Local Failure Modes and Critical Buckling Loads of a Meta-Functional Auxetic Sandwich Core for Composite Bridge Bearing Applications

This paper presents a novel meta-functional auxetic unit (MFAU) cell designed to improve performance and weight ratio for structural bridge bearing applications. Numerical investigations were conducted using three-dimensional finite element models validated by experimental results. The validated models were exposed to compression and buckling actions to identify structural failure modes, with special attention placed on the global behaviours of the meta-functional auxetic (MFA) composite bridge bearing. This bearing uses an unprecedented auxetic sandwich core design consisting of multiple MFAU cells. Numerical predictions of the elastic local critical buckling loads of the MFAU cell were in excellent agreement with both the analytical and experimental results, with an observed discrepancy of less than 1%. These results demonstrate that local buckling failures of MFAU cells can potentially be incurred prior to yielding under compression due to their slenderness ratios. Surprisingly, the designed sandwich core used in the MFA composite bridge bearing model can mimic an auxetic structure with significant crashworthiness, implying that this novel core composite structure can be tailored for structural bridge bearing applications. Parametric studies were thus carried out in order to enrich our insight into the MFA composite elements. These insights, stemming from both experimental and numerical studies, enable a novel design paradigm for MFAU that can significantly enhance the structural performance of MFA composite bridge bearings in practice.

Deep time structural evolution of retroviral and filoviral surface envelope proteins

The retroviral surface envelope protein subunit (SU) mediates receptor binding and triggers membrane fusion by the transmembrane subunit (TM). SU evolves rapidly under strong selective conditions, resulting in seemingly unrelated SU structures in highly divergent retroviruses. Structural modeling of the SU of several retroviruses and related endogenous retroviral elements with AlphaFold identifies a TM-proximal SU β-sandwich structure that has been conserved in the orthoretroviruses for at least 110 million years. The SU of orthoretroviruses diversified by differential expansion of the β-sandwich core to form domains involved in virus-host interactions. The β-sandwich domain is also conserved in the SU equivalent GP1 of Ebola virus although with a significantly different orientation in the trimeric envelope protein structure. The unified structural view of orthoretroviral SU and filoviral GP1 identifies an ancient, structurally conserved and evolvable domain underlying the structural diversity of orthoretroviral SU and filoviral GP1.

Analysis of contact interaction of polymer honeycomb core and CFRP base layers in sandwich-core constructions

The article considers the challenge of studying the mechanical properties of composite sandwich constructions at the interface between the base layers and the lightweight core. The results of strength tests are presented for specimens of sandwich-core panels with coats made of high-strength carbon fiber-reinforced plastics (CFRP) and polymer honeycomb core considering various loading conditions. It is noted that a discrepancy in the values of shear stresses occurs in four-point bending and shear tests due to the complex stress-strain state of the specimens during bending. In order to interpret the experimental data, numerical analysis of the area of contact interaction between the coats and the filler of the sandwich-core composite structures is carried out. It is noted that in the presence of significant normal stresses in the adhesive coat the base layers separate from the core during shear tests and there is underestimation of the values of shear stresses by about 20%. Recommendations for the assignment of ultimate shear stresses for the use in practical design of sandwich-core composite constructions are put forward.

Analisis Pengaruh Metode Pembersihan Core, Pengeringan Core, dan Bonding Test Block pada Uji Flatwise Sandwich Carbon Epoxy dengan Glass Core

Penggunaan komposit sebagai pengganti material logam dalam bidang rekayasa sudah semakin banyak digunakan salah satunya panel komposit dengan struktur sandwich. Core pada komposit sandwich memiliki peranan penting sebagai penopang dari skin yang digunakan. Pengujian ini bertujuan untuk mengetahui nilai kekuatan tarik flatwise dari variasi yang digunakan beserta pengaruhnya. Pengujian yang dilakukan adalah uji flatwise (ASTM C297). Hasil uji flatwise dengan nilai tertinggi ada pada variasi pembersihan menggunakan spray MEK, pengeringan menggunakan suhu ruang, dan bonding menggunakan tablepress dengan nilai rata-rata 5,67 MPa. Dari variasi yang digunakan, keseluruhannya memberikan pengaruh pada hasil pengujian.