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3D printed concrete exhibits a high magnitude and rate of plastic shrinkage (early age drying-induced shrinkage) compared to conventional cast concrete. This study investigated if restraining this shrinkage adversely affects the long-term durability and mechanical performance. Shrinkage was restrained by inserting reinforcement-like rods into the fresh concrete and exposing the specimen to a moderate evaporation rate . The interlayer bond strength, permeability and ion penetration of the unrestrained and restrained specimens were then compared. The results show that shrinkage causes shear strain concentrations at the interlayers due to a lack of particle interlocking and non-uniform pore water evaporation from the undulated evaporation face. Consequently, discrepancies in the transfer of shrinkage between layers occur, a phenomenon coined as interlayer slip. Evidence is presented of a 12% reduction in interlayer bond strength, a 70% higher permeability and 17% higher chloride ion penetration. These adverse consequences were due to interlayer slip and microcracking. Nonetheless, the durability of uncracked printed concrete is satisfactory, even with localised interlayer slip and microcracking.

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The preliminary difficulties involved in exciting single animal fibers to act as elastic waveguides at 0.5 MHz have been overcome. Propagation constants of the lowest-order vibration modes were used to calculate the respective elastic constants of the fibers.

The removal of kemp fibers during the carding of mohair has been studied. Selective kemp collection by the card clothing takes place mainly because of the greater centrifugal force acting on the mohalr fibers of higher density, which move to the outer layers on the card rollers, causing a relative migration of kemp towards the card clothing; also, higher roller surface speed increases the kemp collecting power. The strippers show the highest selective kemp collecting power and the workers the lowest. The material collected by the card clothing consists mainly of short fibers. Fiber breakage in carding is less for kemp than for mohair.

Fiber-diameter measurements can be carried out by applying the principle of the diffraction of white light. An instru ment (Mikronmeter) based on this principle is described. A sample of randomly arranged fibers produces a circular diffraction pattern the size of which is determined by the diameter of the fibers. Well-trained operators can measure fibre diameters very accurately, while randomly chosen operators can determine fiber diameter with a 95% confidence interval of about ±0.8 microns. Occasionally, some operators cannot use the instrument correctly.