Dynamic Testing Machine Research Articles

動的三点曲げ試験によるアクリル樹脂発泡フィルムの荷重緩和の評価

In this research, impact reduction effect of acrylic foam film was clarified by using dynamic three-point bending testing machine. The specimens were an aluminum alloy (JIS A6063) beams with an acrylic foam films on surfaces of the beams. The acrylic foam film had thickness of 700 μm and density of 0.5 mg/mm3 on a polyethylene terephthalate substrate film with a thickness of 38 μm. The aluminum alloy beam had thickness of 3, 6 and 10 mm. The input and output bars in the three-point bending testing machine were made of aluminum alloy (JIS A7075-T6). The bars were 2 m in length and 12 mm in diameter. The striker made of polycarbonate was 200 mm in length and 12 mm in diameter. Impact load was applied to the input bar by colliding the striker. Impact load and reaction load were calculated from strain histories of the input and output bars due to one-dimensional elasto-dynamic theory. Histories of the impact loads for the specimens with the acrylic foam film were lower than the one for the specimens without the acrylic foam film. The maximum impact loads for the specimens 10 mm in thickness with the acrylic foam film was 20% smaller than the one for the specimens without the film. The acrylic foam films were found to be effective to the impact load reduction for higher stiffness of a structure.

Mechanical behaviour of a granular solid and its contacting deformable structure under uni-axial compression – Part I: Joint DEM–FEM modelling and experimental validation

This paper proposes an exquisite confined compression experiment to validate a recently developed numerical method (Joint DEM–FEM approach). A uni-axial compression apparatus was designed to investigate the mechanical behaviour of a granular solid under vertical loading and the load transmission to the containing wall. This tester consists of an instrumented thin-walled circular cylinder, two platens, a commercial dynamic material test machine (MTS 810), a bottom load cell and twelve bi-axial strain gage rosettes. Experiments were conducted on polystyrene beads. The delicately-designed confined compression test provides abundant experimental data for proving the validity of the proposed modelling technique.The corresponding simulations were performed by the developed numerical approach with the linking of discrete element method (DEM) and finite element method (FEM). To attain a high level of quantitative validation, the important particle properties required for DEM simulation were not simply assumed but measured directly in laboratory tests. Characteristics of the compression system, such as load–displacement response, force transmission to boundary surfaces, lateral pressure ratio, bulk wall friction, and stress distribution in the cylindrical wall, were evaluated. A comparison between the numerical and experimental results was made and discussed in this paper. The majority of compared physical quantities show reasonable to good agreement, thus giving a convincingly quantitative validation for the developed Joint DEM–FEM modelling technique. This proposed linking methodology is shown to give plausible results and can be used as a first step to solve the particulate solid–structure interaction problems.

THE TESTS AND FAILURE CRITERIA OF FULL LIGHTWEIGHT SHALE CERAMSITE CONCRETE UNDER TRUE TRIAXIAL COMPRESSION

The experiments of full lightweight shale ceramsite concrete LC30 were carried out under true a triaxial compressive state in proportional loading by the large-scale static and dynamic triaxial testing machine in Dalian University of Technology. The failure modes of samples were observed, and the ultimate triaxial strength, plastic strains, peak strains, total strains, and stress-strain curves were also recorded. The results show that the strength and deformation of full lightweight shale ceramsite concrete under triaxial compression are much larger than that of uniaxial ones, there is a very apparent ‘Platform of Plastic Flow (PoPF)’ on a stress-strain curve, and also present four failure modes as normal concrete, thusly the stress and the strain corresponding to PoPF should be design strength and strain during an engineering design for lightweight aggregate concrete. Also, the effects of intermediate principal stress on strength and deformation are analyzed under triaxial compression, the ultimate stresses were predicted by triaxial strength model, and the absolute values of relative errors are all less than 6%, which proves the test results are accurate and reliable. Finally, the failure criteria of stress and strain are established based on an octahedral stress-strain space respectively. The relevance of test points and curves are better to the former; the tension-compression meridians intersects the hydrostatic pressure axis in high-pressure stress area; and the failure surface is closed; although the latter is worse than the former, which can reflect effectively the outward expansion trend for the failure surface, the characteristics of meridians are smooth and convexity.

