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The interfacial shear strength (IFSS) of a specific carbon fiber/epoxy composite (T650/Cycom 5320-1) was investigated to determine how changes in post cure temperature affects the fiber/matrix adhesion. The degree of cure of the Cycom resin cured with the same post cure temperatures was also determined using a DSC technique. The mechanical and viscoelastic properties of the samples made from Cycom 5320-1 resin were also measured and related to the degree of cure. It was shown that the mechanical and viscoelastic properties changed as the curing temperature, and hence the degree of cure, increased. The results of the micro-droplet tests showed the interfacial adhesion increased with increasing the post cure temperature. This was attributed to the higher degree of cure and change in mechanical and viscoelastic properties of the resin, as well as the residual stresses as the post cure temperature increased.

Several oleo-based pressure-sensitive adhesives (PSA) were studied as substitutes for current petroleum-based PSAs; however, PSAs derived from plant oils present challenges, such as relatively low biobased contents (20–90%) and complex processes (i.e., purifying, emulsifying, and drying steps). This paper demonstrates the possibility of transparent PSAs from neat acrylated epoxidized soybean oil (AESO) via fast and simple UV free-radical polymerization with 97–100% biobased contents. In this study, we controlled the degree of free radical polymerization by modulating the amount of UV irradiation to obtain a balanced cohesion and adhesion strength for PSA applications. This AESO PSA tape on a polyester film carrier had better peel and significantly higher shear strength on glass surfaces compared with a commercial reusable tape (Post-it®, 3M, St. Paul, MN, USA). The adhesion of the AESO PSA corresponded to its dynamic rheological properties. In addition, the adhesion/cohesion behavior of the PSAs was chara...

In situ synchrotron imaging and diffraction on beamline 1-ID-C at the Advanced Photon Source (APS) has been used to investigate the internal features present during the stable tearing fracture phenomenon in low-constraint metallic specimens. The results that are obtained from this investigation show that the internal features are identifiable with these techniques, and this initial investigation lays the groundwork for future, more in-depth investigations with some improvements to the methods.

Tubular structures play an important role in energy absorbing components and structural members requiring high strength-to-weight ratio. The theory of buckling of circular, square and rectangular tubes is relatively well established in the literature. The study of buckling of triangular tubes, however, has received much less attention. In this paper, an analytical solution for the elastic buckling of isosceles triangular tubes was obtained by considering the buckling characteristics of individual walls of the triangular tube with appropriate edge conditions. The results from this analytical solution were compared with previously published work in the literature and finite element simulations. The comparison revealed good agreement between these results.

Objective: To (1) compare the effect of a collateral ligament sparing surgical approach with an open surgical approach on mechanical properties of proximal interphalangeal joint (PIPJ) arthrodesis, and (2) to determine the percentage of articular cartilage surface removed by transarticular (TA) drilling with different diameter drill bits. Study Design: Randomized paired limb design. Sample Population: Cadaveric equine limbs (n=76). Methods: Cadaveric PIPJ were drilled using a 3.5, 4.5, or 5.5 mm drill bit at 80–84° to the dorsal plane to remove articular cartilage and subchondral bone from the distal articular surface of the proximal phalanx (P1) and the proximal articular surface of the middle phalanx (P2). Bone ends were photographed and the percentage of the projected surface area that was denuded of cartilage was measured. PIPJ arthrodesis constructs (3-hole dynamic compression plate [DCP], two 5.5 mm TA screws inserted in lag fashion, medial and lateral to the DCP; DCP-TA) were created using 2 surgical approaches in paired limbs. A conventional open approach was used in 1 limb and a collateral ligament sparing approach used in the other limb. Constructs were tested to failure in single-cycle 3-point dorsopalmar/plantar or lateromedial bending. Maximum load, yield load, and composite stiffness were compared between techniques. Results: The 3.5, 4.5, and 5.5 mm drill bits removed 24±4%, 35±5%, and 45±7% of total PIPJ articular cartilage surface, respectively. Constructs with the collateral ligament sparing approach had significantly greater mean yield load (11.3±2.8 versus 7.68±1.1 kN, P=.008) and mean maximum load (13.5±3.1 versus 10.1±1.94 kN, P=.02) under lateromedial bending. Under dorsopalmar/plantar bending there was no significant difference between surgical approaches. The collateral ligament sparing arthrodesis technique had a shorter surgical time (19±3 minutes) compared with the open technique (31±3 minutes). Conclusion: A collateral ligament sparing surgical approach to the PIPJ with removal of articular cartilage by TA drilling and arthrodesis by DCP-TA was faster and stronger in mediolateral bending than arthrodesis constructs created with an open surgical approach. Clinical Relevance: Preservation of the collateral ligaments and TA drilling for cartilage removal during PIPJ arthrodesis may be a superior approach to the conventional open approach and warrants clinical evaluation.

