PSI - Issue 12

A. Castriota et al. / Procedia Structural Integrity 12 (2018) 71–81 Castriota et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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by a pin at the free end of the spar. In addition, anti-warping teflon-coated guides on the edges of the spar cap near the hole were inserted to avoid unexpected out of plane displacement, which could occur especially during residual strength static test.

Tab . 1. Number of plies and staking sequence for the constituent spar parts

No. plies

Part

Material

Staking sequence

Geometry

[45/-45/90/0/90/45/ -45/45/-45/0] ([45/-45/90/0/90/45/ -45/45/-45/0] s ([45/-45/0/45/-45/90/45/ -45/0/-45/0/90/45/90] s

Spar Cap

CFRP

10

Spar Web

CFRP

20

Skin T

CFRP

28

[45/-45/0/45/-45/0/90/45/- 45/45/-45/45/0/45/90/0/-45/0/- 45/0/-45/0/90/45/90] S

Skin L

CFRP

50

The experimental campaign was conducted at the EMILIA laboratory of Università del Salento using a base frame and two large cubic structures to constraint the component. A hydraulic actuator driven by a closed loop controller was used to apply the load (Fig. 1). During test, strain measurements were made in several points of the spar. The zones in which the strain gauges and the rosettes were applied were chosen according to the criterion of monitoring the deformation field in the longitudinal direction of the wings of the spar and the deformation field that is generated near the edges of the hole with repair placed on the center of the spar web. Since the component is subjected to bending, the most stressed areas are the spar caps; moreover, the presence of the hole requires particular attention for monitoring the repair on the edges. In total, 32 monoaxial strain gauges and 10 strain gauge rosettes were used in accordance with the strain gauge map (Fig. 2). In addition, a LVDT was used to monitor the deflection of the spar.

a

b

Fig. 1. Experimental set-up in the Laboratory EMILIA (a) and connection spar with the actuator (b).

3.1. Test procedure

Preliminarily to the application of the random fatigue load and the expected breaking load, a calibration of the test system and of the measurement system (Step 0) was carried out by bending the spar with a load equal to 14.28% of the expected breaking load. In this way, it was verified that the axis of the actuator was contained in the symmetry