Fatigue resistance of denture teeth

AimsThere is no standard test to determine the fatigue resistance of denture teeth. With the increasing number of patients with implant-retained dentures the mechanical strength of the denture teeth requires more attention and valid laboratory test set-ups. The purpose of the present study was to determine the fatigue resistance of various denture teeth using a dynamic load testing machine. MethodsFour denture teeth were used: Bonartic II (Candulor), Physiodens (Vita), SR Phonares II (Ivoclar Vivadent) and Trubyte (Dentsply). For dynamic load testing, first upper molars with a similar shape and cusp inclination were selected. The molar teeth were embedded in cylindrical steel molds with denture base material (ProBase, Ivoclar Vivadent). Dynamic fatigue loading was carried out on the mesio-buccal cusp at a 45° angle using dynamic testing machines and 2,000,000 cycles at 2Hz in water (37°C). Three specimens per group and load were submitted to decreasing load levels (at least 4) until all the three specimens no longer showed any failures. All the specimens were evaluated under a stereo microscope (20× magnification). The number of cycles reached before observing a failure, and its dependence on the load and on the material, has been modeled using a parametric survival regression model with a lognormal distribution. This allowed to estimate the fatigue resistance for a given material as the maximal load for which one would observe less than 1% failure after 2,000,000 cycles. ResultsThe failure pattern was similar for all denture teeth, showing a large chipping of the loaded mesio-buccal cusp. In our regression model, there were statistically significant differences among the different materials, with SR Phonares II and Bonartic II showing a higher resistance than Physiodens and Trubyte, the fatigue resistance being estimated at around 110N for the former two, and at about 60N for the latter two materials. ConclusionThe fatigue resistance may be a useful parameter to assess and to compare the clinical risk of chipping and fracture of denture tooth materials.

Morphological Impact on the Fatigue Behaviour of Short Fibre Reinforced Polypropylene

The fatigue behaviour of short fibre reinforced thermoplastics is highly dependent on the morphological conditions. The capability of simulating fatigue behaviour and damage mechanisms of fibre reinforced polypropylene increasingly interests industrial partners of the presented study. For the morphological analysis both destructive and non-destructive methods such as computed Xray tomography and a combination of polishing and microscopic methods were applied. The determination of the composite morphology (fibre distribution, orientation tensor, fibre length distribution) was assisted by several methods of specific automatic data evaluation concepts. Fatigue testing was done on a servohydraulic dynamic testing machine using a testing frequency of 10 Hz, which is in the range of the real loading in application of the components. The analysis included thermal investigations (IR camera) and local strain measurements.

Dynamic Modulus Measurements of Bound Cement-Treated Base Materials

AbstractOne of the most common methods used in road-pavement construction is the stabilizing of the conventional pavement base course layer. This is achieved by adding cement or lime to gain better material performance. However, obtaining modulus input parameters from a cement-stabilized base course layer for pavement-response analysis under real traffic conditions has proven difficult in that, to date, only ambiguous results have been produced. Using the flexural modulus or elastic modulus in the response analysis has certain limitations in embracing real pavement behavior under traffic and temperature conditions. Accordingly, a more reliable modulus input parameter for pavement analysis under traffic (cyclic) loads is required to obtain more precise and reliable outputs. Moreover, there is, at present, no test protocol to determine a suitable modulus for a cement-stabilized base material under the cyclic loading regime. This study aims to examine the real dynamic responses of cement-stabilized base course materials with a view to adapting the asphalt mixture performance tester (AMPT), a specifically designed dynamic modulus test machine used on asphalt concrete material. The AMPT dynamic modulus test has as an advantage in that loading and temperature regimes based on real pavement conditions can be rationally simulated and directly applied to the test samples. As such, the dynamic moduli of a cement-stabilized base course material can be obtained under different temperature and loading rates. Moreover, the effects of the dynamic strain range, cement content, and curing duration on the dynamic responses of a cement-stabilized base course material may also be examined. Cement-stabilized base course materials of 4 %, 5 %, and 6 % cement contents (by mass) were used as the study materials. The findings of this study indicate that curing durations and cement contents significantly influence the dynamic modulus values of cement-stabilized base course materials. However, the dynamic modulus is insignificantly affected by the changes in temperature and loading rates within a specific range of testing conditions in this study. The test results also reveal that cement-stabilized base course materials under examination behave in the manner of an elastic material when subjected to an axial compressive deformation of 45–105 μstrains. This is because of the dynamic modulus having no impact upon changes in the dynamic strain ranges or on the magnitudes of cyclic loads. Moreover, the dynamic moduli from this study were found to be much higher than the elastic moduli suggested by previous studies. However, the flexural moduli, which are derived from standard flexural tests, demonstrated close values to those of the dynamic moduli obtained in this study. In the study, the dynamic modulus of cement-stabilized base course materials, derived from the dynamic modulus using AMPT, could more reasonably embrace the dynamic responses of a material under traffic-loading conditions. This leads to a somewhat more reliable modulus input for the cement-stabilized base course materials used in a rational pavement design and analysis method.

