رضا رحماني

Hybrid aluminum-composite structures exhibit high energy absorption capacity under axial and transverse crushing loads. In this thesis, taking advantage of adhesive bonding, the local reinforcement of a square aluminum energy absorber by composite material has been carried out. In this regard, a theoretical analysis for predicting the average crushing force and energy absorption of hybrid structures is proposed. The accuracy of the theoretical model is confirmed by experimental results. In this thesis, four L-shaped composites are locally bonded to the four corners of the aluminum structure, both inside and outside, using Araldite 2015 adhesive. A finite element model has been developed to analyze these hybrid structures. Five different fiber orientation states [15 , -15], [45 , -45], [90 , 90], [90 , 0], and [0 , 90] are considered for the composite. Similarly, the number of composite layers varies from 2 to 8 layers. The proposed theoretical model can quickly predict the average crushing force and energy absorbed by the structure when the geometric parameters and mechanical properties of the composite and metals are given. The results showed that compared to aluminum and aluminum-composite energy absorbers, due to the adhesive bonding between aluminum and composite in the locally reinforced aluminum-composite sample, the composite, by following the aluminum collapse pattern and creating continuous fracture and collapse modes, increased energy absorption by 155.75% compared to aluminum alone and by 22.99% compared to aluminum-composite. Among the selected modes, the optimal number of composite layers for the locally reinforced aluminum-composite energy absorber is 4 layers, and the optimal angle for internal reinforcement is [0 , 90]. The findings show that increasing the fiber angle, layer thickness, and number of CFRP layers generally increases the energy absorption capacity. In addition, the geometric parameter alpha is introduced to eva‎luate local reinforcement. Also, using experimental results from impact tests, a correction factor for the theoretical relationship is extracted to predict the average crushing force under impact loading. It can be observed that for DAF, values reach up to 19% for externally reinforced structures and 9% for internally reinforced structures at a constant impact velocity of 20 m/s. It is noteworthy that DAF for hybrid structures is lower than that of aluminum structures, indicating that the inertia effect in hybrid structures is less than in empty structures.

قابليت ضربه‌پذيري , دستگاه سقوط وزنه , اتصال چسبي , خمش سه‌نقطه , سازه هيبريدي فلز- كامپوزيت , ضريب تقويت ضربه اي , لايه گذاري الياف

Crashworthiness , drop Hammer , Adhesively bonded , three-point bending , Metal/composite hybrid structures , DAF , stacking sequence , CFRP

Reza Rahmani

Dr. Hamed Saeidi Googarchin