The lack of durability in concrete repairs induces repair failures in field and endless “repair of repairs”. Most often drying shrinkage of “new” repair material restrained by “old” concrete substrate causes cracking in the repair material, combined with interface delamination between the repair and the concrete substrate, which may also introduce chlorides, oxygen, moisture, alkali or sulphate...

The scales of the arapaima (Arapaima gigas), one of the largest freshwater fish in the world, can serve as inspiration for the design of flexible dermal armor. Each scale is composed of two layers: a laminate composite of parallel collagen fibrils and a hard, highly mineralized surface layer. We review the structure of the arapaima scales and examine the functions of the different layers, focus...

For laser assisted Shape Deposition Manufacturing (SDM), residual stresses caused by the temperature gradient and material property mismatches result in part inaccuracy, warpage, or even delamination. The use of low coefficient of thermal expansion (CTE) materials such as Invar promises to reduce deformations caused by internal stresses [2]. Thus, to obtain high quality of prototypes for moldin...

A mechanical model for the prediction of mode I delamination failure of a laminated double cantilever beam (DCB) type specimen is presented. The volume of material ahead of the crack tip that experiences high stresses due to the presence of the crack tip was replaced by a nonlinear elastic spring foundation. The volume undergoing global deformation due to the external loading was replaced by a ...

A low concentrated polystyrene (PS) additive to epoxy is used, since it is able to reduce the curing reaction rate but not at the cost of increasing viscosity and decreasing glass transition temperature of the curing epoxy. The modified epoxy is cocured with a compatible thermoplastic interleaf during the vacuum assisted resin transfer molding (VARTM) to toughen the interlaminar of the composit...

Nano materials possess unique mechanical, physical, and chemical properties. They are small, and have an ultrahigh surface area, making them suitable for air filter applications since air filtration is necessary to protect sensitive components from harmful particulates and gaseous contaminants. The electrospinning method has been recognized as an efficient technique for fabricating polymer nano...

A self-healing fiber-reinforced structural polymer matrix composite material is demonstrated. In the composite, a microencapsulated healing agent and a solid chemical catalyst are dispersed within the polymer matrix phase. Healing is triggered by crack propagation through the microcapsules, which then release the healing agent into the crack plane. Subsequent exposure of the healing agent to th...

A stretch/bend method for the in situ measurement of the delamination toughness of coatings attached to substrates is described. A beam theory analysis is presented that illustrates the main features of the test. The analysis is general and allows for the presence of residual stress. It reveals that the test produces stable extension of delaminations, rendering it suitable for multiple measurem...

Evaluation of interfacial toughness of sub-micron-thickness layers deposited on a ductile substrate is a challenging task which has motivated different experimental approaches. Fragmentation testing was used in the present study as a means of interface characterization of a silicon–nitride-coated polyimide substrate. During the test, after an initial rapid segmentation–cracking phase, the coati...