Biomechanical Analysis of an Arthroscopic Broström Ankle Ligament Repair and a Suture Anchor-Augmented Repair.

Secondary surgical repair of ankle ligaments is often indicated in cases of chronic lateral ankle instability. Recently, arthroscopic Broström techniques have been described, but biomechanical information is limited. The purpose of the present study was to analyze the biomechanical properties of an arthroscopic Broström repair and augmented repair with a proximally placed suture anchor. It was hypothesized that the arthroscopic Broström repairs would compare favorably to open techniques and that augmentation would increase the mean repair strength at time zero. Twenty (10 matched pairs) fresh-frozen foot and ankle cadaveric specimens were obtained. After sectioning of the lateral ankle ligaments, an arthroscopic Broström procedure was performed on each ankle using two 3.0-mm suture anchors with #0 braided polyethylene/polyester multifilament sutures. One specimen from each pair was augmented with a 2.9-mm suture anchor placed 3 cm proximal to the inferior tip of the lateral malleolus. Repairs were isolated and positioned in 20 degrees of inversion and 10 degrees of plantarflexion and loaded to failure using a dynamic tensile testing machine. Maximum load (N), stiffness (N/mm), and displacement at maximum load (mm) were recorded. There were no significant differences between standard arthroscopic repairs and the augmented repairs for mean maximum load and stiffness (154.4 ± 60.3 N, 9.8 ± 2.6 N/mm vs 194.2 ± 157.7 N, 10.5 ± 4.7 N/mm, P = .222, P = .685). Repair augmentation did not confer a significantly higher mean strength or stiffness at time zero. Mean strength and stiffness for the arthroscopic Broström repair compared favorably with previous similarly tested open repair and reconstruction methods, validating the clinical feasibility of an arthroscopic repair. However, augmentation with an additional proximal suture anchor did not significantly strengthen the repair.

Moisture sorption in polyamide 6.6: Experimental investigation and comparison to four physical-based models

Water sorption in polyamide 6.6 has been characterized for a wide range of temperature (25°C to 80°C) and various water activities using a Dynamic Vapor Sorption testing machine. Complex sorption mechanisms govern the water uptake in the material. The competition between two main temperature dependant mechanisms has been observed: a Henry's sorption mechanism that mainly governs the sorption curve at low water activities, and a second mechanism at high water activities that could be related to the formation of water clusters. It is observed that the temperature dependency can mainly be attributed to the Henry's contribution. Four physically based models are then used and identified thanks to the extended experimental database. It is shown that a simple Flory-Huggins model is not able to capture the experimental observations at very high water activities for all the temperatures tested. The ENSIC model is a better choice, but good prediction for very high water activity cannot be obtained. Both modified Park and GAB models can accurately predict the volume fraction of water for the whole ranges of water activity and temperature, although the modified Park model should be preferred considering the number of parameters and the mathematical simplicity.

