Record earnings for the second quarter and the first half of 1980 were announced yesterday by General Dynamics Corps.

The company said second-quarter earnings were $54.4 million ($2.01 per share), up 14 percent from 1979 second-quarter earnings of $47.8 million ($1.77). Earnings for the first half were a record $90.7 million ($3.34), compared with $77.3 million ($2.85) in the first six months of 1979.

General Dynamics is engaged in diverse manufacturing operations in the aerospace, marine and electronic fields.

Sales for the quarter were $1.18 billion, compared with $1.02 billion for the same period last year. Six-month sales this year were $2.25 billion, compared with $1.91 billion for the sameperiod last year.

David S. Lewis, chairman and chief executive officer, said -- earnings increased in the company's aerospace, electric boat and material service divisions.

"However, this strong performance wasoffset partially by reduced sales and earnings in some of our telecommunications and natural resources operations resulting from the down-turn in the U.S. economy and by an extended strike that curtailed operations at our Canadian subsidiary, Asbestos Corp. Ltd.," Lewis said.

Amstar Corp., the sugar and manufacturing combine, earned $1.78 a share in the second quarter, up from $1.22 a share a year ago on a rise in sales of $384.35 million from $262.53 million.

In the first half, Amstar earned $29.68 million ($3.32) on sales of $1.285 billion, up from $21.18 million ($2.38) a year ago on sales of $1.056 billion.

President Robert Quittmeyer said that, although sales of industrial products were strong, the gains were made chiefly on cane and beet sugar and high fructose corn syrup. Better prices were a big factor.

Losses on newsprint mill and lumber operations cut earnings of the Times Mirror Co. for the second quarter and first half despite of gains in publishing and broadcasting operations.

Net income for the 16-week quarter was $35.8 million ($1.05 a share) on revenues of $517.8 million, compared with $38.5 million ($1.14) a year ago on revenues of $450 million.

For the half, Times Mirror earned $60.1 million ($1.76) on revenues of $921.1 million, compared with $66.8 million ($1.97 a year ago on revenues of $792.5 million. The figures actually are for 28 weeks.

Higher interest expenses on capital imporvements also cut earnings.

Newspaper display advertising linage was strong, but classified advertising slipped a little. The Hartford Courant, however, had some advertising weakness.