the recycled carbon fibers.

This work studies the analysis of the resistant capacity of cable nets for the stabilization of slopes. Two tests have been carried out, one with a distributed longitudinal load and the other with distributed transversal load, in order to simulate in situ the working conditions of these systems. Tensile tests were also carried out on the cable elements of the network in order to obtain the non-linear mechanical properties. On the one hand, the proposed numerical procedure uses the finite element method (FEM) and it takes into account the material and geometrical non-linearities due to the geometrical change in the cable net substructure. On the other hand, the contour (boundary) beam is modelled by linear beam elements with contact between them. The numerical results of the longitudinal and cross tests were simulated for different geometrical configurations, generating convergent results with respect to strain and resistance, which permit the extrapolation from tested cable nets to untested simulated cable nets, maintaining a basic configuration of constant parameters. The laboratory tests only provide information about the strain and maximum resistance, but they do not establish a relationship between the values of stresses of each net element. These data have been obtained through the computational simulation by FEM. A reliable model of the interaction of the flexible contour beam with the cable network enables the achievement of more efficient solutions in the design analysis. Finally, we compare the structural behaviour of the numerical and experimental results by means of the equivalent elastic modulus and the equivalent Poisson ratio. Excellent agreement between the predicted results by FEM and test observations was found. Besides, conclusions and suggested procedures of calculation applied on the cable networks are given and numerical models to evaluate the stability of the slope protection systems are presented.

Authors have made a study of the effect of the thicker plates urged by the need to solve the following constructional problem of 45, 000 DWT ore and oil carrier which our yard is planning of build.The construction of this ship as it is shown in the Fig. 1-Midship section, there is a large opening in the centre of upper deck. In this case, in way of supporting upper deck sectional area, there arose a question whether we shall adopt the doubling system which is usually applied to ore carrier, or boldly do away with the doubling plate and use extra thick plate instead. To be more in detail, if (a) two lines of doubling plates were passed on one side the plate thickness of upper deck would be sufficient by being 38 mm, but if (b) the doubling plates were limited to a single line then the thickness of plates requires to be 40mm and in case of (c) no doubler the thickness must be 47 mm.In consideration of the work in the spot, the compensation by the doubling involves a diffecult job. On the other hand, in consideration of the quality of steel and its weldability it seems more undesirable as the thickness of the steel plates become larger. As far as the thickness of the plates is concerned, there is not much difference in the effect 'between 38mm and 40 mm, so our consideration of the problem was focussed to whick should we choose, (b) or (c).The steel to be used for the purpose which came to our mind was C class steel of AB Rule, but when the thickness of steel becomes so large it is questionable whether we many obtain a suitable material that comes within the specifications of C class steel and a satisfactory joinability of the same time. So with a view to find out which possesses better joinability and the weldability for service, we made the following tests in order to make a comparative study between (b) and (c).1. Tension Test in room temperature.2. Standard V-Charpy Impact Test in the range of temperature -40°C to +60°C.3. Longitudinal Bead Bending Test (Kommerell Test) in the rang of temperature -60°C to +40°C.From these tests we could reach to the following conclusions.(1) According to the static tension test of both plates, of cf .Fig. 4, the normalizing will increase both yield strength and elongation, but gives hardly any effect to the tensile strength. (cf Fig. 5)(2) In the V-Charpy test, cf Fig. 6, the normalizing will lower 40 ft-1b transition temperature of the steel of both plates, but there was not hardly notceable of the effect to 15 ft-1b transition temperature. (cf Fig. 9) Generally 47mm thick plates, in comparison with 40mm thick plates, the notch sensitivity is somewhat larger, but the impact value in low temperature was sufficiently large when normalized. (cf Table 3 and Figs 7-13)(3) In the Kommerell test, cf Figs 14 and 27, both plates showed much larger bending angle than what is required under Austrian Welding Standard (cf Fig. 27). (cf Fig. 28). When low hydrogen electrode was used, the toughness of the weldments was very high, and even when the other types of electrode were used, if weldment was preheated it regained its toughness very noticeably. (cf Figs. 22-26)

