بررسي رفتار خستگي سازه‌هاي ساندويچي با پوسته‌هاي هيبريدي نامتقارن و هسته فومي تحت بارگذاري كشش - كشش‌

FATIGUE FAILURE OF FOAM CORE SANDWICH COMPOSITES WITH UNSYMMETRICAL HYBRID FACES UNDER TENSION-TENSION LOADING

In thi s pap er , the fatigue respouse of a foam core sandwich composite with unsymmetrical hybrid faces has been investigated . The sandwich laminat es were manufactured using th e same method for a corr esponding selected element in a real composite st ruct ure . Two similar woven E-glass fibers (designated by G1& G2), following unidirectional carbon fibers (C) with Epoxy resin , were used as the face sheet over a PVC foam core. The lamination sequ ence and angles are, as follows, resp ectively : (G1 jC jC jC jG2j Foam j G2jCj CjG1], (O jOjOjOj± 45jC orej±45jOj OjOj. Exteusive fati gue data were generated for the S-N diagram for such a lamiuate. Based on static analysis of th e two FEM models, critical points in the specimen ca using static failure were explained. The effect of using each of th e two different proposed designs for specimeus were shown . FEA and expe riment s results both give an improvement in the failure zone and st rengt h values for an oblique type design of th e gauge int erface. The failure modes, after final failure of the sandwich laminate, have been discussed . From four typ es of damage recognized for th e laminate, two of th em were nucleat ed and grown in th e foam core, first in thickness and then par allel to the length of the gauge. By increasing th e overall st ress level, th e parallel cracks were shorte ned. COMPARISON