Microstructure, transformation behavior and mechanical properties of a (Ti50Ni38Cu12)93Nb7 alloy

A (Ti50Ni38Cu12)93Nb7 alloy is fabricated by arc melting, forging and drawing. The microstructure, transformation behavior and mechanical properties were investigated by means of scanning electron microscope (SEM), differential scanning calorimeter (DSC), dynamic mechanical analyzer (DMA) and tensile test machine. SEM observation showed that the as cast alloy is composed of TiNiCu and Nb-rich phases. After drawing, the alloy showed single step transformations during heating and cooling within the whole annealing temperature range from 400°C to 800°C. With the increase of the annealing temperature, both the transformation temperatures and the damping capacity increased first and then decreased. The ultimate strength of the alloy after annealing at 400°C is over 1500MPa and the maximum elongation of the alloy after annealing at 800°C is more than 20%.

OS1004-478 動的曲げ試験によるアクリル樹脂発泡フィルムの荷重低減の評価

In this research, impact reduction effect of acrylic foam film was clarified by using dynamic three-point bending testing machine. The specimens were an aluminum alloy (JIS A6063) beams with an acrylic foam films on surfaces of the beams. The acrylic foam film had thickness of 700 μm and density of 0.5 mg/mm^3 on a polyethylene terephthalate substrate film with a thickness of 38 μm. The aluminum alloy beam had thickness of 3, 6 and 10 mm. The input and output bars in the three-point bending testing machine were made of aluminum alloy (JIS A7075-T6). The bars were 2 m in length and 12 mm in diameter. The striker made of polycarbonate was 200 mm in length and 12 mm in diameter. Impact load was applied to the input bar by colliding the striker. Impact load and reaction load were calculated from strain histories of the input and output bars due to one-dimensional elasto-dynamic theory. Histories of the impact loads for the specimens with the acrylic foam film were lower than the one for the specimens without the acrylic foam film. The maximum impact loads for the specimens 10 mm in thickness with the acrylic foam film was 20% smaller than the one for the specimens without the film. The acrylic foam films were found to be effective to the impact load reduction for higher stiffness of a structure.

Simulation Method Based on the Stress Circle for the Moment Output of Car Wheel Dynamic Bending Fatigue Testing Machine

Simulation Method Based on the Stress Circle for the Moment Output of Car Wheel Dynamic Bending Fatigue Testing Machine

The influence of momentary retention forces on patient satisfaction and quality of life of two-implant-retained mandibular overdenture wearers.

The purpose of this study was to assess the influence of momentary retention forces on patient satisfaction and quality of life of two-implant-retained mandibular overdenture wearers. Edentulous patients who had been rehabilitated with two-implant-supported mandibular overdentures with single attachments and maxillary complete dentures at a university clinic were included in this study. The overdenture attachments were either ball or locator attachments. All the patients completed the Turkish version of the Oral Health Impact Profile-14 (OHIP-14) and the visual analog scale (VAS) satisfaction questionnaires. Momentary retention forces of the overdentures were measured using a custom-made dynamic testing machine. Fifty-five patients were included in this study. No statistically significant association was detected between momentary retention forces and VAS scores (P > .05), but higher retention forces presented significantly better quality of life scores in the social disability and handicap domains of OHIP-14 (P < .05). Within the limitations of this clinical study, it may be presumed that although higher instant retention force of an implant-retained overdenture provides better quality of life, it does not affect patient satisfaction.

Structural Properties of the Native Ligamentum Teres.

Background:A majority of studies investigating the role of the ligamentum teres (LT) have focused primarily on anatomical and histological descriptions. To date, however, the structural properties of the LT have yet to be fully elucidated.Purpose:To investigate the structural properties of the native LT in a human cadaveric model.Study Design:Descriptive laboratory study.Methods:A total of 12 human cadaveric hemipelvises (mean age, 53.6 years; range, 34-63 years) were dissected free of all extra-articular soft tissues to isolate the LT and its acetabular and femoral attachments. A dynamic tensile testing machine distracted each femur in line with the fibers of the LT at a displacement-controlled rate of 0.5 mm/s. The anatomic dimensions, structural properties, and modes of failure were recorded.Results:The LT achieved a mean yield load of 75 N and ultimate failure load of 204 N. The LT had mean lengths of 38.0 and 53.0 mm at its yield and failure points, respectively. The most common (75% of specimens) mechanism of failure was tearing at the fovea capitis. On average, the LT had a linear stiffness of 16 N/mm and elastic modulus of 9.24 MPa. The mean initial length and cross-sectional area were 32 mm and 59 mm2, respectively.Conclusion:The human LT had a mean ultimate failure load of 204 N. Therefore, the results of this investigation, combined with recent biomechanical and outcomes studies, suggest that special consideration should be given to preserving the structural and corresponding biomechanical integrity of the LT during surgical intervention.Clinical Relevance:The LT may be more important as a static stabilizer of the hip joint than previously recognized. Further studies are recommended to investigate the appropriate indications to perform surgical repair or reconstruction of the LT for preservation of hip stability and function.