Inhomogeneous microstructure and properties along the thickness of stir zone in friction stir welded SAF 2507 super duplex stainless steel joint

The evaluation of the mechanical properties of weld metals in structural steels is one of the most important factors of weld quality control. Improvements in methods of tensile strength assessment could facilitate the choice and development of suitable filler materials. For low-alloyed ferritic steel weld metals, the mechanical properties depend strongly on the cooling rate of the weld. Since the formation of ferrite and bainite is diffusion controlled, the solid state phase transformation temperatures are also influenced by the cooling rate. In this paper, experimental analyses of the mechanical properties of welded joints in high-strength structural steels are made taking into account the phase transformation temperature of the weld metal. Therefore, joint welds of quenched and tempered and TMCP high-strength structural steels in the yield strength range between 690 and 1100 MPa were carried out using the gas metal arc welding process. Within the welding setup a pyrometer was used to acquire the cooling curve of the weld metal surface. This allowed to apply the single-sensor DTA method for the determination of phase transformation temperatures. A comparison with longitudinal tensile test results showed that a correlation between tensile strength and phase transformation start temperature exists for the welded joints under investigation. Even for yield strength and notch impact toughness, a relationship could be observed. For a reduced phase transformation temperature, higher yield strength and impact toughness were found.

The Tsai‐Wu Quadratic Failure Criterion provides satisfactory strength predictions for fiber‐reinforced composite materials but requires five experimental tests to determine the strength parameters. This paper presents two modifications of this criterion, which employ micromechanics to determine these parameters. Experiments on uniaxial and multiaxial vinyl ester/fiberglass composite laminates show that the first modified failure criterion, which is based solely on fiber and resin properties, predicts strength within an average absolute error of 25.4% in comparison to the experimentally determined strength. The addition of a single longitudinal tensile test to the modified expression (second modified failure criterion) reduces the average absolute error to 15.9%. This compares well with the Tsai‐Wu Failure Criterion, which gives an average absolute error of 9.4%. The proposed modified criteria are shown to provide satisfactory failure predictions, while greatly reducing the amount of testing required.

In this report, we undertook studies of the viscoelastic properties of wood from the viewpoint of the fine structure and properties of the constituent materials in the wood cell wall. To measure the mechanical properties of the wood as the behavior of the cell wall, it is required to perform the longitudinal tensile test using a homogeneous specimen. In this study, microtomed specimens of sugi (Cryptomeria japonica D.Don) earlywood were used for the creep test, which were conducted at the fiber saturation point. The substantial creep compliance of the cell wall was simulated using a simplified viscoelastic model consisting of a Voigt element and an independent spring in series. Based on the experimental results, the values of the parameters were optimized. The results were as follows: (1) the longitudinal tensile creep deformation tends to increase with the elapsed time, similar to the bending creep behavior; (2) the magnitude of the longitudinal creep function increases with MFA; and (3) each parameter in the simplified viscoelastic model is markedly affected by the MFA. Based on these results, the mechanism of the longitudinal tensile creep deformation of wood is discussed.

Two 617-type filler metals with different Carbon and Boron contents were used to deposit TIG all-weld metal. Longitudinal Varestraint testing was utilized to evaluate and compare their weld metal cracking susceptibility. Hardness, tensile, and impact toughness testing were conducted on the all-weld metal samples, and light optical microscopy as well as scanning electron microscopy, equipped with energy dispersive spectroscopy were adopted for the microstructural inspection of the Varestraint tested samples. Computational thermodynamics supported in calculating the solidification interval and predicting the phases formed. Results showed that the modified Alloy 617 (617mod.) with higher Boron and lower Carbon content is the preferred filler metal, because it showed lower hot cracking susceptibility than the regular version of Alloy 617. In addition, the impact toughness of the modified Alloy 617 was almost three times higher than for Alloy 617 but showed lower tensile strength. In terms of microstructure, the modified Alloy 617 disclosed less precipitates along the cracks than the regular Alloy 617. These observations were supported by computational thermodynamic calculations.