Post Doc's

Madhu Parlapalli

ctw/pt

Postdoc

Postdoc Project:

Damage Healing in Thermoplastic Composite Plates by Employing Shape Memory Alloy Wires

Contact Information:

Department of Production Technology, CTW,

Room N131, “Horst”,

University of Twente

Email: A.Sridhar@ctw.utwente.nl


Start / End:

August 2007 to August 2009

Partners:




This project is sponsored by the IOP ‘Self Healing Materials’.



Thermoplastic composite materials are used to manufacture strong, stiff yet light structures for a wide range of applications such as aerospace, automotive, marine, etc., due to their high strength-to-weight and stiffness-to-weight ratios. However, defects in composite laminates in the form of delaminations occur due to manufacturing defects or impact of foreign bodies such as birds, micro-meteors and debris. Presence of delaminations in the composite laminates greatly affect their mechanical performance, particularly under compressive loading, which generates a local, mixed-mode or global buckling mode. It has been demonstrated experimentally and theoretically that adequate through-thickness reinforcement prevents the unstable growth of delaminations by bridging the delamination cracks. The through-thickness reinforcements include stitching or weaving continuous fibre tows and inserting discontinuous fibrous or metal rods and z-fibres. The resistance to delamination is increased by means of tougher matrices, better fibre/matrix interface or interleaving concepts.

Recently, researchers have been focusing on self-healing of damages in materials by means of various approaches. Self-healing is a novel concept for advanced composite materials to recover the functionality after damage using the inherent resources of the material system. The potential of damage healing in thermoplastic composite laminates by using moulded-in shape memory alloy (SMA) wires is investigated. SMAs are able to return to a “remembered” size or shape when heated over the martensite-to-austenite transformation temperature. This unique effect of returning to an original geometry after a large inelastic deformation (near 8%) is known as Shape Memory Effect (SME). This SME effect is used to exert a compressive force on both sides of a delaminated region, while the thermoplastic matrix material is in its soft and ductile state in order for the delaminated region to heal. In these conditions, a purely physical healing process takes places, which will repair the damaged region.


Fig. Shape memory effect.

Thermoplastic composites are selected in this study, as it does not require storing a liquid healing agent in microcapsules, or filling embedded hollow glass fibres (HGF) within a composite laminate with a resin. A thermoelastic constitutive model is developed to predict the thermomechanical performance of an SMA hybrid composite plate. Experiments are carried out on Glass/PMMA composite laminates with a single delamination stitched without and with prestrained SMA (Nitinol) wires. The quality of the healed interface is determined by microscopy, dynamic analysis and measuring the fracture toughness and compression-after-impact strength of the laminate using Double Cantilever Beam (DCB) and Compression-After-Impact (CAI) tests, respectively. The damage healing efficiency is investigated by conducting parametric studies in terms of distribution, strategic locations and number of SMA wires. In addition, the progress of healing as a function of time, temperature and pressure is studied. Results show that the SMA wires are able to heal the delaminated regions and the healing efficiency is significantly effected by the distribution, strategic locations and number of SMA wires.

A. Journal Papers

1.MR Parlapalli, G Bin, D Shu, Y Fujii. Dynamic Response Measurement of Head Arm Assembly of a Hard Disk Drive by Numerical Analysis and Experiments (Accepted. International Journal of Precision Engineering and Manufacturing).

2.YC Wee, CG Boay and MR Parlapalli. Effect of flexural stiffness estimates on the buckling load of delaminated composite beams (Accepted. Proceedings of the Institution of Mechanical Engineers, Part L, Journal of Materials: Design and Applications).

3.MR Parlapalli, KC Soh, DW Shu and M Guowei. Experimental investigation of delamination buckling of stitched composite laminates. Composites Part A: Applied Science and Manufacturing, Vol. 38A, 2007, No. 9, PP 2024 - 2033.

4.MR Parlapalli and D Shu. S-shaped mode in the lower and upper bounds of the buckling of composite beams with two equal delaminations. Composite Structures, Vol. 81, 2007, No. 2, PP 185 – 194.

5.MR Parlapalli and D Shu. Buckling of composite beams with two non-overlapping delaminations: Lower and Upper bounds. International Journal of Mechanical Sciences, Vol. 49, 2007, PP 793-805.

6.M Parlapalli and D Shu. Effects of bridging on buckling of trilayer beams with separated delaminations. AIAA Journal, Vol. 44, No. 9, September 2006, PP 2108-2117.

7.Parlapalli MSRao and D Shu. Buckling analysis of two layer delaminated beams with bridging. European Journal of Mechanics: A/Solids, Vol. 25, No. 5, Sept/Oct 2006, PP 834-853.

8.M Parlapalli, DW Shu and GB Chai. Analytical and numerical analyses of delamination buckling in layer beams. Solid State Phenomena, Vol. 111, April 2006, PP 75-78.

