| The immaculate and fitted dressing has been in great demand since early societies.Currently,fabric handle has become a classic measure of the comprehensive property of fabrics,playing an important role on evaluating the aesthetics,comfort and market value of the apparel.The development of acceptable fabric handle is an important concern for textile material and engineering studies,and the research on the quantitative characterization techniques is one of the basic subjects for textile discipline.Many investigations into the theory,measurement and instrument of the handle characteristic of fabrics were carried out;however,most of present devices for evaluating fabric handle were designed to measure one pure property during one test,which make it difficult to effectively assess the comprehensive physical and mechanical behaviour of fabrics.China,as a textile country,is still lack of a well-designed handle evaluation system and an agreed assessment criterion.Also,the “one belt one road” development strategy is considered to promote the textile trade significantly.Therefore,it is neccessery for our country to develop a set of handle evaluation system for fabrics.This study used a quasi-three-point pulling-out test to construct complex handle deformation of fabrics based on a multiple-properties-reported-by-one-test principle.A pulling-out force – displacement curve was obtained by the pulling-out test,and this curve and the corresponding pulling-out process could be divided into five stages based on the deformation and force analysis of the measured fabrics.The five stages are non-touching,weighting,bending,friction and stretching stages;thereinto,the stretching stage can be used to characterize the thickness evolution under tension by designing the corresponding thickness testing components.The elastic mechanics theory was used to analyze the force and moment equilibrium of the fabric segments and the element in order to develop the mathmatics-mechanics models of the pulling-out process.Calculus of variations was employed to calculate the hanging locus of a fabric during the weighting stage,and the mass and bending rigidity of samples were considered to establish the weighting theoretical model.Concerning the bending stage,cantilever beam theory was used to investigate the bending process of a fabric,and the element was ultilized to include more force factors to develop the bending theoretical model with friction and extensibility effects.According to the bending investigation results,the friction theoretical model was also established by considering the bending effect.By using the equivalence relation between the calcaluated sample length and setted length and considering the bending,friction and poisson's ratio effects,a theoretical stretching model was also developed to analyze the effect of bending,friction and poisson's ratio on the stretching test process in order to give a theoretical guidance for improving the measurement accuracy of the pulling-out test process.Moreover,the comparisons of theorectical and experimental results indicated the reasonability of the established theoretical models.Each stage of the entire pulling-out process was investigated based on the established models,and the force and influencing factors were extracted and analyzed.Some conclusions were drawn as follows:(1)The effect of the mass and bending indices was analyzed based on the bending theoretical model.The linear coefficient of determination between the masses per square meter from theoretical and experimental results was 0.983,and the prediction error was limited within 15.03 g/m2 at 0.95 confidential level,which stated that the bending theoretical model with mass and bending effects could reflect the main features of the weighting stage.Based on this,the sensitivity of the pulling-out force to bending rigidity and mass of fabrics was analyzed on the basis of the general range of the bending rigidity and mass per square meter for wear fabrics.Also,experiement comparisons were carried out.The results showed that the mass and bending rigidity of fabrics were two factors to control the cuve pattern of the weighting stage,but the mass is still the main factor for the curve pattern,which enables the average weighting force measured by the CHES-FY to characterize the mass of fabrics for handle evaluation based on the pulling-out test.(2)From the investigation into the effects of friction and extensibility of fabrics on the bending stage,it revealed that fabric's friction had significant effect on the bending testing(the maximum increase rate up to 27%),and the curve parameters tended to be larger by including the friction effect.The increase rates of the bending slope were 6.4% and 6.9% for the fabrics with the bending rigidity at 0.15 c N·cm and 0.05 c N·cm,respectively,when the friction coefficients of fabrics increase from 0.2 to 0.3,indicating that the friction effect could be reduced for the wearing fabric with friction coefficient ranging from 0.2 to 0.3 based on the theoretical bending model.However,the effect of the extensibility of samples was almost negligible for testing the bending propery of wear fabrics,as the maximal relative error was less than 4% for the fabric where the tensile elastic constant was higher than 50 c N/cm% based on the mean value of the fabric samples used in this study.(3)The effect of bending and friction on the friction stage of the CHES-FY was discussed based on the friction theoretical model in two cases,and the effect of bending rigidity on friction test was analyzed.Results showed that the bending rigidity had great effect on the friction force – displacement curve,as indicated by the 3 times higher average friction force with bending rigidity changing from 0 to 0.15 c N·cm.Moreover,the average friction force tended to increase with the increase of the bending rigidity.Thus the friction force – displacement curve was a combine effect of the friction coefficient and bending rigidity of fabrics.In addiction,the model also detected that it showed an approximate linear relationship between the bending rigidity and average friction force for bending rigidity within 0-0.4 c N·cm.The increase rate was 20% with 0.02 c N·cm increase of the bending rigidity,and then it decreased below 10% when the bending rigidity was higher than 0.2 c N·cm.This further indicated that the bending rigidity was an important factor that affected the friction stage.(4)By using the theoretical stretching model,the effect of bending rigidity,friction and poisson's ratio on the stretching stage was analyzed.The results showed that bending rigidity and friction of fabrics were the important factors that affected the test results of the stretching stage.The bending and friction effects tended to enhance the slope of the theoretical curve.However,the effect of poisson's ratio was small and could be neglected(variation of the curve feature was less than 0.7% when poisson's ratio ranges from 0 to 1).Moreover,the relationship between the bending indices,i.e.? and k,and the diameter of the bi-pressing pins and pulling pin was discussed.It has been confirmed that the effect of the bending rigidity on the stretching curve strongly depended on the diameter of the bi-pressing pins and pulling pin.The model also detected that the friction effect became more remarkavble for fabric with a high tensile elastic constant.Using the stretching stage,the fabric thickness and thickness evolusion were studied.Results showed that the thickness tested by the CHES-FY had good linear relationship with that measured by the standard thickness tester(R = 0.99),and indicated that thickness strain-axial strain curves were nonlinear and could be divided into three approximate linear regions,making it possible to define the out-of-plain poisson's rato.The evaluation of fabric handle was investigated based on the theoretical and experimental results.The stiffness handle was divided into three sub-handle characteristics,i.e.bending stiffness handle(BSH),friciton stiffness handle(FSH)and extension stiffness handle(ESH).After that,the subjective evaluation process was carried out,and the mean,variance,correlation coefficient and Kendall consistent coefficient W were used respectively to verify the effectiveness of the subjective assessment.The results showed that the six judges displayed high sensitivity and strong agreement amongst themselves in assessing the three handle characteristics of the 51 fabrics.In addition,the curve feature parameters were selected and extracted from the Pulling-out force – displacement curve based on the experimental and theoretical results,and stepwise multiple regression was used to model the three handle characteristics based on analysis of variance(ANOVA)and t-test.Also a set of fabrics was utilized to validate the established models.The reasonably high coefficients of determination(R2 = 0.981,0.992 and 0.986)and the low root mean square errors(RMSE)between the model prediction results and subjective evaluation results showed that the established models gave good predictions for the handle characteristics.The CHES-FY together with the models could provide a convenient and efficient method to evaluate the stiffness handle of woven fabrics,especially for winter suits. |
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