Mcdonnell Douglas Corporation

Andrew S Bicos

Donald L Edberg

Shu-Yau Wu

In a system for in-situ delamination detection in composites, the invention employs a system which evaluates the mechanical vibration response of composite material structures. The damping characteristics of the composite structure are extracted from the detected wave properties generated by imbedded piezoelectric ceramic actuators and received by imbedded high strain sensitive fiber optic sensors. Such a sensor system is simple to operate for real-time non-destructive strain and displacement monitoring and delamination detection, without the need to remove the tested surface from operation. During the routine structural integrity monitoring operation, mechanical vibration pulses are launched into the composite from one actuator. The strain signal's propagation patterns are measured in real time by the fiber-optic sensors at different grating locations. Different travel times are computed dependent on the location of the receiving gratings. Propagation of the waves through a delaminated area results in wave modal properties (damping characteristics) which show a difference from those propagating through the delamination-free area. Successive signals from different locations permit computation of the location of the delamination defect.

System for in-situ delamination detection in composites

An apparatus for controlling the motion of a structural member on a space platform truss structure, launch vehicle, automobile, building, or the like is comprised of a first driving piezoelectric element and a second constraining piezoelectric element. The first piezoelectric element is embedded in or bonded onto the structural member. The second piezoelectric element is bonded onto the structural member, with a viscoelastic material (VEM) layer sandwiched between the structural member and the second piezoelectric element. The first and second piezoelectric elements are electrically connected in opposite phase. When the structural member is deformed by an applied force, the first driving piezoelectric element is correspondingly deformed, generating an electrical field. The electrical field is then applied in an opposite sense to the second piezoelectric element through the electrical connections, thereby oppositely deforming the second piezoelectric element with respect to the first piezoelectric element. This opposite deformation induces a large shear strain in the VEM layer, giving the apparatus a large damping capacity. Because the system is passive, it has great advantages over prior art systems, because of its greater simplicity, lower cost, easier maintainability, and lower weight.

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Arcadia, CA, United States of America

Andrew S Bicos