Development of Dynamic Load Strength Test Machine Based on Automotive BIW

The dynamic load strength test of automotive BIW is an important parameter for vehicle passive safety, but different test standards, different test requirements, which caused much trouble to the test authority. To solve the shortcomings of the traditional machines, such as low automation, poor universality and weak ability of data processing, this paper designs a new test machine for the dynamic load strength trials of automotive BIW on the basis of three typical standards. The test results indicated that this test machine embodies the characteristic of easy operation, stable function, and wide suitability, which improves the measurement accuracy and efficiency, at the same time, solves the problem of the database construction.

Consequences of Tibial Tunnel Reaming on the Meniscal Roots During Cruciate Ligament Reconstruction in a Cadaveric Model, Part 1

Background: The current standard for treating complete tears of the anterior cruciate ligament (ACL) is reconstruction, which requires reaming a tibial tunnel. Based on recent anatomic and biomechanical studies, this reconstruction tunnel may cause injuries to the anterior meniscal root attachments. Purpose/Hypothesis: The purpose was to determine if injuries occurred to the anteromedial (AM) and anterolateral (AL) meniscal root attachments because of reaming a tibial reconstruction tunnel in the anatomic center of the ACL footprint. It was hypothesized that tibial tunnel reaming for ACL reconstruction would result in significant decreases in the attachment area and in ultimate failure strength for the AL root. Study Design: Controlled laboratory study. Methods: Twelve matched pairs of human cadaveric knees were tested. One knee from each pair remained intact, while the contralateral knee was reamed with a tibial tunnel for an anatomic ACL reconstruction. The attachment areas of the anterior meniscal roots were measured with a coordinate measuring device before and after tunnel reaming. The anterior meniscal roots were then pulled to failure with a dynamic tensile testing machine. Results: There was a significant mean decrease in the attachment area for the AL root (%Δ, 38%; 95% CI, 25-51) after ACL tunnel reaming compared with the intact state (P = .003). The mean ultimate failure strength of the native AL root (mean, 610 N; 95% CI, 470-751) was significantly stronger (P = .015) than that of the AL root with a reamed ACL reconstruction tunnel (mean, 506 N; 95% CI, 353-659). Tunnel reaming did not significantly affect the AM root attachment area or ultimate failure strength. Conclusion: Tibial tunnel reaming during anatomic single-bundle ACL reconstruction significantly decreased the AL meniscal root attachment area and ultimate failure strength. The AM root was not significantly affected by reaming of the ACL reconstruction tunnel. Future studies should investigate the clinical importance of these iatrogenic injuries to the AL root. Clinical Relevance: The ACL reconstruction tunnels reamed in the center of the ACL tibial footprint caused a significant decrease in the attachment area and ultimate strength of the AL meniscal root attachment. Clinically, repositioning guide pins placed in the lateral aspect of the ACL attachment before tibial tunnel reaming may minimize iatrogenic injuries to the AL meniscal root attachment.