9.Parlapalli MSRao, S Hao and D Shu. Buckling analysis of tri-layer beams with overlapped delaminations. Journal of Composite Materials, Vol. 39, No. 2, PP 109-125, 2005.

10.Parlapalli MSRao, T Wenge and D Shu. Buckling analysis of tri-layer beams with enveloped delaminations. Composites Part B: Engineering, Vol. 36, No. 1, PP 33-39, Jan 2005.

11.MSRao Parlapalli and D Shu. Buckling of two-layer beams with an asymmetric delamination. Engineering Structures, Vol. 26, No 5, April 2004, PP 651-658

12.Parlapalli MSRao, D Sylvain, D Shu and CN Della. Buckling analysis of tri-layer beams with multiple separated delaminations. Composite Structures, Vol. 66, Issues 1-4, Oct 2004, PP 53-60.

13.Parlapalli MSRao and D Shu. Buckling analysis of tri-layer beams with double delaminations. Computational Materials Science Vol. 30, Issues 3-4, 2004, PP 482-488.

14.CN Della, Dongwei Shu and Parlapalli MSRao. Vibrations of beams with two overlapping delaminations Composite Structures, Vol. 66, Issues 1-4, Oct 2004, PP 101-108.

15.D Shu, Parlapalli MSRao. Buckling analysis of bimaterial beams with single asymmetric delamination. Composite Structures, Vol. 64, Issues 3-4, June 2004, PP 501-509.

16.CN Della, D Shu and MR Parlapalli. Vibration of Prebuckled beams with multiple delaminations (Under review).

17.MR Parlapalli, D Shu and GB Chai. Buckling of composite beams with two enveloped delaminations: Lower and Upper bounds (Under review).

18.CN Della, D Shu and MR Parlapalli. Vibration of Prebuckled beams with enveloped delaminations (Under review).


B. Conferences

1.MR Parlapalli, G Bin, D Shu, Y Fujii. Dynamic Response Measurement of Head Arm Assembly of a Hard Disk Drive by Numerical Analysis and Experiments. 8th International Symposium on Measurement Technology and Intelligent Instruments, September 25-27, 2007, Sendai, Japan.

2.BJ Shi, DW Shu, B Gu, MR Parlapalli, CN Della, QY Ng, Air Bearing Slider Simulation and Modeling for Hard Disk Drives with Ultra-Low Flying Heights. Computational Mechanics Conference ISCM2007, July 30-August 1, 2007, Beijing, China.

3.MR Parlapalli, KC Soh and DW Shu. Delamination Buckling of Kevlar and Twaron Stitched Glass\Epoxy Composite Laminates by Experiments. Symposium Q, Advanced Structural and Functional Materials for Protection - International Conference on Materials for Advanced Technologies ICMAT 2007, 1 - 6 July 2007, Singapore.

4.M Parlapalli, DW Shu and GB Chai. Analytical and Numerical Analyses of Delamination Buckling in Layer Beams. Symposium S, Science and Technology of Hybrid Materials-International Conference on Materials for Advanced Technologies & IUMRS ICMAT 2005, 3 - 8 July 2005, Singapore.

5.Vi Kumar, D Gangacharyulu, Parlapalli MSRao and RS Barve. CFD analysis of cross flow air to air tube heat exchanger. International PHOENICS Users Conference - Melbourne Australia - May 3rd-7th, 2004, http://www.phoenics.cn/others/tube.htm.

6.Parlapalli MSRao, T Wenge and D Shu. Buckling analysis of tri-layer beams with enveloped delaminations. International Conference on Precision Engineering (ICOPE), 2nd-5th Mar. 2004, Singapore.

7.Parlapalli MSRao and D Shu. Buckling analysis of tri-layer beams with double delaminations. 2nd International Conference on Materials for Advanced Technologies & IUMRS – International Conference in Asia – Singapore- 7th - 12th Dec. 2003.

8.Parlapalli MSRao, D Sylvain, D Shu and CN Della. Buckling analysis of tri-layer beams with multiple separated delaminations. 12th International Conference on Composite Structures (ICCS/12). Monash University-Australia- 17th-19th Nov. 2003.

9.CN Della, D Shu and Parlapalli MSRao. Vibrations of beams with two overlapping delaminations. ICCS/12. Monash University-Australia- 17th-19th Nov. 2003.

10.US Dixit and Parlapalli MSRao. Determination of yield strength and hardening coefficients by hardness testing. ISTAM (The Indian Society of Theoretical and Applied Mechanics) conference, Regional Engineering College, Warangal, India, Dec. 22nd –25th, 1999.

Parlapalli MSRao and Sudharsan A. Waste energy as useful energy source, TRYST-97, (The All Indian Students Technical Session), Indian Institute of Technology – Delhi, India, Jan. 1997.