This research paper presents an experimental investigation on the compression and compressive resilience properties of warp-knitted spacer fabric composites with different resin content and different kinds of resin. By means of hand roller coating technology, four kinds of warp-knitted spacer fabric composites were made. The experiments were tested according to GB/T1453-2005 and ISO3386/2:1984. It is shown that the resin content and resin type seriously affect the compression and compressive resilience properties of warp-knitted spacer fabric composite. The data indicated that when the warp-knitted spacer fabric composite coated with the same kind of resin, with increasing resin content the elastic modulus added and the compressive resilience decreased. Having the same resin content, the compression properties of pacer fabric composite increase with the increase of flexural strength of resin; while the compressive resilience decrease.

A single tensile overload (OL) applied during a constant amplitude fatigue test could have a positive or negative influence on improving the subsequent fatigue-crack growth rate (da/dN). The resulting variation in da/dN was very relevant to both the OL level and the fatigue loading conditions. Comprehensive tests on 2024-T4 Al-alloy specimens were carried out to rationalize the variation trend of da/dN after a single tensile OL. It was found that the trend of the fatigue-crack growth after the OL is not unique, but strongly depends on the OL stress-intensity factor KOL and the applied stress-intensity factor Kapp just before OL. Three potential trends of variation in da/dN, related to both the KOL and the KOL/Kapp ratio, were proposed in this study: initial deceleration and then recovery (Type I); initial slight-acceleration, subsequent retardation and final recovery (Type II); and initial major-acceleration, subsequent retardation and final recovery (Type III). Among the three types, the type II with the medium KOL/Kapp ratio and the low Kapp is the optimal OL type for improving the fatigue life of a 2024-T4 Al-alloy specimen. Keywords: overload, fatigue crack growth trend, fatigue retardation, overload-induced fracture zone Med testom utrujanja s konstantno amplitudo so uporabili posamezen natezni preizkus s preobremenitvijo (OL; angl.: single tensile overload) ter ugotovili, da ima lahko le-ta pozitiven ali negativen vpliv na nadaljnjo hitrost rasti razpoke (da/dN). Nastala razlika v da/dN je bila tesno povezana tako z nivojem OL kot tudi s pogoji utrujanja. Avtorji~lanka so izvedli ob{irne preizkuse na vzorcih Al zlitine 2024-T4, da bi razumeli trend variiranja da/dN po OL. Ugotovili so, da trend hitrosti rasti razpoke po OL ni enoten, temve~je mo~no odvisen od razmerja OL-faktor intenzitete napetosti KOL in uporabljenega nivoja napetostnega faktorja intenzitete Kapp tik pred OL. V tej {tudiji so avtorji predlagali tri mo`ne trende variiranja da/dN glede na KOL in razmerje KOL/Kapp: za~etno zmanj{evanje hitrost (zaviranje) in nato popravo (Type I); za~etno rahlo pospe{evanje, odla{anje in nato popravo (Type II) in za~etno izrazito pospe{evanje, kateremu je sledilo odla{anje in kon~na poprava (Type III). Med vsemi tremi je tip II s srednjim KOL/Kapp razmerjem in nizkim Kapp optimalen OL tip za izbolj{anje dobe trajanja vzorcev iz Al zlitine 2024-T4. Klju~ne besede: preobremenitev, trend rasti utrujenostne razpoke, odla{anje utrujanja, s preobremenitvijo inducirana cona loma

In this paper, the vibration performance of hybrid sandwich composites plates with different stacking was investigated by modal test. The results showed that the reduction in layer numbers of the unidirectional carbon fiber epoxy prepreg in 0odirection will result the decrease in the natural frequency values for bending modal, the increment of layer numbers of 2D woven epoxy prepreg with plain weave will result the enhancement the of torsional modal. The reinforcements of unidirectional carbon fiber epoxy prepreg in ±45odirection has a preferential effect on the torsional modal natural frequency of the plate than that of 2D woven epoxy carbon prepreg with plain weave in 0odirection.