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Durability of a woven fabric panel subject to low-velocity impact and post-impact tension was investigated using the GENOA code. The results were in good agreement with the experiments. The building block approach and advanced damage tracking are the key factors in the success of the analysis.
(Published on April 2006 – JEC Magazine #24)
BY FRANK ABDI, CEO AND FOUNDER, ALPHA STAR CORPORATION
Progressive failure analysis
A computational approach for prediction of structural fracture in monolithic or composite materials is required to determine: (a) probable fracture modes; b) the causes of fracture initiation; and c) the mechanisms of crack saturation and interaction leading to final fracture. The GENOA computer code is capable of simulating the progressive failure of composite structures subject to impact and post-impact loadings. The post-impact progressive failure analysis accounts for the structural damage and the deformed geometry obtained from the impact simulation.
Three-dimensional dynamic equations of motion were used to model the progressive failure response of an impacted composite structure. Within each time increment, the direct integration of the equations of motion is carried out using the adaptive mesh refinement if required. The structural damage, nodal displacements, velocities and accelerations at the end of each time interval were used as the initial conditions for the subsequent time increment.
The present work considers the progressive failure response of a woven fabric composite panel subject to low-velocity impact followed by post-impact tension. Results of the GENOA analysis were validated through a comparison with available test data.
Results and discussion
The progressive failure analysis of a woven panel subject to lowvelocity impact was carried out using the GENOA code. The panel had six 0.35mm thick layers of G30-500/R3676 fabric with a fibre volume fraction of 60%. The layers were arranged in a [45/- 45/[0/90]2]S lay-up with a total thickness of 2.13mm. The panel was assumed to be clamped during the impact simulation. The span of the panel was 127mm in the length and width directions. These boundary conditions and span lengths simulated the experimental set-up, where the 254mm-wide by 280mm-long panel was sandwiched between the two supporting plates so that only a square of 127mm was exposed. The mass of the 25.4mm diameter impactor was 24.38kg. The impact velocity and energy were 919.7mm/sec and 10.28 joules, respectively.
The GENOA impact simulation showed that after 0.0029 seconds, when the impactor velocity decreased to 511.8mm/sec, the transverse tensile damage initiated in the bottom plies over the area of 127x127mm under the impactor. The magnitude of the contact force at this instant of time was 233kg. With a further decrease in the impactor velocity, the transverse tensile damage was propagating over the increasingly larger area around the impacted centre of the panel. At the end of the impact event, the damaged area was 30.5x30.5mm (fig.1). The GENOA simulation showed that the impact damage of the panel was limited to the matrix cracking. No fibre breakage was detected in the simulation. The maximum contact force and the corresponding mid-span deflection of the panel were in good agreement with the experimental values of 407kg and 5mm, respectively (fig.2).
The post-impact progressive failure analysis of the woven panel subject to tensile loading was conducted based on the computed damaged pattern caused by the impact event. The predicted residual strength of the panel was in good agreement with the experiment.
The GENOA failure propagation analysis was applied to the simulation of the low-velocity impact and post-impact tension of the woven laminated composite plate. Good agreement between the measured and simulated response parameters demonstrates that the GENOA code can be used successfully to accurately simulate the progressive failure phenomenon in composite structures subject to transient dynamic loads. The analysis is capable of reliably predicting damage initiation, development and propagation throughout a composite structure.
- Capable of simulating the progressive Failure of advanced composite structures subject to impact and post-impact loadings. - Building block approach and advanced damage tracking. - Low velocity impact and post impact tension for the woven panel, with excellent agreement with the experiment.
This is more about the code - Material and structural simulation for design and analysis of composite, ceramic and metal structures. - Durability and Damage Tolerance (D&DT), Time Dependent Reliability, Virtual Testing and Virtual Manufacturing. - Simulates material properties degradation under environmental and service conditions. - Predicts Where, When and Why failure occurs during the service life. - Reduces experimental tests, especially for laminate and textile composites.