3,009 research outputs found
Remarks on preparation of indandione detection reagents
A modified Claisen condensation with sliced sodium at a higher temperature was recommended for the production of ungranulated charcoal. A new ninhydrin production method by oxidation of benzaldiketohydrinden using available reagents was tried and was unsuccessful. Triketohydrinden was obtained by boiling ninhydrin in acetic acid anhydrides
Internal geometry of structurally stitched NCF preforms
Internal geometry of a textile reinforcement is an important factor of the reinforcement performance during the composite manufacturing and service life. In this article, generalized geometrical models of structural stitching loops are presented for the sewing, tufting, and dual-needle stitching methods. The term 'structural' presumes here that the stitching yarn does not only consolidate the plies (as the non-structural one does) but forms also a through-the-thickness (3D) reinforcement. The models account for the general features of the yarn loop geometry and are believed to allow for enough precise modelling on the meso-scale (textile unit cell) level. The modelling approach is validated with experimental data
A statistical treatment of the loss of stiffness during cyclic loading for short fiber reinforced injection molded composites
Injection molded short fiber reinforced composites (SFRC) have different local fiber orientation distribution (FOD) at every point. SN curves of short fiber reinforced composites are known to depend on the fiber orientation distribution. Such materials also suffer from continuous loss of stiffness during cyclic loading. It is not known whether the loss of stiffness is different for SFRC with different FOD. A statistical analysis of the loss of stiffness curves is presented in this paper. Tension-tension fatigue experiments are performed and loss of stiffness is collected for every data point in the SN curve. A systematic method for comparing the loss of stiffness is developed. It is concluded that the difference in loss of stiffness curves for coupons of SFRC with different FOD is not statistically significant. (C) 2016 Elsevier Ltd. All rights reserved
Unfolding spinor wavefunctions and expectation values of general operators: Introducing the unfolding-density operator
We show that the spectral weights used for the
unfolding of two-component spinor eigenstates can be decomposed as the sum of the
partial spectral weights calculated for each
component independently, effortlessly turning a possibly
complicated problem involving two coupled quantities into two independent
problems of easy solution. Furthermore, we define the unfolding-density
operator , which unfolds the
primitive cell expectation values of any
arbitrary operator according to
. As a proof of concept, we apply the method to
obtain the unfolded band structures, as well as the expectation values of the
Pauli spin matrices, for prototypical physical systems described by
two-component spinor eigenfunctions
Finite element modelling of inter-ply delamination and intra-yarn cracking in textile laminates
The aim of the current study is to demonstrate the effect of inter-ply delamination on stiffness degradation of multi-ply woven composites. Such a demonstration becomes possible due to new technique of modelling textile laminates. It is based on set of boundary value problems for unit cell of a single ply, where boundary conditions imitate interaction with the other plies. Once these problems are solved, local stress distribution and stiffness of the laminate are determined analytically as function of number of the plies and local stress/strain fields obtained in these problems. Hence, it opens the road for an efficient modelling of delamination, which is described as gradual reduction of plies in the laminate
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