Search results for "Curing"

Hydrothermal ageing of radiation cured epoxy resin-polyether sulfone blends as matrices for structural composites

2010

Abstract The hydrothermal ageing of epoxy–thermoplastic blends, used as matrices for carbon fibre composites, cured by electron beam, has been studied. Two different thermoplastic percentages have been adopted. A suitable choice of both curing process and formulation parameters allows to carry out irradiation at mild temperature with several advantages, coming from a “non thermal” process, for both the final properties of the materials and the environment. Nevertheless the occurring of vitrification phenomena needs the use of a short thermal treatment after irradiation on the already solid materials, in order to complete the cure reactions. Radiation cured epoxy based matrices have been sub…

Carbon fibre composite materials produced by gamma radiation induced curing of epoxy resins

2008

It is well known that ionizing radiation can initiate polymerization of suitable monomers for many applications. In this work an epoxy dlfunctional monomer has been used as matrix of a carbon fibre composite in order to produce materials through gamma radiation, for aerospace and advanced automotive applications. Radiation curing has been performed at different absorbed doses and, as comparison, also thermal curing of the same monomer formulations has been done. Furthermore some Irradiated samples have been also subjected to a post Irradiation thermal curing in order to complete the polymerization reactions. The properties of the cured materials have been studied by moisture absorption isot…

High energy radiation cure of resin systems for structural adhesives and composite applications

2002

Abstract Radiation cure polymerisation of a commercial diglycidyl ether of bisphenol F epoxy resin has been achieved using a 60Co irradiation source, compounding the monomer with few percentage of an onium salt catalyst. The cure process has been monitored by a gamma-calorimetric technique and systems irradiated at doses corresponding to different positions in the gamma-calorimetric curve have been characterised via solubility tests and dynamic mechanical torsion analysis. Changes in both the measured gel fractions and tan δ values were associated with the progress of polymerisation and crosslinking reactions and these were dose dependent. Furthermore, systems irradiated at lower doses exhi…

E-beam curing of epoxy based blends in order to produce high performance composites

2007

In this work, blends of a difunctional epoxy monomer and a thermoplastic toughening agent are E-beam irradiated at two different dose rates and two different total absorbed doses. The influence of the processing conditions on the thermal properties and on the morphology of the obtained matrices has been investigated. In particular, it is shown how the increase of the dose rate causes an increase of the temperature during irradiation, thus inducing a simultaneous thermal and radiation curing. On the contrary, at low-dose rate the system mainly undergoes to radiation curing, thus making the cured material very sensible to a post-irradiation thermal treatment with a significant improvement of …

Mode I fracture toughness behavior of hydro-thermally aged carbon fibre reinforced DGEBA-HHPA-PES systems

2012

In this work the Mode I fracture toughness behavior of unidirectional CFRP laminates is investigated by means of Double Cantilever Beam (DCB) tests. The composite samples were manufactured by thermal curing after impregnation of a Carbon fabric with a DGEBA epoxy and anhydride HHPA curing agent. One resin batch was also mixed with a PES thermoplastic monomer to enhance the matrix toughness. Two lots of samples, toughened and un-toughened, were then left to soak in hot water to achieve various degrees of aging. The influence of matrix toughening and hydrothermal aging on the delamination behavior of the composite have then been assessed and correlated with characterization data from Dynamic …

Synthesis od epoxy/carbon fiber composites induced by e-beam. Study of the effect of hydrothermal ageing on thermal and mechanical properties

2010

Teaching the placement of posterior resin-based composite restorations in Spanish dental schools

2012

Objectives: In an area of esthetic dentistry such as posterior composites, in which new materials and techniques are being devolved continuously, it is important to confirm that dental students have a clear understanding of the basic principles of clinical application of this knowledge. Considering that the preparation of dental graduates in Spain may be of interest to competent dental authorities and employers with whom they can work worldwide, this study investigated the teaching of posterior composite restorations in Spanish dental schools. Study design: In late 2009/ early 2010, a questionnaire seeking information on the teaching of posterior composites was emailed to the professor resp…

Comparisons of processing and strength properties of two adhesive systems for composite joints

2007

Abstract In the present study rheological, static and impact tests are carried out on two adhesive resins usually employed in marine applications; then single lap joint tests are conducted on composites joints evidencing the effect of the curing time of both resins on the mechanical properties of the joint. The applicability and workability conditions of the adhesive resins are determined evaluating the curing evolution by a preliminary rheological analysis; then the relation of curing properties with the mechanical performances of the resins themselves and with ones of the composite joints is estimated. Static flexural and Izod impact tests are performed on the resins at increasing time af…

RADIATION CURING OF CARBON FIBRE COMPOSITES

2012

Skuteczność zabezpieczeń podatkowych ustanowionych przed ogłoszeniem upadłości po dacie ogłoszenia upadłości. Glosa do wyroku Wojewódzkiego Sądu Admi…

2021

Problematyka skuteczności zabezpieczeń ustanawianych na majątku podatnika, co do którego następnie sąd upadłościowy ogłosił upadłość, budzi liczne kontrowersje i problemy natury praktycznej. Wbrew stanowisku Wojewódzkiego Sądu Administracyjnego (WSA) w Białymstoku1 nie można przyjąć założenia, że zabezpieczenia ustanowione w trybie regulacji podatkowych mają pierwszeństwo przed zasadami prawa upadłościowego oraz są wykonalne i skuteczne także po ogłoszeniu upadłości podatnika. Przyjęcie takiego rozwiązania oznaczałoby uprzywilejowanie określonej grupy wierzycieli. Tym samym, mając na uwadze respektowanie tych zasad w postępowaniu cywilnym i karnym, należy uznać stanowisko WSA w Białymstoku …