Compression Properties of Woven Carpet Performance under Dynamic Loading

Received May 27, 2017 Revised June 15, 2017 Accepted June 17, 2017 Although carpets are seen as decorative products for consumers, it is important that they must have optimum quality performance. The most important features affecting quality performance are pile fiber, pile yarn, pile height, pile density, carpet surface structure (cut pile or loop pile), carpet construction etc. During usage the carpet are exposed to a number of forces due to compressional loading such as dynamic or static. To counteract these forces, the resilience of pile yarn is vital. This paper demonstrates the influence of pile density and pile height of structure parameters on compression performance which was exposed to dynamic loading. In that respect, acrylic fiber was used as pile to manufacture Wilton face-to-face cutpile carpets at two pile densities (2400 piles/dm, 2880 piles/dm) and three pile heights (7 mm, 11 mm and 16 mm). To determine the compression properties, carpets were subjected to dynamic loading at 50, 100, 200 and 1000 impacts. Thickness of carpets was taken at each of these four impacts. Finally, thickness loss of carpets as well as compression performance was detected. In order to identify the effect of pile density, pile height and number of impact on thickness loss of carpet after dynamic loading, analysis of variance was performed statistically. Results showed that pile height, pile density and number of impact have statistically significance on compression performance of carpet samples. Keyword:


Introduction
Carpet is predominantly used in home floor covering as an indispensable decorative product and also preferred by its heat and sound insulation feature.Compression performance in general terms of mechanical properties influences carpet performance under dynamic or static loads.Carpet thickness will be deformed when it is exposed to dynamic and static loads which are created by walking and furniture, respectively.During daily usage of the carpet, thickness loss is directly affected by raw material, pile height, carpet construction, pile density etc.There are a lot of studies focused on effects of these parameters on carpet performance based on static loading, dynamic loading and compressibility [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].Javidpanah et al. studied cut-pile carpets made of heat process modified polyester pile yarn thickness loss of cut-pile carpets after dynamic loading.Four different 1800 denier and 96 filament in the cross section of air textured polyester pile yarns; normal, frieze, heat set and twist heat set were used as pile yarn.In order to analyze the carpet compression performance 50, 100, 200, 500, 1000 and 2000 dynamic impacts were acted on carpet samples.It was stated that physical and mechanical properties of air textured polyester pile yarns do not have significant changes after heat processing [4].Çelik and Koç investigated on some selected carpet samples made of wool, acrylic and polypropylene pile yarns to evaluate the performance of carpets under dynamic loading.In this study, carpets were exposed 50, 100, 200, 500 and 1000 dynamic impacts and then thickness losses were analyzed.They put forward that an increase in the number of impacts increase the thickness loss.It was found that acrylic fiber carpet had highest recovery capability than wool and polypropylene fiber carpets [13].Çelik determined the effect of acrylic fineness, 2.75 denier, 6 denier and 8 denier, on carpet performance.Among the all analyses in order to identify carpet performance, dynamic loading tests were performed under 50, 100, 200, 1000 and 2000 impacts.It was resulted that acrylic fiber fineness had significant effect on thickness loss of carpet samples.The highest thickness loss was detected at carpet sample produced from acrylic pile yarn with 2.75 denier fiber fineness [8].The aim of this study is to investigate the influences of pile height and pile density on woven carpet compression performance under dynamic loading with 50, 100, 200 and 1000 impacts.To determine the relationships between independent variable (pile height, pile density and number of impact) and response variable (thickness loss) multivariate variance analysis (MANOVA) was performed by SPSS package program.