The crack tip opening angle (CTOA) fracture criterion is one of the most promising fracture criterion used to characterise the stable tearing process in metallic materials. Traditional methods used for the experimental characterisation of the CTOA involve accurate identification of the crack tip at each tearing event. Recently alternative methods have been proposed that reduce the necessity of accurately defining the current crack and rely more on the shape of the crack flanks to define the CTOA. In addition, these methods define an ‘apparent crack tip’, which may be different from the actual surface crack tip and may provide insight into the amount of crack-front tunnelling that is occurring. In the current research, compact tension specimens fabricated from 6.35 mm thick 2024-T351 aluminium alloy plate were evaluated to investigate different CTOA measurement methods and their potential for estimating crack-front tunnelling. In addition to characterizing the CTOA, fatigue marker bands were employed to map the evolution of crack-front tunnelling. The experimental critical CTOA values obtained from the alternative methods were noticeably lower than that obtained from the traditional approach and showed noticeably more scatter. When compared to the experimentally obtained marker bands, the alternative methods indicated limited potential for predicting crack-front tunnelling.

The fruit fly Drosophila melanogaster is a model system for studying pathways regulating responses to cocaine. We describe a new method for delivering cocaine to Drosophila. Freebase cocaine dissolved in ethanol is sprayed onto cold-anaesthetized flies using a graphic arts airbrush modified to reproducibly control the drug dosage. Cocaine dose response curves were generated to characterize the behavioral responses of flies using the airbrush method or the established cocaine smoke method of drug delivery. The stereotypic responses observed with the airbrush showed a dose-dependent increase and were qualitatively similar to those elicited by cocaine smoke. The variation in behaviors of flies dosed with the airbrush was smaller than that of the smoke-dosed flies, indicating that the airbrush method gives better reproducibility. Since flies are exposed to alcohol as well as cocaine in the airbrush behavioral paradigm, it was important to control for possible effects of ethanol. Control experiments indicated that none of the stereotypies elicited with cocaine were caused by vehicle alone and very little ethanol remains in the flies following this protocol. The utility of the airbrush method was demonstrated by its use in a pilot genetic screen that identified a cocaine resistant mutant.

Although the crack-tip-opening angle (CTOA) has been shown to be well suited for modeling stable crack growth and instability for thin-sheet aluminum alloys, its behavior for increasing thickness has not been thoroughly evaluated. This paper presents the results of two-dimensional and three-dimensional finite element based fracture analyses that were performed to characterize the critical CTOA for C(T) specimens made of 2024-T351 aluminum alloy with thicknesses of 2.3, 6.35, 12.7, and 25.4 mm. Computed CTOA, based on a center-node release methodology, was generally higher than experimentally determined surface CTOA measurements for the same thicknesses. For the C(T) specimens analyzed in this work, with the crack length and uncracked ligament generally greater than four times the specimen thickness, the generated global constraint factor data fell within those reported for M(T), DE(T), and SE(B) specimen configurations that also satisfy the above mentioned dimensional guideline. Strengthening the observation that, although critical CTOA is dependent on absolute material thickness, the CTOA characterization process is independent of specimen/loading types and specimen dimensions for cases satisfying this dimensional guideline. The CTOA values generated using 3D finite element analyses were used within a 2D finite element analysis framework to estimate plane strain core (PSC) height values for all evaluated thicknesses. The resulting PSC heights increased with increasing specimen thickness and appear to be on the order of specimen thickness.

Although the crack-tip-opening angle (CTOA) has been shown to be well suited for modeling stable crack growth and instability for thin sheet aluminum alloys, its behavior for increasing thickness has not been thoroughly evaluated. To investigate this behavior, fracture tests were performed on specimens made of 2024-T351 aluminum alloy with thicknesses of 2.3, 6.35, 12.7, and 25.4 mm. The surface CTOA exhibited an initially high value followed by a transition to a “constant” value after a short amount of crack extension, with this transition decreasing significantly with increasing specimen thickness. The critical CTOA was shown to decrease with increasing specimen thickness and appears to possibly be approaching a lower limiting value.