Consequences of Tibial Tunnel Reaming on the Meniscal Roots During Cruciate Ligament Reconstruction in a Cadaveric Model, Part 2

Background: Recent emphasis has turned to reconstructing the posterior cruciate ligament (PCL) after injury. However, single-bundle PCL reconstruction of the anterolateral bundle may potentially injure the posterior meniscal roots. Purpose/Hypothesis: The purpose of this study was to determine if posterior meniscal root injuries occurred because of tunnel reaming for single-bundle PCL reconstruction. It was hypothesized that tibial tunnel reaming within the anterolateral bundle footprint during PCL reconstruction would result in clinically significant decreases in posteromedial (PM) root attachment areas and in ultimate failure strength for the PM root. Study Design: Controlled laboratory study. Methods: Testing was performed on 12 matched pairs of human cadaveric knees. For each pair of knees, one knee was left intact, while the contralateral knee was prepared with a tibial tunnel placed 5 mm anterior to the center of the tibial PCL attachment and within the previously described footprint of the anterolateral bundle of the PCL for single-bundle PCL reconstruction. The attachment areas of the posterior meniscal roots were measured with a coordinate measuring device before and after PCL tunnel reaming. The posterior meniscal roots were then pulled to failure with a dynamic tensile testing machine. Results: There was a significant mean decrease in the attachment area of the PM root (%Δ, 28%; 95% CI, 16-40) after PCL tunnel reaming compared with the intact state (P = .005). The mean ultimate failure strength of the native PM root (mean, 440 N; 95% CI, 347-534) was also significantly stronger (mean, 40%; 95% CI, 18-61; P = .005) than that of the PM root after PCL tunnel reaming (mean, 243 N; 95% CI, 176-309). No changes were found for the posterolateral (PL) root after PCL tunnel reaming. Conclusion: Tibial tunnel reaming for single-bundle PCL reconstruction in the anterolateral bundle footprint significantly reduced the ultimate failure strength and attachment area of the PM meniscal root. The attachment area and ultimate failure strength of the PL root were unaffected by tunnel reaming. Clinical Relevance: Tibial tunnels reamed in the footprint of the anterolateral bundle during single-bundle PCL reconstruction can cause iatrogenic damage to the PM meniscal root attachment. Thus, tibial tunnels should strive to be reamed in the center of the entire tibial PCL attachment site during PCL reconstruction.

Gamma Titanium Aluminides Behavior at High Temperature Static Short-Term Stress

Today conventional titanium-based alloys represent one third of the weight of modern aircraft engines and, are the second most used engine material following Ni-based superalloys. [1] Titanium aluminide alloys based on intermetallic phases γ (TiAl) and α2 (Ti3Al) and the most recent – orthorhombic titanium aluminide, are widely recognized as having the potential to meet the design requirements for high temperature applications. The outstanding thermo-physical and mechanical properties of these materials rely mainly on the strongly ordered nature and the directional bonding of the compounds. These involve: high melting point, above 1460°C, low density of 3,9-5 g/cm3, according the alloying degree, high elastic modulus (high stiffness), high yield strength and good creep resistance at high temperature, low diffusion coefficient, good structural stability at high temperature. The main objective of our paper are focussed on the short-term mechanical properties if Titanium niobium aluminide at 850°C. High temperatures mechanical properties evaluation was performed by tensile testing at temperature of 850°C on universal static and dynamic testing machine Instron 8802, equipped with high temperature system, for maximum 1000°C, and extensometer with a measuring basis of 40 mm. The mechanical tensile test was performed according the ASTM E8, with control of deformation and a testing rate of 10-4 mmsec.-1. Short-term behavior request of the support uncovered alloys, at 850°C has proved to be modest and it seems obvious that the alloys based on titanium aluminides cannot be used without protective coatings. Key words: titanium aluminides, high temperatures, mechanical properties

Characterization of clearcoats containing phosphoric acid-functionalized acrylic polyols for automotive precoated metal sheet coatings

