Post-Impact Thermo-Mechanical Response of Woven Mat Composites Subjected to Tensile Loading

2016 ◽  
Author(s):  
Raghu V. Prakash ◽  
Deepika Sudevan
Keyword(s):  
Plastic Deformation ◽  
Tensile Testing ◽  
Mechanical Response ◽  
Impact Damage ◽  
Temperature Response ◽  
Tensile Loading ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Cfrp Laminates ◽  
Prior Plastic Deformation

The thermo-mechanical response of carbon fiber reinforced polymer (CFRP) laminates subjected to continuous tensile loading and programmed interrupted tensile loading is examined to understand the changes due to damage progression. Quasi-isotropic laminates were prepared using 500 GSM twill weave carbon fabric with LY 556 resin and HY 991 hardener by hand lay-up technique, followed by curing under hot compression. A few specimens were subjected to an impact loading to 23 J and 51 J energy levels using a hemispherical tip to induce low velocity impact damage. Passive thermal imaging of woven CFRP laminates during tensile testing was captured using a TIM 160 Micro-epsilon infrared thermal camera. Temperature response during tensile testing provided a good correlation with deformation mode esp. for specimens impacted with 51 J of energy. Tensile tests were interrupted at periodic loads and unloaded and reloaded to study the thermal response after prior plastic deformation damage in the specimen. Unlike the case of GFRP specimens, distinct changes in thermo-elastic slope due to prior plastic deformation damage could not be clearly identified. As impact damage resulted in de-lamination of some layers, active thermography technique was used to study the rate of cooling of specimen with time when the damage is closer to the camera face as well as when it is away from the camera face. The cooling curves obtained were found to be dependent on the location of the damage, as well as on heating face of the specimen.

scholarly journals Impact Damage Detection in Patch-Repaired CFRP Laminates Using Nonlinear Lamb Waves

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 219
Author(s):  
Zhenhua Yin ◽  
Cheng Li ◽  
Ying Tie ◽  
Yuechen Duan
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Detection System ◽  
Impact Damage ◽  
Impact Resistance ◽  
Numerical Procedure ◽  
Low Velocity Impact ◽  
Patch Repair ◽  
Low Velocity ◽  
Cfrp Laminates

Carbon fiber-reinforced polymer (CFRP) laminates, a key composite material, are widely used in aircraft structures and are susceptible to low-velocity impact (LVI) damage from bird strikes, lightning strikes, hail impacts and other situations. Therefore, finding a method that repairs the damaged structure and detects the effect of these repairs under LVI is a very important goal. In this work, the repair effect of LVI damage in CFRP laminates repaired with patches of various sizes is investigated via experimental and numerical nonlinear Lamb wave analyses. An integrated numerical procedure that combines LVI with nonlinear Lamb wave detection is developed to predict the nonlinear Lamb wave behavior in LVI-damaged patch-repaired CFRP laminates. The CFRP laminate damage in the nonlinear Lamb wave simulation is evaluated based on relative acoustic nonlinearity parameters (RANPs). As a result, the integrated numerical procedure is validated with drop-weight impact tests and RAM-5000 SNAP nonlinear ultrasonic detection system. An optimal patch design is established via interpolation to optimize the absorbed energy, delamination surface area, second RANP and third RANP with different patch repair sizes. These parameters exhibit consistent curve fitting trends, indicating that they can be used as important indicators of impact damage. The optimal circular patch design with a radius of 2.5 r has better impact resistance behavior and repair performance.

Initiation and Propagation of Impact-Induced Damage in CFRP Laminates

2007 ◽  
Vol 345-346 ◽  
pp. 437-440
Author(s):  
Seung Min Jang ◽  
Tadaharu Adachi ◽  
Akihiko Yamaji
Keyword(s):  
Impact Damage ◽  
Matrix Crack ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Element Analysis ◽  
Cfrp Laminates ◽  
Initiation And Propagation ◽  
Back Face ◽  
The Matrix ◽  
The Impact

This paper investigated the initiation and propagation characteristics of impact-induced damage in carbon-fiber-reinforced-plastic (CFRP) laminates with different stacking sequences and thicknesses under low-velocity impact. Impact force histories were measured with a drop-weight impact tester. A strain gauge was attached on the back face of CFRP laminates to measure exactly when a matrix crack on its back face was initiated. It was found from fractographic observation that impact-induced damage in CFRP laminates was initiated at the matrix crack on the back face of CFRP laminates due to bending deformation during impact. Finite element analysis was conducted using the impact forces derived from the experimental results of the impact test. Its results clarified that the tensile stress normal to the fiber on the back face of the specimen was the criterion to initiate impact damage in CFRP laminates.

Investigation of Low Velocity Impact Damage in Aluminum Alloys

2012 ◽  
Author(s):  
Benjamin Cooper ◽  
Andrei Zagrai
Keyword(s):  
Plastic Deformation ◽  
Impact Damage ◽  
Low Velocity Impact ◽  
Time Of Arrival ◽  
Low Velocity ◽  
Velocity Impact ◽  
Object A ◽  
Impact Detection ◽  
Aluminum Plates ◽  
The Impact

In structural health monitoring (SHM), impact detection and characterization techniques often focus on identifying parameters of impact such as the location and velocity of an impacting object. A distributed network of sensors is used to passively detect the mechanical wave created by the impact. Various techniques are used to analyze the signals based on time of arrival, amplitude and phase. A simpler architecture could be used to determine whether an impacting event was benign or caused damage and requires further evaluation. This research focuses on detecting attributes of impact-generated elastic wave signals that are indicative of local damage at the impact site. Waveforms deviate insignificantly for undamaged materials, however, when a material is stressed to plastic deformation or damaged the waveform of propagation through the material is noticeably affected. This change in wave speed may be detectable by SHM sensors, and can be used as an indicator of damage. Low velocity impact experiments were conducted on thin aluminum plates instrumented with piezoelectric and magneto-elastic sensors at various locations. The sensors acquired the initial passage of the impact wave signal before reflections off the boundaries became a significant element. By inspecting the signal for deviations induced by damage (such as plastic deformation), a routine for evaluating damage can be inferred. Further work may correlate features of the signal with damage severity providing an extra level of information in determining the next step in evaluating the damage. Using this approach, it may be possible to evaluate impact damage using limited numbers of passive sensors.

scholarly journals Experimental And Finite Element Analysis Of Mechanical Response On Unidirectional Glass Fibre Epoxy Laminate

2011 ◽  
pp. 100-104
Author(s):  
Rajeshpandian R ◽  
R. Muruganandhan
Keyword(s):  
Glass Fibre ◽  
Mechanical Response ◽  
Impact Damage ◽  
Detailed Comparison ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Element Analysis ◽  
Out Of Plane ◽  
Laminate Design ◽  
The Impact

Research in low velocity impact loading of composites is aimed at reducing the degree of damage in order to improve the damage tolerance. A number of approaches have been used to improve the impact damage resistance and tolerance of composite materials. These include control of fiber/matrix interfacial adhesion, laminate design and through the thickness reinforcement. One of the techniques of arresting delamination is providing through-the-thickness reinforcement like stitching. The objective of this work is to understand the influence of stitching on the impact of the laminate. In this paper, the drop weight impact properties of stitched and unstitched glass fibre epoxy laminate are compared experimentally and the damaged specimen are assessed using back lighting photographic technique. A detailed comparison between the stitched and unstitched laminates experimentally confirmed that the stitching effectively suppressed the out of plane impact damage.

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