Dynamic response of hybrid carbon fibre laminate beams under ballistic impact

This novel hybrid fibre composites combining stiff composites with soft composites are developed to improve the ballistic impact resistance of composite beams while maintaining good quasi-static loading bearing capacity. The ballistic impact performance of the hybrid beams have been investigated experimentally at a projectile velocity range of , including ballistic limits, failure modes, energy absorption capacity and the interaction between stiff and soft composite parts. For each type of monolithic beams, i.e. stiff, soft and hybrid monolithic beams, three categories of failure modes have been identified: minor damage with rebound of projectile at the low impact velocities, fracture of beam at the medium impact velocities and perforation of beam at the high impact velocities. The critical velocity of hybrid monolithic beam was similar to that of the soft monolithic beam under the same failure mode, and higher than that of the stiff monolithic beam. For the sandwich beams with stiff, soft and hybrid face sheets, the failure modes were similar to those of the monolithic beams. Among the monolithic beams, the hybrid and soft monolithic beams exhibited better energy absorption capacity than the stiff monolithic beams. As for the sandwich beams, the hybrid-face sandwich beams absorbed more kinetic energy of projectile than the soft-face sandwich beams at higher projectile velocity. The advantages of the stiff/soft hybrid construction include: (i) at lower impact velocity, the soft composite part survived with negligible damage under impact; (ii) due to the buffer effect of the soft part at the front face, stress distribution within the stiff part of the hybrid monolithic beams is more uniform than that of the stiff monolithic beams

Dynamic response of high-performance honeycomb cores and hybrid fibre composite laminates for lightweight sandwich structures

Lightweight sandwich structures that are composed of high–performance core and face sheets, have been attracting attention in both civilian and military applications due to their outstanding mechanical properties. Honeycomb cores and fibre reinforced composite face sheets have specific advantages for resisting dynamic impact. For example, honeycomb cores possess higher specific-strength (ratio of strength to relative density) than the other sandwich cores under compression, and carbon fibre composites possess high tensile strength and low density. This thesis focuses on the understanding of the dynamic compressive response of high-performance honeycombs and the ballistic impact resistance of stiff/soft hybrid fibre composite laminate beams. For honeycomb cores, the out-of-plane compressive behaviour of the AlSi10Mg alloy hierarchical honeycombs and commercially available Nomex honeycombs have been experimentally and numerically investigated. Owing to the complex in-plane topology, hierarchical honeycombs were fabricated using the Selective Laser Melting (SLM) technique. The experimental measurement and finite element (FE) calculation indicate that the two hierarchical honeycombs, specifically two-scale and three-scale honeycombs, both offer higher wall compressive strengths than the single-scale honeycombs. With an increase in relative density, the single-scale honeycomb experiences a transition in terms of failure mechanism from local plastic buckling of walls to local damage of the parent material. Alternately, the two-scale and three-scale hierarchical honeycombs all fail with solely parent material damage. The dynamic compressive strength enhancement of the hierarchical honeycombs is dominated by the strain rate sensitivity of the parent material. For Nomex honeycombs, the dynamic failure mode under out-of-plane compression is different from the quasi-static failure mode, i.e. the honeycombs fail due to stubbing of cell walls at the end of specimens under dynamic compression, whereas fail due to local phenolic resin fracture after elastic buckling of the honeycomb wall under quasi-static compression. The dynamic compressive strength of Nomex honeycombs increases linearly, and the strength enhancement is governed by two mechanisms: the strain rate effect of the phenolic resin and inertial stabilization of honeycomb unit cell walls. The inertial stabilization of unit cell walls plays a more significant role in strength enhancement than the strain rate effect of the phenolic resin. In addition, the effect of key parameters such as impact method and initial geometrical imperfections on the compressive responses of honeycombs has also been numerically investigated. For face sheets, the ballistic resistance of the beams hybridizing stiff and soft carbon fibre composites has also been experimentally studied, and these results were compared with those of stiff and soft composite beams with identical areal mass. The failure modes of composite beams under different velocity impacts have been identified to be different. For monolithic beams, the hybrid and soft monolithic beams exhibited similar energy absorption capacity. As for the sandwich beams, the hybrid sandwich beams behaved better in terms of energy absorption than soft sandwich beams at high projectile velocities. Both the hybrid and soft composite beams absorbed more kinetic energy from projectiles than stiff composite beams. The advantages of the stiff/soft hybrid composites can be summarized as follows: (i) the soft composite part survives at low velocity impact; (ii) the stiff composite part of the hybrid monolithic/sandwich beams has a more uniform stress distribution than the stiff monolithic/sandwich beams owing to the buffer effect of the soft composite part. This work identifies the advantages of high performance honeycomb cores as well as fibre composite face sheets. These findings can be used to develop high strength, low weight and multi-functional sandwich structures, thereby widening their applicability to a wider array of fields