In this study, the various physical and mechan- ical properties of clearcoats prepared through a new crosslinking method were investigated. The method was aimed at developing clearcoat systems to improve the deep-draw processing and formability performance in precoated metal (PCM) sheets for automotive applica- tions. From phosphoric acid-functionalized acrylic poly- ols (PAFAPs) first synthesized in this study and glycidyl methacrylate-modified acrylic copolymer (GMAMAC), phosphoric acid-GMA modified acrylic polyols (PAGMAPs) were newly prepared as new binders in automotive clearcoats. Several clearcoats were formu- lated with different molecular weights and hydroxyl contents from PAFAPs and GMAMAC. Using clear- coats themselves, the crosslinking reactions for these clearcoats were compared by evaluating the curing behaviors with a rigid-body pendulum test (RPT) and the changes of chemical structures via attenuated total reflectance FTIR spectroscopy. The mechanical proper- ties of the clearcoats were systematically characterized, using dynamic mechanical analysis (DMA) and universal testing machine analysis (UTM). Also, various tests were carried out using PCM sheets by depositing clearcoats above the same PCM-based primers and basecoat layers on galvanized steel. The fracture and deformation patterns related to surface damages on the clearcoat surface were visualized using a nano-scratch test, in association with atomic force microscopy. In particular, deep-draw processing tests, based on forming process simulations, were employed to scrutinize the effect of clearcoats developed in this study on the forming feature in PCM sheets. From the results of RPT, DMA, and UTM tests, the primary crosslinking networks of PAGMAPs from the synthesized PAFAPs and GMAMAC, and also succeeding secondary crosslinking networks between PAGMAPs and blocked isocyanates, were closely corre- lated with the degree of crosslinking (Xc), in accordance with the molecular weight between crosslinks (Mc), and glass transition temperature (Tg). As a result, the presented clearcoats with a long pendulum period, a low rubbery modulus, and a large tensile strain value, which are the significant factors for developing automo- tive PCM sheet technology, have truly demonstrated more superior formability during the deep-draw process. It is confirmed that properties of clearcoats with tough- ness and flexibility could be optimally controlled by PAGMAPs for automotive coatings.

Nitrile functionalized benzoxazine/bismaleimide blends and their glass cloth reinforced laminates

ABSTRACTA novel high‐performance resin blend composed of nitrile functionalized benzoxazine (CNBZ) and bismaleimide (4,4′‐bismaleimidodiphenyl methane) (BMI) was prepared via solvent method. Its curing behaviors, thermal properties, and mechanical properties were studied by differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and universal testing machine, respectively. The results showed that the addition reaction between phenolic hydroxyl group and the double bond occurred except for the homopolymerization of CNBZ and BMI. When BMI content was more than 40%, the cured CNBZ/BMI blends exhibited higher glass transition temperatures (Tgs) than CNBZ and BMI homopolymers, which reached up to 334°C. Meanwhile, when BMI content was 40%, the tensile strength, flexural strength, and shearing strength reached up to 69, 235, and 12.9 MPa, respectively, which exhibited the comparable mechanical properties with BT resin. Furthermore, the glass cloth (GF) reinforced laminates based on these blends were prepared. The results showed that when BMI content was 40%, their tensile strength, flexural strength, and impact strength reached up to 334 MPa, 593 MPa, and 145 KJ m−2, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41072.

Dynamic multiaxial strength and failure criterion of dam concrete

Dynamic multiaxial strength experiments on both dam and wet-screened concretes were carried out by using a large static and dynamic triaxial electro-hydraulic servo testing machine. The dynamic strength under uniaxial compression (C), uniaxial tension (T), biaxial compression–compression (C–C), biaxial compression–tension (C–T), triaxial compression–compression–tension (C–C–T) and triaxial compression–compression–compression (C–C–C) are presented in the paper. The influence of strain rate (ranging from 10−5/s to 10−2/s) and stress ratio on the failure modes and dynamic strength of dam and wet-screened concretes is analyzed. It is found that the failure modes of both dam and wet-screened concretes were mainly dependent on the stress ratio, but independent of the strain rate. The ultimate strengths of dam and wet-screened concretes are found to increase with the increase of strain rate. Particularly, the dynamic increasing factor (DIF) increases obviously when the tensile stress is included. It is noted that the maximum DIF existed in the triaxial C–C–T stress state and the minimum DIF corresponded to the triaxial C–C–C state. The octahedral normal and shear stresses are increased but the similar angle is kept constant with the increase of strain rate in the octahedral stress space. The dynamic failure criterion is developed after analyzing the effect of octahedral normal stress and similar angle on the dynamic strength.