scholarly journals Design and Validation of a Modified Compression-After-Impact Testing Device for Thin-Walled Composite Plates

2020 ◽  
Vol 4 (3) ◽  
pp. 126 ◽  
Author(s):  
Markus Linke ◽  
Felix Flügge ◽  
Aurelio Jose Olivares-Ferrer
Keyword(s):  
Residual Strength ◽  
Composite Structures ◽  
Composite Plates ◽  
Impact Testing ◽  
Testing Device ◽  
Testing Procedures ◽  
New Device ◽  
Compression After Impact ◽  
Thin Walled ◽  
Impact Damages

Thin-walled fibre reinforced composites like carbon fibre reinforced plastics are very susceptible to strength reductions due to low-velocity impact damages. In aerospace engineering, the dominating failure mechanisms of impact damaged composite structures are usually investigated based on the compression after impact (CAI) test procedure. This enables the determination of the influence of impact damages on the static residual compressive strength. CAI testing procedures are typically applicable to composite plates with thicknesses larger than 3–4 mm. If thinner panels are used, they typically fail near one of the loaded edges of the CAI device, in particular the area of the free edge (which is needed for compressing the panel) and not within the free measuring area. As a consequence, the investigated samples cannot be used as valid tests for the evaluation of the residual strength in CAI testing. In order to enable an investigation of the residual strength of thin-walled plates in CAI testing, a CAI testing device is developed based on an available CAI fixture and a standardized one. For comparability reasons, this new device exhibits the same dimensions as standardized fixtures. It shows a significant improvement with respect to standardized devices concerning the measurement of mechanical behaviour during CAI testing.

scholarly journals Contribution to Reduce the Influence of the Free Sliding Edge on Compression-After-Impact Testing of Thin-Walled Undamaged Composites Plates

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1708 ◽  
Author(s):  
Markus Linke ◽  
Juan García-Manrique
Keyword(s):  
Impact Test ◽  
Composite Plates ◽  
Free Edge ◽  
Standard Test ◽  
Impact Testing ◽  
Reinforced Plastics ◽  
Compression After Impact ◽  
Fiber Reinforced Plastics ◽  
Thin Walled ◽  
Edge Influence

Standard Compression-After-Impact test devices show a weakening effect on thin-walled specimens due to a free panel edge that is required for compression. As a result, thin-walled undamaged samples do not break in the free measuring area but near the free edge and along the supports. They also show a strength reduction due to the free edge which can become potentially relevant for very weakly damaged panels. In order to reduce the free edge influence on the measured strength, a modified Compression-After-Impact test device has been developed. In an experimental investigation with carbon fiber reinforced plastics, the modified device is compared with a standard device. It is shown that thin-walled undamaged specimens investigated with the modified device now mainly break within the free measuring area and no longer at the free edge and along the bearings as it is the case for standard test devices. The modified device does not cause a free edge weakening effect in comparison to standard devices. The modified device is therefore more suitable for determining the compression strengths of undamaged thin-walled composite plates.

scholarly journals Effect of Thermal Ageing on the Impact Damage Resistance and Tolerance of Carbon-Fibre-Reinforced Epoxy Laminates

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 160 ◽  
Author(s):  
Irene García-Moreno ◽  
Miguel Caminero ◽  
Gloria Rodríguez ◽  
Juan López-Cela
Keyword(s):  
Carbon Fibre ◽  
Residual Strength ◽  
Composite Structures ◽  
Impact Resistance ◽  
Thermal Ageing ◽  
Low Velocity Impact ◽  
Impact Tests ◽  
Compression After Impact ◽  
Structural Applications ◽  
The Impact

Composite structures are particularly vulnerable to impact, which drastically reduces their residual strength, in particular, at high temperatures. The glass-transition temperature (Tg) of a polymer is a critical factor that can modify the mechanical properties of the material, affecting its density, hardness and rigidity. In this work, the influence of thermal ageing on the low-velocity impact resistance and tolerance of composites is investigated by means of compression after impact (CAI) tests. Carbon-fibre-reinforced polymer (CFRP) laminates with a Tg of 195 °C were manufactured and subjected to thermal ageing treatments at 190 and 210 °C for 10 and 20 days. Drop-weight impact tests were carried out to determine the impact response of the different composite laminates. Compression after impact tests were performed in a non-standard CAI device in order to obtain the compression residual strength. Ultrasonic C-scanning of impacted samples were examined to assess the failure mechanisms of the different configurations as a function of temperature. It was observed that damage tolerance decreases as temperature increases. Nevertheless, a post-curing process was found at temperatures below the Tg that enhances the adhesion between matrix and fibres and improves the impact resistance. Finally, the results obtained demonstrate that temperature can cause significant changes to the impact behaviour of composites and must be taken to account when designing for structural applications.

