Model of CEL for 3D Elements in PDMs of Unidirectional Composite Structures

Progressive damage models(PDMs)have been increasingly used to simulate the failure process of composite material structures.To accurately simulate the damage in each ply,3D PDMs of composite materials have received more attention recently.A characteristic element length(CEL),which is an important dimensional parameter of PDMs for composite materials,is quite difficult to obtain for 3D elements,especially considering the crack directions during damage propagation.In this paper,CEL models for 3D elements in PDMs of unidirectional composite structures are presented,and their approximate formulae are deduced.The damage in unidirectional composite materials can be divided into fiber cracks and inter-fiber cracks.The fiber crack and inter-fiber crack directions are considered in the CEL derivations,and thus,the CELs of 3D elements that have various damage modes and damage directions could be obtained relatively precisely.Static tensile and compressive tests of open-hole laminates were conducted,and the corresponding numerical analyses by the progressive damage method,including the proposed CEL models and those models from the literature,were performed.The numerical results are in good agreement with the experimental results,which proves the fidelity and effectiveness of the proposed CEL models.In addition,the proposed CEL models have better performance in improving the mesh independence of the numerical models.

Numerical and Experimental Study on Stiffened Composite Panel Repaired by Bolted Joints under Compressive Load

Numerical and experimental study was conducted to investigate the failure mode and strength performance of stiffened composite panel repaired by bolted joints under compressive load, and the results were then compared with those from virgin stiffened composite panel without any damage. A finite element analysis model was established for repaired and virgin stiffened composite panels under compressive load, the 3D Hashin criteria was applied to identify the composite structure failure, and the secondary stress criteria was adopted to identify the adhesive failure between the base laminate and the stiffener. The failure modes of repaired stiffened composite panels were stiffened composite panels breaking off along the bolt joints. The experimental results were consistent with the finite element analysis results, indicating the reliability of the finite element analysis model.

Origin of the DUPAL anomaly in the Tethyan mantle domain and its geodynamic significance

Mantle heterogeneity has revealed systematic differences in Pb isotopic compositions between the Indian OceanSouth Atlantic mantle in the Southern Hemisphere and the Pacific Ocean-North Atlantic mantle in the Northern Hemisphere.This large-scale difference in mantle isotopes in the Southern Hemisphere is known as the DUPAL anomaly,but its origin remains controversial.Based on a systematic review of the Nd-Pb isotopic evolution of the Tethyan mantle domain,this study identified the long-term presence of the DUPAL anomaly in this domain since the early Paleozoic,characterized by long-term and high mantle thorium/uranium(Th/U)ratios.By comparing the Nd-Pb isotopic compositions of the Tethyan mantle domain with the Panthalassic-Pacific mantle domain(the Paleo-Asian,Paleo-Pacific,and modern Pacific oceans),it is shown that the mantle initially had low Th/U features due to early Earth crust-mantle differentiation,with the crust having high Th/U ratios.As such,the mantle initially had uniformly low Th/U ratios that were inherited throughout the Panthalassic-Pacific mantle domain.However,the plate tectonics and continental collisions in the Tethyan domain affected its characteristics,leading to the long-term and large-scale DUPAL anomaly.During the opening of and subduction in the Tethys Ocean,Gondwanaland fragmentation and frequent continent-continent collisions led to long-term and extensive crust-mantle interactions and the continuous input of highTh/U mantle sources,which thus modified the mantle.This process formed not only the unique DUPAL anomaly in the Tethyan mantle domain,but also the Tethyan tectonic domain dominated by continental collisions.Moreover,the high DUPAL anomaly in the Proto-and Paleo-Tethyan mantle domains records the effects of mantle plumes,which might have occurred primarily during the formation of the Proto-and Paleo-Tethys oceans during the early evolution of the Tethyan domain.Therefore,the inherent coupling of mantle domain properties and plate tectonic mechanisms provides important insights for understanding plate tectonics and geodynamic processes in the Tethyan domain.