Dynamic compressive response of additively manufactured AlSi10Mg alloy hierarchical honeycomb structures

Periodic honeycombs have been used for their high strength, low weight and multifunctionality. The quasi-static and dynamic compressive responses of three types of additively manufactured AlSi10Mg honeycomb structures, specifically a single-scale honeycomb and two hierarchical honeycombs with two and three levels of hierarchy, respectively, have been investigated using experimental measurement and finite element (FE) simulations. The validated FE simulation has been employed to investigate the effects of relative density of the honeycombs and the key experimental parameters. The following failure modes of the three types of honeycombs have been observed both under quasi-static and dynamic compression: (1) the single-scale honeycomb experienced a transition of failure mechanism from local plastic buckling of walls to local damage of the parent material without buckling with the increase of the relative density of the honeycomb; (2) the hierarchical honeycombs all failed with parent material damage without buckling at different relative densities. For both quasi-static and dynamic compression, the hierarchical honeycombs offer higher peak nominal wall stresses compared to the single-scale honeycomb at low relative density of ; the difference is diminished as relative density increases, i.e. the three types of honeycombs can achieve similar peak wall stresses when Numerical results have suggested the hierarchical honeycombs can offer better energy absorption capacity than the single-scale honeycomb. The two-scale and three-scale hierarchical honeycombs achieved similar peak nominal wall stresses for both quasi-static and dynamic compression, which may suggest that the structural performance under out-of-plane compression is not sensitive to the hierarchical architecture. This work indicates that the structural advantage of hierarchical honeycombs can be utilised to develop high performance lightweight structural components

Treatment Experience of 16 Cases in Combined with Posterior Condylar Fractures Schatzker types II and III Tibial Plateau Fracture

Objective: Exploring the treatment of combined posterior lateral approach with open reduction and internal fixation for the treatment of combined fractures of the ankle on the treatment of tibial plateau fractures with Schatzker types II and III. Method: Between April 2012 and March 2015, 16 cases of Schatkzer types II and III tibial plateau fractures were treated with T or L type limited contact dynamic compression plate (LC-DCP). Results: All 16 cases were followed-up for 12 to 36 months, with an average of 18.3 months. According to the Merchant score, 10 cases were excellent, good in 4 cases, and in 2 cases, the excellent and good rating was 87.5%. Conclusion: After treatment, anatomical reduction and stability of the posterior condyle was emphasized, and there were early functional usage and recovery of the joint functions. At the same time, the external side of the incision can be used to restore the external and rear sides to avoid replacement of the body position and improve the operation efficiency

MALAT1 Activates the P53 Signaling Pathway by Regulating MDM2 to Promote Ischemic Stroke

