东华大学纤维集合体力学2016年期中考试试题

2016~ 2017学年第 1 学期研究生期中考试试题

考试学院：纺织学院

考试专业：修习本课程硕士生

考试课程名称：纤维集合体力学

（考生注意：答案必须写在答题上，写在本试题纸上一律不给分）[试题部分]

[注]: 本试卷共计8大题，均为必答题。满分100分。

一 (10)

二 (10)

三 (10)

四 (10)

五 (10)

六 (10)

七 (10)

八 (10)

九 (10)

十 (10)

总分

2016~ 2017学年第 1 学期研究生期中考试试题

考试学院：纺织学院

考试专业：修习本课程硕士生

考试课程名称：纤维集合体力学

（考生注意：答案必须写在答题上，写在本试题纸上一律不给分）[试题部分]

1 (10’s)

Fig.1 Schematic of the microstructure of the spider silk fibre consisting of nanocrystals interlinked by a fraction of pre-strained chains in the amorphous matrix.

Spider dragline silk possesses superior mechanical properties compared with synthetic polymers with similar chemical structure due to its hierarchical structure comprised of partially crystalline oriented nanofibrils.(As shown in Fig.1).

Derive the elastic stiffness of spider fiber silk from the macomolecular configuration and conformation.

Fig.2 Schematic representation of the free energy landscapes of PA assemblies under conditions with relatively high (front) and low (back) charge repulsion between PA molecules As shown in Fig.2, at low intermolecular repulsion, long PA fibres with β-sheets are favoured and monodisperse short fibres represent a metastable state. Using the structure diagram, explaining the

crimp shape of a single fiber under free state.

Fig.3 Surface morphology of the cotton fibers before and after grafting

Explaining the multi-scale surface structure of grafted cotton fiber based on Fig.3 4 (10’s)

From the general visco-elastic equation:

()()()()00d d d d i j n

m

i j i j i j a b t t σε===∑∑

deriving the elastic, visco, parallel and series visco-elastic equations.

Fig.4 Schematics of idealized yarns depicting: the cross-sectional view of the yarn model, randomly distributed fibers hierarchical structure of a 3-D ideally twisted yarn consisting of

hexagonal close-packed discontinuous fibers.

To developing a Weibull model for predicting the mechanical properties of fiber yarns from the hierarchical yarn structure in Fig.4.

6 (10’s)

Fig.5 Mechanics of materials comprising crimped fibrous structures

A suitable arrangement of crimped fibers (or yarn in textiles) enables to obtain a non-linear macroscopic mechanical response of the fiber-reinforced structural element, fulfilling specific design purposes (see Fig. 1). Crimped fibers under uniaxial traction are indeed characterized by a low-stiffness regime for small forces (associated with fiber straightening and the disappearance of fiber crimp).

Herein, explaining the process to pull out a crimped fiber from a staple yarn.

7 (10’s)

Fig.6

Fig.6 Yarns in woven fabric

From Fig.6, present the flowchart of calculating: (1) tensile deformation; (2) tensile strength of woven fabric.