Adakites related to subduc-tion in the northern margin of Junggar arc for the Late Paleozoic:Products of slab melting

Volcanic rocks with adakitic compositional signature have been recognized in the northern margin of ancient Junggar island arc for the Late Paleozoic. These adakites for the early Devonian from the Tuoranggekudouke Group (D1t) are characteristic of high Sr, Sr/Y and (La/Yb)N but low Y, Yb and HREE. Their compositional characteristics are much similar to those of the typical adakites in the world but distinct from those of the normal arc volcanic rocks from the same Group. We conclude that these adakitic volcanic rocks were produced by slab melting during the early period of Paleoasia-ocean lithosphere subduction. This infers that the Paleoasia Ocean in the north Junggar area began a new subduction process in the early Devonian.

Identification of an Early–Middle Jurassic oxidized magmatic belt,south Gangdese,Tibet,and geological implications

The south Gangdese region is the site of subduction of the Neo-Tethys and subsequent continental collision. Compared with widespread Cretaceous and Cenozoic magmatism, Early–Middle Jurassic magmatic rocks and related deposits are rarely reported. Our work identified a >200 km long felsic rock belt associated with Cu mineralization in the south Gangdese region. We report here zircon U–Pb ages, zircon Ce^(4+)/Ce^(3+)values, and mineral assemblages of two Cu mineralized intrusions within the belt. A hornblende granite and a diorite porphyry were emplaced at 177.3 Ma and 166.3 Ma, respectively.Geological occurrence and magmatic hematite–magnetite–chalcopyrite intergrowths suggest that Cu mineralization formed coeval with Jurassic intrusions. Mineralized intrusions have high zircon Ce^(4+)/Ce^(3+)and EuN/Eu?N ratios, and hematite–magnetite intergrowths, suggesting their parent magmas were highly oxidized. Hornblende is common and primary fluid inclusions are found in titanite and apatite,indicating their parent magmas were water-saturated and exsolved volatile phases at early stage of magmatic evolution. Those magma characters contribute to the formation of porphyry Cu deposits. Given that majority subduction-related porphyry Cu systems have been eroded following uplift and denudation, the well-preserved Early–Middle Jurassic Cu mineralized igneous rocks in south Gangdese are favorable prospecting targets for subduction-related porphyry Cu deposits.

Discovery of Mg-righ volcanic rock series in western Altay area, Xinjiang and its geologic significance

A series of Mg-rich volcanic rocks, including rare Mg-rich dacites in the Asherle copper mine, western Altay Area, has been found. This suite of Mg-rich volcanic rocks is characterized by high SiO2, MgO and low Ti contents. Compared with the island arc tholeiite and MORB, these rocks are depleted in HFSE and are therefore similar to boninite. The dacites show V-shaped distribution REE patterns whereas the basalts display flat or

Nonlocal thermo-elastic constitutive relation of fibre-reinforced composites

The effective properties of composite materials have been predicted by various micromechanical schemes.For composite materials of constituents which are described by the classical governing equations of the local form,the conventional micromechanical schemes usually give effective properties of the local form.However,it is recognized that under general loading conditions,spatiotemporal nonlocal constitutive equations may better depict the macroscopic behavior of these materials.In this paper,we derive the thermo-elastic dynamic effective governing equations of a fibre-reinforced composite in a coupled spatiotemporal integral form.These coupled equations reduce to the spatial nonlocal peridynamic formulation when the microstructural inertial effects are neglected.For static deformation and steady-state heat conduction,we show that the integral formulation is superior at capturing the variations of the average displacement and temperature in regions of high gradients than the conventional micromechanical schemes.The approach can be applied to analogous multi-field coupled problems of composites.

Discovery of the highly depleted N-MORB-type volcanic rocks: new evidence for the Mianlue paleo-ocean

The highly depleted N-MORB-type volcanic rocks have been discovered in Mianlue mélange of Qinling orogenic belt, central China. These mafic rocks are associated with the meta-peridotites, showing LREE-depleted pattern, similar to N-MORB and typical ophiolites. It is indicated that an ancient ocean existed in the Mianlue area of Qinling orogenic belt during the late Paleozoic.