Trans RINA, Vol 152, Part B1, Intl J Small Craft Tech, 2010 Jan-Jun
Figure 13: Voids due to insufficient vacuum.
Five samples approximately 18 mm wide were cut for testing from selected areas of the fusion bonded joints, and another set of four 14 mm wide samples from the pre-made panel. Since the joint samples followed the hull curvature (Figure 16), certain bending forces probably affected them during tensile tests. Their curvature was measured, being within 2.4% of vertical deviation. Thus, this effect was considered small and consequently disregarded,
evaluation of the results. It must also be noted that most of the hull material is usually subjected to simultaneous and/or alternating tensile, compressive
and bending
forces during its service. However, it was considered that a simple tensile test would provide a reliable first indication of the performance of the repair.
Figure 15: Tensile tests results for the type “b” repair joint and the pre-made panel. Type “a” repair joints (not included) were stronger than the hull, which failed first. Bars indicate 95% confidence.
especially considering the comparative
Figure 16: Typical tensile test results for pre-made panel and joint type“b”, and estimation curve for type “a” joint.
Figure 14: Different scarf lengths in fusion bonded joints obtained in the repair (not at scale).
Results of the tensile tests are shown in Figures 15-17. Tests showed that type “a” joints (100% scarf length) were stronger than the hull laminate, which failed first. This is why their strength is not included in Figure 15, and only an estimation of the test curve is available (Figure 16). For type “b” joints (65% scarf length), the failure load per linear mm (failure load divided by joint length, N·mm-1) was approximately 50% of that of the pre-made panel for the same fibre orientation.
The scarfed patched joint repair formed fibre
discontinuity lines, rich in resin, along the boundaries of the reinforcing extra material and the scarfed joints. The fusion bonded joint failed sequentially, as expected, along these fibre discontinuity lines (Figure 17).
Figure 17: Tensile tests. Type “b” joint prior to loading (left) and after failure (right). Numbers on the right link the failure sequence with the test curve in Figure 15.
©2010: The Royal Institution of Naval Architects B-39
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