Buckling and Post-Buckling Behaviour of Impacted Glass Reinforced Composite Plates under Compression after Impact Tests

2017 ◽  
Vol 754 ◽  
pp. 87-90
Author(s):  
Roberta Cristiano ◽  
Gaetano Perillo
Keyword(s):  
Numerical Simulations ◽  
Glass Fibre ◽  
Residual Strength ◽  
Composite Plates ◽  
Compressive Test ◽  
Low Velocity ◽  
Reinforced Composite ◽  
Compression After Impact ◽  
Post Buckling ◽  
Glass Fibre Reinforced

The present work deals with the Compression After Impact numerical simulations on low velocity impacted glass fibre reinforced composite plates configurations characterised by three different stacking sequences. The damaged numerical FEM models, deriving from impact explicit analyses, have been used as an input to perform explicit analyses simulating the compressive test. The drop, in terms of compressive residual strength, is analysed and discussed. Considerations on the buckling and post-buckling behaviour of these plates under compression are then introduced.

Compression-after-Impact Testing of CFRP Laminates Subjected to Simulated Lightning Damage Monitored by Acoustic Emission

2012 ◽  
Vol 224 ◽  
pp. 73-76 ◽  
Author(s):  
Oh Yang Kwon ◽  
Jae Ha Shin
Keyword(s):  
Acoustic Emission ◽  
Carbon Fibers ◽  
Composite Structures ◽  
Impact Testing ◽  
Nano Particles ◽  
Lightning Strike ◽  
Lightning Strikes ◽  
Cfrp Laminates ◽  
Compression After Impact ◽  
Coated Carbon

CFRP laminates made of nano-particles-coated carbon fibers and damaged by a simulated lightning strike were tested under the compression-after-impact (CAI) mode, during which the damage progression was monitored by acoustic emission (AE). The effects of nano-particles coating on the degree of lightning-damage and the mechanical integrity of composite structures damaged by lightning strikes have been evaluated in terms of AE activities.

Preliminary Review of Physically Based Methodologies for Predicting the Strength of Visibly Damaged Composite Laminates

2010 ◽  
Vol 654-656 ◽  
pp. 2587-2591 ◽  
Author(s):  
Alex Harman ◽  
Andrew Litchfield ◽  
Rodney Thomson
Keyword(s):  
Residual Strength ◽  
Composite Laminates ◽  
Composite Structures ◽  
Prediction Method ◽  
Cost Effective ◽  
Preliminary Review ◽  
Management Guidelines ◽  
Compression After Impact ◽  
Physically Based

Approaches to detect, assess, monitor and repair damage in critical aircraft components fabricated from composite materials are essential for safe and cost effective operation. In metallic aircraft structures, it is common to leave some fractures in situ for a prescribed period until it is convenient to repair, provided strict inspection and verification processes are in place. Under current military aircraft structural management guidelines, visible damage to critical composite components requires either immediate repair or replacement. Much has been learnt about the behaviour of damaged composite structures, but further investigation is required to develop validated residual strength and life prediction tools. A preliminary review of an early physically based, residual strength prediction method was conducted. The accuracy of this method for use in predicting the strength of composite following a complex damage was tested by comparing the results with compression-after-impact test data for a composite laminate representative of F/A 18 fracture critical structure.

scholarly journals Introduction to Macroscopic Optimal Design in the Mechanics of Composite Materials and Structures

2021 ◽  
Vol 5 (2) ◽  
pp. 36
Author(s):  
Aleksander Muc
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Constitutive Relations ◽  
A Priori ◽  
Chemical Properties ◽  
Composite Plates ◽  
Failure Criteria ◽  
Lagrange Equations ◽  
Homogenization Methods ◽  
Mechanics Of Composite Materials

The main goal of building composite materials and structures is to provide appropriate a priori controlled physico-chemical properties. For this purpose, a strengthening is introduced that can bear loads higher than those borne by isotropic materials, improve creep resistance, etc. Composite materials can be designed in a different fashion to meet specific properties requirements.Nevertheless, it is necessary to be careful about the orientation, placement and sizes of different types of reinforcement. These issues should be solved by optimization, which, however, requires the construction of appropriate models. In the present paper we intend to discuss formulations of kinematic and constitutive relations and the possible application of homogenization methods. Then, 2D relations for multilayered composite plates and cylindrical shells are derived with the use of the Euler–Lagrange equations, through the application of the symbolic package Mathematica. The introduced form of the First-Ply-Failure criteria demonstrates the non-uniqueness in solutions and complications in searching for the global macroscopic optimal solutions. The information presented to readers is enriched by adding selected review papers, surveys and monographs in the area of composite structures.

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