Accession Number:

ADA109281

Title:

Impact Response Characteristics of Polymeric Materials

Descriptive Note:

Final rept. 27 Apr 79-30 Apr 81

Corporate Author:

GENERAL ELECTRIC CORPORATE RESEARCH ANDDEVELOPMENT SCHENECTADY NY

Personal Author(s):

Report Date:

1981-11-01

Pagination or Media Count:

98.0

Abstract:

This report describes the concluding work on a series of studies concerned with determining, understanding, and trying to predict the behavior of polymethylmethacrylate PMMA and polycarbonate PC under impact. In the present work the impact velocity was extended to 2.1, 125, and 220 ms using a 4.5 mm steel ball as the projectile. Because of dispersion effects the pulse detected using an instrumented Hopkinson impact bar was markedly distorted. A new semi-empirical procedure for correcting the pulse was developed that overcame difficulties encountered in the theoretical methods. Analysis of the data showed that the deduced Youngs modulus of PMMA slowly increases with increasing impact velocity. However, the derived modulus of PC decreases by a factor of five when the impact velocity was increased from 2.1 to 220 ms. This decrease in stiffness is unexpected and anomalous, but is beneficial to reducing the potential for impact damage. A theoretically-based model was formulated to predict the impact response of the two materials from their elastic modulus, densification properties, and stress-relaxation laws. This modified spring dashpot model allows the response of the polymers to be continuously varied between series-like and parallel-like. The PMMA was found to require a predominantly series-like mode description, whereas the PC response was more parallel-like.

Subject Categories:

  • Plastics
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE