The a-e curves for type A and B are shown in Fig. 3a, b, respectively. Furthermore, the fiber properties can be found in Table 3. The Young’s modulus is

Table 2 Number of creep specimens per load level and fiber type

Load level (%)

Type A

Type B

22

0

2

36

4

2

43

4

2

53

6

2

63

0

4

Total

14

12

Fig. 3 r—e curve for a type A and b type B

Table 3 Mechanical properties of both fibers

Type A

Type B

Average strength (CoV^{a})

387 MPa (2.8 %)

451 MPa (1.8 %)

Average strain at maximum stress (CoV)

10 % (2.6 %)

16 % (6.2 %)

Average Young’s modulus (CoV)

6200 MPa (2.7 %)

4400 MPa (2.3 %)

^{a}CoV: coefficient of variation, ratio of the standard deviation w.r.t. the mean

calculated according to the revision proposal of EN 14899-2. It is noted that the strength and Young’s modulus is relatively low as compared to other commercially available macro-synthetic fibers.

Creep Deformations

The creep results of fiber type A and B are shown on a logarithmic time scale in Fig. 4a, b, respectively. In these figures x and ? denote fiber creep failure, the former representing failure in the middle of the fiber, the latter failure near the clamps. О denotes an aborted test due to time constraints. Note that for both fiber types, the strain axis is the same to highlight differences more clearly.

The average time to failure and strain at failure, tf_{aaure} and &f_{a}n_{ure} respectively, are summarized in Table 4.

It is clear that the load level significantly influences the time to failure as well as the total strain at failure. Overall, very large strains can be expected in relatively short periods of time: the time to failure ranges from several hours to several months for fibers loaded at 63 or 43 % of their strength.

In all cases however, failure is sudden with no noticeable strain acceleration on a linear time scale (contrary to the logarithmic time scale in Fig. 4), that is usually associated with tertiary creep.