In the current study, the effect of the thickness and the foam density in three-dimensional integrated woven sandwich composites on quasi-static mechanical properties under three-point bending was investigated. Bending modulus and core shear modulus were determined by subjecting the samples, which were cut with varying span lengths according to their core thicknesses, to three-point bending test. Obtained results were optimized by taking core thickness, foam density and panel weights into consideration. Damages that occurred on the tested samples were reported. When compared to conventional foam core sandwich composites, it was found that three-dimensional integrated sandwich composites have superior mechanical properties and due to the fact that the pile yarns in the core and the foam support each other, contrary to conventional sandwich composites no catastrophic core breakage occurs under load, thus the load bearing capacity of the structure is sustained.

In this paper, the low velocity impact characteristics and impact damage of sandwich composites, produced at four different core thicknesses from 3-dimensional (3D) integrated sandwich fabrics, with and without foam filling, have been examined. The 3D sandwich fabrics have been produced using the same yarn and weaving densities. Thus, the impact characteristics are only affected by the core thickness and whether foam filling is used or not. Low velocity impact tests have been conducted at 32 and 48 J energy levels. The impact behavior has been determined as a function of the peak load, the energy to peak load, the time to peak load and the absorbed energy. The impact damage and the change in the compressive strength after impact have been analyzed. The findings obtained indicate that core-skin delamination on 3D sandwich composites has been fully prevented. Impact tests carried out on integrated 3D sandwich structures have shown that impact damage is limited to the vicinity of the point of impact and does not affect the integrity of the structure. This indicates that such damage can be easily repaired and the service life of the product can be sustained.

In the current study, the effect of the thickness and the foam density in three-dimensional integrated woven sandwich composites on quasi-static properties was investigated. For this purpose, produced samples were subjected to uniaxial flatwise compression tests and their compression strength and moduli were determined. Obtained results were optimized by taking core thickness, foam density and panel weights into consideration. Damages that occurred on the tested samples were reported. When compared to conventional foam core sandwich composites, it was found that three-dimensional integrated sandwich composites have better compression properties and due to the fact that the pile yarns in the core and the foam support each other.

This paper presents the experimental study of fiber type, fabric structure, orientation of fabric plies and thickness on the ballistic impact behavior of aramid and ultra-high molecular weight polyethylene (UHMWPE) composite laminates. Aramid composite laminates are reinforced by three kinds of fabric structures and UHMWPE composite laminates are reinforced by two kinds of fabric structures. The laminates are fabricated via autoclave curing process. The ballistic behavior of composite laminates is evaluated by ballistic limit velocity, and energy absorbed at ballistic limit. Through a series of ballistic tests, it is demonstrated that unidirectional composite laminates exhibit higher ballistic limit velocity and energy absorption on unit weight basis compared to other laminates. Interesting results are shown by UD-UHMWPE-H62 Õ and UD-UHMWPE-Endumax Õ fabric-reinforced laminates. Orientation of fabric plies is found to have insignificant effect on ballistic behavior irrespective of material type. A bi-linear relationship is found between the ballistic limit velocity, energy absorption and specimen thickness.

In this study, the mechanical properties of composite materials obtained from carbon and carbon-aramid hybrid woven fabrics produced in different constructions with the same yarn and under the same production conditions were determined, and the effects of weaving structure and hybridization on the mechanical properties were investigated. For this purpose, the geometric properties of carbon fabrics made from 12 K carbon yarn with four different weaving structures and two carbon-aramid hybrid fabrics made of 12 K carbon yarn and aramid yarn with two different structures were defined, and the mechanical properties of the composite materials were investigated under uniaxial tensile loading. The mechanical properties of the composite materials produced from the carbon and carbon-aramid hybrid fabrics were compared. The effects of weaving structure and hybridization on the mechanical properties were determined. Based on the weaving construction, Young’s modulus and the tensile strength declined approximately 34–39% and 24–27%, respectively. However, Young’s modulus was 16–63% higher than the expected value for the hybrid composites.