Background/Aims: This study focused on evaluating the effect of MALAT1 and MDM2 on ischemic stroke through regulation of the p53 signaling pathway. Materials: Bioinformatics analysis was performed to identify abnormally expressed lncRNAs, mRNAs and their associated pathways. Oxygen-glucose deprivation/reoxygenation (OGD/R) in cells and middle cerebral artery occlusion/reperfusion (MCAO/R) in mice were performed to simulate an ischemic stroke environment. Western blot and qRT-PCR were used to examine lncRNA expression and mRNA levels. Fluorescence in situ hybridization (FISH) LncRNA was used to locate mRNA. MTT and flow cytometry were performed to examine cell proliferation and apoptosis. Finally, immunohistochemistry was used to observe the expression of genes in vivo. Results: MALAT1 and MDM2, which exhibit strong expression in stroke tissues, were subjected to bioinformatics analysis, and the p53 pathway was chosen for further study. MALAT1, MDM2 and p53 signaling pathway-related proteins were all up regulated in OGD/R cells. Furthermore, Malat1, Mdm2 and p53 pathway related-proteins were also up regulated in MCAO/R mice. Both MALAT1 and MDM2 were localized in the nuclei. Down regulation of MALAT1 and MDM2 enhanced cell proliferation ability and reduced apoptosis, resulting in decreased infarct size in MCAO/R brains. Conclusion: These results indicate that MALAT1/MDM2/p53 signaling pathway axis may provide more effective clinical therapeutic strategy for patients with ischemic stroke

Experimental and numerical analysis of dynamic compressive response of Nomex honeycombs

Lightweight phenolic resin-impregnated aramid paper honeycombs, commercially known as Nomex®honeycombs, are promising cores for sandwich structures in aerospace applications due to their high ratios of stiffness and strength to density. The out-of-plane compressive properties of the Nomex honeycombs have been widely investigated under quasi-static and low strain rates (up to 300 s-1). There is a need to understand the behaviour of this structure under higher strain rate compression. This will widen the applicability of these structures to more areas such as debris impact and other impacts which induce high strain rates. This paper reports the out-of-plane compressive responses of Nomex honeycombs subject to quasi-static loading and high strain rate dynamic loading up to 1500 s-1. The work involves experimental measurements and numerical modelling and validation. The compressive responses of the honeycombs were measured using a sensitive magnesium alloy Kolsky bar setup with front and back face impacts. The failure modes of the Nomex honeycombs were identified to be different under quasi-static and dynamic compressions. Under quasi-static compression, the honeycombs failed with local phenolic resin fracture after the elastic buckling of the honeycomb walls. For the dynamic compression, the honeycombs failed with the stubbing of cell walls at the ends of specimens. A finite element (FE) numerical model was devised and validated with the experimental data. The FE model considered the strain rate effect of phenolic resin material. The model predictions were in good agreement with the experimental measurements and facilitated interpreting the out-of-plane compressive response of the Nomex honeycombs. It was shown that there was a linear compressive strength enhancement up to 30% from quasi-static to strain rate of 1500 s-1. The strength enhancement was governed by two mechanisms: the strain rate effect of the phenolic resin and inertial stabilization of the honeycomb unit cell walls, where 61%-74% of the enhancement was contributed by the inertial stabilization of the unit cell walls. In addition, it was shown that the impact method and initial imperfections had negligible effect on the compressive response of the Nomex honeycombs

Modeling the Total Allowable Area for Coastal Reclamation : a case study of Xiamen, China

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Ocean & Coastal Management 76 (2013):38-44, doi:10.1016/j.ocecoaman.2013.02.015.This paper presents an analytical framework to estimate the Total Allowable Area for Coastal Reclamation (TAACR) to provide scientific support for the implementation of a coastal reclamation restriction mechanism. The logic of the framework is to maximize the net benefits of coastal reclamation subject to a set of constraints. Various benefits and costs, including the ecological and environmental costs of coastal reclamation, are systematically quantified in the framework. Model simulations are developed using data from Tongan Bay of Xiamen. The results suggest that the TAACR in Tongan Bay is 5.67 km2, and the area of the Bay should be maintained at least at 87.52 km2.The study was funded by the National Oceanic Public Welfare Projects (No. 201105006) and the Fujian Natural Science Foundation (No. 2010J01360

