Bending Damage Research Articles

Analysis of Bending and Impact Damage Behavior of CFRP/Al7075 Hybrid Composite Plate by NDT Technology

Analysis of Bending and Impact Damage Behavior of CFRP/Al7075 Hybrid Composite Plate by NDT Technology

Basic Study on Damage Restraint of Coating Film (2nd Report, Improvement of Damage Restraint Effect)

Recently, coating materials are widely used in the several fields. However, it is being taken up as a serious problem that the large-scale destruction of the structure will be occurred at the time when the damage of the coating film generates. In the previous report, the basic study on the efficiency of actively restoring the bending damage of the film by adopting the concept called smart material or smart structure was proposed, and the effectiveness was shown. However, the problems of improvement on the reactivity of the actuator and application of the flexible processor function were pointed out. In this paper, the smart structure body is reported that is constituted by the information from the added strain gauge as the sensor function and the applied neural network as the processor function. As the result, it was showed that the problems of the previous report could be improved.

Ice Damage in a Chronosequence of Agroforestry Pine Plantations in Arkansas, USA

Acute (broken and leaning) and transient (bending) damage to loblolly pine (Pinus taedaL.) were assessed in a case study of experimental agroforestry plantations following a December 2000 ice storm. Stand ages were 7-, 9-, and 17-years-old and tree density ranged from 150 to 3,360 trees ha−1 in rectangular and multi-row configurations. Wider tree spacing or lower stand density of 7-year-old trees increased stem breakage, while closer spacing increased bending. There was substantial straightening of bent 7-year-old trees 8 months after the storm, and this recovery was determined more by degree of initial bend rather than height or diameter. Nine-year-old loblolly pine had 19% more top breakage and 59% more stem breakage than shortleaf pine (P. echinataMill.) (P < 0.001). Agroforestry design influenced ice damage in 7-year-old stands, but no design had catastrophic loss. Thinning from above caused an increased susceptibility of ice damage to a 17-year-old stand compared to a nonthinned stand. The case study supports the cultivation of loblolly pine in areas prone to ice damage.

HHI secures Angolan FPSO contract

Protection structures for FPSO (Floating Production Storage and Offloading) caissons should be sufficiently strong so as not to contact caisson pipes even when the protection structure is damaged by an impact by attendant vessels. In the present structural design process, non-linear commercial packages are employed for collision analyses. However, non-linear collision analyses using commercial packages are time-consuming and expensive to operate, especially in the initial design stage. In this study, substantiation of the adopted commercial package was first performed using collision test results on single pipes and H-shape pipes. Then, a rigorous parametric study was conducted by changing the design variables. A simple analytical expression was derived assuming that the kinetic energy of the striking vessel was dissipated by the plastic elongation of pipes and rotation of plastic hinges. Using the parametric study results, design equations to predict the maximum deflection and overall bending damage were obtained by which the effects of local denting and dynamic behaviour could be considered. Additionally, an equation to predict the extent of local denting damage was also derived. The developed procedure was numerically substantiated using the predicted extent of damage to an actual protection structure.

Response of forest tree seedlings to simulated litterfall damage.

Litterfall is an important cause of seedling mortality in many forests ranging from wet tropical to boreal. However, there is a lack of studies that investigate differences between species in seedling resilience to litterfall damage. We selected seedling pairs of seven tree species and simulated litterfall damage by pinning one of each pair to the ground. The mortality and growth rates varied significantly between species for pinned individuals, but were similar for unpinned seedlings. The mortality of pinned Nestegis cunninghamii and Prumnopitys ferruginea was significantly greater than that of unpinned individuals (P < 0.05). However, contrary to expectations, the growth rates of pinned Hedycarya arborea and Nothofagus menziesii were much greater than for those left unpinned (P < 0.05). In general, seedling resilience to the bending damage differed substantially between species. N. cunninghamii and P. ferruginea suffered high mortalities and did not increase growth rates in response to damage, whereas, H. arborea and N. menziesii suffered few mortalities and regained height quickly. Other study species demonstrated intermediate resilience. This study demonstrates that some species are more likely to survive in high-risk litterfall regimes than are others. Given that litterfall risk can vary greatly between microsites, these results suggest that litterfall can contribute to regeneration niche differentiation.

A study on residual fatigue bending strength and damage behavior of CFRP composites subjected to impact loadings

This paper evaluates the static and fatigue bending strengths of CFRP (carbon-fiber reinforced plastic) laminates having impact damages, e.g., foreign object damages (FOD). Composite laminates used in this experiment are CF/EPOXY and CF/PEEK orthotropy laminated plates with two-interfaces [0°4/90°4]s A steel ball launched by an air gun collides against the CFRP laminates to generate impact damages. The damage growth during a bending fatigue test is observed by a scanning acoustic microscope (SAM). When the impacted side is compressed, the residual fatigue bending strength of CF/PEEK specimen P is greater than that of CF/EPOXY specimen B. On the other hand, when the impacted side is in tension, the residual fatigue bending strength of CF/PEEK specimen P is smaller than that of CF/EPOXY specimen B. In the case of impacted-side compression, the fracture is propagated from the transverse crack generated near the impact point. In the case of impacted-side tension, however, the fracture develops toward the impact point from the edge of interface-B delamination.

Study of Impact Damage of Composite Laminates Using Five-Point Bending

The low-velocity impact of composite laminates can induce high transverse shear strains, resulting in severe damage within the laminate. This type of damage may be studied by the use of a five-point bending test configuration. An investigation of composite laminate failure induced by transverse shear strains is described in the present paper. In order to gain insight into the representation of low-velocity impact damage by the five-point bending configuration, low-velocity impact tests were performed. Five-point bending tests were also perforned, producing transverse shear cracks, delaminations, and other types of failures. Since transverse shear strain causes failure under conditions of low-velocity impact, a comparison between the results of the five-point bending tests and established results of impact tests is presented, showing that both types of tests produce the same failure modes. Also, AS4-PEEK graphite-thermoplastic is shown to be more resistant to five-point bending damage than is AS4-3502 graphite-epoxy.

Behavior of Damaged Tubular Structural Members

An analytical model of dented tubular members is constructed. Using this model, an ultimate strength interaction relationship between axial force and biaxial bending moments is derived. The implementation of this interaction relationship to take account of denting and bending damage in the analysis of nonlinear behavior of tubular space frames by ISUM (the Idealized Structural Unit Method) is described. An experimental study of the behavior of dented members subjected to pure bending is reported. Comparison with theoretical predictions is presented.

El-plastic Behavior and Ultimate Strength of Damaged Tubular Members

An analytical model of dented tubular members is constructed. Using this model, an ultimate strength interaction relationship between axial force and biaxial bending moments is derived. The implementation of this interaction relationship to take account of denting and bending damage in the analysis of nonlinear behavior of tubular space frames by ISUM (the Idealized Structural Unit Method) is described. An experimental study of the behavior of dented members subjected to pure bending is reported. Comparison with theoretical predictions is presented.