Pullout length

Fibre Matrix/sintering additives Hot-pressing conditions Maximum fibre pullout length (pm)... 

When M M, disentanglement is nearly instantaneous but approaches tro when M 8Me, which is the strain hardened (A. 4) upper bound for chain pullout without bond mpture. For welding, the relaxation times Trq refer to the minor chains of length /(/) such that the retraction time is approximated by Tro /(/). When M > 8Me, the chains cannot disentangle completely at the Rouse time and... 

Fig. 4.39. Comparisons of initial debond stress,

The AFM chip, containing the AFM cantilever and tip, is then translated away from the polymer surface, resulting in continued bending of the cantilever. The nanotube pulls out of the polymer at a critical bending of the cantilever (b). This bending deflection, D, is calculated from the position of the cantilever before and after the pullout. The nanotube embedded length is calculated by the difference between the nanotube free length in (a) and (b). With permission from to Wiley and Sons (22). 

In order to determine 4, we now consider a simple model of a fiber of length / embedded in a polymer matrix (see Fig. 15.20b). The tensile stress on the fiber required to produce fiber debonding and pullout is determined in a first approximation by balancing the tensile and shear forces,... 

Let <5 denote the length of the connector chain pulled out from the polymer by a force / as shown in Fig. 8. When 6=1, where l is the total connector chain length, the chain is completely pulled out and the force/vanishes. Assuming that the chains are pulled out normal to the interface so that the tangential component of the pullout force is zero, then a, the traction stress component normal to the planar interface, is related to the force/and 2, the number of chains crossing a unit area of the interface, by ct=/2. a is related to the rate of chain pullout <5(f, x) and the remaining chain length l - by ... 

The crack, semi-infinite in length, is assumed to propagate along the interface of two linearly elastic half spaces with a steady state velocity of a under small-scale yielding conditions, which implies that the region of pullout is small compared with typical specimen dimension. The interfaces are reinforced by chains which obey the pullout laws stated above. The steady state condition implies that all quantities are independent of time with respect to an observer moving with the crack tip. 

In yam pullout test a rectangular fabric sample (for simplicity a plain pattern is considered here) is clamped to the two opposite side of a U frame. The pullout force is applied to a single yam (for instance at the middle) with a specific free end length as shown in Figure 1. The yam is pulled out in three steps, the detail of which will be given in the discussion part of the chapter. 

The pullout test repeated Qve times for each fabric. In the execution of the yam pullout test, a fabrie sample was clamped to each side of a U form frame. The weft yams of the fabric were free. The frame was connected to the movable lower head of a Zwick tensiometer model 1440-60 . The middle weft yam was tied to the stationary upper head while a free length at the end was set to be 1 cm. The length of the yams between the upper head and the fabric was set to be 6 cm for all samples. The lower head moved down at a velocity of 10 mm/min. The pullout force was measured by a load cell with a maximum capacity of 500 N while the pulled yam fully pulled out of the weave. 

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