Buckling of plates and tubes plays an important role in structural safety and energy absorption. Although buckling of plates and tubes has been studied theoretically and experimentally in the past, the effects of aspect ratio and side constraint on buckling of multi-wall structures and tubes has not been investigated systematically. In this work, finite element simulations have been carried out to investigate the buckling behavior of multi-wall structures and tubes. A series of one- to three-panel walls and square tubes with various aspect ratios were simulated. The critical aspect ratios causing buckling mode transition were obtained and compared with theoretical predictions available in the literature. Effects of wall angle and side constraint on buckling behavior were investigated. The relevance of research findings to honeycomb-like structures was discussed.Copyright © 2011 by ASME

To (1) compare the effect of a collateral ligament sparing surgical approach with an open surgical approach on mechanical properties of proximal interphalangeal joint (PIPJ) arthrodesis, and (2) to determine the percentage of articular cartilage surface removed by transarticular (TA) drilling with different diameter drill bits.Randomized paired limb design.Cadaveric equine limbs (n=76).Cadaveric PIPJ were drilled using a 3.5, 4.5, or 5.5 mm drill bit at 80-84° to the dorsal plane to remove articular cartilage and subchondral bone from the distal articular surface of the proximal phalanx (P1) and the proximal articular surface of the middle phalanx (P2). Bone ends were photographed and the percentage of the projected surface area that was denuded of cartilage was measured. PIPJ arthrodesis constructs (3-hole dynamic compression plate [DCP], two 5.5 mm TA screws inserted in lag fashion, medial and lateral to the DCP; DCP-TA) were created using 2 surgical approaches in paired limbs. A conventional open approach was used in 1 limb and a collateral ligament sparing approach used in the other limb. Constructs were tested to failure in single-cycle 3-point dorsopalmar/plantar or lateromedial bending. Maximum load, yield load, and composite stiffness were compared between techniques.The 3.5, 4.5, and 5.5 mm drill bits removed 24±4%, 35±5%, and 45±7% of total PIPJ articular cartilage surface, respectively. Constructs with the collateral ligament sparing approach had significantly greater mean yield load (11.3±2.8 versus 7.68±1.1 kN, P=.008) and mean maximum load (13.5±3.1 versus 10.1±1.94 kN, P=.02) under lateromedial bending. Under dorsopalmar/plantar bending there was no significant difference between surgical approaches. The collateral ligament sparing arthrodesis technique had a shorter surgical time (19±3 minutes) compared with the open technique (31±3 minutes).A collateral ligament sparing surgical approach to the PIPJ with removal of articular cartilage by TA drilling and arthrodesis by DCP-TA was faster and stronger in mediolateral bending than arthrodesis constructs created with an open surgical approach.Preservation of the collateral ligaments and TA drilling for cartilage removal during PIPJ arthrodesis may be a superior approach to the conventional open approach and warrants clinical evaluation.

Cocaine exposure elicits a set of stereotypic behaviors in Drosophila that are strikingly similar to the cocaine-induced behaviors observed in vertebrates. This provides a valuable model for the study of cocaine abuse and has led to the discovery of a connection between the cocaine response pathway and the circadian system. This article describes a simplified assessment of cocaine-induced behavior combined with an image acquisition system, which allows the assay to be semiautomated. With this new system, cocaine response can be evaluated in a fraction of the time required by the previous assay, and subjectivity in scoring is reduced dramatically.

Cocaine exposure elicits a set of stereotypic behaviors in Drosophila that are strikingly similar to the cocaine-induced behaviors observed in vertebrates. This provides a valuable model for the study of cocaine abuse and has led to the discovery of a connection between the cocaine response pathway and the circadian system. This article describes a simplified assessment of cocaine-induced behavior combined with an image acquisition system, which allows the assay to be semiautomated. With this new system, cocaine response can be evaluated in a fraction of the time required by the previous assay, and subjectivity in scoring is reduced dramatically.

The purpose of this study was to experimentally characterize the compressive behavior of square-cell titanium honeycomb cores according to the American Society of Testing and Materials Standard C365-05. By varying the honeycomb cell size and height, as well as the foil thickness, many configurations of titanium honeycomb were manufactured utilizing a laser welding and expansion method. The test matrix consisted of 1080 compression specimens. The compression specimens were split evenly into stabilized and bare tests. At the conclusion of the characterization, a comprehensive statistical analysis was performed on the data. It was determined that the compressive behavior has a strong dependence on the relative density of the honeycomb. The compressive strength was found to be slightly affected by the presence of a stabilizing face sheet, and largely unaffected by specimen core height. The compressive modulus was affected by both the core height and the presence of a face sheet. The compression behavior of the honeycomb was compared with experimental results of honeycomb from existing publications and found to be consistent.

Over the past several years, the crack tip opening angle (CTOA) has been identified as one of the most promising fracture parameters with which to characterize low constraint stable tearing and instability in structural metallic alloys. This study presents the results of experimental stable tearing characterizations performed on three typical structural metallic alloys, two aerospace grade aluminums and a titanium alloy. Specific attention is given to the measurement methods used and the correlation between CTOA and δ5. The effects of the material and the measurement method on CTOA are observed, and a clear relationship is seen.