Finite Element Analysis of Adhesively Bonded Lap Joints

Adhesive bonding is a preferred method of joining aerospace structural components, since it provides fewer points of stress concentration compared to fastener joints. Geometrically nonlinear analysis of adhesively bonded lap joints is presented in this paper using both linear and non-linear material properties of the adhesive. The numerical results show beneficial effects of material non-linear behaviour of the adhesive which decrease the stress concentration at the ends of the lap Length. This paper also presents the estimation of strain-energy-release rate components in the presence of debond in the adhesive. The studies have relevance in structural integrity assessment of the joints

Failure prediction of adhesively bonded lap joints between metal and composite adherends

Most of the modern civilian or military aircrafts use advanced composite materials for their primary structural components, in addition to metals. The components are joined together by using either fastener or adhesively bonded joints. But with the introduction of composite materials in aircraft industries, adhesively bonded lap joints are most preferred. This is due to the fact that they develop smooth load transfer and fewer points of stress concentration as compared to fastener joints. The failure prediction of such joints is extremely important, to avoid catastrophic failures during aircraft service period. In the present investigation, an adhesively bonded lap joint between metal-composite (i.e., Al 2024-T3/CFRP) adherends bonded with Redux 319-A adhesive has been analyzed using finite element method considering geometric non-linearity and incorporating adhesive material nonlinear behavior. The failure has been predicted using plastic zone size criterion of adhesive material, which is innovative approach of this study. Also, experimental program is carried out on such joints to correlate with the predicted failure load obtained from numerical model. In this study, the failure of joint is assumed to take place due to adhesive failure only. Plastic zone size in adhesive at failure load of joint is taken as 15 % of the lap length as established from the previous work of the authors. It is observed that the failure load of the adhesively bonded lap joint between composite-metal adherends as obtained from numerical model is well compared with that obtained from experimental study. Results are discussed

Attractive Alternatives of "X" Craft

USNS “X-Craft” built as a catamaran with decreased water-plane area shows some practical advantages as multi-hull combatants. It comprises of a large deck area per tonne of displacement, wide (and free from superstructure) upper deck, high performance in terms of high-speed and enhanced seaworthiness. In this paper two alternatives have been proposed based on the concept of vessels with small water-plane area, which would allow for similar payload, useful deck area but sufficiently better seaworthiness at higher speeds. Resistance and seakeeping characteristics based on test results of the conceptual hull shapes have been illustrated. The new hull shapes of small water-plane area (SWA) ship with additional hydrodynamic lift from foils would ensure higher achievable speeds and better seaworthiness at corresponding displacement

Electromechanical and Dynamic Characterization of In-House-Fabricated Amplified Piezo Actuator

A diamond-shaped amplified piezo actuator (APA) fabricated using six multilayered piezo stacks with maximum displacement of 173 μm at 175V and the amplification factor of 4.3. The dynamic characterization of the actuator was carried out at different frequencies (100 Hz–1 kHz) and at different AC voltages (20V–40V). The actuator response over this frequency range was found neat, without attenuation of the signal. Numerical modeling of multilayered stack actuator was carried out using empirical equations, and the electromechanical analysis was carried out using ABAQUS software. The block force of the APA was 81 N, calculated by electromechanical analysis. This is similar to that calculated by dynamic characterization method

Strength Prediction of Adhesively Bonded Joints using Plastic Zone Size Criterion

The prediction of the strength of adhesively bonded joints has been an issue of considerable interest in literature. This exercise requires numerical techniques combined with experimental programs and matching the two to arrive at a viable criterion. The configurations used for the study are single lap adhesively bonded joints between (i) aluminium (Al) – aluminium (Al) and (ii) carbon fibre reinforced composite (CFRP) and aluminium adherends with Redux-319A epoxy. Geometric and material non-linear finite element analysis was conducted using the NASTRAN software package to establish the proposed plastic zone size (PZS) failure criterion. On the same configuration both experimental program for joint strength and numerical analysis were conducted. The plastic zone size corresponding to failure load was initially estimated from Al-Al joints. The same value was used to predict failure load for CFRP-Al bonded joint. The average experimental value and numerical predictions for CFRP-Al joints matched within 7%. This study suggests an alternative method of strength prediction of adhesively bonded single lap joint in presence of inelastic behaviour of adhesive material

A Novel Approach for Development and Evaluation of LiDAR Navigated Electronic Maize Seeding System Using Check Row Quality Index.

Crop geometry plays a vital role in ensuring proper plant growth and yield. Check row planting allows adequate space for weeding in both direction and allowing sunlight down to the bottom of the crop. Therefore, a light detection and ranging (LiDAR) navigated electronic seed metering system for check row planting of maize seeds was developed. The system is comprised of a LiDAR-based distance measurement unit, electronic seed metering mechanism and a wireless communication system. The electronic seed metering mechanism was evaluated in the laboratory for five different cell sizes (8.80, 9.73, 10.82, 11.90 and 12.83 mm) and linear cell speed (89.15, 99.46, 111.44, 123.41 and 133.72 mm·s-1). The research shows the optimised values for the cell size and linear speed of cell were found to be 11.90 mm and 99.46 mm·s-1 respectively. A light dependent resistor (LDR) and light emitting diode (LED)-based seed flow sensing system was developed to measure the lag time of seed flow from seed metering box to bottom of seed tube. The average lag time of seed fall was observed as 251.2 ± 5.39 ms at an optimised linear speed of cell of 99.46 mm·s-1 and forward speed of 2 km·h-1. This lag time was minimized by advancing the seed drop on the basis of forward speed of tractor, lag time and targeted position. A check row quality index (ICRQ) was developed to evaluate check row planter. While evaluating the developed system at different forward speeds (i.e., 2, 3 and 5 km·h-1), higher standard deviation (14.14%) of check row quality index was observed at forward speed of 5 km·h-1