Harsh Baid

Bio: Harsh Baid is an academic researcher from California State University, Long Beach. The author has contributed to research in topics: Lamb waves & Guided wave testing. The author has an hindex of 7, co-authored 17 publications receiving 220 citations. Previous affiliations of Harsh Baid include University of California, Los Angeles.

Micromechanics-based progressive failure analysis prediction for WWFE-III composite coupon test cases

Abstract: As a part of a world-wide study, a commercial code (General Optimization Analyzer), based on multi-scale (micro–macro) progressive failure analysis (PFA), is used to provide theoretical predictions...

Detection of disbonds in a honeycomb composite structure using guided waves

Abstract: Advanced composites are being used increasingly in state-of-the-art aircraft and aerospace structures. In spite of their many advantages composite materials are highly susceptible to hidden flaws that may occur at any time during the life cycle of a structure and if undetected, may cause sudden and catastrophic failure of the entire structure. An example of such a defects critical structural component is the "honeycomb composite" in which thin composite skins are bonded with adhesives to the two faces of extremely lightweight and relatively thick metallic honeycombs. These components are often used in aircraft and aerospace structures due to their high strength to weight ratio. Unfortunately, the bond between the honeycomb and the skin may degrade with age and service loads leading to separation of the load-bearing skin from the honeycomb (called "disbonds") and compromising the safety of the structure. This paper is concerned with the noninvasive detection of disbonds using ultrasonic guided waves. Laboratory experiments are carried out on a composite honeycomb specimen containing localized disbonded regions. Ultrasonic waves are launched into the specimen using a broadband PZT transducer and are detected by a distributed array of identical transducers located on the surface of the specimen. The guided wave components of the signals are shown to be very strongly influenced by the presence of a disbond. The experimentally observed results are being used to develop an autonomous scheme to locate the disbonds and to estimate their size.

NDE of composite structures using ultrasonic guided waves

Abstract: Composite structures require a rigorous program of nondestructive inspection and maintenance to detect and characterize hidden defects at an early stage of their occurrence so that preventive measures can be taken before the structure loses its load carrying capacity or suffers from catastrophic failure. Current methods for defects detection in large aircraft and aerospace structures are slow, labor intensive and costly. This is especially true for composite structures where conventional techniques are often ineffective. Ultrasonic guided waves offer an attractive complementary tool for improving inspection techniques in relatively large plate-like structural components due to their large propagation range and sensitivity to defects in their propagation path. Since the waves are affected by the geometrical structural features (e.g. stringers) as well as harmful defects (e.g. delaminations), the application of guided waves in the NDE or SHM of real structures requires a good understanding of these interaction effects. This will help identify the defects from their distinguishing features in the signal in structural components with complex geometry. In this paper a detailed study of the interaction of guided waves with defects in an aluminum plate and a honeycomb composite sandwich structure is carried out using numerical simulations and laboratory experiments. The simpler aluminum plate is used for model validation and understanding the basic characteristics of the interaction phenomena. The agreement between the simulated waveforms and those measured from the experiments are found to be excellent in both cases indicating the possibility of applying guided wave based techniques to more realistic structures.

Mechanical properties and details of composite laminates for the test cases used in the third world-wide failure exercise:

Abstract: This paper gives details of the input data and a full description of a set of 13 test cases provided to the participants of the third world-wide failure exercise for use in their theoretical models...

A comparison between the predictive capability of matrix cracking, damage and failure criteria for fibre reinforced composite laminates: Part A of the third world-wide failure exercise:

Abstract: This paper provides a set of concluding remarks on Part A of the third world-wide failure exercise where a comparison has been made between the capabilities of 12 different mathematical models for predicting the evolution of matrix cracking, damage and failure in continuous fibre-reinforced polymer composites when subjected to multi-axial loading. The originators (or their collaborators) of those theories have employed their methods to 13 carefully selected challenging problems (test cases) addressing the cracking and damage evolution arising from ply thickness, lay-up sequence, size effects and a variety of loading conditions (biaxial, bending, thermal loading and loading-unloading) of a number of unidirectional and multi-directional glass and carbon epoxy laminates. These covered eight different lay-ups consisting of 0°, [0°/90°/0°], [0°/90°8/0°], [0°/90°]s, [±45°]s, [±50°]s, [30°/90°/−30°/90°]s and a family of [0°m/45°m/90°m/−45°m]s, [45°/0°/90°/−45°]s and [0°/45°/−45°/90°]s quasi-isotropic laminates. ...