Materials and Methods
Six acrylic cut-pile carpets were manufactured by Wilton face-to-face carpet weaving machine with three rapiers which enables three weft shots.The structure for all carpets was chosen as 2/3V weave construction which is illustrated in Figure 1.
Figure 1.2/3 V weave construction [16,17] Acrylic fiber was used as pile with 5.6 denier linear density.All carpet production parameters were kept constant such as machine speed, weft and warp yarns used, construction.Carpet compositions are shown in Table 1.Carpet specifications are given in Table 2 with respect to pile height and pile density variables.[18].Five test specimens were prepared as 125mm*125mm dimensions for each carpet.In order to perform dynamic loading test WIRA dynamic loading machine which drops free falling weight on carpet specimen at every five seconds was used.Carpet specimen was clamped on to a steel plate that is slowly and continuously traversed in such a way that there is 3.2 mm movement between each drop of the weight at each impact.Tests were conducted according BS ISO 2094:1999 [8,19,20].Before applying dynamic loading all carpet thickness were measured in accordance with ISO 1765:1986 with WIRA digital thickness gauge under standard pressure of 2 ±0.2 kPa and this process repeated after 50, 100, 200 and 1000 impacts immediately [21].Thickness loss in percentage was determined as a difference between the thickness at zero impact and at each stage of impact by using Equation (1).
where: ℎ 0 is initial thickness and ℎ  is thickness after dynamic loading at each stage of impacts.
For statistical analysis SPSS package program was used to assess the effect size significance of pile height, pile density and number of impact on thickness loss of carpet for each stage of impact at 95% confidence interval.

Results and Discussion
Thickness losses in percentage of acyclic carpets with different pile densities and pile heights after 50, 100, 200 and 1000 impacts are shown in Figure 2. Thickness loss of acrylic cut-pile carpets increases from 50 to 1000 impacts with the increase in number of impact.Performance of carpets at 7 mm pile height for each pile density against compression is higher than that of 11 mm and 16 mm carpets.In addition, it is clearly seen that increase in pile density contributes to the compression performance of carpets with 11 mm and 16 mm pile heights.This situation can be explained with having more pile yarns within the unit area results higher resistance against dynamic load impacts.On the other hand, the same situation is not directly observed for carpets with 7 mm pile height.Thickness loss difference between 2400 piles/dm 2 is lower 3% than that of 2880 piles/dm 2 for 100 impacts.Total thickness loss in percent of cut-pile acrylic carpet samples with different pile density and pile height is shown in Figure 3.When constant pile height is taken into consideration, the difference of thickness loss in percent for 2400 piles/dm 2 carpet has the higher value of 4.7% than 2880 piles/dm 2 .This result is similar for 11 mm and 16 mm cut-pile carpets the thickness loss value of 32% and 9.7%, respectively.In conclusion, the influence of pile density on thickness loss is clearly stated that the higher the pile density, the lower the thickness loss after dynamic loading at 1000 impacts.MANOVA results for thickness loss after dynamic loading for independent variables are seen in Table 3.
When the effect of pile height, pile density and number of impact on thickness loss is examined, thickness loss values are seen as statistically significant (R 2 = 96.6 %).
In order to evaluate the effects of subgroups for number of impact and pile height (pile density was not considered because of lower than three subgroups), Duncan's multivariate range tests were achieved and results are illustrated in Table 4 and Table 5, respectively.In Table 4, increase in number of impacts affects the carpet thickness loss negatively.Furthermore, carpets with higher pile height have lower resistance to dynamic loading with higher thickness loss (Table 5).

Conclusion
In order to assess the influence of pile density and pile height on thickness loss of carpet exposed to dynamic loading at different impacts, acrylic cut-pile carpets were used in this study.It is expected and desired that the carpets should have the highest performance under the dynamic loading which simulate the traffic wear during the usage.In accordance with the statistical analysis, both the pile density and pile height parameters have significant effect on dynamic loading performance of the carpet samples.As a conclusion to the test results, it can be said that the lowest thickness loss was obtained with the carpet sample at 7 mm pile height and 2880 piles/dm 2 pile density.Since performance of carpets at 7 mm pile height for each pile density against compression is higher than that of 11 mm and 16 mm carpets, it can be resulted that lower pile heights provide better dynamic loading performance.It is also clearly seen that increase in pile density contributes to the compression performance of carpets with 11 mm and 16 mm pile heights.

Figure 2 .Figure 3 .
Figure 2. Thickness loss of cut-pile carpet samples versus to number of impact

Table 1 .
Carpet samples composition

Table 3 .
MANOVA for thickness loss under dynamic loading

Table 4 .
Duncan's multivariate range test results according to number of impacts

Table 5 .
Duncan's multivariate range test results according to pile heights