Phenolic Core Research Articles

Experimental and numerical analysis of an innovative GFRP sandwich floor panel under point load

A new glass fibre reinforced polymer (GFRP) sandwich panel has been developed for flooring system. The new panel is made of modified phenolic core and E-CR glass skins. This paper presents the results of the experimental behaviour and the non-linear finite element analysis (FEA) of the GFRP sandwich panel. The experimental works investigate the behaviour of the GFRP sandwich panel, skin–core interaction, and core behaviour. A non-linear finite element model was developed to simulate the behaviour of the skin–core interaction, and the model was verified by comparing the results with those obtained from testing. The non-linear FE model was applied to a single span GFRP sandwich floor panel under point load test. The GFRP sandwich floor panel demonstrated a linear behaviour under point load. The results of the numerical simulations show a good agreement with the experimental results.

Behaviour of glued fibre composite sandwich structure in flexure: Experiment and Fibre Model Analysis

The behaviour of glued composite sandwich beams in flexure was investigated with a view of using this material for structural and civil engineering applications. The building block of this glue-laminated beam is a new generation composite sandwich structure made up of glass fibre reinforced polymer skins and a high strength phenolic core material. A simplified Fibre Model Analysis (FMA) usually used to analyse a concrete beam section is adopted to theoretically describe the flexural behaviour of the innovative sandwich beam structure. The analysis included the flexural behaviour of the glued sandwich beams in the flatwise and the edgewise positions. The FMA accounted for the non-linear behaviour of the phenolic core in compression, the cracking of the core in tension and the linear elastic behaviour of the fibre composite skin. The results of the FMA showed a good agreement with the experimental data showing the efficiency and practical applications of the simplified FMA in analysing and designing sandwich structures with high strength core material.

Solution-Phase Synthesis of Branched DNA Hybrids Based on Dimer Phosphoramidites and Phenolic or Nucleosidic Cores

Branched oligonucleotides with "CG zippers" as DNA arms assemble into materials from micromolar solutions. Their synthesis has been complicated by low yields in solid-phase syntheses. Here we present a solution-phase synthesis based on phosphoramidites of dimers and phenolic cores that produces six-arm or four-arm hybrids in up to 61% yield. On the level of hybrids, only the final product has to be purified by precipitation or chromatography. A total of five different hybrids were prepared via the solution-phase route, including new hybrid (TCG)(4)TTPA with a tetrakis(triazolylphenyl)adamantane core and trimer DNA arms. The new method is more readily scaled up than solid-phase syntheses, uses no more than 4 equiv of phosphoramidite per phenolic alcohol, and provides routine access to novel materials that assemble via predictable base-pairing interactions.

Behaviour of structural fibre composite sandwich panels under point load and uniformly distributed load

An innovative fibre composite sandwich panel made of glass fibre reinforced polymer skins and a modified phenolic core material was developed for building and other structural applications. The behaviour of this new generation sandwich panel was studied with reference to the main fibre orientation in floor applications, so that the effect due to erroneous installation could be evaluated. The two- and four-edge supported sandwich panels with different fibre orientations and fixity systems between panel and joist were tested under point load and uniformly distributed load (UDL) to determine their strength and failure mechanisms. The results of this experimental investigation show that the panels behave similarly under both loading conditions. Moreover, the fixity does not have a major effect on its failure mode and deflection.

In-plane shear behaviour of fibre composite sandwich beams using asymmetrical beam shear test

The in-plane shear behaviour of a new generation composite sandwich beam made up of glass fibre skins and modified phenolic core material was investigated to determine its application as shear loading component in a structural beam. Iosipescu shear test was conducted to characterise the shear properties of the fibre composite skins and the phenolic core material. The fibre composite sandwich beams were then tested under asymmetrical beam shear to determine its behaviour under in-plane shear loading. The results show that the in-plane shear behaviour of the composite sandwich beam is similar to that of the skins. A theoretical prediction of the in-plane shear strength of the composite sandwich beam was proposed and showed a good agreement with the experimental results. Based on the results of the study, the asymmetrical shear test is recommended as a test method for determining the shear properties of sandwich structures with high strength core materials.

Flexural behaviour of structural fibre composite sandwich beams in flatwise and edgewise positions

The flexural behaviour of a new generation composite sandwich beams made up of glass fibre-reinforced polymer skins and modified phenolic core material was investigated. The composite sandwich beams were subjected to 4-point static bending test to determine their strength and failure mechanisms in the flatwise and the edgewise positions. The results of the experimental investigation showed that the composite sandwich beams tested in the edgewise position failed at a higher load with less deflection compared to specimens tested in the flatwise position. Under flexural loading, the composite sandwich beams in the edgewise position failed due to progressive failure of the skin while failure in the flatwise position is in a brittle manner due to either shear failure of the core or compressive failure of the skin followed by debonding between the skin and the core. The results of the analytical predictions and numerical simulations are in good agreement with the experimental results.

