FEATURE / BONDED JOINTS straining the nodes. Pre-test and post-test finite element models as essentially the same except that the fiber compression modulus was used in the post-test analysis and stress release length in the model was increased by un-constraining nodes in the frame region. The general-purpose finite-element code, Abaqus Standard 6.139, was used to perform the finite-element analysis (FEA). Solid elements (C3D8) were used to discretize core, adhesive and gap filler regions. The face sheet and splice plate were discretized using shell continuum (SC8R) elements. Table 1. Test data of AEWC coupons. AEWC Specimen ID Pristine Coupon Testing & PFA Correlation Ten pristine coupons were tested and the average failure load was 179.938 kN as listed in Table 1. The failure mode of these coupons were in the form of fiber failure in the face sheet at grips and delamination between face sheet plies which is an after effect of earlier failure mode. Pre-test and post-test progressive failure analysis (PFA) generated the failure load of 195.722 kN and 185.935 kN, which is 8.8% and 3.3% respectively from the test failure load and load vs. end shortening curves are presented in Figure 8. The failure modes (fiber failure at the grips) of the test coupons and the failure modes simulated by PFA are presented in Figure 9. One can notice a good agreement between the test and PFA with respect to location of failure initiation and the path. The crack paths are indicated by red color in the PFA model. Hoop Edge-Wise Compression (HEWC) Coupons The test stand and compression test setup for the HEWC coupons is the same as in the AEWC test shown previously in Figure 6. The coupon is placed between a flat square platen at the bottom, and a thick rectangular steel block, covering the entire width and thickness of the coupon, on the top. A circular cross-section steel block is placed above the thick steel block. The joint testing included 7 pristine HEWC sub-element test coupons. Progressive Failure Analysis of Pristine Coupon Progressive failure analysis of HEWC was performed by adopting the damage model mentioned in previous sections for predicting in-plane failure modes such as fiber and matrix damages. After closer examination of loading and geometric configuration of the coupon, it was inferred that delamination between plies or any sub-assemblies would be primary mode of failure. Hence, the finite element model was developed to simulate fiber and matrix damages in the face sheet plies as well as delamination between face sheet plies and splice (doubler) 16 | SAMPE JOURNAL | Test Failure Load (kN) CTE-301-3-AEWC-1 179.877 CTE-301-3-AEWC-3 188.084 CTE-301-3-AEWC-4 171.666 CTE-301-3-AEWC-5 177.871 CTE-301-4-AEWC-1 172.542 CTE-301-4-AEWC-2 188.124 CTE-301-4-AEWC-3 179.806 CTE-301-4-AEWC-4 181.078 CTE-301-4-AEWC-5 180.398 Average 179.938 Figure 8. Load vs. end shortening of AEWC PFA. (a) Typical failure mode of AEWC coupon (b) Failure mode predictions from PFA Figure 9. Typical failure mode of AEWC coupon. M AY/J U N E 2 0 2 0 w w w. s a m p e . o r ghttp://www.sampe.org