Characterization Of Structural Weak-Links By Fiber Profile And Tensile Analyzer (FiPTA)

Fiber weak-link (FWL) is one of the most important flaws affected on the processing and end-use performance of fibers. The theory characterizing FWL and methods of testing FWL are always the key problems. Although there are several characterizing and testing methods, such as OFDA, SIFAN, OM+XQ, but the precision-is low and testing. procedure is waste of time.FiPTA (fiber profile and tensile analyzer) is designed to provide an actual, reliable and simple method to test FWL. Based on FiPTA, FWL of wool fiber, kevlar129 and carbon fiber are characterized. The detail as follows:①Through the optimization of hardware and software of FiPTA, it can held and rotate single fiber, remove the twists on the fiber, scanning the profile of sample from different angles, locate the thinnest point along the fiber, draw fiber, catch the broken point during fiber's damage. So it comes true to combine the two methods of testing fiber's profile and tensibilities in situ.②Results from the experiments, designed to valuate FiPTA, prove that stabilities of speed and measuring strength, precisions of scanning and tensile testing, can meet or exceed the requirement of related standards of testing single fiber. The parameters of operate FiPTA are confirmed. What is more, scanning speed and scanning precisions are linear, which helps to select proper speed to scanning.③Based on FiPTA, the profiles and tensile properties of wool fiber, kevlar129 and carbon fiber are combined to test in situ. The amount of samples decreases sharply, comparing with the numbers needed in traditional test. FiPTA can exactly locate the thinnest point of fiber, overcoming the uncertainness of the real thinnest point because of more than one this point, appearing during testing from single angle. The broken probabilities judged from the critical stress and critical strain rule can agree with the one judged from the average stress and critical strain rule. It seams that FiPTA can improve the precision of judging broken types and decrease the possibility of misjudging. All three fibers mostly break at the thinnest point. And profile is the biggest factor that effects the damage of wool fiber, the second keclar129, the third carbon fiber. While structural defect is most factor for carbon fiber, second, kevlar129, third, wool fiber. ④Based on FiPTA, adopt the distribution simulation method to discuss the fitted distribution of the broken parameters of fibers by means of Gauss, Lorentz and Weibull functions, and to get the relative coefficients and applicability of these functions to the tensile curves. Generally speaking, distributions of wool fiber are the same with these of flexible fibers, i. e. distributions of tenacity, stress and elongation are fitting to Gauss distribution, and distribution of energy fitting to Lorentz distribution. While distributions of kevlar129 and carbon fiber are the same with these of brittle fibers, i.e. distributions of all parameters are fitting to Weibull distribution.⑤Based on FiPTA, combine the tensile curves and the fractography of broken fibers, to characterize the micro-structure of FWL. The micro-structures of structural FWL of wool fiber observed in the experiment are similar to these reported before, which proved that it is feasible to characterize FWL by FiPTA. The broken types of Kevlar129 consist of main-region tear and multi-region tear. The characterizations of micro-structure of FWL conclude the bulk of tearing belts, the amount of tearing region, The lubricity of the fractography of region, the area of break. These micro-structures can well agree with corresponding tensile curves. The broken types mostly are vertical-plat, declining-plat, and ladder-plat. The strengths of the three types of fiber are high, meddle and low.