Dynamic response of high-performance honeycomb cores and hybrid fibre composite laminates for lightweight sandwich structures

Lightweight sandwich structures that are composed of high–performance core and face sheets, have been attracting attention in both civilian and military applications due to their outstanding mechanical properties. Honeycomb cores and fibre reinforced composite face sheets have specific advantages for resisting dynamic impact. For example, honeycomb cores possess higher specific-strength (ratio of strength to relative density) than the other sandwich cores under compression, and carbon fibre composites possess high tensile strength and low density. This thesis focuses on the understanding of the dynamic compressive response of high-performance honeycombs and the ballistic impact resistance of stiff/soft hybrid fibre composite laminate beams. For honeycomb cores, the out-of-plane compressive behaviour of the AlSi10Mg alloy hierarchical honeycombs and commercially available Nomex honeycombs have been experimentally and numerically investigated. Owing to the complex in-plane topology, hierarchical honeycombs were fabricated using the Selective Laser Melting (SLM) technique. The experimental measurement and finite element (FE) calculation indicate that the two hierarchical honeycombs, specifically two-scale and three-scale honeycombs, both offer higher wall compressive strengths than the single-scale honeycombs. With an increase in relative density, the single-scale honeycomb experiences a transition in terms of failure mechanism from local plastic buckling of walls to local damage of the parent material. Alternately, the two-scale and three-scale hierarchical honeycombs all fail with solely parent material damage. The dynamic compressive strength enhancement of the hierarchical honeycombs is dominated by the strain rate sensitivity of the parent material. For Nomex honeycombs, the dynamic failure mode under out-of-plane compression is different from the quasi-static failure mode, i.e. the honeycombs fail due to stubbing of cell walls at the end of specimens under dynamic compression, whereas fail due to local phenolic resin fracture after elastic buckling of the honeycomb wall under quasi-static compression. The dynamic compressive strength of Nomex honeycombs increases linearly, and the strength enhancement is governed by two mechanisms: the strain rate effect of the phenolic resin and inertial stabilization of honeycomb unit cell walls. The inertial stabilization of unit cell walls plays a more significant role in strength enhancement than the strain rate effect of the phenolic resin. In addition, the effect of key parameters such as impact method and initial geometrical imperfections on the compressive responses of honeycombs has also been numerically investigated. For face sheets, the ballistic resistance of the beams hybridizing stiff and soft carbon fibre composites has also been experimentally studied, and these results were compared with those of stiff and soft composite beams with identical areal mass. The failure modes of composite beams under different velocity impacts have been identified to be different. For monolithic beams, the hybrid and soft monolithic beams exhibited similar energy absorption capacity. As for the sandwich beams, the hybrid sandwich beams behaved better in terms of energy absorption than soft sandwich beams at high projectile velocities. Both the hybrid and soft composite beams absorbed more kinetic energy from projectiles than stiff composite beams. The advantages of the stiff/soft hybrid composites can be summarized as follows: (i) the soft composite part survives at low velocity impact; (ii) the stiff composite part of the hybrid monolithic/sandwich beams has a more uniform stress distribution than the stiff monolithic/sandwich beams owing to the buffer effect of the soft composite part. This work identifies the advantages of high performance honeycomb cores as well as fibre composite face sheets. These findings can be used to develop high strength, low weight and multi-functional sandwich structures, thereby widening their applicability to a wider array of fields

Segment data fitting method for support pressure monitoring

When support pressure monitoring system is used in over-length workface, it is very difficult to meet both demands of real-time transmission and capturing burst signals in the pressure because of limitation of bus querying period. A segment data fitting method was proposed for support pressure monitoring. In the method, data is divided as a segment according to querying period of the system. If data amount in a data segment is less than amount of fitting coefficients, the data is transmitted directly. If the data amount is larger, data polynomial fitting method is used to fit the data, thus fitting coefficients are gotten and transmitted. The experimental result shows that the method reduces amount of data transmission significantly, reserves important information and fixes data transmission amount in each querying period for clear data transmission management