Mass Spectrometric Identification of Multihydroxy Phenolic Compounds in Tibetan Herbal Medicines

A highly selective and accurate method based on derivatization with dansyl chloride coupled with liquid chromatography–mass spectrometry has been developed for identification of natural pharmacologically active phenolic compounds in extracts of Lomatogonium rotatum plants (Tibetan herbal medicine) obtained by solid-phase extraction. The number of hydroxyl groups on the dansylated phenols was estimated by LC–MS–MS analysis in positive-ion mode. Dansyl derivatization of the compounds introduced basic secondary nitrogen into the phenolic core structures and this was readily ionized when acidic HPLC mobile phases were used. MS fragmentation of the derivatives generated intense protonated molecular ions of m/z [MH]+ (phenol aglycones were transformed into the corresponding free phenols by cleavage of an aglycone bond). Collision-induced dissociation of the protonated molecule generated characteristic product ions of m/z 234 and 171 corresponding to the protonated 5-(dimethylamino)naphthalene sulfoxide and 5-(dimethylamino)naphthalene moieties, respectively. Selected reaction monitoring based on the m/z [MH]+ to 234 and 171 transitions was highly specific for these phenolic compounds. Characteristic ions with m/z values of [MH – 234]+, [MH – 2 × 234]+, and [MH – 3 × 234]+ were of great importance for estimation of the presence of multihydroxyl groups on the phenolic backbone.

The Effect of a Honeycomb Core on the Mechanical Properties of Composite Sandwich Plates

When comparing composite sandwich analysis with an exact solution, the results of finite element modeling with an ANSYS shell 91 element agreed well with the exact solution. The practical applications of the shell 91 element are demonstrated with a four-point bend test conducted on sandwich beam specimens. The specimens comprised carbon/epoxy fabric face sheets and a honeycomb core. Two kinds of honeycomb cores were used to fabricate the composite sandwich specimens: an aluminum one and a glass/phenolic one. The predictions with the shell 91 element were also agreed well with the experimental results. A variety of tests was conducted; namely, a long beam flexural test, a short beam shear test, a flatwise tensile test, a flatwise compression test and an edge compression test. The sandwich plate with the aluminum honeycomb core had a specific bending stiffness that was 1.7 to 2.0 times higher than that of the sandwich plate with the glass/ phenolic honeycomb core.

Modern sandwich core materials offer new attractive design possibilities

Activities in trying to make the airplane interiors more attractive to passengers increase the demand for complex, three‐dimensional sandwich structural parts. The realization of three‐dimensional contours often failed in the past, due to a lack of process ability or the enormous production costs caused by the processing of conventional phenolic cores. The new structural foam cores based on thermoplastic polytherimide (PEI), AIREX R92, offer the highest design freedom in combination with a reduction of the processing costs. Furthermore, they fulfil the highest possible fire‐smoke‐toxicity specifications.

Perspectives in ultra-high load solid (gel) phase peptide synthesis

Abstract A novel approach to ultra-high load solid (gel) phase peptide synthesis is reviewed and some recent developments discussed. The approach utilises a phenolic bead-form core network at an initial matrix loading of 5.0 mmol g−1, the theoretical maximum. Consecutive repeating units along the polymer backbone each form a point of attachment for a growing peptide chain, synthesis proceeding via the stepwise elaboration of a series of quasi-homogeneous peptide gel networks. The success of the method, which has proved effective in the laboratory preparation of gram and multi-gram quantities of peptides, is ensured by the judicious choice of reaction conditions, reagents and solvents, so as to secure efficient gelation for all intermediate peptide gel networks. These may be regarded as quasi-homogenous, both in covalent network architecture and in network distribution within the gel particles.

Polymer-supported biopolymer synthesis: 5. Ultra-high load solid (gel) phase peptide synthesis—the stepwise elaboration of quasi-homogeneous peptide gel networks?

An approach to ultra-high load solid (gel) phase peptide synthesis is described in which a bead-form phenolic core polymer, crosslinked poly[N-{2-(4-hydroxyphenyl)ethyl}-acrylamide], is used as a support matrix at near theoretical maximum loading. Consecutive repeating units of the core polymer carry peptide chains undergling stepwise elongation. Synthesis proceeds through a series of solvated networks, which consist mainly of protected peptide. The solvated networks are deemed to be quasi-homogeneous, insofar as each has a regular covalent framework and each is believed to be uniformly distributed throughout the gel beads. Illustrative synthesis of two fully-protected acylpeptide hydrazide segments, corresponding to dynorphin(6–12) and to β h-endorphin (18–26), are described.