PSI - Issue 28

1252 J. Weiland et al. / Procedia Structural Integrity 28 (2020) 1249–1257 Weiland et al. / Structural Integrity Procedia 00 (2019) 000–000 �� � ��� � ��� � �� �� � � � �� � (1) The Asahi Kasei DB-500 POF having a numerical aperture of NA = 0.5 �� ��� � ���� was used for these investigations. It consists of a 480 µm thick core of Polymethyl methacrylate (PMMA) coated with a 10 µm thick cladding of a fluorinated polymer, see figure 2. 4

Fig. 2: Cross sectional shape of polymer optical fiber – Asahi Kasei DB-500

Figure 3 shows a representative stress-strain diagram for the POF in axial direction under tensile loading. The maximum yield stress is 87.47 MPa at a strain of 5.75 %. Up to the yield point, the stress-strain curve is linear. This means that an elastic deformation behavior is assumed. For a permanent use of the POF as a fiber optic sensor, the POF should not be stressed above a strain of about 5 %. The analytic determined Young’s modulus is 2667.48 MPa. The ultimate tensile stress is reached at 91 % of strain and is 141.50 MPa. 3.2. Adhesive The two-component polyurethane adhesive 3M Scotch-Weld DP 609, 3M Neuss, Germany, was used for this investigation because of the good bonding properties for polymers. For the mechanical characterization of the adhesive, five bulk dog-bone specimens according to DIN EN ISO 527-2 were prepared by injection. The specimen has a size of 150 mm – 20 mm and a thickness of 4 mm. The curing conditions for the specimens were 7 days at room temperature. After curing, the samples were tested according to DIN EN ISO 527-1. The displacements were detected by means of an optical extensometer. The result of the tensile test is shown graphically in the Figure 4. The maximum yield stress is 9.41 MPa at a strain of 52.60 %. The analytic determined Young’s modulus is 69.90 MPa.